Strange heron

We went canoeing on the Charles today, where we saw this heron. Note the white neck: great blue herons usually have a much greyer neck. We’re unclear if this individual is an accidental visitor (the grey heron from Europe and the cocoi heron from South America look somewhat like this), a hybrid with a great white heron (from Florida), or if this coloration is just natural variation.  I’ve certainly never seen one like this before.

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