What is hancock bird?

The term "Hancock bird" does not refer to a specific bird species. It's possible that you might be referring to something specific to a local region, a nickname, or perhaps it is related to a personal name or context that is not widely recognized. If you have more specific information or context, I would be happy to help further. If you meant something like Hancock's work on birds or another related term, please let me know so I can assist you better.