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| | Fact Sheets - Smithsonian Migratory Bird Center - National Zoo| FONZ |
 | | Several species, including the Blackpoll Warbler (Dendroica striata), American Golden-Plover, (Pluvialis dominica), and Red Knot (Calidris canutus), take an over-water route in the autumn from the coast of New England or southern Canada to the Caribbean and South America, a distance of 3,000 to 4,000 kilometers. |
 | | The Blackpoll Warbler's over-water flight to South America keeps it aloft for 80 to 90 continuous hours, an effort which researchers Tim and Janet Williams conclude "requires a degree of exertion not matched by any other vertebrate; in man the metabolic equivalent would be to run a 4 minute mile for 80 hours. |
 | | Secondly, instead of one form of hemoglobin in the red blood cells as is typical in non-migrants and other classes of vertebrates, some migratory birds possess two forms of hemoglobin which differ in their oxygen carrying and releasing capacities. |
| nationalzoo.si.edu /ConservationAndScience/MigratoryBirds/Fact_Sheets/default.cfm?fxsht=4 (1763 words) |
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