Friday, August 19, 2011

Frigatebird or Pirate?

Magnificent Frigatebird
The large black bird soaring overhead, with pointed wings and narrow tail, is a Frigatebird. I've seen them in Florida, but never knew there are two different species, the Magnificent Frigatebird (Fregata magnificens) and the Great Frigatebird (Fregata minor), both of which live in the Galapagos.

Magnificent Frigatebird Male - purple sheen
The Galapagos Magnificent Frigatebird is an endemic subspecies we saw nesting on the islands of: North Seymour and Floreana. The Great Frigatebirds are harder to spot because they tend to fly away much farther out at sea, while the Magnificent tends to fly above the Islands and is thus easier to see. Their wingspan is around 7.5 feet and their deeply forked scissor-like tails afford them ultimate maneuverability, and their overall length is about a meter. It is hard to distinguish the males because they are alike except for the colors of the neck and wing feathers, which can only be seen when they aren't flying.
Magnificent Frigtebird Female
The females are much easier to distinguish. The female Magnificent Frigatebird has a dark throat and blue eyering. The female Great Frigatebird has a white throat and breast and red eye ring.

Magnificent Frigatebird Juvenile
The juveniles can also be easily told apart. The juvenile Magnificent Frigatebird's head is entirely white...

Great Frigatebird Juvenile
 ...while the Great Frigatebird chick has a rusty head. Easy, right?

In the northern hemisphere, birds breed in the spring, of course. So how can they tell when to breed at the equator, when there really are no seasons? The birds have this problem too, apparently, so you can't actually predict when to find them puffing up to impress a female. I didn't see any doing his song and dance during our trip. The male pumps air into a large bright red throat pouch until it's the size of a party balloon. When a hot babe flies by, he erupts into fits of rapturous head-shaking and vibrating, while uttering a shrill, high-pitched cry.

I borrowed a video from YouTube, and they sound like bagpipes on wings! How could you resist a stud like this?

The nest is a flimsy thing built in a low bush of guano and twigs. Only a single egg is laid, and it sometimes falls through to the ground. Incubation is 42 days (in the hot equatorial sun), but the chick relies on the adults for up to a year or more, even though it can fly about five to six months after hatching. Full sexual maturity is not reached for five year. The male will often leave during this period to mate with another female. She raises a chick once every two years, while he breeds once every year and a half.
So why do people think they are pirates? They are masters of aerial maneuvers, fast flight and in some cases kleptomania! Great Frigate birds steal from other frigates, as well as other species, like Blue-footed Boobies and Tropic birds, forcing them to disgorge their recent catch, which the Frigatebird then seizes in air. They also steal nesting materials as well. It doesn't matter how they feed, what counts is that they survive. This skill in flight allows then to pluck small fish from the very surface of the water, dipping only the bill into the sea or even preying on flying fish in their mid-flight.
Ethics aside, though, they are most wondrous flyers, aren't they?

1 comment:

Mary Howell Cromer said...

Wonderful, wonderful and yet, my favorite is the Great Frigatebird Juvenile, what gorgeous feather colourations!!!