Migration of alder flycatchers (empidonax alnorum) and willow flycatchers (empidonax traillii) through the tuxtla mountains, Veracruz, Mexico, and the identification of migrant flycatchers in collections

We sequenced a diagnostic fragment of the mitochondrial Cytochrome b (Cyt b) gene in 144 flycatchers, identified only as "Traill's flycatchers," which were collected during spring and fall migration of 1973 and 1974 in the Tuxtla Mountains, Veracruz, Mexico. We found 135 E. alnorum, 3 E. traillii, 3 E. virescens, and 3 that did not match any known Empidonax sequence. Thus, E. traillii is an infrequent migrant in spring and fall in northern Veracruz, and instead likely passes along the southern part of the Isthmus of Tehuantepec as other studies have found. We also sequenced Cyt b mitochondrial DNA from toe pads of study skins of these species. Of 11 identified on the label as E. alnorum, one was E. traillii whereas the rest were E. alnorum. Of 16 specimens identified on the label as E. traillii, only one was actually this species; fourteen were E. alnorum and one was an E. virescens. Thus, we suggest that the species identification of specimens labeled as E. alnorum and E. traillii taken during migration should be considered speculative.