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Migratory state and patterns of steroid hormone regulation in the pectoralis muscle of a nomadic migrant, the pine siskin (Spinus pinus)Free, publicly-accessible full text available August 1, 2022
Physiological preparations for migration generally reflect migratory strategy. Migrant birds fuel long-distance flight primarily with lipids, but carrying excess fuel is costly; thus, the amount of fat deposited prior to departure often reflects the anticipated flight duration or distance between refueling bouts. Seasonal pre-migratory deposition of fat is well documented in regular seasonal migrants, but is less described for more facultative species. We analyze fat deposits of free-living birds across several taxa of facultative migrants in the songbird subfamily Carduelinae, including house finches ( Haemorhous mexicanus ), American goldfinches ( Spinus tristis ), pine siskins ( Spinus pinus ) andmore »Free, publicly-accessible full text available June 29, 2022
Many animals differentially express behaviours across the annual cycle as life stages are coordinated with seasonal environmental conditions. Understanding of the mechanistic basis of such seasonal changes in behaviour has traditionally focused on the role of changes in circulating hormone levels. However, it is increasingly apparent that other endocrine regulation mechanisms such as changes in local hormone synthesis and receptor abundance also play a role. Here I review what is known about seasonal changes in steroid hormone receptor abundance in relation to seasonal behaviour in vertebrates. I find that there is widespread, though not ubiquitous, seasonal variation in the expressionmore »
Migratory state is not associated with differences in neural glucocorticoid or mineralocorticoid receptor expression in pine siskinsAbstract Although the endocrine system likely plays an important role in orchestrating the transition to a migratory state, the specific mechanisms by which this occurs remain poorly understood. Changes in glucocorticoid signaling are one proposed mechanism that may be important in migratory transitions. Although previous work has focused on the role of changes in circulating glucocorticoids, another potential mechanism is changes in the expression of its cognate receptors. Here, we test this hypothesis by comparing mRNA expression of the genes for the mineralocorticoid receptor ( MR ) and glucocorticoid receptor ( GR ) in two brain regions implicated in themore »