The Audubon Societies 



235 



arrives and accepts him for a mate, however, she does not at the same time 

 accept the home which he has built; for even though she may decide to use 

 one of the boxes where he has already started a nest, she usually proceeds to 

 throw out all of the sticks which he has laboriously brought in before starting 

 a nest of her own. I have never known any bird in which the males and 

 females worked equally at nest-building though with many of the common 

 birds the male makes a pretense at helping. It is his duty to see that no 

 other male or even female 

 of the same species intrudes, 

 and this takes so much of 

 his time that, though he 

 may accompany the female 

 back and forth on her trips, 

 he has little time or in- 

 clination for gathering nest- 

 ing material. Judging from 

 the way the female usually 

 treats his occasional offering 

 of nesting material, it would 

 seem that his lack of ex- 

 perience has so warped his 

 judgment that he does not 

 know the proper material 

 when he sees it. 



This brings up the ques- 

 tion of what determines the 

 proper nesting material for 

 each species. Practically 

 all birds build nests that 

 are characteristic of the 

 species. The materials vary 

 somewhat in different local- 

 ities depending upon what 

 is most convenient but, in 

 general, House Wrens use twigs, Bluebirds use grasses, Yellow Warblers use 

 cotton, and so on, though often curious substitutes are employed. I have, for 

 example, a Wren's nest built largely of hair-pins and wire clippings, and a 

 Robin's nest in which the customary grasses were replaced by long, narrow 

 strips of paper from a nearby paper factory. But only such materials are used 

 as permit the bird to build the type of nest characteristic of the species. Balti- 

 more Orioles normally weave their nests from vegetable fibers such as the 

 inner bark of milkweed. They will take pieces of yarn or string or horse- 

 hair just as readily but never, to my knowledge, will they use sticks, straws, 



MALE CHESTNUT-SIDED WARBLER ON GUARD 



When the male bird is brighter than the 1 female, he usually does 



not condescend to incubate but either feeds the female on the 



nest or stands guard awaiting her return from feeding excuisions. 



This species does either way 



