It’s officially spring here (autumn I guess for any Southern Hemisphere Readers) and as March comes to a close, the beginning of the field surveying season Last week we snapped, crackled and buzzed electric with the uh Electric Eel. This time we keep the echolocation from last weeks issue, and place it on a pair of wings. Hope you guys enjoy.
Issue #113 – Oilbird
Kingdom – Animalia
Phylum – Chordata
Class – Aves
[Clade]* – Steatornithes
Family – Steatornithidae
Genus – Steatornis
Species – caripensis
*There is some debate over whether the Oilbird is one of the nightjars: Caprimulgiformes, or if it is genetically unique enough to form its own order the Steatornithes
Related Species – At current the Oilbird is the only member of the much debated Steatornithes Order. (1)
The Bird that thinks it’s a Bat
Oilbirds are medium sized mottle brown birds, with a body length of 40cm, and a wingspan of just under a meter. The wings are curved, very much like that of a swift or a nightjar, and are used in conjunction with the short tail to perform a slow but continuous flight, allowing for a short turning radius, useful when flying through crowded forests. The legs, like those of the nightjars, are small and are limited in use outside grasping onto roosts and nesting ledges. Mostly active after dark, Oilbirds navigate using their large light sensitive eyes, echolocation and most unusually a well-developed sense of smell (2).
This sense of smell comes in handy for finding the fruit that the birds feed on. The birds pluck the fruit, whilst hovering, from the trees using their hooked beaks, swallowing them whole and storing their meal in their stomachs, due to the Oilbird lacking the crop found in the oesophagus of many other bird species. While Oilbirds are not actively predated on, when they are disturbed from their roosts the birds utter a haunting cry said to sound like a man being tortured.
Oilbirds roost and breed in caves, with the female and male birds building a nest formed of excrement, fruit pulp and seeds held together by spittle, with a pair of oilbirds using the same nest for many years until it is too damaged to hold the weight of their chicks. Once laid the eggs (usually one to three) take a month to hatch, with the chicks being covered in grey down upon birth. Like their parents the chicks feed entirely on fruit, and eat up to one quarter of their body weight every night, with chicks soon weighing more than their parents (320g for an adult female compared to 600g for a 70 day old chick), but eventually loose the excess weight the closer they get to fledging at an age of around 115 days (3).
Five Fun Oilbird Facts
The name Oilbird, comes from the cooking of captured chicks to release the stored excess fat in their bodies. This fat was clear, and burnt clean making it an excellent source of lamp oil. (4) Fortunately, while widespread, the Oilbird population was never depleted, and the species is fairly common throughout most its range.
Due to their unusual screams, Oilbirds have earned the local name ‘diablotin’ or ‘little devil’ in Trinidad
The Oilbird is one of only two groups of birds to use echolocation, the other being the Cave Swiftlets (Colloclia sp) from South East Asia
That said the echolocation of an Oilbird is very crude compared to that of a bat, with the birds calling at 2KHz, a frequency that’s audible to human ears.
The Oilbird is one of just two nocturnal fruit eating birds, the other being the flightless Kakapo (Strigops habroptilus)
2 - Brinkløv S, Fenton MB, Ratcliffe JM. Echolocation in Oilbirds and swiftlets. Frontiers in Physiology. 2013;4:123. doi:10.3389/fphys.2013.00123.
3 – http://www.lynxeds.com/family-text/hbw-4-family-text-steatornithidae-oldbird
4 – BirdLife International (2012). "Steatornis caripensis". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature.
1 - http://01271bfede0954168758-da1041207dde8e2d0a75af6fbedebedf.r83.cf1.rackcdn.com/20070418034636.jpg
2 - http://www.birdphotos.com/infonaturamaps/steatornis_caripensis.gif
3 - http://ibc.lynxeds.com/files/pictures/Nid_du_Guacharo_des_cavernes_-_copie.JPG
4 - http://cdn.zmescience.com/wp-content/uploads/2014/04/oilbird.jpg
Ah so not so simple is seems, next week we have a stinker of an issue (literally) followed by a ghoulish request from @cbishop. Well we’ll see next week, but until then critic, comment and suggest future issues as well as making sure you check past issues in Impurest’s Bestiary.