34 



MIGRATION. 



Emigration 

 of Birds. 



Distance 

 covered by 

 migrants. 



Origin of the 

 Charadriidae. 



Origin of 

 Migration . 



The modern ornithologist has discovered that migration is the rule and not the 

 exception, and, holding the theory that all birds are descended from common ancestors, he 

 is obliged to admit that the only possible way in which they could have become practically 

 cosmopolitan was by emigration, and that, too, on no insignificant scale. The emigrations 

 of birds have been as widespread and as complicated as those of the human race, though 

 they have been unchronicled by historians, and have left but few traces behind them, 

 except the present areas of the distribution of nearly allied species, which are most suggestive 

 of the past history of the genus. 



The Charadriidae may be regarded as the most migratory family of birds. In no 

 group of birds is the percentage of migratory species greater, nor do any migratory birds 

 undertake journeys of such extraordinary length. The Sanderling (Tringa arenaria) breeds 

 on the shores of the Arctic Ocean ; I have shot it in the lagoon of the Petchora in lat. 70° 

 north, in the middle of the breeding-season, and have watched it in our winter feeding on 

 the coast of South Africa, about eight thousand miles further south. The Knot (Tringa 

 canutus) has even a wider range, breeding further north, and sometimes wintering further 

 south ; there can be little doubt that some of its " fly-lines " measure ten thousand miles. 

 It is not remarkable that birds that perform such extraordinary feats of migration require 

 new sets of flight-feathers before each journey. As soon as the duties of incubation are 

 over most Waders may be seen in full moult, with perhaps a primary and a secondary in 

 each wing only half-grown, all the quills being gradually renewed during the month of 

 September. Precisely the same state of things may be seen in South Africa during the 

 month of March. 



Emigration, being doubtless an older habit than migration, ought perhaps to be 

 discussed first, but it is undoubtedly wiser to begin with the subject with which we are 

 best acquainted — to proceed from the known to the unknown. 



The Charadriidae are unquestionably an arctic family. Of 190 species which it 

 comprises 70 breed within the Arctic Circle ; and of 19 genera only 9 are unrepresented in 

 the Arctic Region. They probably originated on the shores of the Polar Basin ; and it 

 is not an improbable assumption that their habits of migration were acquired in the Arctic 

 Regions in pre-Eocene times, when the conditions of life near the Pole were very different 

 to what they are now. The first migrations of the ancestors of the Charadriidae were 

 probably not in search of warmth, for the climate of the Polar Basin was in those remote 

 ages mild enough ; nor in search oifood, which was probably abundant all the year round ; 

 but in search of light, during the two or three months when the sun never rose above the 

 horizon. 



The habit of migration thus formed became deeply rooted in the species, in accordance 

 with the law of heredity ; and doubtless acquired additional force when the terrors of a 

 Glacial Epoch exterminated the conservative party amongst the Charadriidae (if any of 

 them were foolish enough to neglect to adapt themselves to the changed circumstances), and 



