Birds in Spain and Morocco are having trouble hearing and copying each other's songs because of the way their habitat has been broken up, according to a study published yesterday.
As a result the birds are living in more isolated groups and only learning songs from their closest neighbors. The researchers believe that these changes in song patterns are an early warning of habitat fragmentation, which could lead to lower genetic diversity and inbred populations.
Paola Laiolo and Jose Tella, of the Estacion Biologica de Donana in Seville, recorded and analyzed the songs of a rare and specialized songbird called Dupont's lark, across 21 localities in Spain and Morocco. This lark has particular requirements and can only live in arid scrub steppe. By comparing song similarity between birds, the researchers could show that broken habitats made the male larks mimic their neighbors' songs more than expected, but lose touch with birds on the other side of the habitat break.
"Neighbors shared up to 70 percent of their phrases, while non-neighbors shared only around 30 percent," Laiolo said. By contrast birds living in pristine habitat shared around 45 percent of their phrases with non-neighbors over a similar distance.
The researchers believe that an increase in agricultural land, forest plantations and roads has fragmented the arid steppe habitat, preventing the Dupont's lark from sharing songs over greater distances.
"The fragmentation confines the species to smaller areas and eventually the genetic diversity of the population will erode," said Laiolo, whose results are reported in the Journal of Applied Ecology.
Such findings are likely to apply to many kinds of wildlife in a variety of habitats and places. Creatures like insects and small mammals that tend to be less mobile than birds are likely to be hit hardest.
For many species in the UK it may already be too late.
"We have been immensely efficient at cutting the country into blocks in the UK," said Andre Farrar, of the Royal Society for the Protection of Birds. "Now we are trying to stitch some of these blocks back together again, not only to improve genetic diversity of species, but also to moderate the impact of natural disasters like climate change."
Laiolo and Tella suggest that their song-matching technique could be used in other places to measure how fragmented a habitat has become.
However, Peter Salter, a birdsong expert at St Andrews University, said: "We would need to know what the songs are normally like before we can use it as a way of measuring fragmentation. Also, not all birds learn their songs from their neighbors."