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Corrections are the most useful thing you can send. If an entry states a figure you can source better, or describes a species behaving in a way your own records contradict, we would rather know.
Send a note
What is useful
A location precise enough to return to, what you counted and how, and the date of the observation. Photographs help; so does a note of what you looked for and did not find, which is harder to publish and often more informative.
What we do not publish
Records of rare species at precise coordinates, and anything that would identify a private site without the owner's agreement.