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Highly migratory in North America, where entire population departs for winter, except birds in S Florida; sedentary in Caribbean. During boreal winter mainly occurs from Guatemala to S Peru and Brazil; some birds move 8800 km, mostly following overland route through C America. Migration patterns highly correlated with wind speed and direction. Autumn peak between mid-Sept and early Oct; spring peak mid-Mar in Panama, late Mar to early Apr in S Texas. During days of peak movement, daily flights may number 1000´s, with up to estimated 100,000 seen in single day in E Mexico; along with B. swainsoni perhaps the most conspicuous North American raptor migrant; because of large concentrated flocks. Some migration concentration points in North America differ in spring and autumn.   (del Hoyo J, Elliott A, Sargatal J (eds), 1994)

• digitised by GROMS, after del Hoyo J A Elliott; J Sargatal (eds) (1994) - www.hbw.com,
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