Bird migration :  eastern hemisphere  [cartographic material] / 
 Bird migration :  western hemisphere  [cartographic material] 
produced by National Geographic Maps for National Geographic Magazine 
 - Washington, D.C., Wash. :  The Society,  2004 
 - 2 maps on 1 sheet 
<br/><br/><label>Subjects--Topical Terms: </label><br/>BIRDS--MIGRATION--MAPS
<br/><br/><label>LC Class. No.: </label>G3201 .D4  / N374B