Photoperiodic Regulation of Testicular Metamorphosis and Fat Deposition in Three Taxa of Rosy Finches

Publisher Website
Google Scholar
Abstract
In order to identify correlations between physiological capacity and migratory habit we investigated testicular metamorphosis, migratory fat deposition, and migratory restlessness (Zugunruhe) in forms of the rosy finch characterized by altitudinal migration (Leucosticte atrata) and by short-distance (L. tephrocotis lit- toralis) and medium-distance (L. t. tephrocotis) latitudinal migration. Testicular recrudescence began in feral L. atrata in mid-February in Utah, and in late Feb. in the other taxa, but mean combined weight of testes was less than 2 mg when the birds left the winter area in late March. Body weight and lipid content increased in some feral birds before departure. Observation of captives held outdoors confirms the existence of migratory fat deposition in all 3 taxa; deposition was least in L. atrata. Testicular recrudescence and fat deposition were induced experimentally by exposing birds to 20-hr. daily photoperiods indoors. The magnitude of fat deposition was similar in all taxa, but usually least in L. atrata. Long-term testicular growth was greatest in L. atrata, intermediate in L. t. littoralis, and least in L. t. tephrocotis. We attempt to correlate these quantitative differences with the requirements of the migratory itinerary, reproductive schedule and environment, and natural photoperiod to which the taxa are exposed.