Wednesday, January 12, 2011

Amazona vittata, The Puertorican parrot, roosting behavior in the wild





Branch used by several parrots to roost, note the way the leaves and smaller branches have been stripped away
There are seventeen parrots in this photo, it was taken just after dawn, at the moment the first sun rays were stricking the tops of the trees

A branch used by a single pair, see how they have stripped the branch of leaves for a considerable lenght.  They sleep together at the very tip of the branch.

Part of one of the largest flocks of this species since the 1950's, there are twenty two birds in the photo, the flock was composed of thirty two birds.
The birds continue circling and calling and sometimes fly around almost until it is too dark to see
In this unique photo you can see a pair at night

The birds have excellent hearing, and probably have a small degree of night vision.
The Rio Abajo wild flock spends the day foraging in the forest, usually in small flocks of a few birds, but during the months of July to December in the evening they tend to form a large flock that sleeps in a single roosting area.  This is related to their breeding cycle, during the breeding season, which lasts from January to July in the RA forest, the birds become more aggressive, territorial and less likely to form large groups.  Once the chicks fledge the parents aggression toward other birds lessens to a considerable degree and they become much more social.
The roosting flock assembles in the evening and the way they choose which tree they will roost is very noisy and interesting.  First the birds start arriving at an area where several trees are used to sleep.  As the birds arrive they start calling and interacting with the other birds.  Then they start flying back and forth between the different trees singly and in small groups.
The impression I get is that they are going through a process of ascertaining where is the larger concentration of parrots, sort of a popularity vote between the different roosting spots.    As nightfall starts the groups in flight become bigger and bigger until at times the whole flock is in the air at the same time.  Just as it is getting too dark to see the flock finally settles in a single spot with all, or nearly all the birds in a fairly small part of the tree.
The parrots keep calling and squabbling for some time after it is dark but eventually they fall silent.  The parrots are not passive users of the roosting trees, they modify favorite sleeping branches by removing leaves for at times a considerable length of the branch.  Then they sleep near or at the very tip of the denuded branch.  MY guess is that this is an anti-predator measure but this is just speculation as any place where the parrots spend a considerable amount of time eventually becomes denuded of leaves and quite wretched looking due to their proclivity to chew with their powerful bills anything that is at hand nearby when they are perched in a spot.
The flock wakes up early but generally doesn’t leave their roost until the rays of the sun start striking the top of the tallest trees.  Then they might take flight in a single large and very noisy group that lands again after circling over the roost a few times.  After this the birds start slowly going their own way in small groups away from the roosting area.
If you happen to run into one of these roosting areas during a hike in the forest I would ask that you please don’t disturb the birds.  If the parrots are disturbed they will flee the area and abandon the roosting tree.  In the nineties the whole PR parrot population that used to live around the area of the old aviary high near El Yunque peak relocated to the east part of the forest near el Verde.   The suspicion of the project scientists is that the birds fled the area they formerly used because they were alarmed and disturbed when military exercises were staged on the forest.  I can’t blame them, I would have moved too.

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