Okay, so I know it's called a portmanteau when you blend the meanings and sounds of two words together to make a new word. But what is it called when you blend the posture and sounds of two birds? 

(Pictured here: A Great Ring-billed Gullegret spotted on the lake this early morning who would really like to know.)

https://cdn.masto.host/mstdngames/media_attachments/files/111/025/567/515/781/979/original/4d6216a62647a6bc.jpg