Subject: Starling behavior-- is it really a flock?
Date: May 11 06:01:57 2001
From: WAYNE WEBER - contopus at home.com


Dennis (and Tweeters),

In regard to the apparent flocking of feeding Starlings, there is a
possibility that you may not have considered-- that the apparent flock
is not really a flock at all, but merely a loose grouping of birds,
each of which is deciding where to feed independently, based on where
it has had best success in finding food-- not based on whether or not
there are other birds nearby. In other words, such a group would be a
passive "aggregation" of birds rather than an active "congregation",
in which the birds are attracted to other feeding birds. You agree
that "flocks" seen in the breeding season are much smaller and less
cohesive than those seen in the winter. I suspect that predator
avoidance is the main advantage of large winter flocks of Starlings.

There has been research in the Netherlands which shows that individual
Starlings decide where to feed based on their success in finding food.
After a few visits to one patch of lawn which result in poor prey
capture rates, a Starling will switch to another patch of lawn, or
even try a totally different area up to half a mile away. On the other
hand, if the capture rate is high, the bird will keep returning to the
same area. The presence of other Starlings may or may not be a factor.
(This work was done in the breeding season.)

Burton Guttman's comment that a flock might "scare up" more insects
than individual birds might be applicable to blackbirds or cowbirds,
but not to Starlings. Starlings feed mainly by probing their long
bills into the ground at random, and pulling out insect larvae or
other invertebrates when they encounter them. Insects found on the
surface are not nearly as important as subterranean insects. However,
a Starling could still gain an advantage by joining a "flock" of other
Starlings which had already discovered that Patch A of lawn had a much
higher density of insect larvae than Patch B.

As you may know, I did some research on Starling feeding ecology (and
other aspects of their biology) many years ago as part of my M.Sc.
thesis. I am still fascinated by many aspects of their biology.

Wayne C. Weber
Kamloops, BC
contopus at home.com


----- Original Message -----
From: Dennis Paulson <dpaulson at ups.edu>
To: <tweeters at u.washington.edu>
Sent: Thursday, May 10, 2001 11:12 AM
Subject: starling behavior


I have been seeing little feeding flocks of starlings around town,
and I wondered why they were in flocks now, in the midst of the
breeding
season. The question was just answered for me.

I have a pair of starlings nesting just above my office windows, so
I can watch what they're doing. I'm looking out on a big courtyard
covered mostly with lawn, and it appears to be a favored feeding place
for
neighborhood starlings. When birds leave the nest hole above me and
fly out onto the lawn, they very commonly (not sure if it's
invariably)
join little flocks of starlings already feeding. There is plenty of
open
starlingless lawn, yet the starlings choose to feed rather close
together. Apparently they are territorial when nesting but social when
feeding, not a common combination in passerine birds.

The starling flocks are by no means stable, just birds constantly
coming and going in all directions and forming and reforming
flocklets. I
just watched one of "my" starlings fly down and land right next to
another, and they fed side by side for many seconds. I thought
perhaps the bird
it joined was its mate, but no, that bird then flew away. The lawn is
obviously a rich feeding ground, as birds are coming to the nest
constantly with prey. Interestingly, one or more House Sparrows joins
a little
flock at intervals, and I think the sparrows may be stealing prey from
the
starlings! I'm fairly sure one darted up to a starling, grabbed
something from it, and flew away.
>
So if you see starlings feeding in little flocks, it doesn't mean
they've already finished with breeding or don't intend to breed; they
are
just being starlings. This is a very watchable and interesting bird,
and
I hope no one ignores them just because they don't like them.
>
> Dennis Paulson, Director phone
253-879-3798
> Slater Museum of Natural History fax 253-879-3352
> University of Puget Sound e-mail
dpaulson at ups.edu
> Tacoma, WA 98416
> http://www.ups.edu/biology/museum/museum.html
>
>