Moults and plumages and testicular regression of post-breeding male Blue-winged teal (Anas discors) and Northern shovelers (Anas clypeata)


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    Present address: Department of Zoology, University of California, Davis, California 95616, U.S.A.


Moults and plumages and testicular regression were compared in post-breeding male Northern shovelers (Anus clypeala) and Blue-winged teal (A. discors). Sequence of moults and plumages was similar between species, except that Northern shovelers became flightless before completion of pre-basic moult and initiated pre-alternate moult before complete regrowth of primaries. Testicular regression was similar in both species, occurring in a two-stage process of from four to six weeks. In all cases, both species had finished testes regression before the initiation of the flightless period. In both species, the lcft testis was larger in spring, regressed slower, and was larger after regression than the right testis.