Oilbird / Steatornis caripensis, Trinidad

Last night, I decided that I would try and start posting the occasional photo taken during a 10-day trip to Trinidad & Tobago with six birding.photographer friends. My scattered photos will at least be together in my three albums from this holiday. I have already posted photos taken on the hike down to the cave.

This outing was one of the highlights of the trip to Trinidad.& Tobago in March 2017. One that I wasn't sure I'd be able to manage, after reading endless accounts and descriptions of how difficult the trail was. In the end, I decided I would go, as I was sure we would see things on the way, even if I wasn't able to do the whole hike. As it turned out, the hike could have been a lot more difficult, so I was really glad that I went after all.

It was too challenging to get a decent shot of the Oilbirds in their cave. No camera flash is allowed, but the Guide allows two people at a time to join her, and she shines her flashlight very briefly on the birds. I keep forgetting how large these birds are.

Link below for a short video (just over 2 minutes) from WildExplorer (Toledo Zoo), taken at the Oilbird's cave. My friends and I did not go into the cave itself:

youtu.be/5Lm5YEsUreY

"The oilbird (Steatornis caripensis), locally known as the guácharo, is a bird species found in the northern areas of South America including the island of Trinidad. It is the only species in the genus Steatornis and the family Steatornithidae. Nesting in colonies in caves, oilbirds are nocturnal feeders on the fruits of the oil palm and tropical laurels. They are the only nocturnal flying fruit-eating birds in the world (the kakapo is flightless). They forage at night, with specially adapted eyesight. However they navigate by echolocation in the same way as bats, and are one of the few kinds of birds known to do so. They produce a high-pitched clicking sound of around 2 kHz that is audible to humans.

This is a large, slim bird at 40–49 cm (16–19 in), with a wing span of 95 cm (37 in). It has a flattened, powerfully hooked, bill surrounded by deep chestnut rictal bristles up to 5 centimetres (2.0 in) long. The adult weighs 350–475 g (12.3–16.8 oz) but the chicks can weigh considerably more, at up to 600 grams (21 oz), when their parents feed them a good deal of fruit before they fly. The feathers of the oilbird are soft like those of many nightbirds, but not as soft as those of owls or nightjars, as they do not need to be silent like predatory species. The oilbird is mainly reddish-brown with white spots on the nape and wings. Lower parts are cinnamon-buff with white diamond-shaped spots edged in black, these spots start small towards the throat and get larger towards the back. The stiff tail feathers are a rich brown spotted with white on either side.

The feet are small and almost useless, other than for clinging to vertical surfaces. The long wings have evolved to make it capable of hovering and twisting flight, which enables it to navigate through restricted areas of its caves. For example the wings have deep wingtip slotting, like New World vultures, to reduce the stalling speed, and the wings have a low aspect ratio and low wing-loading, all to make the oilbird capable of flying at low speeds.

The eyes of oilbirds are highly adapted to nocturnal foraging. The eyes are small, but the pupils are relatively large, allowing the highest light-gathering capacity of any bird (f-number of 1.07).[8] The retina is dominated by rod cells, 1,000,000 per rods mm2, the highest density of any vertebrate eye, which are organised in layers, an arrangement unique among birds but shared by deep-sea fish. They have low numbers of cone cells, and the whole arrangement would allow them to capture more light in low light conditions but probably have poor vision in daylight.

Although they have specially adapted vision to forage by sight, they are among the few birds known to supplement sight by echolocation in sufficiently poor light conditions, using a series of sharp audible clicks for this purpose. The only other birds known to do this are some species of swift." From Wikipedia.

en.wikipedia.org/wiki/Oilbird

Information about Oilbirds from Asa Wright Nature Centre:

asawright.org/about-oilbirds/