North Seymour Frigates

Beez Neez
Skipper and First Mate Millard (Big Bear and Pepe)
Fri 3 May 2013 22:07

North Seymour Island





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Low profile with Baltra (South Seymour) opposite


North Seymour Island: was named after the English nobleman, Lord Hugh Seymour (own blog). Just point seven square miles with a maximum altitude of ninety two feet, this tiny island is home to the largest population of blue-footed boobies, also swallow-tailed gulls, tropicbirds and both great and magnificent frigate birds nest here. Pecalins and the soundo masses as expected and a number of land iguanas. The island was created by seismic uplift rather than being of volcanic origin, flat topped with cliffs only a few yards from the shoreline is perfect for the swallow-tail gulls and tropicbirds who sit perched on the ledges.



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A tiny forest of silver-grey Palo Santo Trees stand just above the landing, usually without leaves, waiting for rain to bring them into bloom. From the track away in the greyness we see the bright flash of a posing chap and a white fluffy chick.



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We passed a resting iguana, a pair of swallow-tails sleeping until their night duty begins and a rather lovely cactus.


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Above us boys coming in.


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Primarily here to see the blue-foots, who didn’t disappoint. The frigates were an added bonus.




The Magnificent Frigatebird (Fregata magnificens), Man of War or Pirate of the Sea - reflecting their rakish lines, speed and aerial piracy of other birds. Widespread in the tropical Atlantic, breeding colonially in trees in Florida, the Caribbean (we visited the largest colony in the world on Barbuda) and the Cape Verde Islands, also breeding along the Pacific coast of the Americas from Mexico to Ecuador including the Galápagos Islands. It has occurred as a vagrant as far from its normal range as the Isle of Man, Denmark, Spain, England and British Columbia.

The Magnificent Frigatebird is thirty nine inches long with an eighty five inch wingspan. Males are all-black with a scarlet throat pouch or gular sac that is inflated like a balloon in the breeding season. The first ever inflation may take an hour but generally the experienced can achieve the massive in twenty to twenty five minutes, emptying can happen in a few minutes but after the breeding season it can take quite a while to be hidden completely by the throat feathers. Although the feathers are black, the scapular feathers produce a purple iridescence (the picture above, I took in December 2009) when they reflect sunlight (in contrast the male Great Frigatebird has a green sheen). Females are black, but have a white breast and lower neck sides, a brown band on the wings, and a blue eye-ring that is diagnostic of the female of the species. Immature birds have a white head and underparts.


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Magnificent frigatebirds perch in low bushes, near the boobies, while watching over their large chicks. These birds look huge and the ninety inch wingspan cannot in any way be called modest. Boobies and frigates have an interesting relationship. Boobies are excellent hunters and fish in flocks, the frigates being pirates, dive bomb the boobies to force them to drop their prey.


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The Great Frigatebird is not quite as big as the Magnificent Frigatebird. The Great Frigatebird measures thirty one to thirty three inches in length with long pointed wings of eighty to ninety inches and long forked tails. Weighing in at one and a half to three and a half pounds, these birds have the highest ratio of wing area to body mass, and the lowest wing loading of any bird. This has been hypothesized to enable the birds to utilize marine thermals created by small differences between tropical air and water temperatures. Male Great Frigatebirds are smaller than females, but the extent of the variation varies geographically. Juveniles are black with a rust-tinged white face, head and throat. The green hue of these boys is rather splendid.



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The female great has a pink eye ring.



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Pair bond formation and nest-building can be completed in a couple of days by some pairs and can take up to four weeks for other pairs. Males collect loose nesting material (twigs, vines and flotsam) from around the colony and off the ocean surface and return to the nesting site where the female builds the nest. Nesting material may be stolen from other seabird species (in the case of black noddies the entire nest may be stolen) either snatched off the nesting site or stolen from other birds themselves foraging for nesting material. The nests are large platforms of loosely woven twigs that quickly become encrusted with guano. There is little attempt to maintain the nests during the breeding season and nests may disintegrate before the end of the season, some eggs are lost when they simply roll off the nest. A single dull chalky-white egg is laid during each breeding season. If the egg is lost the pair bond breaks; females may acquire a new mate and lay again in that year. Both parents incubate the egg in shifts that last between three and six days; the length of shift varies by location, although female shifts are longer than those of males. Incubation can be energetically demanding, birds have been recorded losing up to a third of their body mass during a shift.



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Incubation lasts for around fifty five days. The chicks begin calling a few days before hatching and rub their egg tooth against the shell. The hungry chicks are naked, helpless and lie prone for several days after hatching. Chicks are brooded for two weeks after hatching after which they are covered in white down, and guarded by a parent for another fortnight after that. Chicks are given numerous meals a day after hatching, once older they are fed every one to two days. Feeding is by regurgitation, the chick sticks its head inside the adults mouth.



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Mum landing by her hungry offspring.


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Others settled.


Parental care is prolonged in Great Frigatebirds. Fledging occurs after four to six months, the timing dependent on oceanic conditions and food availability. After fledging chicks continue to receive parental care for between a hundred and fifty to four hundred and twenty eight days; frigatebirds have the longest period of post-fledging parental care of any bird.



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The length of this care depends on oceanic conditions, El Nino years are longer. The diet of these juvenile birds is provided in part by food they obtained for themselves and in part from their parents. Youngsters will also engage in play; with one bird picking up a stick and being chased by one or more other fledglings. After the chick drops the stick the chaser attempts to catch the stick before it hits the water, after which the game starts again. This play is thought to be important in developing the aerial skills needed to fish.



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