o4 Tyler, Brown Creeper in Massachusetts. uan. 



"May 26. The Concord nest, 4 p. m. After an interval 

 when both birds are absent, one bird visits the nest three times and 

 the other once; all four visits are made within five or ten minutes. 

 The bird which comes oftener is paler than the other. This pale 

 one in every instance enters and leaves the nest cavity by a tiny 

 opening just above the protruding material, six inches below the 

 entrance used during incubation (May 19). As this bird comes 

 out head first, it must turn around inside. The darker bird in its 

 one visit uses the upper hole in entering and leaving. It brings 

 from the nest a bit of white excrement which appears almost globu- 

 lar in shape and flies away with it. The birds collect food for the 

 young from the bark of the trees nearby — small insects. Once 

 Mr. Faxon made out a spider in a parent's bill." 



As in the case of the Lexington Creepers, the difference in color 

 was diagnostic only when the birds were together. 



On the second of June, from 11 A. M. till noon, Mr. Faxon and 

 I watched the Concord Creepers feeding their young. The parents 

 brought food to the nest every few minutes and during the entire 

 period were almost always within sight or hearing. We soon con- 

 vinced ourselves that each bird used a different hole, both on enter- 

 ing and leaving the nest and from the fact that the incubating bird 

 had always entered by the upper hole we suspected that the female 

 was still using this entrance while the male came and went below. 

 On one occasion, we saw the "upper hole bird" creep down to the 

 next and stand over the young with half-spread wings for a minute 

 or two. This maternal brooding by the supposed female strength- 

 ened our opinion and when on June 3rd I heard the male sing 

 repeatedly while the female who had entered by the upper crevice 

 and who afterwards left by it, was in the nest, we felt no doubt 

 of the respective sexes of the two birds. At our visit on June 2, 

 it appeared to us that the male bird was as diligent as the female in 

 feeding the young birds and in carrying away their excrement. 



In order to determine this point with mathematical accuracy, 

 I stationed myself at 7:15 the next morning (June 3) eighteen 

 feet from the nest and, for the succeeding hour and a half, recorded 

 at each visit of the parents which entrance was used and whether 

 or not excrement was taken away on leaving. The following table 

 indicates the result. 



