Any good field scientist needs a good camera. At the very least you have to document your sampling sites, record samples, and get good photographs of your methods for the inevitable presentations. A field camera needs to be compact, flexible, easy to use, light on batteries, and durable. Of course, the more advanced photographer may scale up to a robust Digital SLR, but at that point, you already know what you need. For the rest of us, a smaller point-and-shoot will suffice.
I shoot with both a heavy duty DSLR and a light-weight point-and-shoot, depending on the conditions, how much space I have available, and how much gear I have to lug around. When it came time to replace my 6-year-old point-and-shoot with something a little more modern, I wanted something that had more flexibility than the run-of-the-mill pointers while still being small enough to carry around in a pocket. I also put a priority on optical zoom (which is definately not the same as digital zoom). I chose the Cannon Power Shot SX130 IS.