BIRD LIFE OF BARTICA 99 



flocks came one after the other, and each evening a dozen or 

 more individuals appeared flying steadily across from the 

 opposite shore of the Mazaruni. 



The details of daily habits such as these, which we found 

 strongly developed in many birds other than caciques, anis 

 and parrakeets, may prove ultimately of fundamental sig- 

 nificance in working out the origin of more extensive migra- 

 tions, whether considered as tropisms or conscious actions. 



During the winter months about thirty species of birds 

 migrate from the United States or farther north to British 

 Guiana. In the Bartica district we observed only seven of 

 these, the Esquimo curlew, yellowlegs, spotted and solitary 

 sandpipers, yellow warblers, purple martins and barn swal- 

 lows. The purple martins and all the waders, except the 

 spotted sandpipers left early in March, but the yellow war- 

 blers lingered until April 10. Families of spotted sandpi- 

 pers were teetering along the Mazaruni shallows in early 

 May the young still in unspotted garb, although the adults 

 had completed their spring molt. The barn swallows lingered 

 amazingly late, and those which we shot on June 1 were in 

 perfect condition and ready to nest in the near future. 

 The last one flew past on June 1C, making its way leisurely 

 in a northward direction. These late birds we saw prob- 

 ably a dozen in June were certainly neither cripples nor 

 abnormal as to breeding condition. The one exception was 

 a spotted sandpiper shot on July 9, which was emaciated 

 although in good plumage, and the only abnormal condition 

 was inflammation of some of the ovarian tissue. 



I can speak less certainly of the seasonal migration of 

 native birds, as at least two successive years and much 'more 

 than five months are necessary for exact data on this point. 

 The few examples I shall mention serve chiefly to point our 

 ignorance of these more or less local movements. I shall 

 refer to them again under breeding season. In the case of 

 birds nesting alone there is, not uncommonly, between the 

 rearing of successive broods, a short migration quite away 



