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GLOBAL warming is singling out and harming species that are already endangered. A study of woodpeckers in the US has found that isolated, inbred populations adapt poorly to climate change, and other troubled animal populations may face a similar threat.

鈥淚t could be an additional nail in the coffin of a species that is already seriously challenged by other stresses,鈥� comments Juha Meril盲 of the University of Helsinki, an expert on the effects of climate change on birds.

It鈥檚 well known that warmer springs in temperate northern latitudes encourage birds to lay their eggs earlier than usual. A couple of years ago Meril盲 and his team found that individual collared flycatchers in Sweden, for instance, adapted their egg-laying habits to the changing climate over a 16-year period (Journal of Animal Ecology, vol 69, p 395).

Although these changes reflect adjustments by individuals rather than any evolutionary change in the populations, Karin Schiegg of the University of Zurich and her colleagues suspected inbred populations might react differently to those with a wider gene pool. To find out, they analysed nearly 20 years鈥� worth of data on red-cockaded woodpeckers in North Carolina.

They found that, on the whole, the birds had been laying their eggs increasingly early in the past two decades. But this was not true for three groups: inexperienced females laying eggs for the first time, experienced females with new mates, and inbred females. These birds brought their egg-laying forward less than the other birds, or not at all, and had fewer young on average than the other birds.

Schiegg thinks that the weakened immunity that tends to plague inbred birds somehow stops them adapting to climate change. This is supported by a study of tree swallows in Ithaca, New York, which found that birds with weaker immune systems laid eggs later than healthier birds (Behavioral Ecology, vol 12, p 93).

Could climate change hurt other endangered species as well, given that they tend to have small, isolated and inbred populations? Schiegg thinks so: 鈥淭he effect may not be apparent in egg-laying date or the start of the breeding season, but in other traits that are tied to climatic cues, such as migration and hibernation.鈥�

Both Schiegg and Meril盲 warn that studies into the long-term impacts of global warming are being threatened by a lack of funding. 鈥淭hey do not necessarily produce results early, but later they turn out to be goldmines,鈥� says Meril盲.