The Breeding Habits and Growth of The Nestling Blackcrowned Night Heron,Nycticorax nycticorax

From 1994 to 1998,observations on the breeding habits and growth of the nestling of black-crowned heron were made in the Changshan and Yuhang Bird Reserve,Zhejiang Province.The results were as following:1)The adults migrated to this reserve in the middle and late April and lefted in the late September.2)Average height of nests from grownd was 8.51 m and the nests were simple,dash-shapped with following measurements:external diameter 30-50 cm,internal diameter 20-30 cm,depth 3.5-8.0 cm.3.)The average number of egg of 35 clutches was 3.49,the incubation period 22-26 days,the survival rate in incubation period 95.45%,the length of nursing period about 30-35 days.4)The body weight of the nesting was 26.8 g at the 1st day of hatching,and increases to a maximun of 556 g at the 51 th day.The growth of weight in 51 days after birth was fitted by the following model:Wt=560/1+e-0.231(t-12) with R2=0.99.The length-weight relationship could be expres sed in the following formula:W=0.000246 L2.5029.5)The process of establishment of homeothermal ability involved 3 periods:(I)the confused growth period (1-16 day);(ii)the growth period (17-28 day);(iii)the homeothermal period (after 28 day).6)The main food of nestlings is Cambaroides (45%),Cyprinidae (40%),Cobitaidae (15%).