A rat-resistant artificial nest box for cavity-nesting birds

The puaiohi or small Kauai thrush (Myadestes palmeri) is an endangered bird endemic to the island of Kauai, Hawaii. The sole population of about 500 birds is currently restricted to remote, higher elevation areas of the Alakai Plateau. Puaiohi nest primarily on steep streamside cliffs, and their distribution and abundance are limited by availability of suitable nesting sites. Black rats (Rattus rattus) cause nest failure and mortality of nesting female puaiohis, and ground-based rodent control has not been effective at reducing nest predation. In 2007, we investigated whether artificial nest structures might be a viable alternative to rodent control by testing nest-box designs to find one that was resistant to rats. In laboratory trials, we evaluated 3 designs that were currently being deployed as artificial nest boxes for puaiohi and found that they were not rat resistant. From these results, we developed and tested an improved design. Captive rats were unable to enter a nest box made from a 36-cm length of 15-cm-diameter plastic pipe with an overhanging entrance cut at an angle of 49 o.