by tracking
1 between
songbird（鸣禽） species,
2 have found that
3 routes are under
4 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
5 routes: some used
intermediate（中间的） routes across less suitable areas, while others used the same routes as one
6 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
7 speciation, that differences in migratory behavior could be
8 as postmating reproductive
9 barriers," said lead author kira delmore.
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