In the Mariana Islands--Looking for big changes in small places.

The brown tree snake (Boiga irregularis) is famous for having caused the extirpation of Guam's avifauna. Agreed to be a tragic and saddening story of invasion. Think, a beautiful tropical island without birds! A scary thought in itself. But what most people do not think of is the ecological effect losing birds. How will the loss of birds change the native forests of Guam?

I am currently working as a field technician on a project that is attempting to answer this question. With funding from NSF and USDA, PI's Joshua Tewksbury, Janneke HilleRisLambers, Ross Miller and Grad student Haldre Rogers are using the Mariana Islands as a huge natural experiment to understand the ecological role of birds in forest systems. The islands north of Guam (Rota, Saipan, and Tinian) still have healthy populations of birds, thus comparisons can be made between the northern islands and Guam. It is the type of experiment ecologist would dream of designing, but could never ethically create.

We are currently focusing on seed dispersal in an attempt to understand how spatial distributions of seed rain vary between the islands. Since birds are the primary disperser of seeds in Guam's forests, the effects of bird loss are predicted to be quite drastic. To measure how far seeds get away from their parent tree, we have hung seed traps in the jungle underneath fruiting trees at 1, 5, 10 and 20 meters away. These traps collect everything that falls into them--which mostly consists of leaves, sticks, frass, etc. We really just want the seeds.

Initially we sorted through all of the samples by hand, individually picking out each leaf and twig until it was possible to find the seeds. This was terribly time consuming. Luckily there are sophisticated machines that separate seeds out from various undesirables--complete with agitators, variable sized sieves, wind chambers and aspirator fans. But as you might imagine they are too spendy for ecologists. So we got creative. Inspired by the designs of seed sorting machines in agriculture we designed and built Kogia sima, our friend, our coworker, our invention. It is quite ingenious if I do say so myself. Kogia sima is not a dwarf sperm whale as the name implies, rather it is a seed sorting machine made of PVC pipe, 2x4's, a tupperware container, an old T-Shirt, and--the heart of the beast--a hair dryer. Dried samples from the seed traps go into the bottom of Kogia sima. The hair dryer blows unwanted leaves out the top like the spray from a blowhole, leaving the seeds down below. Although we still have to sort and identify the different species of seeds, Kogia sima greatly lessens the work load by removing all of the leaves and other light weight debris, which is helping us understand how changes in the dispersal of seeds by birds may impact the forest of Guam over time.