Waxes seasonal changes

There are interesting seasonal changes in the production of waxes and oils by the uropygial gland. These have been most extensively studied in male and female Mallards. For most of the year, the Mallard drake produces waxes in which over 80% have short-diain fatty adds, but during eclipse after the postnuptial moult, he produces waxes that have predominantly long-chain fatty acids, with about 20% short chain. This occurs for a two month period... 

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