Date: Mon, 7 May 2001 11:48:49 -0500 Reply-To: Maryland Birds & Birding Sender: Maryland Birds & Birding From: Maurice Barnhill Subject: Re: bird migration and weather MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Shireen Gonzaga wrote: > > Hi ... I'm increasingly puzzled about the correlation between > migration fallouts in our area and weather. This is the first > year I'm seriously paying attention to songbirds, and I've been > puzzled by the low numbers. > [snip] > ... I also checked Birdcast to see > their May 3 evening forecast: "Analysis 3 May evening: > Weather conditions over the Birdcast area were favorable > for bird migration. W and S winds and warm temperatures > allowed bird migration to occur. " > Their web site: http://www.birdsource.org/Birdcast/home.html > (They're doing neat work, please contribute your sightings > to help them along....) > Birdcast's analysis and predictions are for the number of moving birds in the air. They should give a good prediction of the days when the most new residents will show up and when the turnover of migrant species might peak. However, it will not be as good at predicting when there will be large numbers of individual migrants to be seen on the ground. They tell you when a large number of birds moved in, but an equally large number of birds moved *out*. We see a peak when a large number of birds suddenly hit unfavorable conditions over our heads at night and land in the trees we will be looking at. It is the change in conditions that gives us a fallout. [Or we can have especially low numbers if conditions above us turn good during the night and our birds leave without being replaced by birds from the south]. That said, the numbers sure do seem low this spring. I had thought we might have a small fallout here yesterday, since the winds at least shifted in direction overnight, but nothing doing. Today was even worse. It is still early in the season, but I suspect birds are mostly overflying us, not landing. Certainly we have not yet, in Delaware, had weather conditions that favored a large fallout. > [snip] -- Maurice Barnhill (mvb@udel.edu) Department of Physics and Astronomy University of Delaware Newark, DE 19716 ======================================================================= To leave the MDOsprey list, send e-mail to listserv@home.ease.lsoft.com with the following message in line 1: signoff mdosprey ======================================================================= =========================================================================