X1014080336-00100-20347</DOCNO> Migration of Birds Migration of Birds When Birds Migrate One ordinarily thinks of the world of birds as sedentary during two periods each year, at nesting time, and in winter.
(Birds Migrate One; ordinarily thinks; of the world of birds; T:during two periods each year)
Birds Migrate One
ordinarily thinks
of the world of birds T:during two periods each year