During the last breeding season of the Galapagos Islands' mangrove finch, the SOS project team identified at least 13 fledged nests out of which have emerged around 19 juveniles. This is a real boost for the population which is thought to number only around 100 individuals. The SOS-funded project aims to protect the Critically Endangered Mangrove Finch (Camarhynchus heliobates) by extending the bird's natural range and protecting its habitat, the mangrove forests.
During the first four months (November 2011 – February 2012) of the last breeding season, nesting success was low and no chicks were confirmed to have fledged. Nests were being abandoned and breeding adults would immediately re-nest nearby; some of them built five nests over five months. Reasons for nest failure included early nestling death by botfly parasitism and desertion due to flooding.
The breeding season of the mangrove finch started in November 2011 with the onset of the rainy season. At this time the males began to sing and establish territories, build nests and find mates. Mangrove finch project field staff (from Charles Darwin Foundation and Galapagos National Park) spent at least two weeks of every month throughout the field season camping at the field sites to conduct population monitoring and surveying for nests.
Trapping of adult Philornis downsi, an introduced parasitic botfly that causes high nestling mortality in Galapagos passerines, was trialed by placing traps throughout the mangrove forest. There is still no effective control method for the fly making it the biggest threat to nest success for the mangrove finch.
The project team followed all breeding pairs and observed their nests to determine fledging success. They set ropes in the nest trees to enable tree climbing so that the nests could be brought down once abandoned to be checked for presence of botfly larvae. Mist netting focused on catching un-ringed adults and new fledglings for marking.
"After so many months of nest failures, it’s great to have confirmed fledging success and to finally find the young birds moving through the forest,” said Francesca Cunningham, project leader.