German birds that spend cold months at U.K. birdfeeders now look slightly different from neighbors that migrate to Spain
Backyard feeders plus a strange sense of direction may have begun to split one bird species into two.
In southern Germany, some 10 percent of blackcaps (Sylvia atricapilla) fly not south, toward warmth, but rather northwest for the winter, says evolutionary biologist H. Martin Schaefer of the University of Freiburg in Germany. This novel journey, on record since the 1960s, probably became survivable thanks to the rise of backyard bird feeding in Britain, he says. Enthusiasts setting out seed and suet have kept the birds from starving until it’s time to wing back to Germany to nest.