Feeding the birds changes species

It seems innocent enough but new research has found feeding birds can alter their migratory pattern, which may cause them to develop into a separate species.

The research, published in today's edition of Current Biology, shows humans can have a significant influence on the evolution of animals.

Dr Gregor Rolshausen of the University of Freiburg in Germany and colleagues studied a population of blackcap birds in central Europe and found that in only 30 years, part of the population had established a new migratory route.

"The new wintering area is 1200 to 1800 kilometres northwest of the traditional Mediterranean overwintering sites," they write.

For more than 30 generations the separated populations of blackcaps have interbred, leading to substantial genetic and physiological changes between the birds.

Ornithologist and evolutionary biologist Dr Leo Joseph of CSIROsays the research team first published results on the genetic divide between the European blackcap population 10 to 15 years ago.

He says the study now shows even more genetic differences and significant physical differences between the two groups.

"Blackcaps migrating along the shorter northwestern route have rounder wings, which provide better maneuverability but make them less suited for long-distance migration," write the study authors.

They also have narrower beaks and differ in beak and plumage colour from their southwest-migrating counterparts.

Human influence

Rolshausen and colleagues believe the migratory divide occurred when humans began offering the birds food in winter.

"[The divide] was favoured by warmer climate and increasing food supply provided by humans", they write.

Associate Professor Steve Cooper of the South Australia Museum says the research is very interesting.

He says the data collected on birds is generally "quite solid because people pay a lot of attention to them".

Cooper agrees that the physical differences between the two populations was triggered by the migratory divide, which caused the two populations to breed in isolation.

"They're not interbreeding in the way they were previously, they're only mating within the same pool of individuals who are on the same migrating route," he says.