Signe Brinkløv, former Ph.D.-student at the Institute of Biology, SDU, now a postdoc at the University of Western Ontario, Canada, is currently in Trinidad accompanied by Assistant Professor John Ratcliffe, Institute of Biology, SDU to collect acoustic recordings of echolocating Oilbirds (Staetornis caripensis) and reports back with a brief account of the field trip this far.
After arriving in Trinidad, practising a little defensive driving and settling in at William Beebe Tropical Research Station, we drove to Asa Wright Nature Centre, excited about our first encounter with the resident Oilbird population of ~ 130 birds nesting in a narrow gorge on the estate. Oilbirds are nocturnal, fruit-eating birds with wingspans close to 1 m and along with the cave-dwelling swiftlets of South East Asia, they are the only bird species known to use echolocation by emitting audible clicks. They also have highly sensitive vision and olfactory senses and do not seem to depend entirely on echolocation unless they are flying in very dark surroundings, such as their nesting caves.
The Asa Wright colony is quite easily accessible, about 15 minutes walk from the main house, but visiting tourists are only allowed to visit the colony if they stay for more than 3 days at the facility and flash photography is strictly forbidden. However, because of the non-invasive nature of this study, using microphone array recordings to investigate the structure, function and limitation of oilbird clicks in a natural context, we have so far been able to record the birds on four nights. This should provide a solid baseline of data for the project, but noise from water running through the cave is overlapping with the bird clicks and we are now working on arrangements for an excursion to a different colony where we are hoping to obtain recordings not influenced by running water. In addition we are planning a second trip to Asa Wright later in 2012 with the object of collecting video footage with a thermal camera of the birds exiting the cave at night which might help us document whether oilbirds change the structure of their clicks depending on how many individuals are crowding the surrounding airspace.
The project is funded by a research grant from the Danish Council for Independent Research - Natural Sciences and carried out in collaboration with the Asa Wright Nature Centre.
02.02.2012
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