. Bird migration . e rate of 20miles per day. This rate is about the slowest of all North Americanbirds and is only slightly increased throughout the whole scoringmigration up the Atlantic coast to Nova Scotia (see fig. 16), wherethe birds arrive about May 20, having averaged less than 25 miles aday for the w^hole 77 days after leaving Cuba. ]\IigTation along the western border of the range is fully as slow asalong the Atlantic coast; on the average, the fnst arrive at Kerr\dlle,Tex., March 9 and in northern North Dakota May 10, having trav-eled 1,300 miles in 60 days, or 22 miles a day. Thenc
. Bird migration . e rate of 20miles per day. This rate is about the slowest of all North Americanbirds and is only slightly increased throughout the whole scoringmigration up the Atlantic coast to Nova Scotia (see fig. 16), wherethe birds arrive about May 20, having averaged less than 25 miles aday for the w^hole 77 days after leaving Cuba. ]\IigTation along the western border of the range is fully as slow asalong the Atlantic coast; on the average, the fnst arrive at Kerr\dlle,Tex., March 9 and in northern North Dakota May 10, having trav-eled 1,300 miles in 60 days, or 22 miles a day. Thence the speed ismore than doubled to the northwestern limit of the range in theMackenzie Valley. (See fig. 16.) 26 BULLETIN 185^ U. S. DEPARTMENT OF AGEICULTURE. Incidentally it may be remarked that the black-and-white warbleris one of the very few migrants which arrive in Texas and Floridabefore they appear at the mouth of the Mssissippi. The van ofmost species reaches southern Louisiana earlier than southern Fig. 11.—Distribution and migration of the Ross snow goose (Chen rossi). This is apparently the onlyspecies that breeds on the Arctic islands, migrates south in fall through the Mackenzie Valley, and whenit reaches the United States, instead of passing south and east to the Mississippi Valley, turns west-ward, crosses the Rocky Mountains, and winters in California. (See p. 23.) The cliff swallow is another species with a slow migration schedule(see fig. 6). It must start northward very early, since by March 10it is already 2,500 miles from the winter home and yet averages only25 miles a day for the next 20 days while rounding the western endof the Gulf of Mexico. It more than doubles this rate while passingup the Mississippi and Ohio River valleys. The crossing of the Alle-gheny Mountains comes next, and there are only 200 miles of progress BIRD MIGRATION. 27 to show for the 10 days flight. By tliis tmie spring has really comeeast of the Allegheiiies, and the swal
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