BIOLOGICAL ASPECTS 317 



some sets taken by A. C. Bent from several American localities. 

 (These sets were deposited in the U. S. National Museum and the 

 information is abstracted from the catalog in the Division of Birds) : 



Eggs in set 



' 1 i 3 4 5 



Pluvialis dominica dominica, Barrow 



(Murdoch) 3 5 11 



Bartramia longicauda, Martha's Vine- 

 yard to Saskatchewan (Bent) 1 9 



Actitis macularia, Massachusetts to 



Labrador (Bent) 6 15 1 



Catoptrophorus semipalmatus semipal- 



matus, South Carolina (Bent) 1 6 



Catoptrophorus semipalmatus inornatus, 

 Saskatchewan to Utah (Bent) 



Erolia bairdii, Barrow (Murdoch) 



Tryngites subruficoUis, Barrow (Murdoch) 



Ereunetes pusillus, Barrow (Murdoch) 1 



Phalaropus fulicarius, Barrow (Bent) 



Lobipes lobatus, Barrow (Murdoch) 2 4 



Lobipes lobatus, Unalakleet (Bent) 



4 



4 



1 



5 



2 



6 



6 



13 



1 



8 



7 



14 



1 



14 



Total 2 8 35 105 2 



Sets of the 7 species of sandpipers listed average a fraction over 3 but 

 less than 4. A. C. Bent's (1927, 1929) published reports on the nest- 

 ing of 50 species of sandpipers (Scolopacidae) in North America, give 

 4 as the characteristic size of a clutch in all cases. He chose to gen- 

 eralize by the criterion of his vast experience with the nesting of 

 birds in concluding what their normal reproductive performance is. 

 Numerous published reports upon the number of eggs charac- 

 teristic of the clutch of each species in different parts of the world, 

 do not allow a determination of whether the bias often present in col- 

 lecting of eggs has been eliminated from the conclusions. It is there- 

 fore necessary to restrict comparison of the number of eggs laid in 

 the arctic and in other climates to cases in which rather large dif- 

 ferences in reproductive effort seem to distinguish arctic birds from 

 those in warmer climates. 



Although the family Scolopacidae, discussed by Bent (1927, 1929) as 

 occurring in North America, includes many species which nest in the 

 north there are some (e.g., Catoptrophorus semipalmatus) wliich do 

 not migrate away from warm temperate regions. Others, like 

 spotted sandpipers {Actitis macularia) , nest over a range extending 

 from warm temperate states to the Arctic. Some of the species which 

 nest farthest north regularly migrate many times as far as those which 

 nest in the south. This condition holds true among North Ameri- 

 can sandpipers ; and the same sized clutch is also characteristic of the 

 sandpipers in Germany and England, for Lack (1947) reported that 



