The Big Day (published in the Monadnock Shopper September 21st, 2010)

By the time you get the shopper in the mail, the big flight will likely be over.  An average of 4,300 broad-winged hawks fly by the Pack Monadnock Raptor Observatory each September based on data from the last ten years, with the bulk of the numbers gliding by the observatory during the middle ten days of the month, September 10-20.  A quick run through the big days of the last seven years reads as follows:

2042 birds September 16, 2009

1448 birds, September 11, 2008

2424 birds September 18, 2008

1352 birds September 13, 2007

2676 birds September 16, 2007

2480 birds September 17, 2007

3044 birds September 11, 2006

1687 birds September 18, 2005

1235 birds September 14, 2004

The determining factor behind which of the ten days the hawks will choose is weather.  The big numbers tend to be recorded when high pressure systems dominate, air-flow is calm, and skies are clear.  If these factors combine after the passage of a cold front, all the better.  The cold air is a wake up call to the birds to get moving.

Additionally, one must consider the hawk’s hardwiring.  If suitable conditions have not converged by September 20 or thereabouts, the birds get restless and jumpy.  Imagine yourself ten minutes late for a hot date but stuck behind a red light.  When the weather clears and the light turns green, rubber burns baby.

As I write, it’s September 16 and no big numbers have passed yet, despite the presence of several pairs of vigilant eyes atop Pack Monadnock every day since September 1.  Thus it is fair to say that most broad-winged hawks are still to the north of us.  The forecast calls for some unsettled weather until Saturday, and then through Monday, NH will be dominated by high pressure, slack winds, and a cold front will pass through early Sunday.  I think most birds will pass through Saturday, Sunday and Monday.  Place your bets now.

Don’t let this be a disincentive to visiting the hawkwatch.  Its open through the end of October, staffed each day by a wonderful hawkwatcher by the name of Henry Walters.  Be sure to introduce yourself.  Henry will be able to point out the other types of hawks that fly by and tell you more about the fascinating lives of these birds.  Remember that in a good year, more than 10,000 hawks of up to fifteen species fly by the observatory.  Even if the big day is this weekend (or last weekend by the time you read this), there might be 5 or 6 thousand more still to come, including many remaining broad-winged hawks.