Date: 11/21/20 3:46 pm
From: Alvaro Jaramillo <chucao...>
Subject: Re: [pen-bird] Glaucous Gull San Gregorio etc.
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 Jaramillo

-----Original Message-----
From: <peninsula-birding...> <peninsula-birding...> On Behalf Of
susan hons via
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

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