Inter-individual differences in foraging tactics of a colonial raptor : consistency, weather effects, and fitness correlates

Background: Consistent inter-individual differences in behavioural phenotypes may entail differences in energy efficiency and expenditure, with different fitness payoffs. In colonial-breeding species, inter-individual differences in foraging behaviour may evolve to reduce resource use overlap among conspecifics exploiting shared foraging areas. Furthermore, individual differences in foraging behaviour may covary with individual characteristics, such as sex or physiological conditions. Methods: We investigated individual differences in foraging tactics of a colonial raptor, the lesser kestrel (Falco naumanni). We tracked foraging trips of breeding individuals using miniaturized biologgers. We classified behaviours from GPS data and identified tactics at the foraging trip level by cluster analysis. We then estimated energy expenditure associated to each tactic from tri-axial accelerometer data. Results: We obtained 489 foraging trips by 36 individuals. Two clusters of trips were identified, one (SF) characterized by more static foraging behaviour and the other (DF) by more dynamic foraging behaviour, with a higher proportion of flying activity and a higher energy expenditure compared to SF. Lesser kestrels showed consistent inter-individual differences in foraging tactics across weather condition gradients, favouring DF trips as solar radiation and crosswind intensity increased. DF trips were more frequent during the nestling-rearing than during the egg incubation stage. Nestlings whose tracked parent was more prone to perform DF trips experienced higher daily mass increase, irrespective of nestling feeding rates. Conclusions: Our study provided evidence that breeding lesser kestrels flexibly adopted different foraging tactics according to contingent weather landscapes, with birds showing consistent inter-individual differences in the tendency to adopt a given tactic. The positive correlation between the tendency to perform more energy-demanding DF trips and nestling growth suggests that individual differences in foraging behaviour may play a role in maintaining key life-history trade-offs between reproduction and self-maintenance

Adcyap1 polymorphism covaries with breeding latitude in a Nearctic migratory songbird, the Wilson's warbler (Cardellina pusilla)

Understanding the genetic background of complex behavioral traits, showing multigenic control and extensive environmental effects, is a challenging task. Among such traits, migration is known to show a large additive genetic component. Yet, the identification of specific genes or gene regions explaining phenotypic variance in migratory behavior has received less attention. Migration ultimately depends on seasonal cycles, and polymorphism at phenological candidate genes may underlie variation in timing of migration or other aspects of migratory behavior. In this study of a Nearctic-Neotropical migratory songbird, the Wilson's warbler (Cardellina pusilla), we investigated the association between polymorphism at two phenological candidate genes, Clock and Adcyap1, and two aspects of the migratory phenotype, timing of spring migration through a stopover site and inferred latitude of the breeding destination. The breeding destination of migrating individuals was identified using feather deuterium ratio (\u3b42H), which reliably reflects breeding latitude throughout the species' western breeding range. Ninety-eight percent of the individuals were homozygous at Clock, and the rare heterozygotes did not deviate from homozygous migration phenology. Adcyap1 was highly polymorphic, and allele size was not significantly associated with migration date. However, Adcyap1 allele size significantly positively predicted the inferred breeding latitude of males but not of females. Moreover, we found a strong positive association between inferred breeding latitude and Adcyap1 allele size in long-distance migrating birds from the northern sector of the breeding range (western Canada), while this was not the case in short-distance migrating birds from the southern sector of the breeding range (coastal California). Our findings support previous evidence for a role of Adcyap1 in shaping the avian migratory phenotype, while highlighting that patterns of phenological candidate gene-phenotype associations may be complex, significantly varying between geographically distinct populations and even between the sexes

The Effect of Moonlight on Scopoli's Shearwater Calonectris diomedea Colony Attendance Patterns and Nocturnal Foraging: A Test of the Foraging Efficiency Hypothesis

Moonlight is known to affect the nocturnal behaviour and activity rhythms of many organisms. For instance, predators active at night may take advantage from increased visibility afforded by the moon, while prey might regulate their activity patterns to become less detectable. Many species of pelagic seabirds attend their colony only at night, in complete darkness, avoiding approaching their nest sites under moonlight. This behaviour has been most often interpreted as an antipredator adaptation ('predation avoidance' hypothesis). However, it may also reflect a lower foraging efficiency during moonlit nights ('foraging efficiency' hypothesis). Indeed, moonlight may reduce prey availability because preferred seabird prey is known to occur at higher depths in moonlit nights. Using high-accuracy behavioural information from data loggers, we investigated the effect of moonlight on colony attendance and at-sea nocturnal foraging in breeding Scopoli's shearwaters Calonectris diomedea. We found that birds departing for self-feeding trips around the full moon performed longer trips than those departing around the new moon. On nights when the moon was present only partly, nest burrow entrances took place largely in the moonless portion of the night. Moreover, contrary to predictions from the 'foraging efficiency' hypothesis, nocturnal foraging activity increased according to moonlight intensity, suggesting that birds increased their foraging activity when prey became more detectable. This study strengthens the idea that colony attendance behaviour is strictly controlled by moonlight in shearwaters, which is possibly related to the perception of a predation risk

Extra food provisioning reduces extra‐pair paternity in the lesser kestrel Falco naumanni

Female promiscuity can function to acquire both direct and indirect benefits from their social mate and extra-pair males. In many raptor species, intense mate-feeding significantly contributes to female energy requirements before and during egg laying. Moreover, females may use mate-feeding effort to assess male quality. In this study of the lesser kestrelFalco naumanni, we aimed at experimentally manipulating the female's perception of mate quality by providing females with extra food during egg laying, and evaluated the occurrence of extra-pair paternity in food-supplemented and control broods by parentage analyses. No extra-pair offspring (EPO) was found among 19 food-supplemented broods, whereas EPO occurred in five out of 17 control broods. No significant differences in morphological traits, body condition and reproductive success were found between faithful and unfaithful females. However, clutches containing EPO were laid later in the breeding season. Moreover, un-cuckolded males had longer tarsi than cuckolded ones, indicating larger body size. Hence, extra food provisioning and early breeding reduced the occurrence of EPO in lesser kestrels. In addition, we confirmed the occurrence of intraspecific brood parasitism, as five nestlings were not the offspring of the brooding female. The results of our food-provisioning experiment support the idea that mate-feeding ability is a reliable indicator of male quality, and are in accordance with the hypothesis that male mate-feeding behaviour is a sexually selected trait

Sequence variation in melanocortin-1-receptor and tyrosinase-related protein 1 genes and their relationship with melanin-based plumage trait expression in Lesser Kestrel (Falco naumanni) males

Lesser kestrel males display inter-individual variation in melanin-based plumage traits, like ventral plumage colouration and breast/underwing spottiness. We explored whether such plumage variability was associated with single-nucleotide genetic polymorphisms of melanocortin-1-receptor (MC1R) and tyrosinase-related protein 1 (TYRP1), two genes involved in the melanogenesis pathway. No statistically significant associations between single-nucleotide mutations and male plumage traits emerged, though in some cases very rare (< 2%) homozygous mutated individuals displayed extreme plumage phenotypes. Hence, large inter-individual male Lesser Kestrel plumage variation, which is consistent between years and partly age related, was only marginally related to untranslated region and coding sequence variation of MC1R and TYRP1

Early exposure to a bacterial endotoxin advances the onset of moult in the European starling

In animals, events occurring early in life can have profound effects on subsequent life-history events. Early developmental stresses often produce negative long-lasting impacts, although positive effects of mild stressors have also been documented. Most studies of birds have investigated the effects of events occurring at early developmental stages on the timing of migration or reproduction, but little is known on the long-term effects of these early events on moulting and plumage quality. We exposed European starling Sturnus vulgaris nestlings to an immune challenge to assess the effects of a developmental stress on the timing of the first (post-juvenile) and second (post-breeding) complete annual moult, the length of the flight feathers, and the length and colouration of ornamental throat feathers. The nestlings were transferred to indoor aviaries before fledgling and kept in captivity until the end of post-breeding moult. Individuals treated with Escherichia coli lypopolysaccharide (LPS) started both moult cycles earlier compared to control siblings. Moult duration was unaffected by the immune challenge, but an advanced moult onset resulted in a longer moult duration. Moreover, female (but not male) throat feather colouration of LPS-injected individuals showed a reduced UV chroma. We argue that an early activation of the immune system caused by LPS may allow nestlings to better cope with post-fledging stresses and lead to an earlier moult onset. The effect of early LPS exposure was remarkably persistent, as it was still visible more than one year after the treatment, and highlighted the importance of early developmental stresses in shaping subsequent major life-history traits, including the timing of moult in birds

Home, dirty home: lesser kestrels prefer to breed in previously used nest sites

Populations of cavity nesting species are typically limited by the availability of suitable nesting sites. However, the factors driving the choice of a suitable nest sites are poorly investigated. For instance, individuals may prefer breeding in previously unused nest sites, that may host less parasites, or in previously used nest sites, which may provide cues of successful breeding attempt. We performed a simple nestbox choice experiment to assess whether breeding individuals prefer dirty and already used nestboxes vs. newly deployed ones. The study was carried out in Matera, which hosts the larger Italian colony of lesser kestrel. All nestboxes used for this experiment were provided within the framework of LIFE project. Before lesser kestrel arrival we crated 40 nestbox dyads, pairing 40 used nest box with 40 new ones with nestbox entrances positioned side by side in order to force the choice. To disentangle the effect of nest substrate from the appearance of the nestbox we randomly exchanged entrance panels (old and new) and nest substrate (organic material from previous nesting attempts vs. sand and gravel). We than assessed which nestbox belonging to each dyads was first occupied. At the end of the egg laying period, 38 of 40 dyads had at least one nestbox occupied. Among these, in 36 cases birds selected the nestboxes with the old substrate. The adjoining nestboxes with new substrate was occupied by a second pair just in 4 case. The experiment suggests a strong preference of lesser kestrel for nest sites already used during previous breeding seasons: despite their possible higher parasitic load, used breeding sites may provide cues of previous breeding attempt. Under a management point of view, this result suggests that conservation actions based on installation of nestboxes can benefit from the translocation of substrates from used nestbox to newly deployed ones