Seasonal changes of the adrenocortical responses to stress in redpolls, Acanthis flammea, in Alaska

Abstract

Male and female redpolls (Acanthis flammea) showed marked increases in circulating corticosterone up to 1 hour after exposure to a common stress-apture, handling and restraint-indicating that their hypothalamo-pituitary-adrenal axis responded to acute stress in a manner similar to that of other vertebrates. We used this protocol as a measure of responsiveness of the adrenocortical cells to acute stress in general and for comparison with gender and across seasons. In both sexes the adrenocortical response to stress was reduced in January (at Fairbanks, 64"N) and maximal when birds were breeding in June at Tbolik Lake (69"N). The elevation of circulating corticosterone following capture and handling in breeding males at Barrow (71'") was significantly less than in breeding males at Toolik Lake. There were also considerable variations among individuals in the intensity of the adrenocortical responses, particularly in the maximum levels of corticosterone attained. This individual variation correlated significantly with fat score andor body mass in both sexes only in breeding birds at Barrow. This difference may be explained by generally lower, and thus reduced variability in body fat and mass in birds sampled in the warmer climate of Toolik Lake. A similar trend was seen in non-breeding birds, but this was not significant. Additionally, in January, baseline cortisterone levels in males were correlated with body mass, although this relationship did not hold when both sexes were considered. Body mass and fat score in winter were similar to those of redpolls sampled at Barrow in June. These data suggest that redpolls may be able to adjust their responsiveness to acute stresses in relation t o fat stores. Those with greater fat depots had reduced responsiveness to stress.

Impacts of acute and long-term vehicle exposure on physiology and reproductive success of the northern spotted owl

“…The fact that females with two young and low T3 showed a decrease in fGCs in response to acute traffic exposure indicates that stress from traffic may cause serious detriment to NSO with high allostatic load. The relationship between T3 and GC responsiveness also suggests that impacts from roads may be lessened when habitat quality is higher, consistent with the results of Franklin et al (2000) and with associations of reduced GC responsiveness in individuals with high body condition-at least in the non-breeding season (Wingfield et al 1994). The results of our study are the first that we know of to reveal the full spectrum of GC response to disturbance within a single population.…”

Effects of corticosterone pellets on baseline and stress-induced corticosterone and corticosteroid-binding-globulin

“…However, since the HPA axis can vary with season, life history stage, environmental conditions, age and sex (e.g. Wingfield et al, 1994;Kitaysky et al, 1999;Romero, 2002;O'Reilly and Wingfield, 2003;Love and Williams, 2008), any additional group should closely match the experimental groups and live under similar conditions and at the same time or season. Indeed, there is individual variation in corticosterone levels as a response to pellet implantation depending on baseline levels (own unpublished data) and nutritional conditions (Almasi et al, unpublished data).…”

Experimental effects of early‐life corticosterone on the hypothalamic–pituitary–adrenal axis and pre‐migratory behaviour in a wild songbird

“…Nestlings were then immediately placed inside a warm cloth bag and restrained for 30 min to elicit a stress-induced HPA axis response (see Wingfield, Vleck & Moore 1992;Wingfield et al 1994). A second blood sample (~35-40 µL) was collected after 30 min of acute restraint using the same methods described above.…”