The most important thing for the cot is that it can be heated in the winter to ensure that the animals are never exposed to frost. To have the possibility to illuminate the cot during winter time, Birdlamps with UV radiation shall be installed for this a power supply is a must.
Also keep in mind that once an animal can get sick, then you have the opportunity to set up an infra-red lamp or similar.
It should also be dry inside, so that in the winter when there is cold, wet weather, that bacteria or fungi not starts to disperse.
The size has to be adapted to the number of animals. The interior should be at least for a breeding couple 3 x 3 m. That it is possible to install perches the height should be min. between 2.5 and 3 m.