Seasonal changes in circulating levels of luteinizing hormone and growth hormone in the migratory Canada goose.

Seasonal changes in plasma levels of LH and GH in the Canada goose (Branta canadensis interior) have been studied. The population examined breeds in the Canadian subarctic region (Fort Churchill, Manitoba) and winters in the southern United States (Swan Lake Refuge, Missouri). Peak levels of LH were observed during spring postmigratory (nestbuilding, early May) and nesting (incubating, early June) periods, while no significant differences were observed during the other periods studied. The highest levels of GH were observed during molting (late July) and the immediately following fall premigratory (early September) period.