Larry, The simple answer is photoperiod. Red-winged BBs and others will migrate when day length reaches a certain threshold for the species. This instinctive response is often coupled to their food requirements so insectivores will wait until the days get longer and most probably correspond to insect hatches enroute. Red-wings are considered half-hearty but I wish them luck finding food other than at feeders right now. The average arrival date was a few days ago. Have seen several reports of TVs all winter long but none on their roost (NWS Fire Academy roof) in Montour Falls.
Of course unless they sense a pressure gradient indicative of an impending storm, they come ahead on that increasing day length. John -- John and Sue Gregoire Field Ornithologists Kestrel Haven Avian Migration Observatory 5373 Fitzgerald Road Burdett,NY 14818-9626 N 42 26.611' W 76 45.492' Website: http://www.empacc.net/~kestrelhaven/ "Conserve and Create Habitat" On Wed, February 25, 2015 13:03, W. Larry Hymes wrote: > About 20 minutes ago I was very surprised to see a TURKEY VULTURE > soaring about near East Hill Plaza. Having heard no reports this > winter, I'm assuming this is an early migrant. I've often wondered why > this bird, and the red-wing blackbirds > > Considering the severe weather and heavy snow cover in our area, why > would this bird, and the RED-WINGED BLACKBIRDS that Dave Nutter saw on > the 22nd, not delay their northward migration until conditions improve > considerably? As they move north, aren't they taking into account the > conditions they are encountering and deciding whether to proceed or wait > it out? Any thoughts!?!? > > Larry > -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
