Wild birds as offerings to the Egyptian gods

Mammals, reptiles, birds: the tens of millions of animal mummies deposited as offerings in the necropolises of the Nile Valley bear witness to an intense religious fervour, and to the practices of collecting and preparing animals that undoubtedly contributed significantly to the economy from the Old Kingdom (3^rd millennium BC) to Roman Egypt (1^st–3^rd centuries AD). However, the origin of these animals and the methods of supply remain unknown. For some tamed species, such as the cat, breeding was probably the most efficient way of supplying large numbers of animals for mummification. But unlike cats, bird mummies cover all stages of development, from egg to adult, which may indicate more opportunistic sourcing practices.

In order to determine the origin –- breeding or hunting – of the mummified birds, tiny fragments of feathers, bones and embalming strips were taken from 20 ibis and birds of prey mummies from the collections of the Musée des Confluences, Lyon. If these birds, which migrate in the wild, had been bred, their diet would have been homogeneous, of local origin and reflected in the uniform isotopic composition2 of the animal remains, regardless as to whether that diet had been produced specifically or derived from that of coexisting humans.

The various tissues were therefore dated using the carbon-14 method; and the isotopic compositions of oxygen, carbon, nitrogen, sulfur and strontium were measured, interpreted in terms of food sources and compared with those of contemporaneous human mummies. However, far from being homogeneous, these isotopic compositions showed a high variability and "exotic" signatures compared to those of ancient Egyptian humans: the birds were wild, migrating seasonally out of the Nile Valley.

These results, combined with that of a genetic study carried out by another team3 , suggest the mass hunting and capture of birds as documented on certain tomb frescoes (for example on the wall of Nakht's tomb in the Theban Necropolis). Indeed, the Egyptians probably exerted a significant ecological pressure on wild bird populations long before the decline in avifauna observed today. 

• 2A chemical element can exist in different versions, called isotopes, which are distinguished by their mass. Isotopic composition refers to the relative abundance of different isotopes of the same element, such as oxygen or carbon.
• 3Mitogenomic diversity in Sacred Ibis Mummies sheds light on early Egyptian practices, Sally Wasef et al., PLOS ONE, 13 November 2019. https://doi.org/10.1371/journal.pone.0223964