Oh frigate

I wrote recently about how fond I am of swifts and swallows and noted how the swifts spend most of their life on the wing, sleeping by switching down half their brain at a time. While on holiday (remember them?) in the Caribbean earlier in the year we heard about the remarkable frigatebird. With its wingspan of over 2 metres it has the largest wing area to body weight ratio of any bird and is found widely across tropical ocean areas.

It is known that that, while travelling huge distances across the water - flying for up to 2 months at heights up to 4000 metres - the frigatebird sleeps for 45 minutes a day in 10 second bursts. (No, I don't know how they did that research).

On land the birds sleep for one minute at a time throughout the day and night, effectively being asleep half the time. Like swifts the frigatebird performs unihemispheric sleep to keep watch while circling in rising air currents.

Frigate birds are well known for badgering smaller birds until they disgorge part digested food which the frigate bird catches in mid air. Just as well because, unusually for a marine bird, they don't come down on the sea: they snatch prey from the surface using their long hooked bills. They bathe by flying low over the ocean surface and splashing themselves but they don't swim and struggle to to take off from the water due to their short legs. They aren't great walkers either, so they sit around a lot.

Besides its heavily forked tail, a distinguishing feature of the male frigatebird is its red gular pouch, which is normally hardly visible:

but which it inflates in a preposterous courtship ritual, rather outdoing a robin:

There are five varieties of frigatebird: Ascension, Christmas, Great, Lesser and Magnificent. So when you hear reference to the magnificent frigatebird it's not a compliment, just its name.

Travel over huge distances has been frequently documented, particularly when they depart the colony where they were born. But they generally remain near the islands where they breed and prefer to stay close to land, usually within the range where they can find flying fish (no need to get wet to take them I suppose).  European sailors learned that local sailors in the tropics thought frigatebirds to be a good omen because their presence indicated land was close.

There are stories that frigatebirds could be relied on to return home and so were used in several island areas to relay messages like carrier pigeons. Polynesian poetry refers to taking pet birds on their sailing canoes as they could be relied upon to fly off in the direction of land, or return if land was not within easy flying range.

Frigatebirds are monogamous and the males and females collaborate in feeding their young for the first three months, after which the male's attendance trails off, leaving the mother to feed the chicks for another 5 or 6 months, amongst the longest duration of parental care for any birds. Which is probably why one of our tour guides on St Vincent this year referred disparagingly to her husband as being just like a "damned frigatebird". I suppose she meant that he sat around a lot half asleep, hung around for a while but then disappeared for months on end leaving her to bring up the kids.

Come to think of it Mrs H might feel I have some things in common with the frigatebird as well as the swift, though in my case I left her with the kids and went to play football. Where I would spend a lot of time shouting at my fellow defenders for being half asleep and to stay alert. Which I seem to have heard somewhere else lately....