620 Recently published Ornithological Works. [Ibis^ 



between the true and apparent lengths of incubation, the 

 former being "the minimum number of days under optimum 

 conditions necessary to hatch a normal bird/' while the 

 latter includes as well errors of observation, and those 

 caused by the " other conditions as retard or suspend 

 embryonic development." 



We feel that the time has hardly yet come to draw con- 

 clusions from such unreliable data^ but we must congratulate 

 Dr. Bergtold on his energy and industry in collecting together 

 so much material for the use of future students. 



Brooks on Falkland Island Birds. 



[Notes on some Falkland Island Birds. By W. Sprague Brooks. 

 Bull. Mus. Comp. Zocil. Cambridge, Mass., Ixi. 1917, pp. 135-1 GO; 

 3 plates of photos.] 



This paper contains a series of field-notes on a collec- 

 tion of birds made by the J. C. Phillips expedition to the 

 Falkland Islands. It is not very clear from the text whether 

 Mr. Phillips took part in the expedition^ nor what was the 

 object of it ; in fact, the introductory paragraphs might 

 have been made a little fuller with advantage. 



The birds to which attention was chiefly devoted were the 

 Penguins ; of these the most abundant are the Gentoo 

 [Pygoscelis papua), the Rock-hopper (Eudyptes nigrivestis), 

 and the Jackass {Spheniscus magellanicus). Full details of 

 the nesting and other habits are given in the case of these 

 three, and the photographs show their appearance on the 

 shore. The vexed question of the Loggerhead or Steamer 

 Duck [Tachyeres) is discussed, and J\Ir. Brooks is quite 

 satisfied that there are both flying and non-flying indi- 

 viduals, but how they can be satisfactorily separated and 

 diagnosed he is unable to state, nor does he find that the 

 distinctions made by Mr. Blaauw in the case of the birds 

 of Tierra del Fuego hold good so far as the Falkland Island 

 birds are concerned, and the whole matter still remains 

 obscure. 



Two new species recently described by Mr. Brooks in the 

 ' Proceedings of the New England Zoological Club ' (vol. vi. 



