Saturday, 1 May 2010
Pigeons of Bristol 8: The Socorro Dove
As recently as 40 years ago, Socorro Doves were still fairly common on Socorro Island, which is the largest of the Revillagigedo Islands a few hundred kilometres south of Baja California. Unfortunately, at about that time feral cats became established on the islands, and a large sheep population began to destroy the dense understorey that it required as a cover and food source. The last wild Socorro Dove was reported in 1972.
Many years earlier however, a small number had been taken to California and bred in aviaries. Some of these were passed on to private aviculturalists in both the US and in Europe, where they were bred. Unfortunately, the Socorro Dove hybridises freely with the common US Mourning Dove Zenaida macroura, and by the time a reintroduction project was planned the only pure Socorro Doves were in Europe.
In appearance, the Socorro dove is a more richly coloured version of the Mourning Dove. The main differences are behavioural – Socorro Doves are distinctly antisocial birds and were never seen in groups larger than a family party (adults + 1 or 2 chicks). Even this size group would rapidly disperse once the young were independent.
The ecology of the Socorro Dove was little studied. It is a terrestrial feeder, mainly on small fruits and seeds, and builds its nest within 2m of the ground in captivity. Socorro Island is an active volcano, rising to 1050 metres, and is mostly covered on the lower ground with Opuntia scrub. Higher elevations have more vegetation, especially Ficus cotinifolia and Prunus serotina.
There are no native mammals on Socorro, but at least 11 endemic bird taxa, of which the Socorro Elf Owl is extinct and the Socorro Parakeet, Socorro Wren, and Socorro Mocking bird are all classed as Endangered. There is also an endemic lizard, the Socorro Tree Lizard Urosaurus auriculatus, also endangered.
Efforts to restore Socorro Island and reintroduce Socorro Doves to their ancestral home have been hampered by political concerns and bureaucracy. However, an action plan has now been drawn up and is slowly getting underway. The plan is as follows:
1) establish a captive flock on Socorro using European birds
2) Eliminate cats and rats (underway)
3) Reduce sheep numbers (done)
4) Restore understorey
5) Finally, reintroduce captive bred birds to the island
Holding aviaries are being constructed on Socorro, and as a first step, European birds have been sent to the Albuquerque Biological Park in New Mexico, where they have begun breeding. These birds will eventually be returned to Socorro.
For more on Socorro Doves, some useful websites can be found here:
Birdlife International http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=2555&m
American Bird Conservancy: http://www.abcbirds.org/newsandreports/releases/081120.html
Image from Wikipedia