Here is an interesting example of a project using a small SUAV to survey grey heron nests in the UK. Interestingly, this doesn’t appear to disturb the birds. This seems partly due to how close the drone gets and partly due to the use of a DJI Mavic Pro, which is quite a small, relatively quiet machine.
Further details can be found here: https://conservationdrones.org/2018/05/19/more-heron-nest-surveys/
AeroEcology Ltd 