By tracking hybrids¹ between songbird（鸣禽） species, investigators² have found that migration³ routes are under genetic⁴ control and could be preventing interbreeding. The research, which is published in Ecology Letters, was conducted using geolocators that, like GPS, record the position of a bird and allow its long distance movement to be tracked. Compared with their parents, hybrids exhibited increased variability in their migratory⁵ routes: some used intermediate（中间的） routes across less suitable areas, while others used the same routes as one parental⁶ group on fall migration and the other on spring migration.

 

"This is the first time we've been able to track songbirds over the entire annual cycle, and the data we collected support a longstanding hypothesis in ecological⁷ speciation, that differences in migratory behavior could be acting⁸ as postmating reproductive isolating⁹ barriers," said lead author Kira Delmore.

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