Hi Iain
Time - lots of comments from others and yourself re the technical qualities so my only comment is that it is a great fun, creative idea.
It is hard sometimes to get away from the literal but to me that is a part of the challenge and this is very original.
Just one point, there are at least 80 days in there but :
"LENGTH OF INCUBATION
Chicken eggs require 21 days to hatch, but the incubation period for the eggs of other species of poultry varies. The approximate periods of incubation required for various species of poultry and game birds are:
Chicken . . . . . . . . . . . . . . . . . . . . . . . 21 days
Turkey . . . . . . . . . . . . . . . . . . . . . . . . 28
Duck . . . . . . . . . . . . . . . . . . . . . . . . . 28
Muscovy duck . . . . . . . . . . . . . . . . 33-35
Goose . . . . . . . . . . . . . . . . . . . . . . . . 29-31
Guinea . . . . . . . . . . . . . . . . . . . . . . . 26-28
Pigeon . . . . . . . . . . . . . . . . . . . . . . . 16-18
Ring-neck pheasant . . . . . . . . . . 23-24
Mongolian pheasant . . . . . . . . . . 24-25
Bobwhite quail . . . . . . . . . . . . . . . . 23
Japanese quail . . . . . . . . . . . . . . . 17-18
Chukar partridge . . . . . . . . . . . . . . 22-23
Peafowl . . . . . . . . . . . . . . . . . . . . . . 28 "
So what was yours?