SOLVED. YA Fantasy | Children go to an island with a giant black bird (dodo?) on it. [s]

[Alistair]

Not sure about much of the plot! I can recall the cover being purple with a big black bird in a nest on it.

I read it in the mid-late 90s, and it was probably published around then.

[Alistair]

That's the one, thank you so much! It turns out my copy had the alternative title 'Monster Mission.' I'm going to seek it out and re-read it, thanks!

[Rainbowheart]

Island of the Aunts for the link.