Travelling far means absent fathers

The benefits of migration have a cost in parental care. A new study on shorebirds shows that long-haul migrations favour males who put little effort into raising their young.

Seasonal migration between the wintering and breeding grounds is very common in many species of birds.

But travelling back and forth takes time and energy and scientists know that males of migratory bird species, especially the ones that fly far, are less involved in parental care, leaving the tasks of raising the chicks to females.

'Previous studies suggested a link between migration and parental care,' says Gabriel García-Peña, a PhD student at the University of Bath and lead author of the article, 'but we did not know how migration and breeding behaviour coevolved.'

Does parental care prevent birds from taking on long migratory flights? Or does migrating far increase the cost of raising chicks and favour early parent desertion?

To find out García-Peña and colleagues investigated 138 species of sandpipers, plovers and other shorebirds and compared their different breeding and migratory behaviours.

The results show that birds that migrate over long distances have a shorter breeding season than species that don't travel far. And far-travelling males tend to care less for their offspring, says the report published last week in Behavioral Ecology.

By looking at the evolutionary history of shorebirds, the researchers were able to conclude that the tendency to prefer long migration came before the decrease in male parental care. This means that, during their evolution, shorebirds first started long-course migratory flights and then, as a consequence, male desertion became a favourable behaviour.

'It seems that natural selection for long-distance migration influenced the evolution of breeding system in birds,' says García-Peña. 'This is a key finding of this study.'

http://planetearth.nerc.ac.uk/news/story.aspx?id=475