Hi Tweets

As a couple of people have already mentioned, there is often a
range of unusual behaviors exhibited by birds that don't fit into
the "normal" behavior for the species.

I don't know much about crow behavior, but among the rooftop gull-
colony that I observe, I have witnessed an odd series female-
initiated attempt at extra-pair mating. Horace, the male on nest-
site #1, seems to have an unwanted suitor. Often when he is
incubating the eggs, another gull, I presume a female, regularly
visits the nest-site and starts prancing around him while head-
tossing (one of the mating behaviors). Horace is quite perturbed
by this, and tries to peck at her and drive her off. However,
when he's incubating, he can't get off the nest, so she stays
just out of pecking range.

I have seen this go on for some time. For a while it seemed like
every time he was on the nest he had his unwanted suitor.
Gertrude, Horace's mate, would sometimes return to help drive off
this intruder, but usually she split before Gertrude got back.
Sometimes, when the harassment had been particularly bad,
Gertrude would return and Horace was so eager to get away from the
nest-site he would just stand up and take off, without waiting for
Gertrude to come and take over. It's like he just said "your
turn" and split.

A few days after the eggs hatch, the chicks can be left uncovered
for short periods of time. Last year, I remember the unwanted
suitor showing up around that time. Things went on like they
normally did, with Horace staying on the nest and trying to peck
at the intruder as she pranced around and head-tossed. Then he
got up, grabbed her by the wing and pinned her to the ground for
around five minutes. After that, her visits to the nest were short
and she was quickly driven off.

In the literature on Gull behavior there are reports of rape and
other non-standard behavior among several species. John Ryder,
researching a Ring-bill colony in Lake Superior found that around
10 out of the 3000 male gulls in the colony chronically ignore
their own mates and harass and rape females, usually attacking
when the female is incubating and the male off hunting. Similar
behavior is also found in Herring-gulls, and Glaucous-wings and
Western Gulls, though it is also frequently unsuccessful, as the
females can fight like hell.

There is also reports in the literature of female Glaucous-wings
initiating extra-pair copulation while trying to beg food out of
neighboring males, and Western Gull females that are paired to
unsuitable mates will also look to their neighbors. When gender
ratio's get significantly out of balance, there have been instances
reported of three-bird "pairs" (one male, two females) and
female-female pairs raising double-sized clutches.

I'm sure Bob B. could add a lot more from his observations on the
SE Farrallons.


John Chapman
Seattle WA
ragweed at igc.org