Frigatebirds (genus Fregata)

This past week I group of friends and I went down to Chicago, and while we were there we visited the Field Museum. It was quite the wonderful museum but the highlight of the day for me was the giant gallery full of stuffed dead animals. This might sound a little  creepy, but it was actually really cool. The only part that disturbed us a bit was the number of exhibits that also had baby animals in them. They had to get those babies from somewhere, after all.

Anyhow, the entire time we were looking at the animal section I had a friend write down notable species, so I could blog about them later. Most of them are birds, as there was quite and extensive bird gallery at the Field Museum. The birds I’m writing about today were the very first to make it on my list.

Frigatebirds are a genus of birds that contains five extant species. They are found in tropical areas above oceans, where they can take advantage of warm updrafts coming off the water. They breed on remote ocean islands, but spend most of their time in the air.

A magnificent frigatebird flying around. Notice the very pointy wing shape - ideal for gliding.  Image source: Wikipedia

A magnificent frigatebird flying around. Notice the very pointy wing shape – ideal for gliding.
Image source: Wikipedia

Frigatebirds range in size from 114 cm (the magnificent frigatebird) to a paltry 71 cm (the lesser frigatebird). Unusually for birds, female frigatebirds are larger than males, sometimes weighing up to 25 percent more than males. All species of frigatebird have largely black plumage, though females tend to have more white markings than males.

The entire body of frigatebirds is designed for extended flight. Their skeletons are ultra-light, and actually weigh less than the birds’ feathers. Their long, pointy wings give frigatebirds the largest wingspan to body-weight ratio of any bird. This allows frigatebirds to soar for long periods of time without expending energy. The birds use their forked tail to steer while in the air, and only rarely have to actually flap their wings. Frigatebirds are so energy efficient that they can stay in the  air for up to twelve days before landing.

By ‘landing’ I mean roosting on a tree or cliff; frigatebirds, while being experts in the air, are quite useless on land and absolutely terrible in the water. So how does a bird that can’t swim feed on seafood? Simple: they feed on flying fish. If that doesn’t work, frigatebirds will harry other seabirds that are returning to land until they drop the catches they have made.

Frigatebirds can breed at any time of year, though breeding usually occurs when there is lots of available food. Males display to attract a mate, gathering in large groups and inflating bright red pouches on their necks. While the female frigate fly around overhead, the males spread their wings and vibrate their pouches, creating a drumming sound that is apparently attractive to the female.

A great frigatebird displaying his massive throat pouch.  Image credit: Jason Corriveau via Wikipedia

A great frigatebird displaying his massive throat pouch.
Image credit: Jason Corriveau via Wikipedia

After a pair is formed, nest building commences, with the male bird gathering sticks and the female actually constructing the nest. A single eggs is laid, that hatches after 41-55 days. At this point the parents take turns feeding the chick, never leaving their baby unguarded. Once the chick is a month old, it is left alone for extended periods of time, though both parents still feed it. In a few months the male gets bored of the chick, and leaves the female to raise the bird on her own — for another six to nine months! This extended period of parental care is one of the longest in all birds.

Two of the five species of frigatebirds are endangered, the Christmas Island frigatebird and the Ascension frigatebird. The former was threatened by use of Christmas Island during WWII and dust pollution, while the latter was eradicated from their breeding colony of Ascension Island by feral cats. The species survived by moving to breed on a nearby rocky outcropping, and have since started to move back to the main island after a conservation program wiped out the feral cats. It’s always nice to hear about successful conservation measures, even if it does mean a lot of cats had to be killed.

Cover image credit: Wikipedia

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