Vol. II, Pt. I] GIFFORD— BIRDS OF THE GALAPAGOS ISLANDS 97 



defatigable on July 18. Inasmuch as the breeding-season 

 extends practically throughout the year, the various plumages 

 do likewise. 



The measurements given below of twenty adult males and 

 twenty-seven adult females reveal the fact that on the average 

 the female is somewhat superior to the male in size. The 

 measurements of length of tail are not very dependable, for 

 the central tail-feathers in this species are very long and hence 

 suffer much from wear. The maximum, minimum, and aver- 

 age dimensions in millimeters are: Males — Wing 412-460 

 (433); tail 200-239 (222); culmen 101-118 (108); tarsus 

 47-55 (50) ; middle toe 64.9-78 (70). Females— Wing 428- 

 465 (447); tail 207-250 (227); culmen 110.6-121 (115.4); 

 tarsus 51-57 (53.7); middle toe 69.4-81 (74.2). 



The eggs of Sula nehouxi, like those of other boobies, have 

 a very pale bluish ground-color over which there is a chalky- 

 white coating. One specimen lacks this coating, and is a pale 

 blue all over. The other G.gg in the same clutch has the 

 coating. 



Seventeen eggs (ten of them composing five sets of two 

 each, the remaining seven composing seven sets) collected by 

 Mr. Beck from a colony on southeast Hood on September 28, 

 1905, yield the following minimum, maximum, and aver- 

 age dimensions in millimeters: Length 57.6-67.7 (62.3); 

 breadth 40.2-45.4 (43.1). The eggs comprising the sets of 

 two each measured by sets: 64.5X41.1, 63X42.9; 61.4X43.6, 

 63.5X44.5; 63.5X43.5, 61.6X42.6; 57.6X42, 59X40.2; 

 61.9X43.6, 61X43.9. 



Sula brewsteri : Brewster's Booby 



It is not unlikely that the birds reported from the Galapa- 

 gos Archipelago as Brewster's Boobies were either the young 

 of the Peruvian Booby or the young of the Blue-footed Booby. 



The three centers of abundance of Brewster's Booby visited 

 by the Galapagos Expedition were San Benedicto, Revilla 

 Gigedo Islands, on July 26; Clipperton Island, Mexico, on 

 August 10; and Cocos Island, Costa Rica, September 3-13, 

 1905. 



We first encountered Brewster's Boobies on July 24, lati- 

 tude 19° 40' North, longitude 112° West. They were com- 



August 8, 1913 



