An apparatus for photographing whole clutches of passerine birds in transmitted light

Abstract

Single eggs have since long been examined in transmitted light in various ways in the field to obtain information on the incubation stage of a clutch. This technique can be rendered more effective by combining it with photographing whole clutches. An apparatus for this purpose is described, dimensioned for work with clutches of small passerines up to the size of thrushes. The photographs reveal more details than is possible to discern during direct examination in the field. Further, the presence of all eggs of the clutch on the same photo facilitates the interpretation in order to estimate certain breeding biology data, such as the time of incubation start and the developmental or hatching asynchrony.