Eight captive-reared Mangrove Finches prepared for return to the wild
By James Hudson
On Friday April 17th, the Mangrove Finch project team transported eight captive reared mangrove finches back to Isabela Island to begin the careful process of preparing the birds for their release back home. On the day of transportation, the youngest fledgling was 35 days old and the oldest 71 days.
This is the second year running of a successful species recovery program to boost mangrove finch population numbers, led by the Charles Darwin Foundation and Galapagos National Park Directorate, in collaboration with San Diego Zoo Global and Durrell Wildlife Conservation Trust.
During February 2015, eggs and one wild hatchling were collected at Playa Tortuga Negra, Isabela Island. Eight fledglings were captive reared at the Charles Darwin Research Station’s (CDRS) rearing facility on Santa Cruz Island. The fledglings (a fledgling is defined as a bird that has recently left the nest) were reared and cared for around the clock by a team led by San Diego Zoo Global and expert staff and volunteers from the Charles Darwin Foundation and Durrell Wildlife Conservation Fund.
Eight fledglings can still be considered a success and a significant boost to the species’ tiny population size. The mangrove finch is found in just two small mangrove forests on Isabela Island and the species has an estimated population size of 80 – 100 individuals. Philornis downsi, the bloodsucking parasitic fly, is a principal cause of chick mortality. Data shows that eggs laid and chicks hatched during the first months of the breeding season would have less than 5% chance of survival because of the threats of Philornis downsi. In normal conditions, it is highly unlikely that any of the eight birds would have survived if left in the wild and few if any of the 30 eggs collected would have survived as nestlings.
During the days and weeks caring for the chicks in captivity at the CDRS, the project team developed techniques to encourage the fledglings to develop the skills needed for survival in the wild. The team made cardboard cut outs in which food items were hidden and the birds then hunted for. Recordings of mangrove finch calls were also played back to the fledglings.
On Friday, the mangrove finch fledglings were transferred to a boat in mosquito proof travel boxes and pre-fitted with individual colored leg rings for identification. The team traveled mostly by night so that the birds could sleep and require minimal feeding.
Upon arrival at Playa Tortuga Negra the eight fledglings will be placed in small cages suspended inside the pre-release aviaries. The birds will be released into purpose built aviaries and held for 3 - 4 weeks to adapt to life in the wild. During this time aviaries will be filled with fallen trunks, bark, fresh leaves and branches and leaf litter. Natural food of mangrove finches like live locally caught insects will be released into the enclosures to encourage natural foraging.
Eventually the aviaries will open and the birds free to leave. Aviary hatches will be left open and supplementary food provided should they return. Tiny transmitters weighing 0.3g will be attached to the tails of the fledglings prior so the field team can monitor their initial distribution and survival for up to 22 days.
Playa Tortuga Negra will also be the home of the Mangrove Finch Project team for the next seven weeks. Now totally off the radar, we wish the team the best of luck and we will provide further updates when they return.
The Mangrove Finch Project is a bi-institutional project carried out by the Charles Darwin Foundation and Galapagos National Park Directorate in collaboration with San Diego Zoo Global and Durrell Wildlife Conservation Trust. The project is supported by Galapagos Conservation Trust, The Mohamed bin Zayed Species Conservation Fund, Durrell Wildlife Conservation Trust, International Community Foundation (with a grant awarded by The Leona M. and Harry B. Helmsley Charitable Trust), Galapagos Conservancy, and The British Embassy in Ecuador.