Pairing Age and Reproductive Success in Black crowned Night Herons at Tai Lake,China

Data on pairing age and age-related reproductive success were collected in Night Herons Nycticorax nycticorax at Tai Lake area in a period from April to June,2001.Of 206 pairs nesting at positions easy to observe,2 pairs were 2-yr old and 4-yr old,39 pairs were "2Y+2Y",34 pairs were "3Y+3Y",and 131 were "4Y++4Y+"(6 abandoned in midcourses).Of the reproductive birds 2- and 3-yr old parents were 35.4%.In 200 nests producing fledglings,there were no differences of the egg volume and brood size in the three age-class parents,but the egg weight,clutch size,hatch rate and the survival rate increased with parents age.