Data from: Ecological crossovers of sexual signalling in a migratory bird

Environmental shifts may induce sudden reversals in the relative quality
or sexual attractiveness of mates (ecological cross-overs) leading to
non-directional sexual selection. Studies on such ecological cross-overs
induced by environmental shifts during the non-breeding season are
particularly rare. We studied the interactive effects between wintering
conditions and a male white wing patch on the breeding success of breeding
pairs and the local survival of females in a migratory passerine
population over a 32-year period. After dry winters, females paired with
large-patched males were more likely to survive than those paired with
small-patched males, and vice versa after moist winters. Moreover, after
dry winters, large-patched males succeeded in attracting females that laid
large clutches, while small-patched males bred with females that laid
small clutches, and vice versa after moist winters. This phenomenon led to
a difference in fledgling numbers only during years with dry winters and
high precipitation during the breeding season. The selection on this male
trait and its signalling value to females thus depended on a complex
interaction between conditions both at the wintering and breeding grounds.
We show that it is important to consider conditions during the
non-breeding season when examining the effects of sexual ornaments on
fitness.