Topics

Brood Parasitism

rferrick@...
 

Witnessed my first "live" example of brood parasitism this afternoon at Pine
Lake Park. I was checking the willows at the west end, when a crying,
fledgling Brown Headed Cowbird appeared in an opening. An adult Dark Eyed
Junco answered the crying by feeding the bird that is at least twice its size
by now. Quite interesting. The Birder's Handbook mentions DE Junco as an
"uncommon Cowbird host" so I thought I would pass it on.

Nothing else to report. Did stop by Sutro Baths yesterday evening but the
only gulls around were Western's.

Rich

Jay Withgott <withgott@...>
 

Yes, Rich, I forgot to mention when I saw you that I'd seen that Cowbird
& Junco too. And I think cowbird parasitism of ground-nesters in
general is much less common than of above-ground cup-nesters. Also of
interest was the fact that a female cowbird who was in the area at one
point perched directly above the vocalizing fledgling and repeatedly
gave the typical cowbird burbly rattle call quite forcefully, looking
around and down in an agitated manner. It was obviously responding to
or communicating with the fledgling cowbird. Might encounters like this
help young cowbirds gain a sense of identity ("species recognition" in
the technical parlance) despite their being orphans?

To all of you SFBirders, today begins my summer-long absence from our
fair city. So I expect to fall swiftly to last place in our fair
competition. But I'll look forward to the fall!

Jay


rferrick@... wrote:

Witnessed my first "live" example of brood parasitism this afternoon at Pine
Lake Park. I was checking the willows at the west end, when a crying,
fledgling Brown Headed Cowbird appeared in an opening. An adult Dark Eyed
Junco answered the crying by feeding the bird that is at least twice its size
by now. Quite interesting. The Birder's Handbook mentions DE Junco as an
"uncommon Cowbird host" so I thought I would pass it on.

Nothing else to report. Did stop by Sutro Baths yesterday evening but the
only gulls around were Western's.

Rich

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Jay Withgott
Freelance science writer
San Francisco, California
415-452-6763
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Alan Hopkins <ash@...>
 

This is the first Cowbird chick I have heard of this year. I have not
been out much, but I've seen lots of Junko chicks and White-crowned
Sparrow chicks in the few times I have been out. It seems to be a good
year so far for those birds.

I have noticed, and I think the SF Breeding Bird Atlas may also show
that the birds that nest in the early spring are less prone to Cowbird
parasitism than those who breed later. It will be interesting to see if
lots of young cowbirds show up soon.

Jay� we'll try to save some good birds for your return.


Alan

Paul Saraceni <Paul.Saraceni@...>
 

I've seen at least 2 young cowbirds at Mt. Davidson recently (6/1), plus 1
female that always seems to be poking around the bushes in which the
White-crowned Sparrows nest -- they are apparently the hosts. Lots of young
White-crowns up there, and 1 young Junco.

Paul

-----Original Message-----
From: Alan Hopkins <ash@...>
To: Jay Withgott <withgott@...>
Cc: rferrick@... <rferrick@...>; sfbirds@...
<sfbirds@...>
Date: Thursday, June 08, 2000 8:59 AM
Subject: Re: [SFBirds] Brood Parasitism


This is the first Cowbird chick I have heard of this year. I have not
been out much, but I've seen lots of Junko chicks and White-crowned
Sparrow chicks in the few times I have been out. It seems to be a good
year so far for those birds.

I have noticed, and I think the SF Breeding Bird Atlas may also show
that the birds that nest in the early spring are less prone to Cowbird
parasitism than those who breed later. It will be interesting to see if
lots of young cowbirds show up soon.

Harry Fuller <harry_fuller@...>