Date: 11/21/20 3:46 pm From: Alvaro Jaramillo <chucao...> Subject: Re: [pen-bird] Glaucous Gull San Gregorio etc.
Joe It is a classic Red-winged behavior, it seems to me that Tricolored blackbirds are mixed but in general I see a preponderance of males on the coast. Yellow-headed Blackbirds also segregate, it would be interesting to see what Great-tailed Grackles do in areas where they are common. The reason is that sexual size dimorphism may be one of the factors in sex segregated flocks. Certainly oropendolas in the Neotropics segregate during the non-breeding season, and they have the largest size dimorphism of any bird. Great-tailed grackles are not too far behind. Alvaro
-----Original Message----- From: <peninsula-birding...> <peninsula-birding...> On Behalf Of susan hons via groups.io Sent: Saturday, November 21, 2020 3:23 PM To: Joe Morlan <jmorlan...>; <peninsula-birding...> Subject: Re: [pen-bird] Glaucous Gull San Gregorio etc.
> On Nov 21, 2020, at 3:14 PM, Joe Morlan <jmorlan...> wrote: > > Al, > > Do Tricolored Blackbirds also segregate into single sex flocks or is > it just Red-wings that do that? > > Thanks. > > On Thu, 19 Nov 2020 10:04:17 -0800, "Alvaro Jaramillo" > <chucao...> wrote: > >> I also have a Northwestern Red-winged Blackbird (subspecies caurinus) at the feeders in the backyard. These females are more streaked than our residents, and have much stronger rusty edging on the upperparts. Often they are in all female flocks around here, and only in winter. The males are not as common on the coast as the females, but they are frequent in the Central Valley in winter. Again, they segregate in winter into single sex flocks. > -- > Joseph Morlan, Pacifica, CA > > > > >