266 AVES 



One of the most beautiful of the birds' nests is that of the Balti- 

 more oriole. It is easily recognized by the long strand suspending it 

 a foot from its supporting branch. It is tightly woven and when the 

 bird is on its nest its weight closes the opening so that no rain can 

 enter. The South American cacique builds a nest similar to that of 

 the oriole and with a much longer anchor. It may hang seven feet 

 from a branch. 



Bird Migration. — Coward classifies birds with respect to their 

 migrations as: 



(i) Permanent residents; (2) Summer residents. (Leaving in autumn 

 and returning in spring); (3) Winter residents. (Leaving in the spring 

 for their breeding area); (4) Birds of passage — or spring and autumn 

 migrants; (5) Irregular migrants — occasional invaders; (6) Stragglers or 

 wanderers. 



The American Golden plover nests along the Arctic coast from 

 Alaska to Hudson Bay; winters in Argentina, after a roundabout 

 oceanic flight of 2,500 miles, passing through Labrador and Nova 

 Scotia with rests and feeding at each of these places, then flies 

 directly across the sea to Guiana and thence after a further rest to 

 Brazil where it feeds until March. The return route is a more 

 direct one. The distance covered in the elliptical indirect route is 

 said to be nearly 20,000 miles. Birds usually migrate in company 

 with other experienced travellers, but they make successful pil- 

 grimages when it is evident that older birds are not there to guide 

 the flock. 



Storks marked in Prussia have been taken in the African Trans- 

 vaal. The Arctic tern nests along the coast of Maine and North- 

 ward to the limit of land, but winters along the borders of the Ant- 

 arctic continent. Thus it migrates about 11,000 miles, probably at 

 sea. Cooke states that the Arctic tern has more hours of daylight 

 than any other animal. " The midnight sun has already appeared 

 before the birds' arrival at the Northern nesting site, and does not 

 set during their entire stay at the breeding grounds. During two 

 months of their sojurn in the Antarctic^ the birds do not see a sunset." 

 They have 24 hours of daylight for at least 8 months of the year. 



Some species fly by day and some by night, others fly both day 

 and night. Some day-migrants follow coast lines or river valleys, 

 guiding themselves by sight. But in the case of the noddy and sooty 

 terns, studied by Watson and Lashley, birds liberated at sea, 600 



