RESIDENCE IN THE ARCTIC 



307 



Table 14. — Progress from migratory to laying condition in 27 species of birds 



at Old Crow 



Species 



First 



First 



Interval 





arrival 



egg 



(days) 



Qavia arctlca 



May 22 



June 15 



24 



Anas platyrhynchos 



Mays 



June 5 



28 



Aythya aflBnis 



May 18 



June 18 



31 



Buteo lagopus 



Apr. 18 



May 5 



17 



Circus cyaneus 



May 5 



May 20 



15 



Falco peregrinus 



May 5 



Junel 



27 



Charadrius semipalmatus 



May 19 



June 7 



19 



Capella gallinago 



May 7 



May 31 



24 



Actltis macularia 



May 22 



June IS 



27 



Tringa solitaria 



May 14 



May 25 



11 



Totanus flavipes 



May 7 



May 28 



21 



Colaptes auratus 



May 16 



June 1 



15 



Petrochelidon pyrrhonota 



May 25 



June 9 



15 



Turdus migratoiius 



Mays 



May 25 



17 



Ixoreus naevius 



May 4 



May 21 



17 



Hylocichla minima 



May 22 



June 9 



18 



Vermivora celata 



May 20 



Junes 



12 



Dendroica petechia 



May 23 



June 11 



20 



Dendroica striata 



May 27 



Jime 12 



16 



Seiurus noveboracensis 



May 20 



June 8 



17 



WUsonia pusilla 



May 20 



June 4 



13 



Euphagus carolinus 



May 10 



May 25 



15 



Acanthis flammea 



May 21 



May 30 



9 



Jxmco hyemalis 



May 15 



May 25 



10 



Spizella arborea 



May 16 



May 26 



10 



Zonotrichia leiicophrys 



May 14 



May 26 



12 



Passere]]a iliaca 



May 14 



May 21 



7 



Total (27) 





(A 



^^er.) (17) 



alike at Old Crow, but considering the long interval apparent in the 

 snow bunting at Barrow, there is variation in the rate of progress 

 toward breeding among the species in this family as well. It is 

 significant that the intervals in four of the five species common to 

 the two localities differ considerably, i. e., yellowlegs {Totanus 

 ■flavipes) 21 and 13 days, robin 17 and 12 days, tree sparrow 10 and 

 17 days, and Gambel's sparrow 12 and 16 days . The best documented 

 very short interval of transition from migratory to laying conditions 

 is afforded by the 7 days recorded at Old Crow for fox sparrows. 

 There is undoubtedly a minimum time, probably differing among 

 species, in which the necessary physiological and behavioral proc- 

 esses can convert a migrating to a laying bird. Evidently external 

 circumstances can variously prolong the physiological process in an 

 individual, or at least prolong the physiological state of readiness 

 to lay. Accordingly, I conclude that the transition of a species from 

 migratory to breeding condition in two localities can be extended 

 beyond the minimum physiological requirement by amounts varying 

 according to local environmental conditions. 



