There are many websites that post jobs involving field work - this list is a small sample of more general websites that mostly post jobs related to conservation, ecology, and evolution. You can also check websites of specific non-governmental organizations, environmental consulting firms, and so on.

Unfortunately, these sites do get exploitative positions posted to them. Watch out for positions that do not pay, or those that require you to pay instead!

Note: Most entry-level field work positions are seasonal contracts for spring/summer, and are advertised mostly between October to February (it can be difficult to find field work jobs in the winter). In general, the sooner you can start looking and applying, the better - many spring/summer positions are taken down by December/January. Ontario government positions, including summer student positions, are usually posted between February to April, depending on the positions.