This thread caught my eye. I saw huge flock out north of DIA and noticed the same thing after looking a photos. Only a few males mixed in as far as I can tell. See high resolution photo... https://flic.kr/p/2kntCXj
On Wednesday, December 30, 2020 at 12:56:13 PM UTC-7 <dle......> wrote:
> Hi All, > > I'm out here in the Bay Area, CA but this topic recently surfaced with > regards to observers noting that Red-winged Blackbirds appear in single-sex > flocks near the coast in winter. Alvaro Jaramillo, who literally wrote the > book on New World Blackbirds (*icterids*), noted the following. > > *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.* > > When asked if Tricolored Blackbirds segregate into single sex flocks, this > was Alvaro's response: > > > > > > > > > *It is a classic Red-winged behavior, it seems to me that > Tricoloredblackbirds are mixed but in general I see a preponderance of > males on thecoast. Yellow-headed Blackbirds also segregate, it would be > interesting tosee what Great-tailed Grackles do in areas where they are > common. The reasonis that sexual size dimorphism may be one of the factors > in sex segregatedflocks. Certainly oropendolas in the Neotropics segregate > during thenon-breeding season, and they have the largest size dimorphism of > any bird.Great-tailed grackles are not too far behind.* > > I hope this info is of interest. > > Regards, > > Derek Lecy > San Rafael, CA (but born and raised in Boulder) > On Tuesday, December 29, 2020 at 11:43:49 AM UTC-8 <charles......> > wrote: > >> All males here as well, both along the South Platte in Denver and on the >> Barr Lake CBC. Definitely a mix of young and adult plumaged birds. And >> try as I might none of them could be converted to Rusty's. >> >> Charlie Chase >> Denver >> >> >> >> On Tue, Dec 29, 2020 at 11:12 AM W. Robert Shade III <wrsh......> >> wrote: >> >>> I have as many as 50 or more Red-winged Blackbirds swarming my feeders >>> every morning. Why are they all females? Males do not look like females in >>> winter do they? This means they must spend the winter in different places. >>> If so, what is the rationale for that? I cannot think of any other species >>> that segregates by gender in winter. >>> >>> Bob Shade >>> Green Mountain >>> Lakewood >>> >>> -- >>> >> You received this message because you are subscribed to the Google Groups >>> "Colorado Birds" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to cobirds+<u......> >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/cobirds/CAFwvYHrG0Sm6E9%<2Bv9Lrbu2ttFZCwhoSgZWjzH9CFQFfWnuGgpg...> >>> <https://groups.google.com/d/msgid/cobirds/CAFwvYHrG0Sm6E9%<2Bv9Lrbu2ttFZCwhoSgZWjzH9CFQFfWnuGgpg...>?utm_medium=email&utm_source=footer> >>> . >>> >>
