Trophic niche width, offspring condition and immunity in a raptor species

Abstract

Strategies developed by organisms to maximize foraging efficiency have a strong influence on fitness. The way in which the range of food resources is exploited has served to classify species, populations and individuals from more specialist (narrow trophic niche) to more generalist (broad trophic niche). Recent studies have provided evidence that many of the considered generalist species/populations are actually composed of different specialist individuals (individual specialization). Even the existence of generalism as an adaptive strategy has been questioned. In this study, we investigated the relationship between trophic niche width, individual quality and offspring viability in a population of common kestrel Falco tinnunculus during 4 years. We showed that the diet of kestrels varied significantly among years and that individuals of better quality fed their offspring with a higher diversity of prey species and a higher amount of food. Moreover, body condition and immune response of nestlings were positively correlated with diversity of prey delivered by parents. Our study suggests that generalism has the potential to increase fitness and that broadening the trophic niche may be an adaptive strategy in unpredictable environments.

Genetic characterization of oropharyngeal trichomonad isolates from wild birds indicates that genotype is associated with host species, diet and presence of pathognomonic lesions

“…We would like to highlight here the case of the common kestrels, in which we have found an important percentage of birds with lesions (9.4%) genotype ITS-OBT-Tg-1 being the most frequent (21/25). This species is characterized by its generalist predator diet, including mainly insects, lizards, small mammals and birds (Navarro-López et al, 2014). Their habitat tolerance, being capable of reproducing in urban environments, has put this raptor species at risk of T. gallinae infection, due to the contact and proximity to columbid preys in these places.…”

Weather‐mediated decline in prey delivery rates causes food‐limitation in a top avian predator

“…Furthermore, mortality in 2012 due to starvation was confirmed in only two cases, and it is likely that additional cases of starvation‐related mortality would have been observed if food supply had been a primary driver for mortality of nestlings less than 14 days of age. However, post‐fledging mortality for nestlings that on average weighed 460 g and 643 g for males and females, respectively, was almost certainly higher for the 2012 cohort compared to the cohorts that were in better body condition (Navarro‐Lopez et al , Resano‐Mayor et al ), and produced in the first two years of the study. We suggest that adult falcons were unable to meet the increase in demand for food from nestlings at some point during or shortly after 10–14 days of age (Steen et al ) due to the increased frequency in wet weather days in 2012 (year 3 of our study), which precluded the corresponding increase in prey delivery rates that were observed during the warm/dry breeding seasons (year 1 and 2 of our study).…”

A negative association between bromadiolone exposure and nestling body condition in common kestrels: management implications for vole outbreaks

“…They prey on a wide variety of prey items, depending on location, season and availability. However, voles are the main prey when present in high abundance, making them an ideal species to study the potential effects of SGARs. In north‐western Spain, common voles are the key prey, varying from an average 48% of the total biomass (range 5.7–82.6%; Navarro‐Lopez J, private communication) to nearly 80% of prey during periods of high vole abundance .…”