Date: 9/29/18 4:20 am
From: Don Simonson <don.r.simonson...>
Subject: [MDBirding] Broadwing Potomac River Crossing spot revealed - LIFTOFF! Broadwinged flight Mont. Co. 9/28/18

Today's Broadwing flight (324 birds seen in 3 hours) started for me with two gorgeous bright BROADWINGED HAWKS lifting off from inside my own backyard! Hilarious because I had been watching a record blue jay flight only a few yards away. About 9:30 I heard a racket and turned to find two Broadwings had just flown out from the tree in the back corner by the farm field and were noisily attacked by the local Red-shoulders, crows, and a Turkey Vulture who was also very low. The day in the yard was also enlivened by a RED-BREASTED NUTHATCH and several warblers and vireos, but nothing to match the hawk and jay spectacular.

A record stream of 208 blue jays in 30 minutes preaged a big flight potential.
Visiting birder from Nokomis FL Julie Baxter and I raced 8 minutes to Violette's Lock on the c and o canal, detouring only for hot coffee! we arrived at 10 am to find broadwings kettling and streaming over the maryland shore and streaming out to the southwest and west southwest across the river to Virginia. AT LAST! FOR DECADES I HAVE OBSERVED BIG FLIGHTS OF BROADWINGED HAWKS IN MY YARD, SOMETIMES IN EXCESS OF 1,000 BIRDS PER DAY EXCEEDING ANY OFFICIAL HAWKWATCH ON THE ENTIRE EAST COAST, INCLUDING HAWK MOUNTAIN PA, CAPE MAY NJ. Based on careful comparison of dates and numbers and hourly counts for HMANA hawk count data from Militia Hill PA, and Cromwell Valley Park MD, I believe the cohort passing Darnestown is the same cohort which passes Militia Hill and Cromwell Valley one day to a few hours prior to passing Darnestown.

But where to they go from Darnestown??? No observer to my knowledge, from Darnestown to Snickers Gap VA and Rockfish Gap VA, has ever posted observations of more than 1,000 Broadwings passing any point on that line, on a yearly basis. There have been spot observations scattered over various years of multi-thousand day flights from Ashburn, Seneca, Chantilly but nothing consistent.

FOR DECADES I HAVE BEEN SEEKING THE POTOMAC RIVER CROSSING and observation point WHERE THIS COHORT OF MIGRANTS CAN BE SEEN and counted. TODAY I FOUND ONE: looking west (upstream) from Violette's lock, Julie Baxter and I counted 269 brodwinged hawks, in a short period, plus 14 other raptors and scores of vultures, crossing, they were heading exactly in a line drawn later on google earth map passing through Militia Hill, Cromwell Valley Park and my house (on Springfield Road in Darnestown).

I am confident there were many many more raptors passing, as the early ones were already quite high and near 8.5x binocular range at 10 AM. we watch many of them disappear into the sky upward. Most birds were detected by scanning with 8.5x to to 10x binoculars, they were too distant to pick out with naked eye, appearing as single birds or a few tiny dots, then by Using a 20x to 60x zoom swarovski scope I was able to observe and count many more birds and determine the kettle count for each of the 'index' birds picked up with binos.

I attempted actual count = 269 vs estimation per Veracruz methods. The conservative estimate (not count), based on the large number of birds incoming at very high (scope-only) altitude is approximately 5x the observed, or approximately 1,400 individuals.

Google earth indicates the longest unobstructed sight line over water from Violette's Lock looking upstream is approximately 3.70 miles westward to WNW. This affords a great transect for More research to follow! Please reply off list if you have observations of raptors crossing the Potomac in numbers in Mont. Co.




Good birding!
Don Simonson,
Darnestown MD

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