Anti-predator behaviour of the red-legged partridgeAlectoris rufa(Galliformes: Phasianidae) to simulated terrestrial and aerial predators

Effect of estradiol and predator cues on behavior and brain responses of captive female house sparrows (Passer domesticus)

The presence of predators can cause major changes in animal behavior, but how this interacts with hormonal state and brain activity is poorly understood. We gave female house sparrows (Passer domesticus) in post-molt condition an estradiol (n = 17) or empty implant (n = 16) for 1 week. Four weeks after implant removal, a time when female sparrows show large differences in neuronal activity to conspecific vs. heterospecific song, we exposed birds to either 30 min of conspecific song or predator calls, and video recorded their behavior. Females were then euthanized, and we examined neuronal activity using the expression of the immediate early gene (IEG) ZENK to identify how the acoustic stimuli affected neuronal activation. We predicted that if female sparrows with estradiol implants reduce neuronal activity in response to predator calls as they do to neutral tones and non-predatory heterospecifics, they would show less fear behavior and a decreased ZENK response in brain regions involved in auditory (e.g., caudomedial mesopallium) and threat perception functions (e.g., medial ventral arcopallium) compared to controls. Conversely, we predicted that if females maintain auditory and/or brain sensitivity towards predator calls, then female sparrows exposed to estradiol would not show any differences in ZENK response regardless of playback type. We found that female sparrows were less active during predator playbacks independent of hormone treatment and spent more time feeding during conspecific playback if they had previously been exposed to estradiol. We observed no effect of hormone or sound treatment on ZENK response in any region of interest. Our results suggest that female songbirds maintain vigilance towards predators even when in breeding condition.

Feeding partridges with organic or conventional grain triggers cascading effects in life-history traits

Farmland birds are declining across Europe and North America and the research of factors behind is the subject of extensive researches. Agricultural intensification is now recognized as a major factor governing the loss of biodiversity with strong evidence that pesticides induced direct bird mortality at a high dose. However, less attention has been given to the long-term effects of chronic exposure to low dose of pesticides. Here, we used an experimental procedure in which grey partridges were fed with untreated grains obtained from either organic (no pesticide) or conventional agriculture (with pesticide) for 26 weeks, thus strictly mimicking wild birds foraging on fields. We then examined a suite of life-history traits (ecophysiological and behavioural) that may ultimately, influence population dynamics. We show for the first time that ingesting low pesticide doses over a long period has long-term consequences on several major physiological pathways without inducing differential mortality. Compared to control partridges, birds exposed to chronic doses i) had less developed carotenoid-based ornaments due to lower concentrations of plasmatic carotenoids, ii) had higher activated immune system, iii) showed signs of physiological stress inducing a higher intestinal parasitic load, iv) had higher behavioural activity and body condition and v) showed lower breeding investment. Our results are consistent with a hormetic effect, in which exposure to a low dose of a chemical agent may induce a positive response, but our results also indicate that breeding adults may show impaired fitness traits bearing population consequences through reduced breeding investment or productivity. Given the current scale of use of pesticides in agrosystems, we suggest that such shifts in life-history traits may have a negative long-term impact on wild bird populations across agrosystems. We stress that long-term effects should no longer be ignored in pesticide risk assessment, where currently, only short-term effects are taken into account.

Anti-predator behavior in pure and hybrid red-legged partridges

The purpose of this study was to examine the anti-predator behavior in pure red-legged partridges (Alectoris rufa) and hybrids with chukar partridges (A. rufa × (A. rufa × A. chukar)). A total of 117 birds (66 pure and 51 hybrid partridges; 74 females and 43 males) maintained in outdoor cages were used at a range of 52 to 55 wk of age. Four active fear tests were performed (novel object test, fear of humans test, emergence test, and restraint test) in order to analyze differences between pure and hybrid populations regarding the escape response type (novel object test and fear of humans test), the withdrawal distance (fear of humans test), and the reaction time (emergence test and restraint test). These variables could determine the ability of pure partridges captive to survive when released into the wild for hunting. There were no significant differences in anti-predator behavior in pure and hybrid birds, only one trend was observed in withdrawal distance (P = 0.09), being greater in pure than in hybrids partridges. There was a significant difference between sexes in the response type in the novel object test (P = 0.05); whereby the females came closer to the object than the males. The results of the present study indicate that active anti-predatory behavior was not associated with the genotype. However, since captivity could reduce the active anti-predator behavior, the results could be different if the wild birds that were tested had been sourced from their natural environment. Both sexes had similar active anti-predator behavior, although the males showing less approach behavior to a novel object that could be related to the sex-dimorphic behavior in natural social structure.

The role of the hypothalamus-pituitary-adrenal/interrenal axis in mediating predator-avoidance trade-offs

Maintaining energy balance and reproducing are important for fitness, yet animals have evolved mechanisms by which the hypothalamus-pituitary-adrenal/interrenal (HPA/HPI) axis can shut these activities off. While HPA/HPI axis inhibition of feeding and reproduction may have evolved as a predator defense, to date there has been no review across taxa of the causal evidence for such a relationship. Here we review the literature on this topic by addressing evidence for three predictions: that exposure to predators decreases reproduction and feeding, that exposure to predators activates the HPA/HPI axis, and that predator-induced activation of the HPA/HPI axis inhibits foraging and reproduction. Weight of evidence indicates that exposure to predator cues inhibits several aspects of foraging and reproduction. While the evidence from fish and mammals supports the hypothesis that predator cues activate the HPA/HPI axis, the existing data in other vertebrate taxa are equivocal. A causal role for the HPA axis in predator-induced suppression of feeding and reproduction has not been demonstrated to date, although many studies report correlative relationships between HPA activity and reproduction and/or feeding. Manipulation of HPA/HPI axis signaling will be required in future studies to demonstrate direct mediation of predator-induced inhibition of feeding and reproduction. Understanding the circuitry linking sensory pathways to their control of the HPA/HPI axis also is needed. Finally, the role that fear and anxiety pathways play in the response of the HPA axis to predator cues is needed to better understand the role that predators have played in shaping anxiety related behaviors in all species, including humans.

Anti-predator behaviour of adult red-legged partridge (Alectoris rufa) tutors improves the defensive responses of farm-reared broods

The aim of this work was to improve natural anti-predator behaviour of farm-reared gamebirds. We evaluated the anti-predator behaviour of reared red-legged partridge Alectoris rufa chicks kept in brooder houses in large groups (>350 chicks), trained and not trained by parent red-legged partridges acting as experienced tutors. The experiment consisted of two conditioned tests (a raptor model and a human) and two control tests, which were conducted during three consecutive phases of life (1-4, 15-17 and 30-32 d after hatching). The motor anti-predator behaviour, its duration, the intensity of response in chicks and alarm calls elicited by adults were recorded. Tutors elicited aerial alarm calls (76% of tests) and showed prolonged crouching (59% of tests) in response to the raptor model whereas uttering the ground alarm call (73% of tests) and showing vigilance behaviour (78% of tests) was the main pattern during the human test. Trained and not trained chicks showed similar motor behaviour in response to the raptor model (crouching) and the human test (escaping), but frequency of strong responses (all chicks responding) from chicks trained with tutors was double that of chicks trained without them, and chicks trained with tutors showed a higher frequency of long responses (41-60 s). This study indicates that anti-predator training programmes before release may improve behaviour of farm-reared partridges which may confer benefits to survival of birds.