414 BIRDS OF AUSTRALIA. 



Gilbert, " are extremely numerous on the Houtmann's Abrol- 

 lios, where they breed in prodigious numbers. The present 

 species lays its eggs in November and December, on a nest 

 constructed of sea-weed, about six inches in diameter and 

 varying in height from four to eight inches, but without 

 anything like regularity of form ; the top is nearly flat, 

 there being but a very slight hollow to prevent their single 

 egg from rolling off. The nests are so completely plastered 

 with the excrement of the bird, that at first sight they ap- 

 pear to be entirely formed of that material ; they are either 

 placed on the ground in a clear open space, or on the tops of 

 the thick scrub, over those of the Onychoprion fidiginosus^ the 

 two species incubating together with the most perfect har- 

 mony, and the bushes presenting a mottled appearance from 

 the great numbers of both species perched on the top : the 

 male 0. fidiginosa sitting quite close to the nest of the 

 Noddy, while its mate is beneath performing the duties of in- 

 cubation. On walking among the nests I was surprised to 

 observe the pertinacity with which the birds kept their post ; 

 in fact they would not remove from off the egg or the young, 

 but would suffer themselves to be trodden upon or taken off 

 with the hand ; and so thickly were the nests placed, that it 

 was no easy matter to avoid crushing either eggs or birds at 

 every step. By the middle of January the eggs were nearly 

 ready to hatch, and there would be an overwhelming increase 

 of this species yearly but for the check which nature has pro- 

 vided against it in the presence of a small lizard which is very 

 abundant about their breeding-places, and which finds an easy 

 prey in the young of this Noddy and of Onychoprion fuligi- 

 nosus. I am satisfied that not more than one out of every 

 twenty birds hatched ever reaches maturity, or lives long enough 

 to take wing ; besides which, great numbers of the old birds 

 are constantly killed : these lizards do not eat the whole bird, 

 but merely extract the brain and vertebral marrow ; the re- 

 mainder is however soon cleared oflp by the Bermedeslarda- 



