External measurements of the animals are made in “het Natuurmuseum” at Rotterdam.
The feet and the beaks of the birds are made out of bronze to prevent damage by curious visitors. The models are made to show the specialised beaks to catch different prey and on the beach.
The encyclopaedia of ornithology
Encyclopaedia of birds,
Fundaments of ornithology,
Ornithology, The Cambridge encyclopaedia,
Grzimek, het leven der dieren.
Strandvogels van Europa,