Monday, August 2, 2010

PostHeaderIcon Juvenile gulls begin to fly. Consequently, many die. (Also, falcon news!)

Alcatraz's new western gulls have acquired their flight feathers and their instincts are driving them into the air. Their inexperienced and ungainly flight, as well as the territoriality of other gulls puts them squarely in harm's way.

Take, for example, this WEGU's compromised position:

If you're new to the wing, this is what the excitement of flight can get you. It's a very common sight on Alcatraz.

Allow me to explain. This is what's called the Parade Ground:

Click on the image to get the full effect.

It's an area of flat pavement, dense shrubs and the remains of apartment buildings constructed to house correctional officers and then razed by the federal government in the 1970s after the closing of the prison and the end of the Indian Occupation. The structures were destroyed in order to ensure that a bunch of troublemakers could never again occupy the area and use it to showcase a loud, chaotic and violent mess.

Clearly the government didn't see this western gull colony coming. The gulls breed on the parade ground in huge numbers in a tightly packed configuration. There, they screech, squawk and fight one another in long and bloody engagements.

Then, as nesting season progresses and the eggs hatch, infanticide is suddenly on the menu and the adults happily indulge. When chicks are small enough to swallow, an adult gull will occasionally regurgitate a pellet containing the tiny indigestible remains of one of its own species.

Then, as the young gulls learn to fly, they've suddenly got a novel means to trespass upon the territories of others. And far be it from an adult WEGU, so imposed upon, to forego a shot at violence:

One pair of gulls has been especially prolific thus far in nailing invaders:

The two living juveniles in the above picture reside in this territory and their parents aggressively defend it. The other two birds, open and horizontal, meant no harm. They were learning to fly and they were flying badly. They were unfortunate enough to stumble into this territory which happens to be bordered by the foot tall remains of a small building. As these two accidental trespassers tried to escape, they failed to achieve enough altitude to clear the short wall and they were killed.

Most gulls are luckier, managing to evade the violence of the adults and escape with their lives. Many young gulls on Alcatraz survive to continue their development but retain these badges of honor, sustained in combat with the older brutes they hope to become:

That is not a good haircut. You'd better believe I would get my money back.

Falcon News!

One of our awesome bird biologists has spotted and photographed an adult falcon on Alcatraz. It's been a while. Our maturing male falcon appears from time to time and was last seen in late June.

On seeing the picture, I immediately took it to be a female. When I bounced my suspicion off of BourbonHawk, she opined that if turns out to be a female, it's probably too dark to be our friend from last year.

After reviewing the photos, I think she's right. It may be a female peregrine, but it's not our female peregrine.

One park ranger and one Parks Conservancy employee have also reported seeing peregrines recently, but no sightings have been made on birds occupying our peregrines' familiar preferred roosts, which is an additional consideration in favor of this being a bird new to Alcatraz.

If this is a female with designs on hanging around for a while and if our heroic young tiercel is still about, this should make him very happy indeed.

The island's gulls knew this day would come

And they've been practicing their battle moves on anything at all with a raptor silhouette:

Here, they harass a harmless turkey vulture.

The video is short but the chase was much longer. The vulture's reaction to the harassment was easy to read and was something along the lines of: Ugh! What? And why? Do! Not! Want!

On the flip side, I had no idea that vultures were so agile in the air. Can I be excused for taking them to be slow, dumb and lazy?

At any rate, most birds hate the sight of a hooked beak and they will instinctively count it as a threat and mount an attack if they are able.

Their instincts fail to make the distinction between a peregrine falcon which sometimes uses its hooked beak to behead live prey and a turkey vulture which means no harm to most living things, but has a sharply hooked beak in order to open the body cavities of the already dispatched.


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