Environmental shifts may induce sudden reversals in the relative quality
or sexual attractiveness of mates (ecological crossovers) leading to
non‐directional sexual selection. Studies on such ecological crossovers
induced by environmental shifts during the nonbreeding season are
particularly rare. We studied the interactive effects between
nonbreeding 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 signaling value to
females thus depended on a complex interaction between conditions both
at the nonbreeding and breeding grounds. We show that it is important to
consider conditions during the nonbreeding season when examining the
effects of sexual ornaments on fitness.