Endocrine Responses to Inclement Weather in Naturally Breeding Populations of White-Crowned Sparrows (Zonotrichia leucophrys pugetensis)

Plasma levels of luteinizing hormone (LH), testosterone, and corticosterone were measured in relation to periods of inclement versus fair weather during the reproductive season of the Puget Sound White-crowned Sparrow (Zonotrichia leucophrys pugetensis). In 1974, cool stormy weather in spring delayed the onset of breeding by one month and also prolonged the period of elevated circulating levels of LH and testosterone, compared with the fair spring of 1975. Inclement weather in 1974 did not appear to be stressful, as indicated by body weights and plasma levels of corticosterone. In late May 1980, however, a storm occurred after nesting activities had begun and all pairs sampled were feeding young. In this case, plasma levels of corticosterone were greatly elevated above those of birds sampled at the same time in the warm spring of 1979 and also above those of birds sampled in spring of both 1974 and 1975. In addition, fat depots were virtually exhausted in birds sampled during the storm of 1980, suggesting that these birds were stressed. Most pairs lost their brood in May 1980, presumably to starvation, and renested after amelioration of environmental conditions in June. These data suggest that although storms may modify the onset and temporal progression of the reproductive cycle, they are stressful to adults only when the nesting phase is in progress. Thus, the underlying mechanisms by which inclement weather delays the onset of breeding or disrupts the nesting once underway are likely to have different endocrine bases.