Date: 9/21/17 5:46 pm From: Stephen Johnson via va-bird <va-bird...> Subject: [Va-bird] large Cowbird flock, Fairfax County 21 September
Fall migration brings many surprises. Today at the Cub Run RECenter (Chantilly, Fairfax county) I found a single flock of over 200 Brown-headed Cowbirds. It was unusual for 2 reasons.
One, eBird flagged it for the large number, and I'm not surprised. I was amazed to see them all in one place. Well actually two places. Half were in a grass strip separating parking lot lanes; and the other were maybe 40 meters away, in grass at the edge of the lot.
I studied the flock carefully, and that brought up reason #2. There was not a single member of any other species, in either half of the flock. I'm used to seeing big migrating groups of mixed Starlings and Cowbirds, and often there's some Grackles, and/or a few Red-winged Blackbirds. Here's the checklist. The Starlings listed were not part of this flock.
I have been seeing lots of young and adult Starlings recently, and ditto Grackles, so I'm pretty familiar with them; so I'm sure I was not seeing any of them in this flock. Very unusual in my experience, a pure-species Cowbird flock. The count is conservative - there were at least 250, maybe 300 birds present.