NESTING HABITS OF OROPENDOLA — CHAPMAN 365 



slight downward dip followed by an ahnijit upward turn which 

 serves to check the speed of the bird's fli<rht. The bird thus flies 

 into its nest without pausinjr on the threshold. The re<rularity with 

 which this procedure is followed is an indication of its importance. 

 "With its back exposed and head concealed a bird, perched at the 

 nest openiui; and lookinjr in, would evidently be at the mercy of a 

 foe from without, and this point of exposure is, therefore, passed 

 as quickly as possible. When leaving the nest, however, the posi- 

 tion and the conditions are reversed and the bird often perches in 

 its doorway and leisilrely surveys the surroundings. 



The use of the nest opening from the day it is available trains 

 the bird's sense of location. I have never knowingly seen a bird 

 make the mistake of entering the wrong nest, even when, as is often 

 the case, several are near together. Under normal conditions it is, 

 indeed, rare for a bird to exhibit the slightest hesitation in finding 

 her own doorway. Changes, however, may occur which for a mo- 

 ment tend to confuse it. For example, when the nests swing widely 

 in a high wind not only are the}' in motion but the actual position 

 of the opening is altered and both factors cause the returning bird 

 to hover for a second or two before slipping into the nest. 



A more pronounced case of this nature occurred through the 

 breaking of one of the limbs to which nest No. 5, group 1, 1927, 

 was attached. The nest now half turned around and then s])un 

 back, the entrance, therefore, being first on one side then on the 

 other. The owner was at first confused but soon adapted herself 

 to tlie new situation though she was usually forced to discover 

 the exact position of the nest opening on each return. 



Once the bird begins to work inside, little can be seen of her while 

 building until she begins to close the nest at the bottom. Then her 

 bill may be observed actively thrusting and pulling as she hangs 

 heatl downward within. 



There is wide variation in the nest-building ability of different 

 birds. Tliis is probably in part individual, but it is doubtless also a 

 mea.sure of the extent to which their in.stinct has been developed by 

 experience. Some birds evidently know exactly what they want to 

 do and work rapidly and effectively; others show but little interest in 

 their work and seem at a loss to loiow how to use the material they 

 have collected. 



The members of groui)s 1 and 2, of the .season of 1027, illustrated, 

 respectively, these extremes. The first, as has before been stated, 

 were apparently an organized group of birds that had been associ- 

 ated before, and hence, presumably were more or less experienced. 

 The second group was composed of birds that had not established 

 communal relations and some of which, at least, seemed to be build- 

 ing their first nest. 



