Genetic diversity and the implications of captive rearing for a small population of Black-tailed Godwits

Black-tailed Godwit Limosa limosa limosa clutches have been collected for headstarting, a captive rearing intervention where eggs are taken from the wild and artificially incubated, and chicks are reared in captivity to fledging, before being released into the wild. This conservation measure has reduced local extinction risk for the UK population, but it may have impacts on genetic diversity and population viability, especially when wild-sourced eggs must be collected from a small population. Comparing the UK population of 42 pairs with the much larger breeding population in the Netherlands (~30 000 pairs), we found that levels of heterozygosity and inbreeding are not currently compromised, and allelic richness in the UK population was not significantly different from the Dutch population, but relatedness estimates suggest that 6.1% of the individuals in the UK are closely related, at the level of half-sibling and up, compared with 1.9% in the Dutch population. Increasing levels of relatedness could further deplete genetic variation, in the absence of immigration or the introduction of wild-sourced eggs from other populations.