Feather corticosterone is lower in translocated and historical populations of the endangered Laysan duck (Anas laysanensis).

Identifying reliable bioindicators of population status is a central goal of conservation physiology. Physiological stress measures are often used as metrics of individual health and can assist in managing endangered species if linked to fitness traits. We analysed feather corticosterone, a cumulative physiological stress metric, of individuals from historical, translocated, and source populations of an endangered endemic Hawaiian bird, the Laysan duck (Anas laysanensis). We hypothesized that feather corticosterone would reflect the improved reproduction and survival rates observed in populations translocated to Midway and Kure Atolls from Laysan Island. We also predicted less physiological stress in historical Laysan birds collected before ecological conditions deteriorated and the population bottleneck. All hypotheses were supported: we found lower feather corticosterone in the translocated populations and historical samples than in those from recent Laysan samples. This suggests that current Laysan birds are experiencing greater physiological stress than historical Laysan and recently translocated birds. Our initial analysis suggests that feather corticosterone may be an indicator of population status and could be used as a non-invasive physiological monitoring tool for this species with further validation. Furthermore, these preliminary results, combined with published demographic data, suggest that current Laysan conditions may not be optimal for this species.

Elevated lead (Pb) in urban European starling (Sturnus vulgaris) feathers is not correlated to physiology or behavior.

Urbanization is rapidly changing the environment and creating new challenges in the lives of animals across the globe. Anthropogenic contaminants-like heavy metals-can persist within the environment for prolonged periods of time and present a widespread problem for those living near contaminated areas. Lead (Pb) was a commonly used heavy metal that continues to threaten the health of all organisms despite being phased out, especially in urban areas where historical use was more common. In this study, a common urban-adapter, the European starling (Sturnus vulgaris), was trapped to explore whether feather Pb burden is greater in birds from urban habitats than rural habitats, as well as whether Pb burdens were correlated with behavior, physiology, and feather development. Across four sites (two rural and two urban), soil Pb concentrations were measured and 197 free-living starlings were captured to measure feather Pb concentrations. Using linear mixed models, this study found that urban starling nestlings had elevated feather Pb burdens compared to rural nestlings. In contrast, there was no correlation between Pb and urbanization in adult birds whose exposure to Pb may reflect a larger spatial range compared to nestlings. For both nestlings and adults, feather Pb was uncorrelated to corticosterone, testosterone, aggressive behavior, or feather growth rates. These findings suggest that starlings may be a useful biomonitoring tool to detect Pb in the local environment, however, the age and spatial range of birds is a critical consideration in applying this tool. Further work is needed to understand the intricate relationship between heavy metals, behavior, morphological development, and physiology in free-living organisms.

The development of behavioral and endocrine coping styles in nestlings from urban and rural sites.

Urbanization is increasing globally and altering the stressors that animals face in their everyday lives. Organisms often differ in their coping styles-both behavioral and endocrine-across urban to rural habitats. For example, urban animals are often bolder, more exploratory, and mount stronger glucocorticoid stress responses compared to their rural counterparts. While these coping styles are important in shaping fitness across the urban-to-rural gradient, it remains unclear when these differences arise in the life of organisms. We explore the development of coping styles in European starling nestlings (Sturnus vulgaris), an urban-adapted species. We test whether breathing rate, handling struggle rate, and bag struggle rate differ across sites and find no difference in the behavioral coping styles of nestlings raised in urban versus rural sites. We also explore differences in baseline and stress-induced glucocorticoids, finding that urban nestlings develop a stronger stress response than rural birds before fledging the nest. We find no significant correlations between behavioral and endocrine traits for urban or rural birds, which supports the two-tiered model of coping styles. One possibility is that behavioral and endocrine differences develop at different times over the lives of organisms. Our findings support prior work suggesting that behavioral and endocrine coping mechanisms act independently of one another, and suggests that endocrine coping mechanisms develop in early life and before differences in behavioral coping styles might arise. Future work on the mechanisms leading to early-life differences in coping styles-from genetics to maternal effects to environmental effects-is needed to best predict how urban-adapted organisms cope with environmental change. Studies across a greater number of sites will help disentangle site from urbanization effects.