Genetic Consequences of Intensive Conservation Management for the Mauritius Parakeet

Genetic consequences of intensive conservation management for the Mauritius parakeet

Claire Raisin,

Supplementary material

Management program history:

The intensity of management of the Mauritius parakeet has varied considerably throughout the conservation program and a number of management techniques to increase productivity have been employed. The technique of ‘double clutching’ was frequently employed when birds started breeding early in the season, whereby the first clutch of eggs was removed from the nest to encourage the pair to lay more eggs. Clutches of multiple fertile eggs were ‘down-sized’ by removing one or more of the eggs (leaving the pair with at least one egg) and transferring the remainder to other wild pair(s) that had produced infertile eggs or removing them to the captive-breeding population. Once hatched, the growth rate of wild chicks was closely monitored and if nestlings were deemed to be developing at an unsatisfactory rate they were rescued to the captive breeding centre. Jones (1993; 1998) provides a detailed account of the methods employed to maximise productivity of breeding pairs amongst the Mauritius parakeet population. However, here we summarise the history of the species’ conservation management program and in doing so set out important background information which subsequently allows us to evaluate the genetic impacts of that management.

Monitoring of the Mauritius parakeet population began in 1973 and the management program was intensified in 1987. Between the years 1990 and 1992 the remaining forest in the Black River Gorges was intensively surveyed for evidence of previously unknown breeding groups. A number of Mauritius parakeet eggs were removed from wild nests and either hand-reared or fostered under rose-ringed parakeets at the Gerald Durrell Endemic Wildlife Sanctuary (GDEWS) in Black River on Mauritius. By 1994 two chicks had been produced by captive birds, however breeding success in the wild population remained limited (for example, no breeding activity was recorded between 1992 and 1994). Between 1994 and 1996 a number of wild clutches of eggs were removed to captivity and successfully fostered under captive rose-ringed parakeets. During these two breeding seasons, four chicks had been recorded to have fledged in the wild and 11 fledged in captivity. One egg had been successfully transferred between wild sites within the Camp region and in the 1995-96 breeding season the first nest site in the southern-most BelOmbre region of the species’ range was discovered.

By the 1996-97 breeding season, seven more wild breeding pairs (or groups – some pairs had additional attendant males) had been discovered and of the 34 wild eggs known to have been laid since the monitoring began 29 of them were brought into captivity. As a result of this harvesting, two breeding pairs produced a second clutch of eggs in the same season. Limited transfers of eggs or nestlings between neighbouring sites were attempted in the wild but the majority of birds were brought into captivity where they were generally fostered under rose-ringed parakeet (Psittaculakrameri) pairs and as such became imprinted on them so were deemed unsuitable for future release.

The first trial releases of captive reared Mauritius parakeets took place in 1997 and by 1999 22 birds had been released into the Camp area of the Black River Gorges. The extensive harvesting and fostering activities, combined with releases of Mauritius parakeets into parts of their former range signalled the onset of the most intensive management period. In 2001 seven birds were released at Camp and a trial release of four birds was performed in Combo. The following season (2001-02) 21 birds were released at Camp, six wild chicks were fostered between sites across the regions and one captive bred chick was fostered to a wild pair. In the 2002-03 season eight chicks were fostered to wild pairs of which seven ended up in geographically different regions from their source. The number of wild birds translocated between 2000 and 2005 and the direction of their translocation are summarised in Table 1.

In the 2004-05 season 34 chicks were transferred between sites, of which 23 were taken to GDEWS to be released at Combo and other suitable release sites. The priority of the conservation program at this time was to increase productivity of wild breeding pairs as rapidly as possible and to boost population size. Consequently, the distribution of genetic diversity across the population was not considered a priority when implementing these management measures and even captive breeding decisions were primarily based on likelihood of successful breeding rather than genetic representation

Structure:

Structure analysis of the entire Mauritius parakeet dataset (including all samples collected between the beginning of the conservation program up to 2008) revealed no evidence of population genetic structure.

Plots of the log likelihood for each of the 10 STRUCTURE runs at each value of K for the pre-intensive management Mauritius parakeet showed a clear asymptote at K=4.

Plots of the log likelihood for each of the 10 STRUCTURE runs at each value of K for the post-intensive management Mauritius parakeet showed a clear asymptote at K=3.

The Evanno calculation of ΔK showed a peak at K=2 suggesting that this is the ‘true’ number of clusters.

Private alleles

Mean number of alleles per locus (open bars) and mean number of private alleles per locus (shaded bars) with standard error, in the southern BelOmbre (BO) and northern Black River Gorges (BRG) populations of the Mauritius parakeet before and after intensive management.