Holarctic (Region)A zoogeographical region which is actually a combination of two such regions, the palearctic and the Nearctic, thus covering the entire Northern Hemisphere north of the tropics. The concept of the Holarctic region can be a useful one because of the basic similarity between the avifauna of the Palearctic and that of the Nearctic.
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From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver