These are a very different type of drone, but I have worked on a site with a large colony of seabirds that also attracted a lot of recreational drone usage due to historical features on the site. These smaller, hovering drones would very obviously disturb the breeding birds in the short term - we would notice the disturbance before spotting the drone quite often - and there was a good deal of discussion about their growing use and possible consequences. The organisation currently has a ban on drones over their properties for this and various other reasons - but of course it is practically impossible to enforce, since you usually can't find the operator when they not present on site.

I have not seen any formal study of the effect of drones on seabirds until this though.