I'm sure this is a greater Vasa. Chester had a very successful pair in the old Oakfield aviaries for many years. I still miss them (the parrots, not the aviaries) as they were my favourite birds in the Zoo.
At one time they did have lesser Vasa parrots too. They were shyer and lived in the avairy behind the Aquarium, but I think they left over 10 years ago.
It's a Greater Vasa Parrot. I still miss these birds. For one thing it was easy to tell if they were nesting because the female lost her head feathers.
They liked to lie on the ground with their wings outstretched and the beak open when sunbathing. Some visitors were concerned that the bird had been injured or had become ill.
Greater Vasa Parrot at Chester Zoo 1985-2009
Lesser Vasa Parrot at Chester Zoo 1982-1994
Both species bred for the first time in the UK at Chester.