. The book of birds; common birds of town and country and American game birds . own in the migration of therobin (page 192). This bird differs frommost others in that throughout its entirecourse northw^ard it adopts springs time-table for its own. The robins average temperature ofmigration is 35° F.; that is, it puts inan appearance soon after the snow be-gins to melt and streams to open, butbefore vegetation has made any conditions occur in the centralMississippi Valley about the middle ofFebruary, and it is the first of March be-fore spring and the robins cross northernMissouri a
. The book of birds; common birds of town and country and American game birds . own in the migration of therobin (page 192). This bird differs frommost others in that throughout its entirecourse northw^ard it adopts springs time-table for its own. The robins average temperature ofmigration is 35° F.; that is, it puts inan appearance soon after the snow be-gins to melt and streams to open, butbefore vegetation has made any conditions occur in the centralMississippi Valley about the middle ofFebruary, and it is the first of March be-fore spring and the robins cross northernMissouri and arrive together in southernIowa. Thence a whole month is con-sumed by the birds in their slow prog-ress—13 miles a day—to central Minne-sota. There their pace quickens, to keepup with the northward rush of spring,and another 10 days at doubled speedbrings them to southern Canada. Here they must make an importantchoice. To the north and northeast liesa land that awakens slowly from its win-ters sleep, and where the sun must wagea protracted contest against the cold of. MAP SHOWING SLMMIvR AND WINTKR HOMIiS OF TIIIv BIRD THAT HATKS DARKNKSS The summer home of the Arctic torn is along the Arctic coast of North America: itswinter home within tlie Antarctic Circle 11,000 miles away. During ciRlit montlis of the yearthe bird hves where the sun does not ro below the horizon. The track of the tern in itsroimd jcuirney of 22,O0O miles is unknown (see page 190). 191 192 OUR GREATEST TRAVELERS
Size: 1233px × 2027px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectbirdsun, bookyear1921
