Feather corticosterone reveals stress associated with dietary changes in a breeding seabird

Abstract

Changes in climate and anthropogenic pressures might affect the composition and abundance of forage fish in the world's oceans. The junk‐food hypothesis posits that dietary shifts that affect the quality (e.g., energy content) of food available to marine predators may impact their physiological state and consequently affect their fitness. Previously, we experimentally validated that deposition of the adrenocortical hormone, corticosterone, in feathers is a sensitive measure of nutritional stress in seabirds. Here, we use this method to examine how changes in diet composition and prey quality affect the nutritional status of free‐living rhinoceros auklets (Cerorhinca monocerata). Our study sites included the following: Teuri Is. Japan, Middleton Is. central Gulf of Alaska, and St. Lazaria Is. Southeast Alaska. In 2012 and 2013, we collected “bill loads” delivered by parents to feed their chicks (n = 758) to document dietary changes. We deployed time–depth–temperature recorders on breeding adults (n = 47) to evaluate whether changes in prey coincided with changes in foraging behavior. We measured concentrations of corticosterone in fledgling (n = 71) and adult breeders' (n = 82) feathers to determine how birds were affected by foraging conditions. We found that seasonal changes in diet composition occurred on each colony, adults dove deeper and engaged in longer foraging bouts when capturing larger prey and that chicks had higher concentrations of corticosterone in their feathers when adults brought back smaller and/or lower energy prey. Corticosterone levels in feathers of fledglings (grown during the breeding season) and those in feathers of adult breeders (grown during the postbreeding season) were positively correlated, indicating possible carryover effects. These results suggest that seabirds might experience increased levels of nutritional stress associated with moderate dietary changes and that physiological responses to changes in prey composition should be considered when evaluating the effect of prey quality on marine predators.

Physical condition and stress levels during early development reflect feeding rates and predict pre- and post-fledging survival in a nearshore seabird

“…Although nestling feather CORT is strongly correlated with environmental conditions during development (e.g. Harms et al ., 2010; Lodjak et al ., 2015; Will et al ., 2015), site- and nest-specific factors can still confound the environment–stress relationship (Fairhurst et al ., 2012; Lodjack et al ., 2015). We did not find a significant influence of either hatch order or number of siblings on feather CORT.…”

“…Feather corticosterone measurements allow for direct comparison of long-term nestling stress levels between different breeding habitats, where variations in nutrition, contamination, predation and parental attendance may affect chronic chick stress even if no outward physical differences are apparent (Bortolotti et al ., 2009; Harms et al ., 2010). Recent laboratory and field studies have demonstrated that chronic nutritional stress affects feather corticosterone levels in both captive and free-living seabirds (Patterson et al ., 2015; Will et al ., 2015), indicating that feather corticosterone is an appropriate metric for evaluating effects of stressors on chick development.…”

The decline of the Turtle Dove: Dietary associations with body condition and competition with other columbids analysed using high‐throughput sequencing

“…These impacts can be beneficial, reducing energy expenditure, improving body condition and increasing breeding performance (e.g., Auman et al., ; Flack et al., ). However, when the novel diet replacing natural foods is of poorer quality, this can cause nutritional stress (Will et al., ), reduce nestling growth, both fledgling (Österblom, Casini, Olsson, & Bignert, ) and adult body mass (Rosen & Trites, ), and also be linked to population declines (Kitaysky, Kitaiskaia, Piatt, & Wingfield, ).…”

Of 11 candidate steroids, corticosterone concentration standardized for mass is the most reliable steroid biomarker of nutritional stress across different feather types

“…In avian biology the technique of measuring stress hormones, glucocorticoids, in feathers is of particular interest as many species grow different groups of feathers at different times of the year. This feature of feathers makes them potentially valuable as indicators of physiological status during life stages when birds are inaccessible to researchers (e.g., Orben et al, ; Ramos, Llabrés, Monclús, López‐Béjar, & González‐Solís, ), over long periods of time (e.g., Fairhurst, Bond, Hobson, & Ronconi, ; Will, Kitaiskaia, & Kitaysky, ), or to assess the response of an individual to conditions over time (e.g., Ganz, Jenny, Kraemer, Jenni, & Jenni‐Eiermann, ; Will et al, ).…”

“…Our previous work on these same individuals showed that rhinoceros auklets experience no ontogenetic patterns in the circulation of corticosterone in plasma, or temporal trends in the concentration of corticosterone in feathers (Figure , Will et al, ). In free‐living individuals raised by their parents, temporal patterns of corticosterone deposition varied both by colony and by year and were associated with diet composition rather than age of the bird (Will et al, ). Due to limitations in detectability of our LC‐MS/MS method, optimized for a suite of steroids, we needed to use whole feathers, and sometimes combined several feathers in the same sample, to have sufficient concentrations.…”