Custer, T. W., 1991, Green coloration of recently laid black-crowned night-heron
eggs: Colonial Waterbirds, v. 14, no. 2, p. 184-185.

Abstract

Color of Black-crowned Night-Heron (Nycticorax nycticorax ) eggs of known
laying order was quantified in a Wisconsin colony. Eggs were of greener intensity
on the day of laying and one day thereafter than earlier laid eggs within a clutch.
Egg color can be used to identify clutches within one day after clutch completion
and to assign laying order within clutches during this period.

Keywords

colour-/ clutch-/ Nycticorax-nycticorax/ USA,-Wisconsin/ bird-eggs; laying-order.