Thence tears flow forth; and amber distilling from the new-formed branches, hardens in the sun; which the clear river receives and sends to be worn by the Latian matrons.
As it seeps from the trunks and branches of injured trees, resin — the tears of legend — traps insects and other small animals. If protected from air, the resin eventually turns into amber. The organisms within are suspended in amber, often preserved so well that they retain internal organs and even DNA.
Poinar, Voisin and Voisin (2007) report a fragment of egg shell preserved in Dominican amber. Although frogs, lizards and bird feathers have been described before, this is the first specimen of a vertebrate egg.
The tiny egg — less than a centimetre long — is thought to belong to a hummingbird. If so, then it also of importance as the earliest known hummingbird in the New World. The amber is of disputed age but is somewhere between 15 and 45 million years old, which makes the shell contemporaneous with hummingbird fossils in Europe but much older than those from the Americas.
Poinar jr, G., Voisin, C. & Voisin, J-F. (2007). Bird eggshell in Dominican amber. Palaeontology. Published online 4 Sept 2007. doi: 10.1111/j.1475-4983.2007.00713.x.