Darker eumelanic barn owls better withstand food depletion through resistance to food deprivation and lower appetite

The intensity of selection exerted on ornaments typically varies between environments. Reaction norms may help to identify the conditions under which ornamented individuals have a selective advantage over drab conspecifics. It has been recently hypothesized that in vertebrates eumelanin-based coloration reflects the ability to regulate the balance between energy intake and expenditure. We tested two predictions of this hypothesis in barn owl nestlings, namely that darker eumelanic individuals have a lower appetite and lose less weight when food-deprived. We found that individuals fed ad libitum during 24h consumed less food when their plumage was marked with larger black spots. When food-deprived for 24h nestlings displaying larger black spots lost less weight. Thus, in the barn owl the degree of eumelanin-based coloration reflects the ability to withstand periods of food depletion through lower appetite and resistance to food restriction. Eumelanic coloration may therefore be associated with adaptations to environments where the risk of food depletion is hig

Wildflower areas within revitalized agricultural matrices boost small mammal populations but not breeding Barn Owls

Agro-ecosystems have recently experienced dramatic losses of biodiversity due to more intensive production methods. In order to increase species diversity, agri-environment schemes provide subsidies to farmers who devote a fraction of their land to ecological compensation areas (ECAs). Several studies have shown that invertebrate biodiversity is actually higher in ECAs than in nearby intensively cultivated farmland. It remains poorly understood, however, to what extent ECAs also favour vertebrates, such as small mammals and their predators, which would contribute to restoring functional food chains within revitalised agricultural matrices. We studied small mammal populations among eight habitat types—including wildflower areas, a specific ECA in Switzerland—and habitat selection (radiotracking) by the Barn Owl Tyto alba, one of their principal predators. Our prediction was that habitats with higher abundances of small mammals would be more visited by foraging Barn Owls during the period of chicks' provisioning. Small mammal abundance tended to be higher in wildflower areas than in any other habitat type. Barn Owls, however, preferred to forage in cereal fields and grassland. They avoided all types of crops other than cereals, as well as wildflower areas, which suggests that they do not select their hunting habitat primarily with respect to prey density. Instead of prey abundance, prey accessibility may play a more crucial role: wildflower areas have a dense vegetation cover, which may impede access to prey for foraging owls. The exploitation of wildflower areas by the owls might be enhanced by creating open foraging corridors within or around wildflower areas. Wildflower areas managed in that way might contribute to restore functional links in food webs within agro-ecosystem

A summary

Coinciding with the Open Access Week 2010 we publish a study on the perceptions and usage trends amongst CSIC scientific community as regards Open Access in general and CSIC institutional repository in particular.Peer reviewe

Corticosterone Promotes Scramble Competition Over Sibling Negotiation in Barn Owl Nestlings ( Tyto alba )

In species with parental care, siblings compete for access to food resources. Typically, they vocally signal their level of need to each other and to parents, and jostle for the position in the nest where parents deliver food. Although food shortage and social interactions are stressful, little is known about the effect of stress on the way siblings resolve the conflict over how food is shared among them. Because glucocorticoid hormones mediate physiological and behavioral responses to stressors, we tested whether corticosterone, the main glucocorticoid in birds, modulates physical and vocal signaling used by barn owl siblings (Tyto alba) to compete for food. Although corticosterone-implanted (cort-) nestlings and placebo-nestlings were similarly successful to monopolize food, they employed different behavioral strategies. Compared to placebo-nestlings, cort-individuals reduced the rate of vocally communicating with their siblings (but not with their parents) but were positioned closer to the nest-box entrance where parents predictably deliver food. Therefore, corticosterone induced nestlings to increase their effort in physical competition for the best nest position at the expense of investment in sib-sib communication without modifying vocal begging signals directed to parents. This suggests that in the barn owl stress alters nestlings' behavior and corticosterone could mediate the trade-off between scramble competition and vocal sib-sib communication. We conclude that stressful environments may prevent the evolution of sib-sib communication as a way to resolve family conflicts peacefull

Barn Owl ( Tyto alba ) breeding biology in relation to breeding season climate

Winter weather has a strong influence on Barn Owl (Tyto alba) breeding biology. Here, we analyzed the impacts of weather conditions on reproductive performance during the breeding season using data collected over 22years in a Swiss Barn Owl population. Variations in rain and temperature during the breeding season played an important role in within-year variation in Barn Owl reproduction. An increase in rainfall during the period from 4 to 2weeks preceding egg laying had a positive effect on clutch size. In contrast, fledgling body mass was negatively influenced by rainfall during the 24h preceding the measurements. Finally, ambient temperature during the rearing period was positively associated with brood size at fledging. In conclusion, weather conditions during the breeding season place constraints on Barn Owl reproduction

Racial differences in systemic sclerosis disease presentation: a European Scleroderma Trials and Research group study

Objectives. Racial factors play a significant role in SSc. We evaluated differences in SSc presentations between white patients (WP), Asian patients (AP) and black patients (BP) and analysed the effects of geographical locations.Methods. SSc characteristics of patients from the EUSTAR cohort were cross-sectionally compared across racial groups using survival and multiple logistic regression analyses.Results. The study included 9162 WP, 341 AP and 181 BP. AP developed the first non-RP feature faster than WP but slower than BP. AP were less frequently anti-centromere (ACA; odds ratio (OR) = 0.4, P < 0.001) and more frequently anti-topoisomerase-I autoantibodies (ATA) positive (OR = 1.2, P = 0.068), while BP were less likely to be ACA and ATA positive than were WP [OR(ACA) = 0.3, P < 0.001; OR(ATA) = 0.5, P = 0.020]. AP had less often (OR = 0.7, P = 0.06) and BP more often (OR = 2.7, P < 0.001) diffuse skin involvement than had WP.AP and BP were more likely to have pulmonary hypertension [OR(AP) = 2.6, P < 0.001; OR(BP) = 2.7, P = 0.03 vs WP] and a reduced forced vital capacity [OR(AP) = 2.5, P < 0.001; OR(BP) = 2.4, P < 0.004] than were WP. AP more often had an impaired diffusing capacity of the lung than had BP and WP [OR(AP vs BP) = 1.9, P = 0.038; OR(AP vs WP) = 2.4, P < 0.001]. After RP onset, AP and BP had a higher hazard to die than had WP [hazard ratio (HR) (AP) = 1.6, P = 0.011; HR(BP) = 2.1, P < 0.001].Conclusion. Compared with WP, and mostly independent of geographical location, AP have a faster and earlier disease onset with high prevalences of ATA, pulmonary hypertension and forced vital capacity impairment and higher mortality. BP had the fastest disease onset, a high prevalence of diffuse skin involvement and nominally the highest mortality

Large-scale sampling of small mammals throughout the year

Small mammals are a staple food for many predator species determining their abundance, distribution, and diversity (Butet, Paillat & Delattre 2006). The abundance of small mammals in agricultural landscapes varies between different habitat types and throughout the year. Mechanical disturbance through harvesting, ploughing and tillage removes shelters, destroys nests and burrows and decrease food availability for small mammals (Tew & Macdonald 1993). Consequently, intensively cultivated agricultural fields might become inhospitable for small mammals, which might only persist in habitat patches with undisturbed areas such as hedges, ditches, road verges, set-aside and wildflower areas (Arlettaz et al. 2010). However, the spatial patterns of occurrence of small mammals, especially over larger areas, are poorly investigated. We studied distribution, abundance and fluctuation of small mammal populations over larger areas and in different habitat types throughout the year. The abundance of small mammals was measured with indirect methods, i.e. field signs and track plates in four regions in Switzerland. We sampled field signs like runways, holes and molehills along transects of 5 m length and set a track plate during three days close to each transect. Our results show that the abundance of small mammals not only fluctuated in annual cycles but also highly between seasons and habitat types. Over larger areas, fluctuations were not synchronous but highly variable between the sampled regions and habitat types. Small mammal populations crashed down in agricultural fields after harvesting, while populations remained more stable during the whole year in less disturbed structures such as hedges and ditches. Such large annual, seasonal and spatial variation patterns might highly determine prey availability for predators and are of major importance for many endangered farmland species feeding on small mammals such Barn Owls and Stoats. Monitoring small mammal populations through indirect methods is a good alternative compared to live-trapping because it allows covering much larger areas with similar efforts. It provides a temporal and spatial resolution which cannot be achieved by live-trapping. Such large-scale samplings of small mammals could help improving conservation measures on larger scales, especially for predator species living in farmlands.peerReviewe

Agonistic behaviour of Palaearctic passerine migrants at a stopover site suggests interference competition

Records of interspecific agonistic behaviour of Palaearctic passerine migrants from their Afrotropical wintering grounds are rare. There are, however, no detailed observations from stopover sites where individuals might concentrate and depress resources that are critical for fat-depleted birds in times of high energy demand. We recorded intraspecific and interspecific interactions of Palaearctic migrant passerine birds at Ouadâne, Mauritania, a stopover site in the Sahara desert. In spring 2003 we made casual records of all aggressive behaviour we observed, whereas in spring 2004 we used focal sampling of foraging birds to record the frequency of aggression. We found that interspecific interactions occurred more often than intraspecific interactions but their relative frequency differed between species. There were also mass-dependent species hierarchies. A comparison with other studies showed that in Willow Warblers the frequency of interspecific aggression was significantly higher at the stopover site than in the wintering grounds farther south. We cannot assess the adaptive advantage of agonistic behaviour, as our approach does not consider the allocation of aggressive interactions in relation to other activities and its influence on the birds' energy balance. Nevertheless, our observations suggest interspecific interference competition because inferior individuals are temporarily deprived of food, which may influence the fitness of migrants. Ostrich 2007, 78(2): 349–35

Barn owl corticosterone heritability

the file contains a table with information barn owl nestling CORT levels and different variables related to CORT measurements (e.g. sampling time, hour and date of sampling, baseline and stress-induced CORT levels) and other variables associated to nestling barn owls (e.g. body mass, age, sex, brood raised and born), and a relationship matrix build on a pedigree of our barn owl populatio

Data from: Baseline and stress-induced corticosterone levels are heritable and genetically correlated in a barn owl population

The hypothalamic-pituitary-adrenal (HPA) axis is responsible for the regulation of corticosterone, a hormone that is essential in the mediation of energy allocation and physiological stress. As a continuous source of challenge and stress for organisms, the environment has promoted the evolution of physiological adaptations and led to a great variation in corticosterone profiles within or among individuals, populations and species. In order to evolve via natural selection, corticosterone levels do not only depend on the strength of selection exerted on them but also on the extent to which the regulation of corticosterone is heritable. Nevertheless, heritability of corticosterone profiles in wild populations is still poorly understood. In this study, we estimated the heritability of baseline and stress-induced corticosterone levels in barn owl (Tyto alba) nestlings from 8 years of data, using a multivariate animal model based on a behavioural pedigree. We found that baseline and stress-induced corticosterone levels are strongly genetically correlated (r = 0.68 – 0.80) and that the heritability of stress-induced corticosterone levels (h2 = 0.24 – 0.33) was moderate and similar to the heritability of baseline corticosterone levels (h2 = 0.19 – 0.30). These findings suggest that the regulation of stress-induced corticosterone and baseline levels evolve at a similar pace when selection acts with the same intensity on both traits, and that contrary to previous studies, the evolution of baseline and stress-induced level is interdependent in barn owls, as they may be strongly genetically correlated