172 TROPICAL WILD LIFE IN BRITISH GUIANA 



The nesting season of .hoatzins has been variously stated 

 to be in January, April, July and October. I found evi- 

 dence that the birds of this region, like many other tropical 

 species, have two periods of breeding. In every small flock 

 of hoatzins I observed immature individuals in adult plum- 

 age, but of considerably smaller size, which I estimated to 

 be about six or seven months old. In late May, I found 

 a few nests with eggs, but the great majority contained 

 young of about two weeks of age. These facts would indi- 

 cate that the beginning of the two breeding seasons was in 

 November and April. While the birds may, as individuals, 

 nest off and on throughout the period from November to 

 May, yet from what I saw of the two very distinct stages 

 of nestlings and three-quarter grown birds, the two annual 

 breeding seasons are quite clearly defined. 



As to the relative number of eggs and young, seventy- 

 five per cent of the nests contain two eggs, while three eggs 

 are found in about one-quarter of the nests. When the young 

 birds have reached the age of two weeks, the relative num- 

 bers already show the effect of some inimical factor in the 

 environment. One-half of the nests now contain only one 

 young bird ; forty per cent hold two young, while those with 

 three young amount only to ten per cent of the whole. In 

 fact, I found only two broods of three young, and it was 

 interesting to observe that in both cases three nests were 

 superimposed one upon the other, as if the same pair of birds 

 had been unusually successful in establishing their home year 

 after year in the same place. And the full complement of 

 young bore testimony to the fact of their parents' ability to 

 meet the difficulties and cope with the dangers of the breed- 

 ing season. 



As I have stated elsewhere, the nests are invariably 

 built over the water, but two which I found were so placed, 

 that at low tide the mud of the river's edge was exposed 

 directly beneath. This was decidedly an error of judgment 

 on the part of the parent birds. Whenever a nest was threat- 



