Sunday, February 28, 2010

PostHeaderIcon Our peregrine pair: Birders love them. Birds do not.

Our gulls certainly do not.

As the pair soared high over the recreation yard today, they alarmed the gulls roosting below and soon the sky was full of angry birds. The sound of their collective threat and unease vocalizations was deafening.

After perhaps fifteen minutes of falcon soaring and gull ambivalence, one falcon disappeared from view and the other descended, hovering in strong winds perhaps 40 feet above me.

Then I made our very first observation of unsolicited mobbing behavior by the gulls towards the falcons. With no clear provocation, three gulls began to pursue and attack the falcon. One managed to bite the falcon's tail several times and each time the falcon issued a vocalization that I would describe as halfway between a screech and a groan.

The falcon then evaded its three pursuers and attacked a soaring gull. Contact was made but the peregrine failed to grab or otherwise harm its target. WEGUs seem a little big for peregrine food so its possible that the attack was an expression of anger at the mob attack.

It gives us cause to wonder. In prior posts, we've speculated and even boldly predicted that the gulls would eventually drive the falcons away. We've seen the gulls handle many a red tailed hawk in this manner and when the gulls mob a raptor during nesting season, they are relentless. As nesting season comes near, will the gulls continue to lose patience with the pair of peregrines that would take Alcatraz as their own?

We'll keep you apprised.

On another note, the common raven pair was again spotted moving nesting materials to its preferred tree on the north side. The presence of the falcons there may not be enough to change their plans after all.

That's it for today.


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