Date: 3/20/17 5:22 am From: Peter <psaracin...> Subject: [cayugabirds-l] Migration Video and question
Folks.......I have a spring migration question and wonder if anyone out there can help. I understand that the lengthening days ignites hormonal responses in birds and, among other things, encourages "migratory restlessness" - an "itch" to begin their respective journeys north. But how does this mechanism work with respect to neo-tropical warblers? After all, for those spending their "winters" in northern So. America the days will be shortening!!! The "photoperiod" will be decreasing.
What, then, is the trigger to get them on the move and heading northward? Thanks for the help.