a minor fourth stand for one bird, and a diminished major seventh another

Fourths and fifths are 'perfect' and so are neither major nor minor, though they can be augmented (up) or diminished (down). And a 'diminished' major seventh would just be called a minor seventh (update: or maybe a dominant seventh depending on context). (Update: and I'd say something about what tye wrote above, but his story is too cool to quibble about music terminology).