Estimating the hatch dates of Australian brush-turkey embryos by candling

Abstract

There are several techniques available for quickly assessing the age of developing avian embryos, all of which rely on determining air cell growth within the egg. As megapode eggs do not form a fixed air space, these methods cannot be used. This study presents a method for estimating the hatching date of Australian brush-turkey (Alectura lathami) embryos quickly and reliably using a candling technique. Eggs were candled using a hand-held torch. The percentage of eggshell covered by the chorioallantois was recorded several times throughout the incubation period for each egg. These percentages and their corresponding values for ‘days until hatching’ (calculated by counting back from the actual hatch date to the date of observation) were used to construct a simple linear regression equation. The reliability of this method was tested by predicting hatch dates of eggs from the 1997/98 breeding season using the regression graph and comparing the estimated hatch dates with the actual hatch dates.