Experiments at Makauwahi Cave Help Conserve Endangered Thrush
The highly endangered Puaiohi (Myadestes palmeri) is a common bird fossil in the sinkhole sediments at Makauwahi Cave. However, only a few hundred individuals survive in the wild today, restricted to a small area of Koke`e State Park and adjacent Alaka`i Swamp, due to a myriad of natural and anthropogenic causes. A major problem for this small native thrush (that nests in rock crevices) is that introduced rats have been raiding their nests and killing both young and adult females. To combat this threat, the state Division of Forestry and Wildlife designed birdhouses that the Puaiohi is happy to use, but the rats are still a problem.
Experimental birdhouse at Makauwahi Cave.
Dr. Lisa “Cali” Crampton and her staff of the state’s Kaua`i Forest Bird Recovery Project have been tweaking the design of the birdhouses to make them rat-proof, but their idea needed testing before full deployment. Makauwahi Cave Reserve was offered as a site to test the new designs, as, despite rat-control efforts, there are still plenty around. Currently, two types of experiments are underway. In one effort, a large rat cage was constructed and birdhouse designs are placed inside with rat “treats” inside the birdhouse (peanut butter and coconut). Dr. Burney has provided a series of live rats for release inside the cage, so that their attempts to reach the birdhouse despite shielding can be evaluated.
In a second experiment, visitors to the sinkhole in past weeks were greeted by a whole line of birdhouses on poles with variations on the rat exclusion devices, also baited with rat treats. An array of remotely triggered game cameras watch the houses night and day, to see if wild rats can get inside. The result has been a remarkable series of still photos and videos of rat acrobatics, as the persistent rodents climb the slick pole, try to somersault past metal exclusion devices, jump onto the roof from adjacent vegetation, and generally behave like rats. “It’s been great to have a site where we can try our designs without worry about disturbing the neighbors or having onlookers disrupt the experiments,” Dr. Crampton observes. “We hope that our new design can make a big difference for the survival of this rare bird endemic to Kaua`i.”
For the cave project, this represents yet another example in which the site can play a role in conserving a species that is represented in the adjacent fossil record.
Forest person working on a birdhouse
In an automated night-time photo from a remote camera trained on the experimental birdhouses in Makauwahi Sinkhole, two rats can be seen climbing the slippery metal pole with ease.
(Photo courtesy of Kaua`i Forest Bird Recovery Project)