Aerodynamic response of a red-tailed hawk to discrete transverse gusts

A limiting factor in the design of smaller size uncrewed aerial vehicles is their inability to navigate through gust-laden environments. As a result, engineers have turned towards bio-inspired engineering approaches for gust mitigation techniques. In this study, the aerodynamics of a red-tailed hawk's response to variable-magnitude discrete transverse gusts was investigated. The hawk was flown in an indoor flight arena instrumented by multiple high-speed cameras to quantify the 3D motion of the bird as it navigated through the gust. The hawk maintained its flapping motion across the gust in all runs; however, it encountered the gust at different points in the flapping pattern depending on the run and gust magnitude. The hawk responded with a downwards pitching motion of the wing, decreasing the wing pitch angle to between -20∘and -5∘, and remained in this configuration until gust exit. The wing pitch data was then applied to a lower-order aerodynamic model that estimated lift coefficients across the wing. In gusts slower than the forward flight velocity (low gust ratio), the lift coefficient increases at a low-rate, to a maximum of around 2-2.5. In gusts faster than the forward flight velocity (high gust ratio), the lift coefficient initially increased rapidly, before increasing at a low-rate to a value around 4-5. In both regimes, the hawk's observed height change due to gust interaction was similar (and small), despite larger estimated lift coefficients over the high gust regime. This suggests another mitigation factor apart from the wing response is present. One potential factor is the tail pitching response observed here, which prior work has shown serves to mitigate pitch disturbances from gusts.

Neurological examination of clinically healthy pigeons (Columba livia domestica), mute swans (Cygnus olor), common buzzards (Buteo buteo), common kestrels (Falco tinnunculus) and northern goshawks (Accipiter gentilis)

BACKGROUND

A neurological examination is essential for determining the localisation of neurological lesions. However, in avian species, quantitative data regarding the practicability and feasibility of neurological tests are very limited. Therefore, the aim of this study was to establish normative data for the neurological examination of clinically healthy birds of different species.

METHODS

Forty-two domestic and feral pigeons (Columba livia domestica), 42 mute swans (Cygnus olor), 12 common buzzards (Buteo buteo), 24 common kestrels (Falco tinnunculus) and six northern goshawks (Accipiter gentilis) were examined. All birds underwent a predefined neurological examination. Interobserver variations between three examiners were investigated in 11 pigeons and 11 mute swans.

RESULTS

All postural reaction tests, except for the drop and flap reaction in mute swans, provoked a consistent response in pigeons and mute swans, whereas postural reaction tests of the legs in raptors were often not performable. Cranial nerve tests and most of the spinal reflexes revealed variable responses in all birds. The gastrocnemius reflex was not provokable in any bird. Interobserver agreement was almost perfect (Gwet's AC1 coefficient ≥0.81) for 16 of 21 parameters in the examination in pigeons and for 14 of 21 in mute swans.

LIMITATIONS

The inclusion of free-ranging birds, which were not used to handling and for which limited information regarding age, history of previous diseases, etc. was available, may have influenced the results.

CONCLUSION

The normative neurological examination data provided in this study will help improve clinicians' interpretation of neurological examination results in the respective bird species.

Binary fire hawks optimizer with deep learning driven non-invasive diabetes detection and classification

Non-invasive diabetes detection refers to the utilization and development of technologies and methods that can monitor and diagnose diabetes without requiring invasive procedures, namely invasive glucose monitoring or blood sampling. The objective is to provide a more convenient and less burdensome approach to screening and management of diabetes. It is noteworthy that while non-invasive method offers promising avenues for diabetes detection, they frequently require validation through clinical studies and might have limitation in terms of reliability and accuracy than classical invasive approaches. In recent times, deep learning (DL) and feature selection (FS) are used to monitor and diagnose diabetes accurately without requiring invasive procedures. This technique combines the FS method with the DL algorithm for making accurate predictions and extracting relevant features from non-invasive data. This article introduces a new Binary Fire Hawks Optimizer with Deep Learning-Driven Non-Invasive Diabetes Detection and Classification (BFHODL-NIDDC) technique. The major intention of the BFHODL-NIDDC technique focuses on the involvement of non-invasive procedures for the detection of diabetes. In the BFHODL-NIDDC technique, data preprocessing is initially performed to preprocess the input data. Next, the BFHO algorithm chooses an optimal subset of features and improves the classifier results. For the identification of diabetes, multichannel convolutional bidirectional long short-term memory (MC-BLSTM) model is used. At last, the beetle antenna search (BAS) algorithm is used for the hyperparameter selection of the MC-BLSTM method which in turn enhances the detection performance of the MC-BLSTM model. A series of simulations were conducted on the diabetes dataset to assess the diabetes detection performance of the BFHODL-NIDDC technique. The experimental outcomes illustrated better performance of the BFHODL-NIDDC method over other recent approaches in terms of different metrics (Tab. 4, Fig. 9, Ref. 23). Keywords: diabetes, non-invasive detection, binary fire hawks optimizer, deep learning, hyperparameter tuning.

Anomalous binocular vision in African Harrier-Hawks

An animal's visual field is the three-dimensional space around its head from which it can extract visual information at any instant1. Bird visual fields vary markedly between species, and this variation is likely to be driven primarily by foraging ecology1,2,3. The binocular visual field is the region in which the visual fields of the two eyes overlap; thus, objects in the binocular field are imaged by both eyes simultaneously. The binocular field plays a pivotal role in the detection of symmetrical optic flow-fields, providing almost instantaneous information on the direction of travel and the time to contact a target towards which the head or feet is travelling; thus, information from the binocular field is crucial in guiding key foraging behaviours2,3. Here, we demonstrate an unusual visual field and binocular extent above the head in African Harrier-Hawks, also known as Gymnogenes (Polyboroides typus) compared to 18 other members of the Accipitridae4,5. We argue that the observed visual field can be attributed to the unusual and specific foraging behaviour of African Harrier-Hawks.

Iridial melanocytoma in a ferruginous hawk (Buteo regalis): A case report and review of avian melanocytic neoplasia

A 21-year-old, suspected female captive ferruginous hawk (Buteo regalis) was followed for 3 years due to an iridial mass of the left eye (OS) that progressively increased in size. Enucleation of OS was eventually recommended due to the iridial mass taking up approximately 75% of the anterior chamber, and the bird seemed less active. A complete physical examination, complete blood cell count, biochemistry, and survey radiographs were performed pre-surgery with no findings indicating metastasis. A subconjunctival enucleation was performed and the globe was submitted for histopathology through the Comparative Ocular Pathology Lab of Wisconsin. The histopathologic evaluation determined the mass to be consistent with an iris melanocytoma, which has not been previously reported in this species. The patient recovered well from surgery and has remained comfortable and active for 117 days post-surgery. This case report aimed to review the current available information on avian ocular neoplasms as well as describe the clinical presentation, medical management and surgical procedure, and long-term follow-up for this patient to enhance clinical understanding of the behavior of iris melanocytic tumors in avian species.

Toxicological responses to sublethal anticoagulant rodenticide exposure in free-flying hawks

An important component of assessing the hazards of anticoagulant rodenticides to non-target wildlife is observations in exposed free-ranging individuals. The objective of this study was to determine whether environmentally realistic, sublethal first-generation anticoagulant rodenticide (FGAR) exposures via prey can result in direct or indirect adverse effects to free-flying raptors. We offered black-tailed prairie dogs (Cynomys ludovicianus) that had fed on Rozol® Prairie Dog Bait (Rozol, 0.005% active ingredient chlorophacinone, CPN) to six wild-caught red-tailed hawks (RTHA, Buteo jamaicensis), and also offered black-tailed prairie dogs that were not exposed to Rozol to another two wild-caught RTHAs for 7 days. On day 6, blood was collected to determine CPN's effects on blood clotting time. On day 7, seven of the eight RTHAs were fitted with VHF radio telemetry transmitters and the RTHAs were released the following day and were monitored for 33 days. Prothrombin time (PT) and Russell's viper venom time confirmed that the CPN-exposed RTHAs were exposed to and were adversely affected by CPN. Four of the six CPN-exposed RTHAs exhibited ptiloerection, an indication of thermoregulatory dysfunction due to CPN toxicity, but no signs of intoxication were observed in the reference hawk or the remaining two CPN-exposed RTHAs. Of note is that PT values were associated with ptiloerection duration and frequency; therefore, sublethal CPN exposure can directly or indirectly evoke adverse effects in wild birds. Although our sample sizes were small, this study is a first to relate coagulation times to adverse clinical signs in free-ranging birds.

Multilevel Hidden Markov Models for Behavioral Data: A Hawk-and-Dove Experiment

Motivated by the analysis of behavioral data taken from an economic experiment based on the Hawk-and-Dove game, this article describes a multilevel hidden Markov model, that includes covariates, autoregression, and endogenous initial conditions under a unified framework. The data at hand are affected by multiple sources of latent heterogeneity, due to multilevel unobserved factors that operate in conjunction with observed covariates at all the levels of the data hierarchy. We fit a multilevel logistic regression model for repeated measurements of player behaviors, nested within groups of interacting players. The model integrates discrete random effects at the group level and Markovian sequences of discrete random effects at the player level. Parameters are estimated by a computationally feasible expectation-maximization algorithm. We model the probability of playing the Hawk strategy, which implies fighting aggressively for controlling an asset, and test the role played by initial possession, property, and other player-specific characteristics in driving hawkish behaviors. The results from our study suggest that crucial factors in determining hawkish behavior are both the way possession is achieved - which depends on our treatment manipulation- and possession itself. Furthermore, a clear time-dependence is observed in the data at the player level as accounted for by the Markovian random effects.

Prevalence of anticoagulant rodenticide exposure in red-tailed hawks (Buteo jamaicensis) and utility of clotting time assays to detect coagulopathy

Anticoagulant rodenticides (ARs) continue to be used across the United States as a method for controlling pest rodent species. As a consequence, wild birds of prey are exposed to these toxicants by eating poisoned prey items. ARs prevent the hepatic recycling of vitamin K and thereby impede the post-translational processing of coagulation factors II, VII, IX, and X that are required for procoagulant complex assembly. Through this mechanism of action, ARs cause hemorrhage and death in their target species. Various studies have documented the persistence of these contaminants in birds of prey but few have attempted to use affordable and accessible diagnostic tests to diagnose coagulopathy in free-ranging birds of prey. In our study free-ranging red-tailed hawks were found to be exposed to difethialone and brodifacoum. Eleven of sixteen (68%) livers tested for AR exposure had detectable residues. Difethialone was found in 1/16 (6%), and brodifacoum was detected in 10/16 (62%) liver samples that were tested for rodenticide residues. Difethialone was found at a concentration of 0.18 ug/g wet weight and brodifacoum concentrations ranged from 0.003-0.234 ug/g wet weight. Two out of 34 (6%) RTHA assessed for blood rodenticide had brodifacoum in serum with measured concentrations of 0.003 and 0.006 ug/g. The range of clotting times in the prothrombin time (PT) and Russell's viper venom time assays for control RTHA were 16.7 to 39.7 s and 11.5 to 91.8 s, respectively. One study bird was diagnosed with clinical AR intoxication with a brodifacoum levels in blood of 0.006 and 0.234 ug/g wet weight in blood and liver respectively, a packed cell volume (PCV) of 19%, and PT and RVVT times of >180 s. No correlation was found between PT and RVVT in the control or free-range RTHA, and there was no relationship found between the presence of liver anticoagulant residues and clotting times in the PT and RVVT.

Ecosystem based approach to delineate coastal degradation of Hawks bay, Karachi, Pakistan

Hawks Bay (HB) a renowned recreational beach, an important small scale fishery and nesting ground of an endangered turtle species encountering massive environmental degradation. Its eastern bay cover scattered mangrove patches and the western bay embraces sandy and rocky beach that terminus the area into great ecological and economic concerns. Here, we have figured out tendency of contamination entering in the ecosystem and elaborate food ∼ web dynamics around HB. An integrated approach was applied to evaluate level of contamination in water, sediments, planktons, seaweeds, mangrove leaves, crabs and fishes. In the sampled population phytoplankton were comprises of (39 Taxa), zooplankton (21), crab (1) and fishes (9) from pelagic demersal domains. The concentration of copper (Cu), iron (Fe), zinc (Zn), lead (Pb) and chromium (Cr) were detected using double-beam Atomic Absorption Spectrophotometer (AAS). The trophic transfer (TTF), contamination factor (CF), pollution load index (PLI), bioaccumulation factor (BAF) and accumulation factor (AF) were calculated round the year. The CF reveals that the area is moderately contaminated whereas PLI (>1) indicate that area is massively polluted by the industrial wastes. Multivariate approach of Principle Component Analysis was applied using pooled data of TTF that defines PC-I (41.56%) and PC- II (31.44%) variability among axes. Evaluation of metal contamination from micro to macro and from surface to bottom exhibits considerable load being received by HB ecosystem echoes stringent actions to curb further degradation of an important area.

Feathers as an integrated measure of organohalogen contamination, its dietary sources and corticosterone in nestlings of a terrestrial bird of prey, the northern Goshawk (Accipiter gentilis)

In this study, we evaluated the suitability of body feathers, preen oil and plasma for estimation of organohalogen compound (OHC) exposure in northern goshawk Accipiter gentilis nestlings (n = 37; 14 nests). In addition, body feathers received further examination concerning their potential to provide an integrated assessment of (1) OHC exposure, (2) its dietary sources (carbon sources and trophic position) and (3) adrenal gland response (corticosterone). While tetrabromobisphenol A was not detected in any sample, the presence of polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ethers and hexabromocyclododecane in body feathers (median: 23, 19, 1.6 and 3.5 ng g^-1 respectively), plasma (median: 7.5, 6.2, 0.50 and 1.0 ng g^-1 ww, respectively) and preen oil (median: 750, 600, 18 and 9.57 ng g^-1 ww, respectively) suggests analytical suitability for biomonitoring of major OHCs in the three matrices. Furthermore, strong and significant associations (0.20 ≤ R² ≤ 0.98; all P < 0.05) among the OHC concentrations in all three tissues showed that body feathers and preen oil reliably reflect circulating plasma OHC levels. Of the dietary proxies, δ¹³C (carbon source) was the most suitable predictor for variation in feather OHCs concentrations, while no significant relationships between body feather OHCs and δ¹⁵N (trophic position) were found. Finally, body feather corticosterone concentrations were not related to variation in OHC concentrations. This is the first study to evaluate feathers of a terrestrial bird of prey as an integrated non-destructive tool to jointly assess nestling ecophysiology and ecotoxicology.

Forecasting factors and outcomes in hawkish inflammatory breast carcinoma - A single center data exploration

INTRODUCTION

Inflammatory breast carcinoma (IBC) is an aggressive clinical syndrome of invasive breast carcinoma. There is paucity of data regarding the outcomes in IBC.

OBJECTIVES

Analyses of OS and Event-free survival (EFS) in nonmetastatic and metastatic IBC and to find prognostic factors influencing them.

METHODOLOGY

In this single center, retrospective study the data of patients fulfilling the clinical criteria of IBC were retrieved from 2016 to 2021. The impact of prognostic factors on OS and EFS were analysed by log rank test (univariate analysis). The OS and EFS were depicted as Kaplan Meier survival curves.

RESULTS

There were 22 patients with IBC. Median follow-up was 17 months. The median OS was significantly better in non-metastatic(M0) compared to metastatic IBC (25 months vs 6 months) with 3year OS rate of 50% vs 0% respectively. The post-menopausal status, grade 2 histology and trimodality treatment showed better outcome while N3 stage at diagnosis had worse outcome in M0 group. The lesser HR expression, lesser pCR rates, higher N3 proportion, liver metastasis and multiple metastatic site involvement contributed to the worse outcome observed in this study.

CONCLUSION

The aggressive clinicopathological features of IBC in the present study resulted in less favourable outcome compared to literature review. Improved outcome with trimodality highlights the emergent need for additional targeted therapy to improve pCR and operability.

Determinants of microbial contamination of cooked foods hawked in Tharaka Nithi County, Kenya: a cross-sectional study

Introduction

hawking of cooked foods is an important socio-economic activity. However, hawked cooked foods are prone to contamination, especially by pathogenic microorganisms.

Methods

this was a cross-sectional study of 151 cooked food hawkers and 151 cooked food samples, one sample each from every respondent. Data was collected through questionnaires, observation checklists, laboratory processes, and key informant interviews. Quantitative data were analyzed using SPSS, while qualitative data were analyzed using the thematic network analysis technique.

Results

adjusted multinomial logistic regression revealed increased odds of microbial contamination in cooked foods hawked by persons with primary-level education (adjusted odds ratio) AOR = 9.278, 95% confidence interval (CI) 2.292, 37.548; p = 0.003), persons earning a profit of Ksh. ≤500.00 (AOR = 4.046, 95% CI 1.825, 8.969; p = 0.001), and in areas infested with rodents (AOR = 6.386, 95% CI 1.877, 21.724; p = 0.003). However, cooked foods hawked by males (AOR = 0.338, 95% CI 0.133, 0.856; p = 0.022), persons trained on food safety (AOR = 0.216, 95% CI 0.064, 0.733; p = 0.014), persons wearing outer garments (AOR = 0.399, 95% CI 0.196, 0.812; p = 0.011), and by persons who stored their garbage in a municipal receptacle or a standard dust bin (AOR = 0.13, 95% CI 0.041, 0.410; p = 0.000) recorded reduced risk of contamination.

Conclusion

hawker´s characteristics, food handling practices, and the condition of the hawking station are important determinants of microbial contamination of cooked foods hawked in Tharaka Nithi County. Targeted interventions need to be developed and implemented to prevent related foodborne diseases.

Validity and intra-examiner reliability of the Hawk goniometer versus the universal goniometer for the measurement of range of motion of the glenohumeral joint

AIM

The aim of this study was to establish the validity of an external measurement system (the Hawk goniometer). This is a digital device which measures joint ranges compared to the universal goniometer for the measurement of shoulder range of motion in healthy adults.

MATERIAL AND METHODS

a correlational study with 157 healthy volunteers completed six shoulder movements (forward flexion, abduction, extension, adduction and internal and external rotation) with each shoulder. The degree of agreement between each goniometer and Hawk measurement was assessed using Intra-class Correlation Coefficients (ICC) and Bland-Altman 95% limits of agreement (LOA).

RESULTS

the tests showed a very strong relationship between the readings of both devices (CI between 0.81 and 0.99) and there were no significant differences between the mean readings of both devices. An intraclass correlation coefficient (ICC) of above 0.9 was obtained, indicating a high intra-evaluator reliability of the Hawk goniometer in repeated measurements of shoulder range of motion.

CONCLUSIONS

the Hawk goniometer is a valid and reliable element for the objective measurement of the range of motion at the shoulder joint.

Comparison of torsional properties between a Fixateur Externe du Service de Santé des Armées and an acrylic tie-in external skeletal fixator in a red-tailed hawk (Buteo jamaicensis) synthetic tibiotarsal bone model

OBJECTIVE

To compare the torsional mechanical properties of 2 external skeletal fixators (ESFs) placed with 2 intramedullary pin (IP) and transfixation pin (TP) size combinations in a model of raptor tibiotarsal bone fracture.

SAMPLE

24 ESF-synthetic tibiotarsal bone model (polyoxymethylene) constructs.

PROCEDURES

Synthetic bone models were fabricated with an 8-mm (simulated fracture) gap. Four types of ESF-synthetic bone model constructs (6/group) were tested: a FESSA with a 1.6-mm IP and 1.6-mm TPs, a FESSA with a 2.0-mm IP and 1.1-mm TPs, an acrylic connecting bar with a 1.6-mm IP and 1.6-mm TPs, and an acrylic connecting bar with a 2.0-mm IP and 1.1-mm TPs. Models were rotated in torsion (5°/s) to failure or the machine angle limit (80°). Mechanical variables at yield and at failure were determined from load deformation curves. Effects of overall construct type, connecting bar type, and IP and TP size combination on mechanical properties were assessed with mixed-model ANOVAs.

RESULTS

Both FESSA constructs had significantly greater median stiffness and median torque at yield than both acrylic bar constructs; FESSA constructs with a 1.6-mm IP and 1.6-mm TPs had greatest stiffness of all tested constructs and lowest gap strain at yield. No FESSA constructs failed during testing; 7 of 12 acrylic bar constructs failed by fracture of the connecting bar at the interface with a TP.

CONCLUSIONS AND CLINICAL RELEVANCE

Although acrylic bar ESFs have been successfully used in avian patients, the FESSA constructs in this study were mechanically superior to acrylic bar constructs, with greatest benefit resulting from use with the larger TP configuration.

Assessing the ability of novel ecosystems to support animal wildlife through analysis of diurnal raptor territoriality

Novel ecosystems have emerged through human intervention and are rapidly expanding around the world. Whether they can support animal wildlife has generated considerable controversy. Here we developed a new approach to evaluate the ability of a novel forest ecosystem, dominated by the exotic tree species Eucalyptus globulus, to support animal wildlife in the medium and long term. To evaluate this ability, we took advantage of the fact that species territory size decreases with increasing habitat quality, and we used territoriality of a raptor guild composed of Northern Goshawk (Accipiter gentilis), Eurasian Sparrowhawk (A. nisus) and Common Buzzard (Buteo buteo) as indicator. We compared the territoriality of these species in the novel ecosystem with that in other ecosystems found in the literature. Average distances between con-specifics in the novel ecosystem were similar, or even shorter, than those in other ecosystems. Average distances between Goshawk con-specifics were among the shortest described in the literature. All three species nested preferably in mixed stands abundant in large exotic trees, with high structural complexity and abundance of native species within the stand. Key factors supporting this diverse and dense raptor community were the special forest management system implemented in the study area and the agricultural matrix located close to forest plantations that complements the supply of prey. Our results suggest that forest management that promotes a complex and suitable forest structure can increase the ability of novel forest ecosystems to support wildlife biodiversity, particularly a diverse nesting community of forest-dwelling raptors and their preys. The results further suggest the suitability of territoriality for assessing this potential of novel ecosystems.

High resolution of colour vision, but low contrast sensitivity in a diurnal raptor

Animals are thought to use achromatic signals to detect small (or distant) objects and chromatic signals for large (or nearby) objects. While the spatial resolution of the achromatic channel has been widely studied, the spatial resolution of the chromatic channel has rarely been estimated. Using an operant conditioning method, we determined (i) the achromatic contrast sensitivity function and (ii) the spatial resolution of the chromatic channel of a diurnal raptor, the Harris's hawk Parabuteo unicinctus The maximal spatial resolution for achromatic gratings was 62.3 c deg-1, but the contrast sensitivity was relatively low (10.8-12.7). The spatial resolution for isoluminant red-green gratings was 21.6 c deg-1-lower than that of the achromatic channel, but the highest found in the animal kingdom to date. Our study reveals that Harris's hawks have high spatial resolving power for both achromatic and chromatic vision, suggesting the importance of colour vision for foraging. By contrast, similar to other bird species, Harris's hawks have low contrast sensitivity possibly suggesting a trade-off with chromatic sensitivity. The result is interesting in the light of the recent finding that double cones-thought to mediate high-resolution vision in birds-are absent in the central fovea of raptors.

Interrupting behaviour: Minimizing decision costs via temporal commitment and low-level interrupts

Ideal decision-makers should constantly assess all sources of information about opportunities and threats, and be able to redetermine their choices promptly in the face of change. However, perpetual monitoring and reassessment impose inordinate sensing and computational costs, making them impractical for animals and machines alike. The obvious alternative of committing for extended periods of time to limited sensory strategies associated with particular courses of action can be dangerous and wasteful. Here, we explore the intermediate possibility of making provisional temporal commitments whilst admitting interruption based on limited broader observation. We simulate foraging under threat of predation to elucidate the benefits of such a scheme. We relate our results to diseases of distractibility and roving attention, and consider mechanistic substrates such as noradrenergic neuromodulation.

Animals should ideally be able to monitor all relevant aspects of their environment constantly and be ever prepared to alter their course of action in the face of unexpected change. However, the impractically high costs of continual monitoring and deliberation mean that a more realistic strategy is required. Here, we explore a solution in which an animal makes provisional commitments to a temporally-extended action while maintaining the ability to interrupt this behaviour prematurely on the basis of more limited sensing. We demonstrate the benefits of such a scheme through the example of foraging under predation risk, and propose a simple mechanism for implementing interruption. We suggest possible relationships between these results and neural substrates, particularly norepinephrine, and also highlight potential relevance to diseases of distractibility.

Flight initiation by Ferruginous Hawks depends on disturbance type, experience, and the anthropogenic landscape

The expansion of humans and their related infrastructure is increasing the likelihood that wildlife will interact with humans. When disturbed by humans, animals often change their behaviour, which can result in time and energetic costs to that animal. An animal's decision to change behaviour is likely related to the type of disturbance, the individual's past experience with disturbance, and the landscape in which the disturbance occurs. In southern Alberta and Saskatchewan, we quantified probability of flight initiation from the nest by Ferruginous Hawks (Buteo regalis) during approaches to nests by investigators. We tested if probability of flight was related to different disturbance types, previous experience, and the anthropogenic landscape in which individual Ferruginous Hawks nested. Probability of flight was related to the type of approach by the investigator, the number of previous visits by investigators, and the vehicular traffic around the nest. Approaches by humans on foot resulted in a greater probability of flight than those in a vehicle. Approaches in a vehicle via low traffic volume access roads were related to increased probability of flight relative to other road types. The number of previous investigator approaches to the nest increased the probability of flight. Overall, we found support that Ferruginous Hawks show habituation to vehicles and the positive reinforcement hypotheses as probability of flight was negatively related to an index of traffic activity near the nest. Our work emphasizes that complex, dynamic processes drive the decision to initiate flight from the nest, and contributes to the growing body of work explaining how responses to humans vary within species.

The Hawk-Eyed Songbird: Retinal Morphology, Eye Shape, and Visual Fields of an Aerial Insectivore

Swallows are a unique group of songbirds because they are active-pursuit predators that execute all aspects of hunting prey in flight: search, detection, pursuit, and capture. We show that swallows have evolved a visual system that is unlike that of any other studied songbird. Swallows have a bifoveate retina that provides sharp lateral and frontal vision, an unusually long eye that enhances spatial resolution, a large posterior blind area, and a narrow binocular field. We also show that swallows and diurnal raptors (hawks and falcons) have converged on a similar visual configuration but that, interestingly, predatory songbirds that ambush prey (flycatchers) have not converged on the same suite of traits. Despite the commonly held belief that predators rely on binocular vision, the temporal (frontally projecting) fovea present in swallows-but not present in other songbirds-is likely not involved in binocular vision. Instead, swallows have four nonoverlapping foveae in a 100° arc around the beak, which can improve the tracking of frontally located aerial prey that are engaging in evasive maneuvers. Overall, vision in pursuit predators reflects the complex sensory demands of hunting in the air at high speeds and emphasizes the importance of acute frontal vision in predators.

Pharmacokinetics of a single intramuscular injection of ceftiofur crystalline-free acid in red-tailed hawks (Buteo jamaicensis)

OBJECTIVE

To determine the pharmacokinetics and adverse effects at the injection site of ceftiofur crystalline-free acid (CCFA) following IM administration of 1 dose to red-tailed hawks (Buteo jamaicensis).

ANIMALS

7 adult nonreleasable healthy red-tailed hawks.

PROCEDURES

In a randomized crossover study, CCFA (10 or 20 mg/kg) was administered IM to each hawk and blood samples were obtained. After a 2-month washout period, administration was repeated with the opposite dose. Muscle biopsy specimens were collected from the injection site 10 days after each sample collection period. Pharmacokinetic data were calculated. Minimum inhibitory concentrations of ceftiofur for various bacterial isolates were assessed.

RESULTS

Mean peak plasma concentrations of ceftiofur-free acid equivalent were 6.8 and 15.1 μg/mL for the 10 and 20 mg/kg doses, respectively. Mean times to maximum plasma concentration were 6.4 and 6.7 hours, and mean terminal half-lives were 29 and 50 hours, respectively. Little to no muscle inflammation was identified. On the basis of a target MIC of 1 μg/mL and target plasma ceftiofur concentration of 4 μg/mL, dose administration frequencies for infections with gram-negative and gram-positive organisms were estimated as every 36 and 45 hours for the 10 mg/kg dose and every 96 and 120 hours for the 20 mg/kg dose, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Study results suggested that CCFA could be administered IM to red-tailed hawks at 10 or 20 mg/kg to treat infections with ceftiofur-susceptible bacteria. Administration resulted in little to no inflammation at the injection site. Additional studies are needed to evaluate effects of repeated CCFA administration.

Chromosomal Diversity and Karyotype Evolution in South American Macaws (Psittaciformes, Psittacidae)

Most species of macaws, which represent the largest species of Neotropical Psittacidae, characterized by their long tails and exuberant colours, are endangered, mainly because of hunting, illegal trade and habitat destruction. Long tailed species seem to represent a monophyletic group within Psittacidae, supported by cytogenetic data. Hence, these species show karyotypes with predominance of biarmed macrochromosomes, in contrast to short tailed species, with a predominance of acro/telocentric macrochromosomes. Because of their similar karyotypes, it has been proposed that inversions and translocations may be the main types of rearrangements occurring during the evolution of this group. However, only one species of macaw, Ara macao, that has had its genome sequenced was analyzed by means of molecular cytogenetics. Hence, in order to verify the rearrangements, we analyzed the karyotype of two species of macaws, Ara chloropterus and Anodorhynchus hyacinthinus, using cross-species chromosome painting with two different sets of probes from chicken and white hawk. Both intra- and interchromosomal rearrangements were observed. Chicken probes revealed the occurrence of fusions, fissions and inversions in both species, while the probes from white hawk determined the correct breakpoints or chromosome segments involved in the rearrangements. Some of these rearrangements were common for both species of macaws (fission of GGA1 and fusions of GGA1p/GGA4q, GGA6/GGA7 and GGA8/GGA9), while the fissions of GGA 2 and 4p were found only in A. chloropterus. These results confirm that despite apparent chromosomal similarity, macaws have very diverse karyotypes, which differ from each other not only by inversions and translocations as postulated before, but also by fissions and fusions.

Advancement flap as a novel treatment for a pododermatitis lesion in a red-tailed hawk (Buteo jamaicensis)

Pododermatitis is a pathologic condition commonly reported in captive raptors and characterized by swelling, excoriation, ulceration, cellulitis, or abscessation of the plantar aspect of the foot. Its cause can be multifactorial, often involving abnormal weight bearing or poor sanitation, and medical and surgical techniques, in addition to environmental alterations, are hallmarks of treatment. In this case, a single pedicle advancement flap was used to treat chronic, nonresponsive grade V/VII pododermatitis of the right metatarsal pad in a red-tailed hawk (Buteo jamaicensis). The advancement flap was formed by using the interdigital skin between digits 3 and 4. The double layer of skin was incised and separated, and the leading edge of the flap was then advanced over the defect and secured with simple interrupted subcutaneous and skin sutures. The foot was bandaged after surgery to take pressure off the surgical site. At 58 days after the surgery, the hawk was deemed medically sound with no signs of pododermatitis and was released to a wildlife rehabilitator. The use of a single pedicle advancement flap has not previously been reported for the treatment of pododermatitis.

Manipulating individual decisions and environmental conditions reveal individual quality in decision-making and non-lethal costs of predation risk

Habitat selection is a crucial decision for any organism. Selecting a high quality site will positively impact survival and reproductive output. Predation risk is an important component of habitat quality that is known to impact reproductive success and individual condition. However, separating the breeding consequences of decision-making of wild animals from individual quality is difficult. Individuals face reproductive decisions that often vary with quality such that low quality individuals invest less. This reduced reproductive performance could appear a cost of increased risk but may simply reflect lower quality. Thus, teasing apart the effects of individual quality and the effect of predation risk is vital to understand the physiological and reproductive costs of predation risk alone on breeding animals. In this study we alter the actual territory location decisions of pied flycatchers by moving active nests relative to breeding sparrowhawks, the main predators of adult flycatchers. We experimentally measure the non-lethal effects of predation on adults and offspring while controlling for effects of parental quality, individual territory choice and initiation of breeding. We found that chicks from high predation risk nests (<50 m of hawk) were significantly smaller than chicks from low risk nests (>200 m from hawk). However, in contrast to correlative results, females in manipulated high risk nests did not suffer decreased body condition or increased stress response (HSP60 and HSP70). Our results suggest that territory location decisions relative to breeding avian predators cause spatial gradients in individual quality. Small adjustments in territory location decisions have crucial consequences and our results confirm non-lethal costs of predation risk that were expressed in terms of smaller offspring produced. However, females did not show costs in physiological condition which suggests that part of the costs incurred by adults exposed to predation risk are quality determined.

Plasmodium circumflexum in a Shikra (Accipiter badius): phylogeny and ultra-structure of the haematozoa

A wild-caught, juvenile Shikra (Accipiter badius) was evaluated for rehabilitation at the Kasetsart University Raptor Rehabilitation Unit (KURRU) with a history of weakness. Plasmodium sp. was observed by both light and electron microscopy in blood obtained on day 1 of evaluation. Based on the appearance of erythrocytic meronts and gametocytes, the parasites were defined as Plasmodium (Giovannolaia) circumflexum. The sequence analysis of the mitochondrial cytochrome b gene from the plasmodia was closely related to parasites found in the Grey-headed woodpecker from Myanmar and the Brown hawk-owl from Singapore. Transmission electron microscopic examination revealed organelles in the haematozoa and heterophils that ingested the plasmodia. This is the first recorded case of Plasmodium circumflexum in a wild Shikra. This note emphasises the molecular characterisation and ultra-structure of the haematozoa.

Valvular endocarditis and septic thrombosis associated with a radial fracture in a red-tailed hawk (Buteo jamaicensis)

A free-ranging adult female red-tailed hawk died suddenly after 3 weeks in rehabilitation for a radial fracture. Cause of death was septic thrombosis from a chronic bacterial valvular endocarditis, probably associated with injury at the fracture site. The challenge of clinical diagnosis of sepsis in wild birds is emphasized.

Hormonal and behavioral responses to stress in lactating and non-lactating female common marmosets (Callithrix jacchus)

In several mammalian species, hypothalamic-pituitary-adrenal (HPA) and behavioral responses to stressors are down-regulated in lactating females, possibly preventing stress-induced disruptions of maternal care. Experimental elevations of HPA axis hormones have been found to inhibit maternal behavior in lactating common marmoset monkeys (Callithrix jacchus), raising the question of whether lactating female marmosets also have blunted endogenous responses to stress. Therefore, we compared HPA and behavioral responses to standardized stressors in reproductively experienced female common marmosets that were undergoing ovulatory cycles and that either were (N=7) or were not lactating (N=8). Each marmoset underwent (1) a restraint stressor during the early follicular phase of the ovarian cycle (approximately 5 weeks postpartum for lactating females) and (2) exposure to a simulated hawk predator during the early to mid-luteal phase (approximately 7 weeks postpartum for lactating females). Lactating females were tested in the presence of one of their infants. Blood samples were collected before, during, and immediately after each test for determination of plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations. Both stressors caused significant elevations in plasma ACTH and cortisol levels, and significant decreases in cortisol:ACTH ratios; however, lactating and non-lactating females showed no significant differences in their endocrine or behavioral responses to either stressor, or in baseline ACTH or cortisol levels. These findings suggest that in contrast to several other mammalian species, lactating female marmosets maintain full behavioral and HPA responsiveness to stress, at least in the presence of their infants.

Relationships between organohalogen contaminants and blood plasma clinical-chemical parameters in chicks of three raptor species from Northern Norway

Organohalogen contaminants (OHCs) may affect various physiological parameters in birds including blood chemistry. We therefore examined blood plasma clinical-chemical parameters and OHCs in golden eagle, white-tailed eagle and goshawk chicks from Northern Norway. Correlation analyses on pooled data showed that alkaline phosphatase (ALKP), glucose and creatinine were significantly negatively correlated to various OHCs (all: p<0.05; r: -0.43 to -0.55; n=23), while alanine aminotransferase (ALAT), total protein, cholesterol, uric acid, total bilirubin, ratios protein:creatinine and uric acid:creatinine were significantly positively correlated to various OHCs (all: p<0.05; r: 0.43-0.96). Based on these relationships, we suggest that the OHC concentrations found in certain raptor chicks of Northern Scandinavia may impact blood plasma biochemistry in a way that indicates impacts on liver, kidney, bone, endocrinology and metabolism. In order to elaborate further on these relationships and mechanisms, we recommend that a larger study should take place in the near future.

INDIVIDUAL CRYOPRESERVATION WITH DIMETHYL SULFOXIDE AND POLYVINYLPYRROLIDONE OF EJACULATES AND POOLED SEMEN OF THREE AVIAN SPECIES

Artificial insemination (AI) has been used for avian reproduction due to the discovery of cryoprotectants extending its usefulness both in production of domestic fowl and conservation of wild species. The goal of this study was to assess the effect on domestic and wild fowl pooled semen and individual ejaculate cryopreservation with dimethyl sulfoxide (DMSO) and polyvinylpyrrolidone (PVP). Twenty ejaculates and twenty samples of pooled semen of roosters, pheasants and hawks were frozen in media containing DMSO or PVP. DMSO and PVP cryopreservation are equally effective both for ejaculates and pooled semen. Even PVP is a good alternative since no significant difference was found when compared to DMSO. The fertilizing capacity of fresh and cryopreserved pooled semen was analyzed through AI of hens and female pheasants. Similar fertility rates using DMSO, PVP or frozen-thawed samples demonstrated that reproduction is possible through the use of cryopreserved semen. In the case of female pheasants, the same values were obtained with both cryopreserved and fresh semen.

Ecological risk assessment of lead contamination at rifle and pistol ranges using techniques to account for site characteristics

Spent ammunition at outdoor rifle and pistol (RP) firing ranges creates a characteristic pattern of contamination, whereby small areas surrounding backstop berms exhibit extremely high soil lead (Pb) concentrations. We characterized sources, pathways and uncertainty in contaminant accumulation for receptors at two RP ranges in southeastern Ontario. Based on these results, we performed risk calculations using kriging to estimate risk across "worst-case" species foraging ranges. Range-normalized hazard quotients (RNHQ) were then calculated to estimate risk across each receptor's foraging range. Monte Carlo simulation was used to provide +2 standard deviation (SD) risk estimates, in order to account for uncertainty in risk parameters. The American robin was found to be most at risk (RNHQ=4.10; +2SD=9.24), followed by the short-tailed shrew (RNHQ=0.113; +2SD=0.243) and the eastern cottontail (RNHQ=0.109; +2SD=0.703). Elevated risk for the American robin and short-tailed shrew was due to their small foraging ranges and habit of eating earthworms, which bioaccumulate Pb. Elevated risk for the eastern cottontail was due to vegetation accumulating Pb to levels that were considerably higher than conventional bioaccumulation models would indicate. The results of this study clearly emphasize the importance of specific characteristics of RP ranges, such as contamination patterns, dust accumulation on plant tissues, and contaminant bioaccessibility. These characteristics should be accounted for, not only in performing risk assessments, but also in choosing remedial options and in routine management practices.

Use of Prey Hotspots by an Avian Predator: Purposeful Unpredictability?

The use of space by predators in relation to their prey is a poorly understood aspect of predator-prey interactions. Classic theory suggests that predators should focus their efforts on areas of abundant prey, that is, prey hotspots, whereas game-theoretical models of predator and prey movement suggest that the distribution of predators should match that of their prey's resources. If, however, prey are spatially anchored to one location and these prey have particularly strong antipredator responses that make them difficult to capture with frequent attacks, then predators may be forced to adopt alternative movement strategies to hunt behaviorally responsive prey. We examined the movement patterns of bird-eating sharp-shinned hawks (Accipiter striatus) in an attempt to shed light on hotspot use by predators. Our results suggest that these hawks do not focus on prey hotspots such as bird feeders but instead maintain much spatial and temporal unpredictability in their movements. Hawks seldom revisited the same area, and the few frequently used areas were revisited in a manner consistent with unpredictable returns, giving prey little additional information about risk.

Testing domains of danger in the selfish herd: sparrowhawks target widely spaced redshanks in flocks

The main tenet of Hamilton's 'selfish herd theory' for the evolution of group living is that individual risk of being killed upon attack by a predator is greater when relatively far from conspecifics. Here we examine the role of spacing using video analysis of encounters between redshanks, Tringa totanus, in flocks on saltmarsh, and sparrowhawks, Accipiter nisus, surprise hunting from adjacent woodland. Targeted redshanks were 35% (approx. 5 body lengths) more widely spaced than their nearest non-targeted neighbours, controlling for proximity to the hawk. Although targeted redshanks were also twice as slow to escape, the effect dropped out of a model containing spacing, which alone accounted for twice as much variation as escape delay. Redshanks were more tightly spaced on the riskiest side of the flock, suggesting they attempted to compensate for the greater risk, while birds on the edges of flocks were more widely spaced than those in the centre. Our analysis controls for most of the confounding effects associated with the edge-centre comparisons that are normally used in similar studies and provides strong support for spacing-dependent differential predation risk in the wild. In general, we suggest that positive selection for tight spacing when prey are stationary is largely due to domains of danger, but that this also leads to positive selection when prey are mobile because of predator confusion.

Acoustic structures in the alarm calls of Gunnison's prairie dogs

Acoustic structures of sound in Gunnison's prairie dog alarm calls are described, showing how these acoustic structures may encode information about three different predator species (red-tailed hawk-Buteo jamaicensis; domestic dog-Canis familaris; and coyote-Canis latrans). By dividing each alarm call into 25 equal-sized partitions and using resonant frequencies within each partition, commonly occurring acoustic structures were identified as components of alarm calls for the three predators. Although most of the acoustic structures appeared in alarm calls elicited by all three predator species, the frequency of occurrence of these acoustic structures varied among the alarm calls for the different predators, suggesting that these structures encode identifying information for each of the predators. A classification analysis of alarm calls elicited by each of the three predators showed that acoustic structures could correctly classify 67% of the calls elicited by domestic dogs, 73% of the calls elicited by coyotes, and 99% of the calls elicited by red-tailed hawks. The different distributions of acoustic structures associated with alarm calls for the three predator species suggest a duality of function, one of the design elements of language listed by Hockett [in Animal Sounds and Communication, edited by W. E. Lanyon and W. N. Tavolga (American Institute of Biological Sciences, Washington, DC, 1960), pp. 392-430].

Using self-organizing maps to recognize acoustic units associated with information content in animal vocalizations

Kohonen self-organizing neural networks, also called self-organizing maps (SOMs), have been used successfully to recognize human phonemes and in this way to aid in human speech recognition. This paper describes how SOMS also can be used to associate specific information content with animal vocalizations. A SOM was used to identify acoustic units in Gunnison's prairie dog alarm calls that were vocalized in the presence of three different predator species. Some of these acoustic units and their combinations were found exclusively in the alarm calls associated with a particular predator species and were used to associate predator species information with individual alarm calls. This methodology allowed individual alarm calls to be classified by predator species with an average of 91% accuracy. Furthermore, the topological structure of the SOM used in these experiments provided additional insights about the acoustic units and their combinations that were used to classify the target alarm calls. An important benefit of the methodology developed in this paper is that it could be used to search for groups of sounds associated with information content for any animal whose vocalizations are composed of multiple simultaneous frequency components.

Osteoarthritis is for the birds

The purpose of this study was to assess birds as a potential model for osteoarthritis. Compromised by confounding factors, it has not been possible to clearly delineate causation in humans. Nonhuman mammals manifest osteoarthritis in the natural state too rarely for comparative study. Artificial environments (of captive animals) are associated with higher frequencies, but are still inadequate for comparative study, and surgical and chemical models provide only limited insight. As frequency of pathology (except trauma-related) in birds has not been systematically examined across species lines, several families were selected for examination. Skeletal collections of major museums were examined for presence of osteophytes in hawks and pigeons. Three percent of 2,243 free-ranging hawks and 9.8% of 2,718 pigeons had osteoarthritis, all localized to the ankle. The bird ankle morphologically resembles the human knee. Frequency in pigeons was significantly greater than in hawks (chi (2)=86.48, p<0.00001), but was no difference in frequency between wild caught and captive birds (chi (2)=1.06). While misconceptions have plagued past perspectives, it turns out that the most common form of arthritis in humans (osteoarthritis) is actually for, or at least, is common in the class Aves (birds). The frequency of osteoarthritis and cacophony of bird morphologies and behaviors provides an opportunity to start to understand such causation.

Pre- and post-hatching effects of corticosterone treatment on behavior of the domestic chick

We investigated the effect of 60 ìg of corticosterone administered to domestic chicks either before or after hatching on the behavioral response to isolation in a novel arena and performance in a task involving the simultaneous identification of food and detection of a predator (overhead silhouette of a hawk moving overhead). Following release into a novel arena, chicks treated with corticosterone at 18 days of incubation emitted more distress vocalizations. In contrast, no difference in the number of vocalizations was found between chicks treated with corticosterone at day 1 post-hatching and controls. Behavior in the home cages was generally similar across treatments, though chicks treated with corticosterone at 18 days of incubation slept more than control chicks. While searching for grain against a background of pebbles, chicks treated with corticosterone at embryonic day 18, but not chicks treated on day 1 post-hatching, took longer to detect the overhead image of a predator than did controls. Corticosterone treatment at both ages increased the rate of pecking at grains and pebbles. Our findings support work on other birds indicating that corticosterone treatment during incubation influences stress reactivity. The impairment in predator detection in chicks treated with corticosterone on day 18 of incubation appears to be caused by the known effects of corticosterone treatment at this age in preventing the development of lateralization of the thalamofugal visual projections. This further supports the hypothesis that brain lateralization provides an advantage in performing more than one task simultaneously.

NATURAL AND EXPERIMENTAL WEST NILE VIRUS INFECTION IN FIVE RAPTOR SPECIES

We studied the effects of natural and/or experimental infections of West Nile virus (WNV) in five raptor species from July 2002 to March 2004, including American kestrels (Falco sparverius), golden eagles (Aquila chrysaetos), red-tailed hawks (Buteo jamaicensis), barn owls (Tyto alba), and great horned owls (Bubo virginianus). Birds were infected per mosquito bite, per os, or percutaneously by needle. Many experimentally infected birds developed mosquito-infectious levels of viremia (>10(5) WNV plaque forming units per ml serum) within 5 days postinoculation (DPI), and/ or shed virus per os or per cloaca. Infection of organs 15-27 days postinoculation was infrequently detected by virus isolation from spleen, kidney, skin, heart, brain, and eye in convalescent birds. Histopathologic findings varied among species and by method of infection. The most common histopathologic lesions were subacute myocarditis and encephalitis. Several birds had a more acute, severe disease condition represented by arteritis and associated with tissue degeneration and necrosis. This study demonstrates that raptor species vary in their response to WNV infection and that several modes of exposure (e.g., oral) may result in infection. Wildlife managers should recognize that, although many WNV infections are sublethal to raptors, subacute lesions could potentially reduce viability of populations. We recommend that raptor handlers consider raptors as a potential source of WNV contamination due to oral and cloacal shedding.

Hailstorms as a cause of mass mortality of Swainson's hawks in their wintering grounds

We describe a mass mortality event of wintering Swainson's hawks (SH, Buteo swainsoni) in central Argentina during November 2003. One hundred thirteen SH were found dead as a consequence of a single hailstorm. In addition, 14 hawks with severe injuries were recovered alive, but only 10 of these survived 1 wk later. Another 45 dead birds of 11 species were collected in the area. Interviews with local land-owners conducted in other areas of the SH wintering grounds provided further evidence of past hailstorm-related mortality involving SH, suggesting that such events commonly occur in the Argentine Pampas. This potential cause of mass mortality of SH wintering in agricultural areas of Argentina may be significant when added to the increased mortality associated with poisoning events during the last decade.

Pathologic and immunohistochemical findings in goshawks (Accipiter gentilis) and great horned owls (Bubo virginianus) naturally infected with West Nile virus

The carcasses of 25 great horned owls and 12 goshawks were investigated for West Nile virus (WNV) infection by immunohistochemistry (IHC) performed on various organs, including brain, spinal cord, heart, kidney, eye, bone marrow, spleen, liver, lungs, pancreas, intestine, and proventriculus, using a WNV-antigen-specific monoclonal antibody and by WNV-specific reverse transcriptase-polymerase chain reaction (RT-PCR), performed on fresh brain tissue only. WNV infection was diagnosed by IHC in all owls and all goshawks. WNV-specific RT-PCR amplified WNV-RNA in the brain of all goshawks but only 12 owls (48%). Cachexia was a common macroscopic finding associated with WNV infection in owls (76%). Myocarditis was occasionally macroscopically evident in goshawks (33%). Microscopically, inflammatory lesions, including lymphoplasmacytic and histiocytic encephalitis, myocarditis, endophthalmitis, and pancreatitis were present in both species but were more common and more severe in goshawks than in owls. The most characteristic brain lesion in owls was the formation of glial nodules, in particular in the molecular layer of the cerebellum, while encephalitis affecting the periventricular parenchyma of the cerebral cortex was common in the goshawks. In owls, WNV-antigen-positive cells were present usually only in very small numbers per organ. Kidney (80%), heart (39%), and cerebellum (37%) were the organs that most commonly contained WNV antigen in owls. WNV antigen was frequently widely distributed in the organs of infected goshawks, with increased amounts of WNV antigen in the heart and the cerebrum. Spleen (75%), cerebellum (66%), heart (58%), cerebrum (58%), and eye (50%) were often WNV-antigen positive in goshawks. In contrast with the goshawks, WNV antigen was not present in cerebral and retinal neurons of owls. WNV infection appears to be capable of causing fatal disease in great horned owls and goshawks. However, the distribution and severity of histologic lesions, the antigen distribution in the various organs, and the amount of antigen varied among both species. Therefore, the diagnostician may choose organs for histology and immunohistochemistry as well as RT-PCR depending on the investigated species in order to avoid false-negative results.

Allometry of Alarm Calls: Black-Capped Chickadees Encode Information About Predator Size

Many animals produce alarm signals when they detect a potential predator, but we still know little about the information contained in these signals. Using presentations of 15 species of live predators, we show that acoustic features of the mobbing calls of black-capped chickadees (Poecile atricapilla) vary with the size of the predator. Companion playback experiments revealed that chickadees detect this information and that the intensity of mobbing behavior is related to the size and threat of the potential predator. This study demonstrates an unsuspected level of complexity and sophistication in avian alarm calls.

Pathologic findings in red-tailed hawks (Buteo jamaicensis) and Cooper's hawks (Accipiter cooper) naturally infected with West Nile virus

Carcasses of 13 red-tailed hawks (RTHAs) and 11 Cooper's hawks (COHAs) were tested for West Nile virus (WNV) using WNV-specific reverse transcriptase-polymerase chain reaction (RT-PCR) on fresh brain tissue and WNV-specific immunohistochemistry (IHC) on various organs. Ten COHAs (91%) and 11 RTHAs (85%) were positive for WNV RNA by RT-PCR. All 11 COHAs (100%) and 10 RTHAs (77%) were positive for WNV antigen by IHC. A triad of inflammatory lesions, including chronic lymphoplasmacytic and histiocytic encephalitis, endophthalmitis, and myocarditis, was common in both species. In COHAs, the heart (54%), cerebrum (50%), and eye (45%) were the organs that most commonly contained WNV antigen. The amount of WNV antigen was usually small. In RTHAs, the kidney (38%), cerebrum (38%), cerebellum (38%), and eye (36%) were the organs most commonly containing WNV antigen. Unlike COHAs, larger amounts of WNV antigen were present in the cerebrum of RTHAs. WNV antigen was detected in similar cell populations in both species, including neurons of brain, spinal cord, and retina, pigmented epithelial cells of the retina, epithelial cells of renal medullary tubules, cardiomyocytes, endothelial cells and smooth muscle cells of arteries, dendritic cells of splenic lymph follicles, exocrine pancreatic cells, adrenal cells, and keratinocytes of the skin. The study presents strong evidence that WNV can cause a chronic fatal disease in RTHAs and COHAs. The lesion distribution of WNV infection in both species is variable, but inflammatory lesions are common, and a triad of lesions including encephalitis, myocarditis, and endophthalmitis is indicative of WNV infection in both species.