Tudor Wharf Draft Environmental Impact Report EOEA # 6744 



the ground. In a more recent study of black- 

 crowned night herons nesting in Plymouth, 

 Massachusetts, Davis (1986) reported that 

 nest site selection "...by black-crowned 

 night herons and snowy egrets was a complex 

 phenomenon that may have been influenced by 

 (1) the time of nesting, (2) the presence of 

 old nests, and (3) the presence of other 

 nesting pairs." 



The determinants of nest site selection and 

 habitat quality in the inner Boston Harbor 

 area has not been determined. Preferred 

 nesting sites are not found in the inner 

 Boston Harbor. The black-crowned night 

 herons prefer to nest in areas more isolated 

 from man's activities such as the Boston 

 Harbor islands. 



Egg Laying and Incubation 



In New England, egg laying usually begins 

 towards the middle of April and ends, 

 typically, early June. This activity varies 

 somewhat according to weather, food 

 availability, habitat quality, sociality, and 

 other variables (Custer et al. 1983, Davis 

 1986) . 



Clutch size in black-crowned night herons 

 varies from 1-6, with 4-5 being the average 

 (Gross 1923, Custer et al . 1983). Northern 

 herons, predictably, have a slightly larger 

 clutch size than southern populations (Custer 

 et al. 1983) . 



Black-crowned night herons commence 

 incubation immediately upon the laying of the 

 first egg. This is typical of other herons 

 as well as raptors and other groups of 

 birds. This behavior results in the 

 asynchronous hatching of the eggs. 

 Therefore, the first egg to be laid is 

 usually the first egg to hatch. 

 Consequently, this stacks the deck in favor 

 of the first chick with respect to growth 

 rate and dominance over its siblings. The 

 duration of incubation lasts approximately 22- 



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