During the winter, British bird-lovers lay out suet rolled with seeds and oats for birds landing in their chilly, barren yards. They believe that these handouts help the birds through winter, but scientists have now discovered that the practice may be splitting a species in two. In the past 50 years, a migratory schism has appeared among central European blackcaps (Sylvia atricapilla). Native to southern Germany and Austria, the small, grayish songbirds used to fly southwest together to Spain to bask in the Mediterranean weather and dine on fruits such as olives. But in the 1960s, bird watchers started noticing some blackcaps wintering in the United Kingdom. These birds had split from their companions, headed northwest, and begun living off the feed left out by generous bird-lovers. Now, roughly 30 generations later, about 10% of blackcaps migrate to the United Kingdom in the winter instead of to Spain.
A recent study showed that this new winter destination has led blackcaps to breed mainly with their migratory companions. The United Kingdom is closer to blackcap breeding grounds in central Europe than is Spain, so the northwest-migrating birds return home 10 days earlier and start mating among themselves.
Read more Feed a Bird, Split a Species -- Torrice 2009 (1203): 2 -- ScienceNOW
A recent study showed that this new winter destination has led blackcaps to breed mainly with their migratory companions. The United Kingdom is closer to blackcap breeding grounds in central Europe than is Spain, so the northwest-migrating birds return home 10 days earlier and start mating among themselves.
Read more Feed a Bird, Split a Species -- Torrice 2009 (1203): 2 -- ScienceNOW