Birdwatch News Archive
Tuamotu Sandpiper photographed on Morane, French Polynesia. Photo: Thomas Ghestemme (BirdLife International).
Tree-nesting nectar-eating sandpiper
Posted on: 02 Aug 2012
Studies of a unique endangered tropical sandpiper have revealed astonishing adaptations to its south sea island home.
Most of the world’s sandpiper species migrate thousands of miles between their arctic breeding grounds and subtropical wintering grounds, but in the not-too distant evolutionary past one group gave up this habit and 'went native' in French Polynesia.
The Endangered Tuamotu Sandpiper, known locally as Titi, is the only surviving representative of a group of at least six species which became full time residents in the region. The other species were extirpated with the arrival of first Polynesians, and after that Europeans, and their small mammal associates. Approximately 1,000 Titi remain, limited to four rat-free or partially rat-free atolls.
In 2008, Marie-Helene Burle, from Simon Fraser University, aided by the Ornithological Society of French Polynesia (BirdLife in French Polynesia), began an intensive graduate research project on this previously unstudied species, working largely in isolation on uninhabited atolls. Her first five-month field season as followed by a second in 2010, and she currently halfway through a lengthy third, which began as she joined an organized expedition to visit two of the additional three atolls where Titi remain.
Marie and her collaborators have discovered remarkable adaptations of this bird to its tropical lifestyle. In sharp contrast to similar-sized migrant shorebirds such as Wandering Tattler, which share the same atolls when not breeding, the Titi is not a bird of the beach or rocky intertidal areas, favouring instead semi-open vegetated areas.
“One reason for this is their reliance on feeding on nectar from flowers, a unique food source for a member of this group”, said Burle. “Functional morphologists have shown that the bird’s tongue is forked, which may allow it to obtain nectar more efficiently”.
Marie captured and marked nearly all of the birds on two atolls and documented their social system. Breeding birds live in pairs on quite small territories of about 120 m2. Marie’s work has sparked others to make observations of the species, and Francis Gazeau discovered that Titi sometimes nest in trees as well as on the ground, in contrast to their arctic-breeding relatives. Females lay two eggs per clutch rather than the average of four laid by Arctic-breeding sandpipers, and many eggs disappear, at least some taken by coconut crabs, as caught on video.
Marie took the first photographs ever taken of newly hatched chicks, which had never previously been described. Sadly, the chicks have extremely low survival and most starve to death. “We speculate that overcrowding in the very few areas where the birds can breed has lead to food shortages and low fledging success,” said Marie.
Towards the very dry conditions at the end of Marie’s second field season, a wind-driven swell event caused salt water to overwash parts of her atolls. About a month later, she realized that many of her birds were dying, as were other landbirds such as Spotted Crake. She believes that saltwater intrusion and a lack of rain stressed the local vegetation, resulting in starvation in species closely adapted to native plants. About half the birds at her main study site died, and a year later there has been no population rebound. The high mortality associated with this event highlights the species' vulnerability, which would also be threatened should Black Rat establish itself on their four remaining refuges.
Marie also helped to eradicate rodents from a small islet within an atoll which recently held rats. “We are waiting to learn whether Titi are now breeding on this rat-free site,” said Marie. “For the longer term, however, the species’ future relies on reintroducing it to more distant sites where independent populations can thrive”.
Marie and colleagues are preparing a survey of potential reintroduction sites. Their experience working with the birds and the knowledge they have obtained about their feeding and breeding ecology and predators provide a sound basis for translocation planning. Building on the success of groups that have removed rats from several islands or atolls it is hoped that, for this one species at least, meaningful conservation measures can be taken at modest additional cost, to substantially decrease the likelihood of its extinction.
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