Comparative Periods of Nestling Life 93 



quickened by forces without and is therefore largely de- 

 pendent upon maturity of fledgling life. 



Fourth. Nothing seems more probable than that the 

 Nidicolae evolved from the Nidifugae, and that if the econ- 

 omj^ of nature denuinded it, all North American Nidifugte, 

 with the possible exception of the Anscres, Shore and Galli- 

 naceous birds would readily yield to nidicolous habits and 

 conditions. 



An interesting writer (Cf. Finn, Bird BcJiavior Psy- 

 chical and PhtjsioJoijical) regards the Passive or Nestling 

 (Nidicola^) type as degenerate, and states that with the 

 exception of the Ospre3% which has variegated down, all 

 Nidicola? appear self-colored, usually black, white, grey or 

 buff, when they have down at all ; while the Active or 

 Chick ,Nidifug;iel type are generally characterized by the 

 more primitive striped, pied marked or spotted down. 



The appended table of periods of nestling life was orig- 

 inally collated not only from my own notes and the manu- 

 script of my friends, but from the pages of our leading 

 American ornithological periodicals and many other 

 ornithological works, for my own personal use in connec- 

 tion with bird banding, and though neither remarkable for 

 the number of volumes searched or ideal for tlie purpose 

 of comparison, it will at least call attention to the need of 

 such data. Perhaps an ideal table would include the en- 

 tire Juvenal life from birth to the acquisition of equilibrium 

 or wing power. 



ALCID^: 



Tufted Puffin, remains in nest until fully feathered and able to 

 take care of itself (Bent quoting Emerson, Life Histories North 

 American Diving Birds, p. 85.) 



Puffin, able to leave burrow in 4 or 5 weeks and follow parents 

 to sea (Bent, Life Hist. N. A. Diving Bds., 92.) 



Homed Puffin, leave nest before able to fly (Bent quoting Tur- 

 ner, Ibid., 101.) 



Rhinoceros Auklet, nearly full grown (Willett, Bird-Lore, xiv, 

 423); evidently estimated at about 30 days (Bent quoting Heath, 

 Life Hist. N. A. Diving Bds., 106.) 



Cassin's Auklet, fully 21 days, until able to fly (Heath, Con- 

 dor, xvl, 34; Bent, Life Hist. N. A. Diving Bds., 113.) 



