Tudor Wharf Draft Environmental Impact Report EOEA # 6744 



Territoriality 



Although described as being communal and 

 having a complex social system, black-crowned 

 night herons are highly territorial within 

 their loosely communal aggregates. Young 

 birds that have left the nest are reported to 

 successfully defend their territory from 

 intruding adults (Nobel et al. 1938). 

 Indeed, young herons still only three weeks 

 old, would defend their nest against adults 

 that were not their parents (Noble and Wurm 

 1942). Lorenz (1938) describes the 

 relationship between young herons and adults 

 rather colorfully: "Such impudent youngsters 

 are not only absolutely immune from attack, 

 but the old birds actually seem afraid of 

 them and will retreat whenever they see one 

 coming." Soon after leaving the nest young 

 herons will aggressively establish and defend 

 territories within their natal tree. It 

 appears that dominant birds defend perches 

 higher in the nesting trees than submissive 

 individuals (Nobel et al. 1938). Alliances 

 among birds, usually siblings, to defend 

 common areas were also noted by Nobel and his 

 colleagues (1938) . Adult birds defend 

 vigorously the immediate location of their 

 nest. 



Nest Construction and Habitat Selection 



Black-crowned night herons are colonial 

 nesters where male and female share in nest 

 construction activities. The male appears to 

 be the one to collect nesting material. 

 Although he initially participates in the 

 actual construction of the nest, he may 

 distribute nesting material to the female who 

 stays in the nest and conducts most of the 

 construction. 



According to Gross (1923), nests he studied 

 on Sandy Neck, Barnstable, Massachusetts, 

 were typically found in trees and constructed 

 of "cedar, oak, and especially of pitch 

 pine." The average height of the ten nests 

 he reported was approximately 17 . 5 feet above 



-250- 



