Effects of developmental conditions on nestling American Kestrel (Falco sparverius) corticosterone concentrations

Abstract

This is an author-produced, peer-reviewed version of this article. AbstractHow nestling birds respond to stressful situations may constitute an important survival component that has lasting developmental effects on the hypothalamic pituitary adrenal (HPA) axis. As birds are exposed to increasing amounts of potential anthropogenic stressors through land use change, understanding how these factors contribute to HPA development is important. We examined whether conditions experienced during the nestling stage affected free-living American Kestrel (Falco sparverius) HPA activity prior to fledging. Kestrels experienced varying levels of human disturbance around their nest and we classified this environmental exposure as high or low environmental human disturbance based on traffic patterns and land use. We then exposed some broods from high and low disturbance areas to a standardized disturbance protocol. Prior to fledging we collected blood samples from 25-day-old nestlings immediately after capture and 15 min post-capture. Corticosterone (CORT) did not vary with environmental human disturbance levels, disturbance protocol treatment, or with an interaction between environmental human disturbance and disturbance protocol treatment suggesting that nestling kestrels may not perceive external conditions related to human disturbance as stressful or kestrels may acclimate to disturbance. We also compared the relative effects of environmental human disturbance outside the nest cavity, conditions within the nest cavity (brood size), and individual condition (nestling fat scores) on baseline and stress-induced CORT. Baseline CORT did not vary with human disturbance level, brood size or fat score. F at scores best explained stress-induced CORT with nestlings in better condition displaying elevated CORT. These results suggest that individual variation is more likely to explain HPA development compared to nest conditions or the external environment. This study demonstrates the importance of considering the effects of developmental conditions on the stress response at several scales.

Feather corticosterone content in predatory birds in relation to body condition and hepatic metal concentration

“…In the present study, significant differences in feather CORT content between species were most evident between buzzard and sparrowhawk (both Accipitriformes species) whereas feather CORT concentrations did not differ significantly between barn owls, kestrels and tawny owls. This is consistent with reports that baseline and stress-induced levels of plasma CORT are similar in barn owls and kestrels (Almasi et al, 2012(Almasi et al, , 2013Meijer and Schwabl, 1989;Müller et al, 2009;Stier et al, 2009;Strasser and Heath, 2011).…”

Reproductive failure of a human‐tolerant species, the American kestrel, is associated with stress and human disturbance

“…The disturbance PC accounted for 80% of the total variation in traffic and developed land values from occupied nest boxes and was positively associated with high numbers of vehicles, speed, number of lanes and proportion of human development (Table in Strasser & Heath ). Disturbance PC scores for nest boxes ranged from −2·40 to 2·57 with a natural break near −0·78.…”

“…We collected blood samples within 5 min. A handling time of < 3 min has been suggested for obtaining baseline CORT (Romero & Reed ); however, there is not a significant increase in CORT for kestrels bled in < 5 min (Strasser & Heath ). We collected blood samples between 0900 and 1400 to minimize time‐of‐day effects on CORT (Wingfield, Vleck & Moore ).…”

“…In the laboratory, blood samples were centrifuged at 17 000 g for 15 mins to separate plasma from the cellular fraction. Plasma was stored at −80 °C until analysis by enzyme‐linked immunosorbent assays (ELISA; Cayman Chemicals, Ann Arbor, Michigan, USA) for CORT as described in Strasser & Heath (). Interassay CORT variation averaged 8·6%, and average intra‐assay variation was 2·0%.…”

Magellanic penguin telomeres do not shorten with age with increased reproductive effort, investment, and basal corticosterone

“…Stressful events such as reproduction (Kotrschal et al, 2007), trauma and injury (Fowler, Wingfield, Boersma, & Url, 2013;Herborn et al, 2014), environmental stressors (food shortage, disturbance, storms, oiling), (Fowler et al, 2013;Walker, Boersma, & Wingfield, 2006;Walker et al, 2005) and high-density living (Bauch, Becker, & Verhulst, 2013;Heidinger et al, 2011;Kotrschal et al, 2007;Reichert et al, 2014;Sudyka et al, 2014) are linked to the production of stress hormones (CORT) and the shortening of telomeres (Epel et al, 2004;Haussmann, Longenecker, Marchetto, Juliano, & Bowden, 2012;Herborn et al, 2014;Kotrschal et al, 2007;Tissier, Williams, & Criscuolo, 2014). Additionally, human disturbance from tourism can increase CORT in birds (Strasser & Heath, 2011) and reptiles (French, DeNardo, Greives, Strand, & Demas, 2010). The release of CORT is correlated with reproduction.…”