Flight initiation distance (FID), a measure of an animal’s tolerance to human disturbance and a descriptor of its fear of humans, is increasingly employed for conservation purposes and to predict the response of species to urbanization. However, most work devoted to understanding variability in FID has been conducted at the population level and little is still known about inter-individual variability in this behaviour. We estimated the heritability of FID, a factor fundamental to understanding the strength and evolutionary consequences of selection of particular phenotypes associated with human disturbances. We used a population of burrowing owls (Athene cunicularia) monitored long-term and for which FID was previously shown to be highly consistent across an individual’s lifespan. Heritability estimates varied between 0.37 and 0.80, depending on the habitat considered (urban-rural) and method used (parent-offspring regressions or animal models). These values are unusually high compared with those previously reported for other behavioural traits. Although more research is needed to fully understand the underlying causes of this resemblance between relatives, selection pressures acting on this behaviour should be seriously considered as an important evolutionary force in animal populations increasingly exposed to human disturbance worldwide.

The 'female nutrition' hypothesis proposes that food provided by males during incubation is an important energy source for females in bird species in which females alone incubate. Females should be able to communicate their needs through begging signals to mates and males may compensate for the energetic limitations of females through their feeding visits, owing to their overlapping reproductive interests. To test whether female begging during incubation is an honest signal of energetic need and whether mates respond to it we experimentally handicapped female pied flycatchers at the beginning of incubation by clipping two primary flight feathers on each wing. Experimental manipulation led females to intensify begging displays arising from condition impairment and males accordingly increased their incubation feeding rates. Female begging intensity explained more than half of the variation in male incubation feeding rate, thereby showing that female nutrition is the main factor explaining male incubation feeding. Moreover, handicapped females consumed a higher proportion of male food deliveries during the first few days after hatching and weighed less at the end of the nestling period than control females. Handicapping had no influence on female incubation behaviour, hatching and breeding success, nestling and male condition or female nestling provisioning. The provisioning rates of males in the late nestling stage were higher in experimental nests. This is the first experimental study showing that males adjust incubation feeding rates to behavioural displays of need by their mates. The ability of females to modify their begging displays according to need may be an important adaptation that allows females to maintain a good energetic condition during incubation. © 2014 The Association for the Study of Animal Behaviour.This study was financed by project CGL2010-19233-C03-02 to J.M. from Spanish MICINN.Peer Reviewe

A key aspect in the study of plumage traits with a potential role in communication is the cost associated with trait production and maintenance, expressed in terms of oxidative stress. In the Iberian Pied Flycatcher (Ficedula hypoleuca iberiae (Witherby, 1928)), males and some females exhibit a white forehead patch and both sexes present conspicuous white patches on the wings. We examined associations between these plumage ornaments and their ability to cope with oxidative stress. Furthermore, we explored oxidative costs of reproductive investment. Total antioxidant status (TAS) in plasma and glutathione (tGSH) levels in red blood cells, as well as a marker of oxidative damage in plasma lipids (malondialdehyde (MDA)), were assessed simultaneously for the first time in studies of avian reproduction. We found negative associations between antioxidants and ornaments in incubating females, although this relationship was positive while feeding nestlings. For males, MDA levels were negatively associated with ornaments, while TAS showed a positive relation. Female MDA showed a positive correlation with intensity of incubation attendance, while this relation was negative for tGSH levels. These results indicate that multiple achromatic plumage ornaments signal the individual capacity to cope with costs related to oxidative stress. Moreover, this study highlights the critical role of incubation for avian life histories.

There is a growing need to understand how species respond to habitat changes and the potential key role played by natal dispersal in population dynamics, structure and gene flow. However, few studies have explored differences in this process between conspecifics living in natural habitats and those inhabiting landscapes highly transformed by humans, such as cities. Here, we investigate how individual traits and social characteristics can influence the natal dispersal decisions of burrowing owls (Athene cunicularia) living in urban and rural areas, as well as the consequences in terms of reproductive success and apparent survival. We found short dispersal movements among individuals, with differences between urban and rural birds (i.e., the former covering shorter distances than the latter), maybe because of the higher conspecific density of urban compared to rural areas. Moreover, we found that urban and rural females as well as bold individuals (i.e., individuals with shorter flight initiation distance) exhibited longer dispersal distances than their counterparts. These dispersal decisions have effects on individual fitness. Individuals traveling longer distances increased their reproductive prospects (productivity during the first breeding attempt, and long term productivity). However, the apparent survival of females decreased when they dispersed farther from their natal territory. Although further research is needed to properly understand the ecological and evolutionary consequences of dispersal patterns in transformed habitats, our results provide information about the drivers and the consequences of the restricted natal movements of this species, which may explain its population structuring through restricted gene flow between and within urban and rural areas.