Color of Black-crowned Night-Heron (Nycticorax nycticorax) eggs of known laying order was quantified in a Wisconsin (USA) 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.
Additional publication details
Green coloration of recently laid black-crowned night-heron eggs