Showing posts with label american crow. Show all posts
Showing posts with label american crow. Show all posts
Friday, May 14, 2010
Bird Census: American crow
10:00 PM | Posted by
Sweep Commander |
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Likes: Intelligence tests suggesting they might be among the smartest of nonhuman animals, carrion, tiny animals, infrequent tool use, nuts.
Dislikes: The West Nile virus, which has reduced the American crow population by half.
Friday, April 16, 2010
Odds, ends... (WE'RE BACK!)
4:07 PM | Posted by
Sweep Commander |
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Our snowy egrets have nests and they've laid eggs.
Canada goslings have hatched! While we're thrilled to behold these little balls of pure cuteness, there's really more tragedy to be had here than anything else. Canada goslings are a very popular food item on Alcatraz and the large, lumbering geese do not effectively protect their young from predation at the beaks of opportunistic gulls and ravens.
Cute while they last
A dead adult goose was found resting atop the rocky cliffs on the west side of the island.
Although we haven't seen them, the rangers tell us that there are now ducklings on the island! We'll be keeping our eyes peeled and our cameras ready.
We've been seeing many pigeon guillemots. The habits of these birds are beyond cryptic and are best left for educated experts to interpret, especially insofar as we go long stretches of time without seeing one, and then all of a sudden, wow, there's a hundred guillemots.
Arguably, the big news on the island is that the park's natural resources arm has elected to destroy most of the intricate stick nesting structures belonging to our pair of common ravens. Last Friday, the deed was done.
The only nesting structure left unharmed had freshly laid ravens' eggs inside. These eggs are soon to be oiled, a process that will prevent them from hatching.
The park service does this to benefit the other birds on the island. The ravens are deadly predators and doubly so when they have three or four extra mouths to feed. The folks at natural resources reason that taking these steps will allow a few extra black crowned night heron fledglings to survive into adulthood.
Though we're admitted amateurs, we intend to examine the raven management policies in the coming days.
These American crows had been inseparable, but recently we've been seeing just one.
Perhaps the other is incubating.
More soon to come.
Wednesday, March 3, 2010
Where did they go?
5:58 PM | Posted by
Sweep Commander |
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Where are our falcons?
I would very much like to see the peregrines establish themselves permanently on Alcatraz but recent observations leave me worried that any raptor pair making a home on a small island populated seasonally by two thousand western gulls faces an arduous task; I hope that our falcon pair hasn't failed already. More on that in a moment.
There is the aforementioned tendency of the gulls to take to the sky in alarm whenever the falcons soar over their roosts. In one such instance, I saw several gulls actually attacking one of the falcons in midair.
There is also a certain reckless aggression practiced by the pair and especially by the male. The ravens are certainly enemies of the gulls but they trespass on the gulls very selectively and very, very carefully. The ravens may harm the gulls by occasionally taking their eggs and young but they are deft enough to avoid being mobbed in large groups.
On the other hand, the male falcon thought that it might be wise to nearly take the head off the female raven as she was soaring by. Far from doing anything to provoke him, she seemed not to notice him until she suddenly dove to evade the attack.
On that same occasion (Monday, March 1st 3:45-4:45pm) I saw the female falcon on the railing of the water tower, stationary, apparently watching the male's antics. He would fly up, join her on her perch, hop around and then take to the sky for a few more laps of ill advised adventure.
As he aggressively darted in, around and through a cloud of angry gulls over the recreation yard and the new industries building on the west side of the island, the female only watched his maneuvers. After one energetic run, he failed to rejoin her. The gulls quieted down and their numbers in the air fell to just a few.
Ten minutes later, I spotted a dead bird on the roof of the new industries building. I reported it to our wildlife biologist and I'm at least 95% sure that it's a western gull but even with binoculars it's difficult to be sure. Tomorrow, I'll have the right hardware to make a final determination. Stay tuned.
Yesterday, in all of my outings, I saw only the female and only for a small part of the day. Today, we saw neither falcon. It's the first time in many weeks that I haven't seen either bird. They are so habit driven and preferential to the same few haunts (the water tower, the power plant, a couple of cypress trees) that it's worrisome not to have made a single sighting on any of our outings.
I know with only one falcon-free day that it's far too early to fret, but the recent conflicts with the gulls and the ravens have left me with the sad expectation that these birds won't succeed in establishing themselves. The gulls have become more numerous since the falcons arrived in November and they have become more assertive. I wouldn't be shocked if one of the falcons fell in a bloody adventure, or if they decided Alcatraz and its thousands of large gulls wasn't friendly to their reproductive prospects.
Here's to pleasant surprises of all kinds.
Odds, ends:
I got my camera back today. Expect visual media. Uh, lots.
I checked in on Lucky the WEGU today, and (s)he is alive and well, chasing adult gulls and begging for food, as is his/her pattern.
We observed a group of four crows on the island today, marauding around, soaring and executing a number of funny diving maneuvers. BourbonHawk can tell a crow from a raven at great distances and if she can't see the birds, she can tell from their calls. I, on the other hand, have some work to do.
That's it for today.
More soon.
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