Comparative Periods of Nestling Life 



91 



* Found dead. ** Departed. 



There is probably no other incident in the life history of 

 our American birds in which our ornithologists are more 

 profoundly ignorant than that of the approximate duration 

 of nestling cycles. That of the Booby is said to be three 

 months or more, tliat of the Gannet five or six months and 

 of the Albatross ten months. Mr. A. C. Bead has returned 

 a nestling blank showing that the Ground Dove had com- 

 pleted a nestling cycle in 27 days. Mr. Charles H. Bogers, 

 in New Jersey, and the writer, in Pennsylvania, found 

 that of the Mourning Dove to be 30-32 days; a much shorter 

 period than that of the somewhat nidifugous Whip-poor- 

 will or Nighthawk, if one bases the completion of tlie cycle 

 at the flying age. Tlie Phoebe usually requires less than 40 

 days (Burns Ms., Vickers Ms.) and the Crested Flycatcher 

 51 days (McKeniion Ms.). Some of our Sparrows, Mock- 

 ers, and the Bobin have a cycle of 30-35 days (Mss. of 

 Burns, Ferry, Link, McKennon and Bedfield) being tsvo or 

 more weeks less than the Baltimore Oriole and I'uiple 

 Grackle. The House Wren and' Bluebird complete in about 

 35-45 days, while the Bewick's Wren and Chickadee re- 

 quire 52-53 days (Wiley Ms., Link Ms.). The Warblers 

 have a short cycle but as a rule are rather tardy nesters. 



I regret that my material is altogether too scanty to 

 more than suggest a few simple conclusions on the nestling 

 life periods of our Nidicolse. 



First. There seems to be a consistant increase in the 

 period of nestling development up to and including family 

 groups, to correspond with the increase in size of the parent 

 bird, and. this must be taken into consideration in making 



