Date: Mon, 27 Aug 2001 09:18:58 -0400 Reply-To: Maryland Birds & Birding Sender: Maryland Birds & Birding From: Scott Crabtree Subject: Unusual Mobbing Behavior MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" On Saturday morning, I took a swing through Soldier's Delight Natural Environment Area, and encountered some unusual behavior. I had arrived at the cut-over area along the Red Trail, just past the old Choate placer mines. (Is this cut-over area being "managed," possibly to return it to serpentine barrens?) I was noticed some very loud and active mobbing behavior - there were Prairie, Pine, Canada, and Black & White Warblers, Baltimore Orioles, many woodpeckers and other common locals, and lots of juvenile Bluebirds, the loudest of the mobbers. I carefully searched around the small oaks where this activity was taking place. My scrutiny yielded a....Common Nighthawk as the target! When it took flight a couple minutes later, the birds scattered in all directions. Fifteen minutes later, on the far east side of the clearing, I encountered the same scenario - lots of vociferous mobbing directed at a perched CONI. (All told, I saw 12 CONI either perched or overhead - those flying were heading North, as has been reported by others recently.) I have never seen nighthawks, or any nightjar, being mobbed before, and was wondering why they would receive such treatment. Theory: the "apparent" instigators of this activity were the juvenile bluebirds, many still spotted in the upper breast, but growing in blue remiges and rectrices. They probably have either a learned or innate template for recognizing a threat shape - there was research in that area years ago that determined that goslings had it innately, but I haven't kept up with the literature to know if that is so in passerines. Do nighthawks match that threat model enough (looking a bit like a swift or falcon) such that naive birds would react to the nighthawks at a threat? Then, the bluebird mobbing turns on everyone else? Has anyone else seen such behavior or can offer an explanation? Scott Crabtree Baltimore, MD ruffleg@empire.eclipse.ncsc.mil ======================================================================= To leave the MDOsprey list, send e-mail to listserv@home.ease.lsoft.com with the following message in line 1: signoff mdosprey ======================================================================= =========================================================================