A photographic guide for determining egg incubation stage in the Superb Fairy-wren Malurus cyaneus

When monitoring the nesting biology of wild birds, nests are often found after the eggs have been laid and incubation has commenced. Candling – the use of a bright light to illuminate egg contents – is a useful method for estimating embryo development and incubation stage. This information is used to estimate when incubation started and predict when eggs will hatch. As the focus of several long-term monitoring studies, a guide for assessing the stage of embryo development in the Superb Fairy-wren Malurus cyaneus will enable a standardised estimation of egg development for nests found after laying has been completed. Here, we present a photographic guide for determining embryo development using candling in the Superb Fairy-wren. In the process of developing this guide, we also address the need for a cost-effective and accessible method for candling eggs in the field with a portable candling device.