There is a possibility of coyotes. They have been spotted in our area before, not sure if they are on the island though. If they are on the island it would really hard to see them since they do not want to be seen.
Flashlights could be a problem though bright lights from houses or streets could be more of a problem if left on. Not familar with the area where these particular nests are.
Seagulls and fishes would cause the biggest threat however.
I wouldn't rule out a random coyote though, and racoons do love them too as was pointed out.
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