35^ BROOKLYN INSTITUTE MUSEUM. SCIENCE BULLETIN 2, 6. 



from the mouth up ahnost to the first falls above Perico. It keeps 

 to the tops of the low trees which overhang the water and on the 

 buds and leaves of which it feeds. Colonies occupy the same general 

 area during the entire year, but at the approach of the breeding 

 season, which varies considerably in different localities along the 

 river, the flocks break up into pairs, each pair keeping to a restricted 

 area of the general breeding grounds. 



The breeding season about Caicara lasts from early in June until 

 mid September. In 1905 I took the first set of eggs June nth. 

 Freshly completed nests had been noted as early as May 25th, when 

 I went scouting for them, but at that time they must have been from 

 five to seven metres above the water. The nest found June nth was 

 between three and four metres above the water at nearly what would 

 be high water mark. On June i8th, seven sets of eggs were collected. 

 With the exception of one set of two, all were fresh. 



In my field record for that date I made the following entry : 

 Although Hoatzin are never hunted and very rarely disturbed in 

 their haunts they are nevertheless decidedly shy. Sitting birds would 

 always leave the nest when, or even before, we came in sight of the 

 same. The parent birds never remained near the nests and by actions 

 manifested but little concern in what was going on. Nests are 

 apparently never placed very close together as in a heronry. I have 

 rarely found them nearer than from twenty-five to fifty metres from 

 -one another. 



Of the seven nests containing eggs found on this date, none were 

 over 1.2 m. above the level of the water. The average was about 

 one meter, although one was only about 45 cm. up. At the rate the 

 river is rising the lowest of these nests would be under water before 

 the week is o\'er. 



On June 22nd seven additional sets of eggs were collected. The 

 nests were on an average between i to 1.25 m. above the water at that 

 time, which means that they would be at the water level, or below, by 

 the time the eggs would be hatched. 



My observations indicate that the nesting season on the Orinoco 

 is controlled to a large degree by the water level in tlie river. The 

 ovaries of nearly all the Hoatzin collected near Bolivar about the 

 middle of April indicated the approach of the breeding season. Speci- 

 mens collected at Caicara early in May did not show a more active 

 condition of the ovaries, but as I have stated above, completed nests 



