Changing from molecular neuroscience to ecology after PhD? Ecologist perspective needed!
I am not an ecologist, but I work with several, and if you squint and don't look very hard I might pass as one.

It will very much depend on the type of ecology you're interested in doing, and what kind of skills you have now. "Ecology" is a very wide open field, which can involve anything from fairly advanced mathematics to lots of field work, and everything in between. It's certainly possible (a lab I know has taken several postdocs from fields further afield than your own), but it would help if you could find a way to either apply your current skill set to an ecological problem.

Failing that, while it's likely still possible, it may take more time and be something of a rougher path.

Short version: "It depends."