WCP3525

[1]

Broadstone, Wimborne

Dec[embe]^r. 3^rd. 1904

Prof. E.A. Schafer¹

Dear Sir

You have near you the greatest authority on the facts of migration. Mr. W. Eagle Clarke² of the Mus. of Sc. & Art.³

As a student of its theory I do not think your idea is correct. All Central Europe, and especially the Central United States swarm with small birds breeding in the spring. There is therefore no need for a longer than 12 hours day. Again, we know that though what are now the Arctic & Sub-arctic regions there was a mild or warm climate & abundant vegetation through the whole Tertiary period. It was under these conditions⁴ [2] that most existing ^{genera & species of} birds were evolved. As the Glacial epoch gradually approached more & more of these regions became uninhabitable by many groups of birds in winter. They therefore inevitably moved southward at that period⁵, & went back in spring. There is the origin of migration, and length of days have no place in it.

Yours very truly | Alfred R. Wallace [signature]

P.S. Another important fact is, that the area of land in the Arctic regions, is excessively small as compared with that of the temp[erate] zone, & the number [3] of birds that go to it to breed is also excessively ^very small, comparatively. Migration is a phenomenon of the temperate as well as of the Arctic zone. So several phenomena cannot have been initiated & determined by very local conditions affecting perhaps a tenth part of the whole area.

A.R.W. [signature]