Date: Wed, 10 Dec 2003 14:14:20 -0500 Reply-To: Maryland Birds & Birding Sender: Maryland Birds & Birding From: Charles Vaughn Subject: Re: avian migration and those pesky hummers In-Reply-To: <3FD7356A.6000107@udel.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed I think the discussion of the genetics of migration has gotten a bit too anthropomorphic. Any substantial population of any species of anything, birds, fish, humans, has a variance about some mean behavior of interest. What with Global Warming and all, it's a good thing many species (unfortunately not all, by any means) have a wide variance in the abilities between INDIVIDUAL within the species. Some individuals of a species are (hopefully) going to make it under conditions that will kill individuals close to the population mean. Put another way, some individual are, so to speak, a bit weird - thank goodness. To say that a "stray" bird has a "defect" misses the idea of this variance. Darwin is turning over in his grave, no doubt. A few tens of Rufous Hummers in the East out of a population of xxx thousands probably (pun intended) isn't unreasonable to expect. Why are we seeing so many more western hummers than in the past? The Patagonia Roadside Picnic Stop has morphed, one copy of which is now in the mid-Atlantic. "Learned" behavior, too, is a bit tricky to deal with. It begs the question of what is learned. A simple first order Monte Carlo simulation (got that) of homing pigeon abilities shows that it doesn't take a very sophisticated bird to get home - some time or other. All the pigeon has to do is be able to point to the home direction within +/-90 degrees, and be able to randomly (uniformly within this +/-90 deg) correct this pointing direction at some points in time. The pigeon will arrive home within the time variance that is seen for a statistically significant group of these birds. All that is required of a single bird is that it recognize its home area within some (small?) number of miles about the loft. That's all that's required; an ability to reorient to within +/-90 degrees of home at various intervals, and some recognition of a home region. Of course there will be those weird individuals that won't make it home. But I've come full circle, so I'll stop. >Charlie Charles Vaughn 1306 Frederick Avenue Salisbury, MD 21801 410-742-7221 essc@comcast.net ======================================================================= To leave the MDOsprey list, send e-mail to listserv@home.ease.lsoft.com with the following message in line 1: signoff mdosprey ======================================================================= =========================================================================