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Due to continuing worldwide urban expansion, research into how urban environments affect local flora/fauna has grown significantly. Studies on the impacts of urbanization on birds have explored a wide variety of behaviors (e.g., foraging, breeding, migratory), but there is little research on the impacts of cities on avian coloniality. Various urban-environmental factors may impact colonial birds. The predominance of impervious surfaces in cities, for example, has been associated with the decline of several bird species due to negative effects on availability and quality of habitat. The urban heat island effect and shifts in resource availability (e.g., food, water) may also affect colonial birds. Here, we used five years of community-science data available in eBird to investigate urban impacts on group size in Cliff Swallows (Petrochelidon pyrrhonota), an abundant colonial bird species that now breeds readily under bridges and other built structures over or near water in Phoenix, Arizona, USA. We hypothesized that, based on the colonial breeding habits of these neotropical migratory birds in this desert environment, swallows in Phoenix would form larger groups in areas with more food and water sources and with more built structures. In fact, we found that proximity to water sources and cropland, but not impervious surface density, was positively and significantly related to group size. These results suggest that, in this desert ecosystem, an abundance of food/water resources provided by humans permits Cliff Swallows to form larger social groups during breeding. Although many studies show harmful impacts of cities on local wildlife, our findings highlight how urban and/or agricultural ‘oases’ may relieve some native species from natural resource limitations and permit them to thrive and increase in group size in human-impacted environments. 

Real-time health assessment is crucial for diagnosing emerging threats to wildlife. Point-of-care instruments now allow detailed, affordable measurements of blood metabolites (e.g., glucose, triglycerides, ketones) in free-ranging animals. Ketones, however, remain understudied, especially in relation to environmental and life-history traits. Here, we assessed blood ketone variation in male House Finches (Haemorhous mexicanus) across two seasons (summer and winter) as a function of body condition, circulating glucose, carotenoids, lipid-soluble vitamins, and habitat urbanization (urban/suburban/rural). In both seasons, the interaction between capture site and glucose concentration predicted ketone levels: urban and suburban birds showed a negative relationship, while in summer, rural birds showed a positive one. Additionally, in winter, ketone levels were negatively associated with plasma carotenoids, indicating birds with higher carotenoid levels had lower ketone concentrations. These findings suggest that similar to patterns seen in biomedical research and our previous work on carotenoids and health, ketone status can serve as a valuable indicator of nutritional condition and fat metabolism in wild birds, particularly in the context of urbanization. 

ABSTRACT Expression of vibrant plumage color plays important communication roles in many avian clades, ranging from penguins to passerines, but comparatively less is known about color signals in parrots (order Psittaciformes). We measured variation in coloration from three plumage patches (red face, blue rump, red tail) in an introduced population of rosy‐faced lovebirds (Agapornis roseicollis) in Phoenix, Arizona, USA and examined color differences between the sexes and ages as well as relationships with several indices of quality, including disease presence/absence (infection with beak and feather disease,Circovirus parrot, and a polyomavirus,Gammapolyomavirus avis), nutritional state (e.g., blood glucose and ketone levels), and habitat type from which birds were captured. We found that different plumage colors were linked to different quality indices: (a) adults had redder faces than juveniles, and birds with brighter faces had lower glucose levels and were less likely to have polyomavirus; (b) males had bluer rumps than females; and (c) birds caught farther from the city had redder and darker tail feathers than those caught closer to the urban center. Our findings reveal diverse information underlying variation in the expression of these disparate, ornate feather traits in an introduced parrot species, and suggest that these condition‐dependent and/or sexually dichromatic features may serve important intraspecific signaling roles (i.e., mediating rival competitions or mate choices). 

Abstract The development of inexpensive and portable point‐of‐care devices for measuring nutritional physiological parameters from blood (e.g., glucose, ketones) has accelerated our understanding and assessment of real‐time variation in human health, but these have infrequently been tested or implemented in wild animals, especially in relation to other key biological or fitness‐related traits. Here we used point‐of‐care devices to measure blood levels of glucose, ketones, uric acid, and triglycerides in free‐ranging house finches (Haemorhous mexicanus)—a common songbird in North America that has been well‐studied in the context of urbanization, nutrition, health, and sexual selection—during winter and examined (1) repeatability of these methods for evaluating blood levels in these wild passerines, (2) intercorrelations among these measurements within individuals, (3) how blood nutritional‐physiology metrics related to a bird's body condition, habitat of origin (urban vs. suburban), poxvirus infection, and sex; and (4) if the expression of male sexually selected plumage coloration was linked to any of the nutritional‐physiological metrics. All blood‐nutritional parameters were repeatable. Also, there was significant positive covariation between concentrations of circulating triglycerides and glucose and triglycerides and uric acid. Urban finches had higher blood glucose concentrations than suburban finches, and pox‐infected individuals had lower blood triglyceride concentrations than uninfected ones. Last, redder males had higher blood glucose, but lower uric acid levels. These results demonstrate that point‐of‐care devices can be useful, inexpensive ways of measuring real‐time variation in the nutritional physiology of wild birds. 

Abstract Animals inhabiting urban areas often experience elevated disease threats, putatively due to factors such as increased population density and horizontal transmission or decreased immunity (e.g. due to nutrition, pollution, stress). However, for animals that take advantage of human food subsidies, like feeder-visiting birds, an additional mechanism may include exposure to contaminated feeders as fomites. There are some published associations between bird feeder presence/density and avian disease, but to date no experimental study has tested the hypothesis that feeder contamination can directly impact disease status of visiting birds, especially in relation to the population of origin (i.e. urban v. rural, where feeder use/densities naturally vary dramatically). Here we used a field, feeder-cleaning experimental design to show that rural, but not urban, house finches ( Haemorhous mexicanus ) showed increased infection from a common coccidian endoparasite ( Isospora spp.) when feeders were left uncleaned and that daily cleaning (with diluted bleach solution) over a 5-week period successfully decreased parasite burden. Moreover, this pattern in rural finches was true for males but not females. These experimental results reveal habitat- and sex-specific harmful effects of bird feeder use (i.e. when uncleaned in rural areas). Our study is the first to directly indicate to humans who maintain feeders for granivorous birds that routine cleaning can be critical for ensuring the health and viability of visiting avian species. 

Carotenoid pigments serve many endogenous functions in organisms, but some of the more fascinating are the external displays of carotenoids in the colorful red, orange and yellow plumages of birds. Since Darwin, biologists have been curious about the selective advantages (e.g., mate attraction) of having such ornate features, and, more recently, advances in biochemical methods have permitted researchers to explore the composition and characteristics of carotenoid pigments in feathers. Here we review contemporary methods for extracting and analyzing carotenoids in bird feathers, with special attention to the difficulties of removal from the feather keratin matrix, the possibility of feather carotenoid esterification and the strengths and challenges of different analytical methods like high-performance liquid chromatography and Raman spectroscopy. We also add an experimental test of current common extraction methods (e.g., mechanical, thermochemical) and find significant differences in the recovery of specific classes of carotenoids, suggesting that no single approach is best for all pigment or feather types.