The unusual bird migration pattern lacking an explanation
Lund biologists Linus Hedh and Anders Hedenström wanted to find out where the common ringed plover (Charadrius hiaticula), which breeds in southern Sweden, migrates to in the autumn. The answer was southwest Europe. However, they discovered more than this through the small geolocators they attached to the backs of the birds, which revealed where the birds had been as well as when they started and finished each flight.
“We were able to ascertain that the males fly to Portugal and Spain while the females spend the winter in France. It is very unusual for the males to migrate further than the females”, says Linus Hedh, who adds:
“There are a number of species in which the males and females spend the winter in different places; however, in those cases it is practically always the females that migrate the furthest.”
A species in North America
One example is the common chaffinch. Carl von Linné gave it the name Fringilla coelebs, freely translated as ‘bachelor finch’. An appropriate name given that the males migrate the shortest distance and return to the breeding sites before the females when spring approaches. There are a few other species in which the males, like the common ringed plover, migrate further than the females. One example is the North American spotted sandpiper. In this case, researchers explain this by the fact that the females establish the breeding territory while the males take care of the offspring.
Mystery of the ringed plover
However, that explanation does not apply to the common ringed plover. It is the same with other explanations such as competition for the best wintering or breeding sites – these explanations are not applicable to the common ringed plover.
“In this way, the species in unique. We still do not know why the males migrate the furthest”, says Linus Hedh.
The results were recently published in an article in Journal of Theoretical Biology.