Stormy petrel and Storm petrel

Stormy petrel noun - Sooty black petrel with white markings; of the northern Atlantic and Mediterranean.

Storm petrel and stormy petrel are semantically related in petrel topic. In some cases you can use "Storm petrel" instead a noun phrase "Stormy petrel", when it comes to topics like bird of ill omen, shearwater.

Storm petrel noun - Any of various small petrels having dark plumage with paler underparts.

Stormy petrel and storm petrel are semantically related in petrel topic. You can use "Stormy petrel" instead a noun phrase "Storm petrel", if it concerns topics such as shearwater.