Migration Remains a Mystery
(This column was first published in the May 24, 1999 Buffalo News.)
I give up.
For years I have been trying to interpret weather patterns in an attempt to associate them with the timing of bird migration. I am not alone in this. Every dedicated bird watcher across North America tries to predict the day when the spring migration will peak so that he or she can take the field early that morning.
It is clear that birds do not return on the same date every year. Close observers report that, despite claims to the contrary, even the famous swallows of San Juan Capistrano in California are irregular in their arrival. Early swallows are disregarded or considered "just scouts." And when the weather is bad in Los Angeles on the arrival date, the missionaries wait until after the storm to look for returning swallows. Here on the Niagara Frontier bird records vary even more widely with arrival dates for individual species differing by as much as a week from one year to the next.
Several years ago I wrote in this column about what I perceived to be the perfect weather scenario for a truly big birding day. It went something like this:
Early May weather across the eastern United States is cold and rainy with front after front moving through from the north and west. The jet stream bellies south along the Mason-Dixon Line holding the flood of spring bird migrants at that latitude.
Now suddenly in mid-May, the weather breaks. The jet stream shifts north above the Canadian border, the weather warms and a high pressure system moves through, closely followed by a low. The air movement between the two cyclonic systems -- the high flowing clockwise, the low counterclockwise -- produces south winds that releases the migrants allowing them to rush north that night in response to their pent-up instinctive drives.
Now one more factor intervenes. After midnight the low moves in bringing rain showers. Migrants that might have simply flown through drop into our woodlands to seek shelter and sustenance. And because of that earlier poor weather, foliage is only beginning to emerge. The birds are forced to search for insects among the low shrubs, thus offering good opportunities for observation when dawn arrives to bring out the birders.
Has this year been like that? All would agree that it certainly has not. We have had week after week of pleasant weather. We are way ahead in local degree days -- the measure gardeners use to indicate how advanced the growing season is. And leaves are out in force by mid-month, not at all conducive to birding.
Despite all this, on May 15 a team of four local birders, Willy D'Anna, Mike Morgante, Steve Taylor and Mike Turisk, set a new record for bird species seen here in a single day -- 170.
Let me place that number in perspective. Even though I have done more birding this year than in any recent year, I had recorded only 143 species by May 15. And that includes some seldom seen here that I picked up in Virginia and Alabama -- chuck-will's-widow, fish crow, dickcissel and blue grosbeak. My list may not compare with some of our finest observers but it still gives an idea of how remarkable is that single day 170 total.
And as if that were not extraordinary enough, a Cornell Laboratory of Ornithology team -- John Fitzpatrick, Steve Kelling, Kevin McGowan, Ken Rosenberg and Jeff Wells -- listed 220 species on the New Jersey state-wide World Series of Birding one day count, enough to earn them the out-of-state team trophy but only second place overall. An in-state team found 223 species.
So much for my weather scenario. -- Gerry Rising