Vol 'i9l9 XVI ] DuBois, Nesting of the Horned Grebe. 179 



The change of color which these eggs undergo, is also worthy of 

 note. I do not refer to the nest-stains caused by contact with the 

 fermenting vegetation of the nest lining, but to a uniform color 

 change of the surface layer of the shell, which is brought about 

 presumably by exposure to light and atmosphere. Referring to 

 the eggs of the second nest by numbers it will be noted that egg 

 number two, when first observed at 7:30 A. M., had apparently 

 just been deposited. As previously stated, its color was a very 

 delicate bluish-green. Egg number one had already attained its 

 final color; a sort of drab-tinted buff, which rendered it less con- 

 spicuous in the nest. Twenty-four hours later, egg number two 

 had changed to the same color as egg number one. No data were 

 recorded for egg number three in this respect. Egg number four, 

 after thirty-six hours, was "nearly but not quite the same color 

 as the others." After it had been in the nest forty-eight hours 

 it was noted as, "same color as other eggs." But egg number five 

 could scarcely be recorded as fully changed after eighty-four hours 

 had elapsed. These notes would seem to indicate that the first- 

 laid eggs change color more rapidly than the later ones. It may 

 be noted in this connection that the first eggs are slightly richer 

 in the light green pigment; possibly, also, they receive less shelter 

 from the parent bird than the later eggs. 



The usual vocal performance of these Grebes, so far as I was able 

 to determine, is a sort of "ko-wee, ko-wee," repeated at regular 

 intervals. It might be compared to the squeak of a dry wheel- 

 barrow producing one double squeak at each revolution of the 

 wheel. It is however of a clearer quality than this comparison 

 might indicate. Each "ko-wee" has rising inflection and its two 

 syllables are run closely together, with the accent on the last 

 syllable. 



The remarkable change of manner which came over these birds 

 as the moult began will be appreciated by reference to the tabulated 

 schedule of visits. The pugnacious bravery of the female at her 

 first nest is amply attested by the photographs, while the records 

 of the second nest show that the birds rarely permitted themselves 

 to be observed, even at a distance, although they had eggs as before. 



These Horned Grebes were absolutely isolated so far as con- 



