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Weather conditions and the visible migration of Short-toed Snake Eagles
that during noon and early afternoon the lower the study area, with the presence of a large flat
limit of migration was lifted off the ground and this zone north of the site, could have further affected
may explain the lower number of raptors observed the observed numbers of Short-toed Snake Eagles,
during this period of the day. Thus, it is possible by decreasing the altitude of migrants reaching the
that visual censuses of Short-toed Snake Eagle watchsite in spring.
along mountain chains could be biased by season, Acknowledgements
due to differences in thermal conditions in these We appreciate the improvements in English
periods of movement (March and September). usage made by Christina Riehl through the
This hypothesis would be consistent with results Association of Field Ornithologists’ program
of other censuses of this species made during both of editorial assistance. MEDRAPTORS (www.
seasons along two mountain chains in central raptormigration.org), a network of ornithologists
and northwestern Italy where higher number of and birdwatchers, works to improve research and
Short-toed Snake Eagles are observed migrating in the protection of migrating birds of prey through
spring than in autumn (Apuane Alps and Ligurian specific projects and observation camps.
Apennines; Baghino and Premuda 2007, Baghino
et al. 2009, Premuda et al. 2010). Finally, in the Hedenström, A. 1993. Migration by soaring
case of Mount Olympus, geographic features of or flapping flight in birds: the relative
importance of energy cost and speed. Phil.
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