An unusual fossil found in Spain is providing the oldest evidence of birds serving as food.
The mass of bones, jumbled together in an area less than 4 square inches, turned up in a layer of fossil-riddled sediments where the other specimens remain complete, intact, and isolated from one another. Analysis shows that the mixed bones came from four baby or juvenile birds of three different species, says José L. Sanz, a paleontologist at the Universidad Autónoma de Madrid.
A still body of water formed the fine-grained sediments encasing the fossil, Sanz and his colleagues report in the Feb. 22 Nature. Therefore, it's unlikely that four immature birds would have washed into the lake and been buried together in a single mass.
Sanz and his colleagues discount the idea that the birds came from a single nest, because ancient birds aren't known to have laid eggs in other birds' nests.