( citation needed ) The sirens of Greek mythology are sometimes portrayed in later folklore as mermaid-like ; in fact , some languages use the same word for both bird and fish creatures , such as the Maltese word ` sirena ' . The sirens of Greek mythology are sometimes portrayed in later folklore as mermaid-like ; in fact , some languages use the same word for both bird and fish creatures , such as the Maltese word ` sirena ' .