Male great reed warblers may be practicing how to woo
L-R: Jason Boyce, M. Sorensen
Male birds’ puzzling off-season singing in winter could be practice for flirting in spring.
Europe’s great reed warblers (Acrocephalus arundinaceus) and some other male long-distance migrants sing extensively when overwintering in sub-Saharan Africa, says Marjorie Sorensen, now at Goethe University in Frankfurt. “Why are they doing this when they’re thousands of kilometers from any possible breeding opportunity?”
Singing seems costly. Reed warbler songs — “very harsh-sounding and creaking,” Sorensen says — are changeable compositions made up from a male’s repertoire of some 40 to 60 sounds. Tests find that singing demands about 50 percent more energy than reed warblers spend resting. Plus, singing cuts into foraging time and risks catching predator attention.