Archive for June, 2012

In the wake of spring migration, sooty, noddy chicks fledging; raptors lurking around Park

Thursday, June 7th, 2012

After crossing into the Park boundaries, it becomes quite apparent that more and more sooty tern chicks are fledging every day. Now the skies are filled not only with the black-on-top, white-underneath adults, but also with the chicks, which are distinguished by a black back spotted with white, and a dark belly with the white just beginning to show through. The masses of dark chicks can be seen loafing on the shores of Bush Key.

Mixed flock of adult and juvenile sooty terns.

No wonder why the island is closed!

The brown noddy chicks are doing well, although they are not nearly as numerous as the sooty chicks. The young noddy chicks can be distinguished from the adults by the incomplete white cap on their crowns; their white is only just starting to emerge, whereas the adults have the full white feather cap.

Brown noddies loafing in the buttonwoods on Garden Key.

Angry brown noddy on the south helipad.

The two black noddies that were present on Bush Key and out at the east boundaries have not been spotted in the last week, but had been sighted regularly within the last six weeks.

Luckily for our Tortugas birders, the brown booby population at the Park has been quite visible most days on Iowa Rock (green channel marker No. 3 on the port side of the vessel en route to the dock). There are sometimes as many as a dozen birds on the marker, and individual birds make frequent flights past Garden Key.

The masked booby colony is still hanging out on Hospital Key, and on flat calm days, it is likely that you may see several sitting in the water on the south side of the island, closer to the vessel en route to the dock, or even the occasional fly by the Fort. Make sure to have your binoculars and spotting scopes at the ready, however, because the pass by Hospital Key is a brief one, and to keep from disturbing the birds, the Yankee stays a safe distance from the colony.

Up-beat of the juvenile masked booby to show the white belly.

Masked booby fly-by of Garden Key.

Several exciting birds have been spotted lately above the deep waters on the way out to the Park, including the bridled terns and Audubon’s shearwaters.  The shearwaters I’ve seen have been in flocks numbering anywhere from ten to fifty, and, as the name implies, they fly very close to the surface of the water. They have a stubby black bill, with dark feathers above, and white below.

There have also been regular sightings of bridled terns on the way to the Park (not many from Bush Key), and I’ve even managed tocapture a few grainy photos of them. When compared to their cousins the sooty terns, the bridled terns have a much grayer feather coat above, paired with a distinctive white collar around the back of the neck, separating the gray head from gray back (the sooty terns lack this white collar).

Close-up of one bridled tern on the way out to the Park. Notice the lighter coloring than that of the sooty, as well as the white neck collar.

Finally, the big birding news for the year at the Dry Tortugas: last week, a juvenile bald eagle was spotted in the Park, flying between Loggerhead Key, Long Key, and Garden Key. This is quite an important bird, because it marks the first recorded bald eagle sighting in Dry Tortugas history! I saw the young bird on Saturday (perched on the Fort Jefferson communications tower), Sunday (flying directly above the parade ground), and Monday (perched in a dead snag on Long Key).  Who knows how long the visitor will stick around, but there is certainly no shortage of fish, rats, and injured tern chicks out there for it to dine on.  The eagle’s presence has been quite disturbing to the tern colonies, for every time the bird takes flight near Bush Key, the terns flush, and thousands of adult and juvenile sooty terns and brown noddies take to the skies, sometimes for as long as half an hour.

A small group of turkey vultures has taken up temporary residence in a dead tree on Bush Key as well, much to the chagrin of the tern colonies. No doubt the numerous chick casualties over the last month has kept them around for a bit.

The turkey vulture posse loafing on Garden Key, working up the tern colonies.

Seen regularly along the Garden Key shores lately is a first year little blue heron, in the middle of its molt from white juvenile plumage to blue adult plumage.

Close-up of the juvenile little blue heron, almost molted out of its white first-year plumage.

A snowy egret (“yellow slippers”) and great blue heron have also been loafing along the beaches.

Snowy egret working the east shore of Garden Key.

A single black-necked stilt was seen last week on the north side of Bush Key, working the beach rack; I believe this is the third stilt sighting of the year (the first two during spring migration).

The lone black-necked stilt hunting on Bush Key.

Another excellent sighting in early May was a lone roseate spoonbill that stopped over in the parade ground for an hour or so to rest; this was shortly after several inches of rainfall, and the parade ground was still saturated with rainwater.

The only regulars left in the parade ground in the wake of spring migration are some weak, thin cattle egrets, one or two yellow-billed cuckoos (late migrants), and a peregrine falcon keeping watch over the whole Fort from the communication tower.  This big beautiful bird, presumably a female due to its large size (female raptors are always larger), has been taking out sooty terns for the last week or two, as I’ve discovered a couple of sooty skeletons picked clean of all the meat. The peregrine is definitely the top predator for the terns at the moment.

One of the very shy yellow-billed cuckoos roosting in the parade ground buttonwoods.

The large female peregrine, every watchful, that's been snacking on sooty terns.

If any birders will be making their way to the Park in the next few days, I hope to see you there and hope that you get a chance to see the young eagle as well. Happy birding!

–Chelsea

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