Posted by: Rob Viens | March 29, 2012

Abrolhos Islands I: Island Rookeries

March 29th – New Islands to explore – for Darwin and for me.  Today the Beagle visited the Abrolhos Islands. Darwin describes them:

“The Abrolhos consisted of 5 small rocky islands, which although uninhabited are not unfrequently visited by fishermen.” (Mar 29)

The name of he islands is believed to come from the Portuguese abro olhos (“open eyes”), as in “watch out”.  This is clearly a reference to the dangerous, shallow shoals that surround the islands – the same ones that had FitzRoy worried about yesterday.

As Darwin noted, there are 5 islands in the small archipelago – Santa Bárbara, Siriba, Redonda, Guarita and Sueste.  Only Siriba receives visitors, and Brazilian law forbids visiting the last 2 islands (Santa Bárbara belongs to the navy). The majority of the archipelago was declared a Marine National Park in 1983, in order to protect the sea bird rookeries and extensive coral reefs around the islands.

Abrolhos Islands (from João Ramos/Bahiatursa via About.com)

Abrolhos Islands

Alas, no such protection was afforded the islands in 1832, when sailors (including those on the Beagle), saw them as the local butcher shop:

“Two parties landed directly after breakfast. I commenced an attack on the rocky & insects & plants. —the rest began a more bloody one on the birds. — Of these an enormous number were slaughtered by sticks, stones & guns; indeed there were more killed than the boats could hold.” (Mar 29)

FitzRoy adds:

“When our boats landed, immense flights of birds rose simultaneously, and darkened the air. It was the breeding and moulting season; nests full of eggs, or young unfledged birds, absolutely covered the ground, and in a very short time our boats were laden with their contents.”

I understand the general need to gather food for a ship full of hungry sailors. However, it is the shear glee with which the men take on this task that I find disturbing. I was talking to colleague about this recently, and when he heard that the average age of the crew was in the low 20’s he said, “Well that explains it. And I bet if they were all ten years younger they’d have all taken out their magnifying lenses to burn any insects they found, too”.

What bird species raise their young in the Abrolhos Islands?  Ironically – since they “collected” so many samples – Darwin gives only a brief mention the bird species on the islands:

“Birds of the family of Totipalmes are exceedingly abundant, such as Sulas Gannets, Tropic birds & Frigates.” (Zoological Notebooks)

In addition, modern sources also include masked boobies (Sula dactylatra), brown boobies (Sula leucogaster), and red-billed tropicbirds (Phaethon aethereus).

A few comments on these birds:

(1) Totipalmes seems to be a name that is no longer used today and appears to have been replace with the term Pelecaniforms.  All of the birds mentioned in the Abrolhos belong to the avian order Pelecaniforms (as do Pelicans, not surprisingly).  (I should note though that there seems to be some controversy about this particular order, and that some of these birds may not be as closely related as there appearance suggests.)

(2) It is unlikely Darwin saw gannets, as their range does not appear to cover the southwestern Atlantic Ocean. Was this a rare Darwin mistake? Sort of, but to be fair he was probably comparing unknown birds to those he was more familiar with in the North Atlantic.

(3) Strangely Darwin crossed out “Sulas”, which are the boobies, yet modern sources suggest they do nest on the islands.  Boobies were also common on St. Paul’s Rocks – were, alas, more gleeful bird-bashing occurred (for more on those birds see St. Paul’ s Rocks I).

Masked Booby and Magnificent Frigatebird (from Wikipedia Commons)

Masked BoobyFrigatebird

(4) The Red-billed tropicbirds and frigatebirds are both beautiful species of pelagic sea birds that are also common around the world.

Red-billed Tropicbird (from Dr. Robert Rothman’s Sea Bird pages)

Red-Billed Tropicbird

Fortunately, all of these bird species do not seem to be threatened today (despite their “tastiness”).  I suspect this is because they have such a wide range that even if a population on a single island was whipped out there would be many more of them to carry on.

Last comment today – Darwin also briefly described the vegetation of the islands:

“The Abrolhos Islands seen from a short distance are of a bright green colour.— The vegetation consists of succulent plants & Gramina, interspersed with a few bushes & Cactuses.— Small as my collection of plants is from the Abrolhos I think it contains nearly every species then flowering” (Zoological Notebooks)

A strange comment, as no plant specimens from the Abrolhos seems to have made it back to England.  Hmmm… maybe they were used to season the bird stew that night.

More on the corals and rocks of the Abrolhos Islands tomorrow. (RJV)

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