Today, while working on the Durham Spring Bird Round-up, I found a backcross Brewster's Warbler at Crow's Pass Conservation Area. Terrie Smith was able to confirm the sighting a few minutes later.
A Brewster's is one of the possible hybrids produced when a Blue-winged Warbler and a Golden-winged Warbler mate. The offspring exhibit characteristics of both parents and either favour the Golden-winged parent (Brewster's) or the Blue-winged parent (Lawrence's). The offspring are sexually capable of producing young. When the hybrid offspring mate with another Brewster's, Lawrence's, Blue-winged or Golden-winged, the result is called a backcross (= second generation hybrid). The bird we saw was a typical second generation Brewster's hybrid, displaying the yellow crown, white breast, gray back and yellow wingbars as pictured in Dunn's & Garrett's "Warblers" and Sibley's "Guide to the Birds". More info can be gleaned from Parkes' article "The Genetics of the Golden-winged x Blue-winged Warbler Complex (Wilson Bulletin Vol 63, No. 1 (1951), pp 4-15) or my paper "Presumed Breeding Record of Brewster's x Brewster's Warbler, Vermivora chrysoptera x pinus, in Ontario (Canadian Field-Naturalist, Vol 97, No. 4 (1983), pp. 458-9). Directions: Crow's Conservation Area is located north of Brooklyn. Exit 401 at Brock St. and go north through Whitby to Brooklyn, go west on Hwy 7 to Ashburn Rd, then north to Middle March Rd. Follow this westerly to where it turns to a dirt road and park your car. Watch out for golfers as the fairway crosses the dirt road where you'll be walking. Walk west to the gate (about 2-300 meters) that leads into the conservation area. Several Blue-winged Warblers may be found here and the Brewster's was just north of the entrance on the east side. Geoff Carpentier Ajax, Ontario _______________________________________________ ONTBIRDS is presented by the Ontario Field Ornithologists - the provincial birding organization. Send bird reports to ONTBIRDS mailing list [email protected] For instructions to join or leave ONTBIRDS visit http://www.ofo.ca/information/ontbirdssetup.php ONTBIRDS Guidelines may be viewed at http://www.ofo.ca/information/ontbirdsguide.php
