Data from: Positive feedback between ecological and reproductive character displacement in a young avian hybrid zone

Character displacement can reduce costly interspecific interactions
between young species. We investigated the mechanisms behind divergence in
three key traits - breeding habitat choice, timing of breeding and plumage
coloration - in Ficedula flycatchers. We found that male pied flycatchers
became expelled from the preferred deciduous habitat into mixed forest as
the superior competitor, collared flycatchers, increased in numbers. The
peak in food abundance differs between habitats, and the spatial
segregation was paralleled by an increased divergence in timing of
breeding between the two species. Male pied flycatchers vary from brown to
black with brown coloration being more frequent in sympatry with collared
flycatchers, a pattern often proposed to result from selection against
hybridization, i.e. reinforcement. In contrast to this view, we show that
brown male pied flycatchers more often hybridize than black males. Male
pied flycatcher plumage coloration influenced the territory obtained in
areas of co-occurrence with collared flycatchers, and brown male pied
flycatchers experienced higher relative fitness than black males when
faced with heterospecific competition. We suggest that allopatric
divergence in resource defense ability causes a feedback loop at secondary
contact where male pied flycatchers with the most divergent strategy
compared to collared flycatchers are favored by selection.