A small, lightweight, and inexpensive "burrowscope" for viewing nest contents of tunnel-nesting birds

Traditional methods of examining the nest contents of burrow-nesting birds have often been destructive, expensive, and/or limited to large-bodied species. Here we present details of a small, efficient, and inexpensive "burrowscope" designed for examining the nest tunnels of very small birds. The burrowscope consists of a tiny (16 mm X 22 mm) video camera and infrared light-emitting diodes, mounted on the end of flexible conduit (20-mm diameter) that houses a live video feed to a small, hand-held monitor display. In total, the burrowscope is only 22 mm wide at its widest point, weighs approximately 900 g, and was built for less than US $400. The burrowscope was tested in the field and could be used at 99.8% of Rainbow Bee-eater (Merops ornatus) nests and 100% of Spotted Pardalote (Pardalotus punctatus) nests (one of the world's smallest burrow-nesting birds). The accuracy of the burrowscope was evaluated by excavating a nest access hole at a sub-sample of Rainbow Bee-eater nests. The burrowscope enabled precise determination of clutch size at 30 of 30 nests, and brood size at 125 of 127 nests. The equipment could be applied to other organisms, including some invertebrates, reptiles, amphibians, and burrow-nesting mammals.