Sexual differences in phenotypical predictors of floating status: body condition influences male but not female reproductive status in a wild passerine

Floaters constitute the sexually mature but non-breeding part of populations. Despite being ubiquitous in most species, knowledge about floaters is scarce. Ignoring this significant number of individuals may strongly bias our understanding of population dynamics and sexual selection processes. We used the spotless starling (Sturnus unicolor) to examine whether phenotypical and non-phenotypical variables from early and adult life predict reproductive status, focusing on the earliest age at which most individuals start to breed, when the percentage of floaters is the highest. We compiled data from a long-term study involving eight female and seven male cohorts of individuals PIT-tagged at birth. We compared a suite of nestling (condition, hatching date and brood size) and adult variables (condition, size and ornamentation) between floaters and breeders. We found that adult and nestling body condition strongly and positively influenced the likelihood of breeding in males. Path analysis revealed that male reproductive status could only be predicted by considering nestling body condition—the influence of this variable superseded adult body condition. Female reproductive status was only negatively associated with hatching date. Ornamentation was not associated with reproductive status in any of the sexes, although path analyses revealed that body condition was positively associated with throat feather length. We conclude that predictors of reproductive status are sex-specific in the spotless starling, suggesting an important role of body condition in access to breeding resources in males. Our results also highlight the long-term influence of early life on life trajectories and their potential implications on floating status.

Food insecurity increases energetic efficiency, not food consumption: an exploratory study in European starlings

Food insecurity—defined as limited or unpredictable access to nutritionally adequate food—is associated with higher body mass in humans and birds. It is widely assumed that food insecurity-induced fattening is caused by increased food consumption, but there is little evidence supporting this in any species. We developed a novel technology for measuring foraging, food intake and body mass in small groups of aviary-housed European starlings (Sturnus vulgaris). Across four exploratory experiments, we demonstrate that birds responded to 1–2 weeks of food insecurity by increasing their body mass despite eating less. Food-insecure birds therefore increased their energetic efficiency, calculated as the body mass maintained per unit of food consumed. Mass gain was greater in birds that were lighter at baseline and in birds that faced greater competition for access to food. Whilst there was variation between experiments in mass gain and food consumption under food insecurity, energetic efficiency always increased. Bomb calorimetry of guano showed reduced energy density under food insecurity, suggesting that the energy assimilated from food increased. Behavioural observations of roosting showed inconsistent evidence for reduced physical activity under food insecurity. Increased energetic efficiency continued for 1–2 weeks after food security was reinstated, indicating an asymmetry in the speed of the response to food insecurity and the recovery from it. Future work to understand the mechanisms underlying food insecurity-induced mass gain should focus on the biological changes mediating increased energetic efficiency rather than increased energy consumption.

Meat quality and lipid fatty acid profile from wild thrush (Turdus philomelos), woodcock (Scolopax rusticola) and starling (Sturnus vulgaris): a preliminary comparative study

Background

The present study aimed to evaluate the nutritional proximate composition, some qualitative traits and fatty acid profile of meat from wild thrush, woodcock and starling hunted in Southern Italy in 2017 and 2018.

Methods

Nutritive composition and physical traits of meat and lipid fatty acid profile were evaluated in breast muscle (Pectoralis major) of gamebirds.

Results

From findings, the meat pH was significantly (P < 0.001) higher in starling when compared to the other two species. Thrush meat was significantly (P = 0.002) darker and had higher redness (P < 0.001) and yellowness (P = 0.004) in comparison to starling and woodcock. Thrush breast muscle showed the highest (P < 0.001) level of lipids and lowest (P < 0.001) protein content. Meat from thrush showed the best lipid fatty acid profile based on the higher (P < 0.001) monounsaturated fatty acids (MUFA) and lower (P < 0.001) saturated fatty acids (SFA) concentrations. Starling breast muscle reported the highest (P = 0.002) polyunsaturated fatty acids (PUFA) level compared to both thrush and woodcock, whereas no differences were detected on total n-3. The ratio n-6/n-3 was higher (P = 0.001) in starling muscle. Thrush breast muscle had the lowest (P < 0.001) atherogenic and thrombogenic indices compared to the other gamebirds.

Conclusions

The findings indicated that meat from the three investigated gamebirds species may represent a healthily lipid food source for human consumption in relation to the prevention of cardiovascular diseases.

Complex patterns of collective escape in starling flocks under predation

ABSTRACT

Collective behaviour of animals has been a main focus of recent research, yet few empirical studies deal with this issue in the context of predation, a major driver of social complexity in many animal species. When starling (Sturnus vulgaris) flocks are under attack by a raptor, such as a peregrine falcon (Falco peregrinus), they show a great diversity of patterns of collective escape. The corresponding structural complexity concerns rapid variation in density and shape of the flock over time. Here, we present a first step towards unravelling this complexity. We apply a time series analysis to video footage of 182 sequences of hunting by falcons on flocks of thousands of starlings close to two urban roosts during winter. We distinguish several types of collective escape by determining the position and movement of individuals relative to each other (which determines darkness and shape of the flock over time) as well as relative to the predator, namely 'flash expansion', 'blackening', 'wave event', 'vacuole', 'cordon' and 'split'. We show that the specific type of collective escape depends on the collective pattern that precedes it and on the level of threat posed by the raptor. A wave event was most likely to occur when the predator attacked at medium speed. Flash expansion occurred more frequently when the predator approached the flock at faster rather than slower speed and attacked from above rather than from the side or below. Flash expansion was often followed by split, but in many cases, the flock showed resilience by remaining intact. During a hunting sequence, the frequencies of different patterns of collective escape increased when the frequency of attack by the raptor was higher. Despite their complexity, we show that patterns of collective escape depend on the predatory threat, which resembles findings in fish.

SIGNIFICANCE STATEMENT

Patterns of collective escape in flocks of starlings have always intrigued laymen and scientists. A detailed analysis of their complex dynamics has been lacking so far, and is the focus of our present study: we analysed video footage of hunting by falcons on flocks of thousands of starlings and show how patterns of collective escape (namely flash expansion, blackening, wave event, vacuole, cordon and split) depend on the preceding pattern and on details of attack. A higher frequency of attack during a hunting sequence resulted in a higher frequency of collective escape events. Flash expansion happened most often when the predator attacks at greater speed. A wave event was most likely when the raptor attacks at medium (rather than high or low) speed. These results provide a first quantitative approach to social complexity in collective avoidance of a predator.

Environmental Influences on Neuromorphology in the Non-Native Starling Sturnus vulgaris

Cognitive traits are predicted to be under intense selection in animals moving into new environments and may determine the success, or otherwise, of dispersal and invasions. In particular, spatial information related to resource distribution is an important determinant of neural development. Spatial information is predicted to vary for invasive species encountering novel environments. However, few studies have tested how cognition or neural development varies intraspecifically within an invasive species. In Australia, the non-native common starling Sturnus vulgaris inhabits a range of habitats that vary in seasonal resource availability and distribution. We aimed to identify variations in the brain mass and hippocampus volume of starlings in Australia related to environmental variation across two substantially different habitat types. Specifically, we predicted variation in brain mass and hippocampal volume in relation to environmental conditions, latitude, and climatic variables. To test this, brain mass and volumes of the hippocampus and two control brain regions (telencephalon and tractus septomesencephalicus) were quantified from starling brains gathered from across the species' range in south eastern Australia. When comparing across an environmental gradient, there was a significant interaction between sex and environment for overall brain mass, with greater sexual dimorphism in brain mass in inland populations compared to those at the coast. There was no significant difference in hippocampal volume in relation to environmental measures (hippocampus volume, n = 17) for either sex. While these data provide no evidence for intraspecific environmental drivers for changes in hippocampus volume in European starlings in Australia, they do suggest that environmental factors contribute to sex differences in brain mass. This study identifies associations between the brain volume of a non-native species and the environment; further work in this area is required to elucidate the mechanisms driving this relationship.

On-farm starling populations and other environmental and management factors associated with the presence of cefotaxime and ciprofloxacin resistant E. coli among dairy cattle in Ohio

Wild birds that forage around livestock facilities have been implicated as vectors of antimicrobial resistant organisms. Although antimicrobial resistant bacteria have been isolated from European starlings (Sturnus vulgaris), their role in the dissemination of antimicrobial resistant elements in livestock facilities needs further investigation. To determine whether on-farm starling density and other factors were associated with the presence of cefotaxime and ciprofloxacin resistant E. coli among dairy cows in Ohio, bovine fecal pats from 150 farms were tested for the presence of cefotaxime and ciprofloxacin resistant E. coli. Each farm was visited twice (during the summer and fall of 2007-2009). Multi-level logistic regression models with a random intercept to account for fecal pats collected within a specific visit to a farm were used to assess the associations. The percentage of samples with cefotaxime and ciprofloxacin resistant E. coli was 13.4% and 13.6%, respectively. The percentage of farms having at least one sample testing positive for cefotaxime and ciprofloxacin resistant E. coli was 56.7% and 48.7%, respectively. The odds of detecting cefotaxime and ciprofloxacin resistant E. coli in the samples was significantly higher in 2007 compared to 2008 and 2009, in fall compared to summer, and from farms closer than 60km to starling night roost sites compared to the farms further than 60km. The presence of starlings during the day had a negative association with the likelihood of detecting cefotaxime resistant E. coli. Presence of calves also had a negative association with the likelihood of detecting both cefotaxime and ciprofloxacin resistant E. coli. European starlings might play a role in the dissemination of antimicrobial resistant agents in livestock facilities related to their daily population movements rather than the specific density of birds on farm during the day.

An in vitro method for determining the bioaccessibility of pharmaceuticals in wildlife

Wildlife can be exposed to human pharmaceuticals via prey that have accumulated the compounds from wastewater, surface water, sediment, and soil. One factor affecting internal absorption of pharmaceuticals is bioaccessibility, the proportion of the compound that enters solution in the gastrointestinal tract. Currently, the bioaccessibility of most pharmaceuticals in prey remains unknown for most wildlife species. The authors evaluated the potential of a 2-compartment in vitro gastrointestinal tract model to compare the bioaccessibility of the antidepressant fluoxetine from invertebrate prey for birds and mammals. Samples of gizzard (or stomach) and intestinal-phase digestive juices were obtained from the in vitro models along with the residual solid material. High-performance liquid chromatographic analysis revealed that the bioaccessibility of fluoxetine in the avian in vitro models was statistically significantly lower than that in the mammalian models as a percentage of what was recovered; however, there were no statistically or biologically significant interspecies difference in terms of the amount recovered per gram of "food" inserted at the start of the simulation. This in vitro model provides a useful method of comparing the bioaccessibility of pharmaceuticals in different prey for species with different gastrointestinal conditions. There is merit for ecological risk assessments in further developing this in vitro approach to improve estimates of internal exposure for organics. Environ Toxicol Chem 2016;35:2349-2357. © 2016 SETAC.

Annual gonadal cycles in birds: modeling the effects of photoperiod on seasonal changes in GnRH-1 secretion

This paper reviews current knowledge of photoperiod control of GnRH-1 secretion and proposes a model in which two processes act together to regulate GnRH1 secretion. Photo-induction controls GnRH1 secretion and is directly related to prevailing photoperiod. Photo-inhibition, a longer term process, acts through GnRH1 synthesis. It progresses each day during daylight hours, but reverses during darkness. Thus, photo-inhibition gradually increases when photoperiods exceed 12h, and reverses under shorter photoperiods. GnRH1 secretion on any particular day is the net result of these two processes acting in tandem. The only difference between species is their sensitivity to photo-inhibition. This can potentially explain differences in timing and duration of breeding seasons between species, why some species become absolutely photorefractory and others relatively photorefractory, why breeding seasons end at the same time at different latitudes within species, and why experimental protocols sometimes produce results that appear counter to what happens naturally.

Salmonella Detection and Aerobic Colony Count in Deep-Frozen Carcasses of House Sparrow (Passer Domesticus) and Starling (Sturnus Vulgaris) Intended for Human Consumption

Wild birds are potential vehicles of zoonotic pathogen transmission to humans. The zoonotic concern increases for small wild birds like house sparrows (Passer domesticus) and starlings (Sturnus vulgaris) which are hunted in developing countries and commercialised in Italy for human consumption. From June to October 2011, 330 house sparrows and 140 starlings were hunted and slaughtered. Deep-frozen carcasses were transported to Italy and stored for 6-8 months at -18°C. Aerobic colony count and Salmonella detection in carcasses were assessed following standard microbiological methods (ISO 4833:2003 and ISO 6579:2004, respectively). Carcasses of house sparrows showed higher levels of aerobic bacteria in comparison to starling carcasses (5.7 vs 3.2 log10 CFU/g). Moreover, 7 out of 11 lots of carcasses of house sparrows were positive for Salmonella. Among the 18 isolates of Salmonella, 14 were S. Typhimurium, 2 were S. Enteritidis, and 2 were not distinguishable. All of them were susceptible to antibiotics. All tested carcasses of starling were Salmonella negative. Deep-freezing was not efficient as a decontamination technique on carcasses of house sparrows.