One of the many similarities between Chaco and Casas Grandes in Chihuahua, in addition to the similar types of effigy vessels, is the presence of significant numbers of scarlet macaw skeletons at both sites. As with most of these parallels, the evidence at Casas Grandes is more impressive in scale, with hundreds of macaws found as compared to dozens at Chaco. It has long been argued that Casas Grandes may have been breeding the macaws, rather than importing them all directly from areas to the south, and that it may have even been the source of most of the macaws found elsewhere in the Southwest. When it was thought that Casas Grandes was contemporaneous with Chaco, it seemed like an obvious source of the macaws found there and in the Mimbres area in between, but it is now known that the rise of Casas Grandes came well after the decline of Chaco, so wherever the macaws at Chaco came from, it wasn’t Casas Grandes.
So, leaving the question of Chaco and other early sites with macaws aside, what was going on with the macaws at Casas Grandes. Were they indeed being bred and traded to other Southwestern sites, such as Wupatki in northern Arizona? Or were they being imported directly from somewhere in Mesoamerica, either for trade or for local use? A recent paper sets out to look at this question using stable isotope ratios, a type of analysis we have been seeing a lot of lately in Southwestern archaeology. Specifically, the paper looks at the ratio of carbon-13 to carbon-12, widely used to determine the diet of an animal and specifically whether it was dependent on maize, and the ratio of oxygen-18 to oxygen-16, which reflects the chemical makeup of the water the animal drank and can be used as a rough proxy for the environment in which it was raised. We’ve seen carbon isotope analysis recently used to show that Anasazi turkeys subsisted mainly on maize. Oxygen isotope analysis is used less in the Southwest, but it is particularly useful here because the ratio varies with elevation, humidity, and proximity to the ocean, all of which are major differences between the high, dry Casas Grandes area and the humid coastal lowlands to the south where the scarlet macaw has its natural range. The ratio thus gives a good sense of whether the birds were brought up from the south or raised right at Casas Grandes. Strontium isotope ratios can pinpoint places of origin with more precision, but to be useful they have to be accompanied by a major sampling effort to determine the ratios in the various possible source areas. The conclusion of this paper suggests that strontium analysis may be in the works, but as a first pass oxygen isotope analysis is a good way to go.
The carbon isotope analysis found that the macaws subsisted almost entirely on maize, although the very youngest nestlings seem to have been fed a more varied diet. Clearly, then, these were not wild macaws captured in their natural habitat and brought north. In addition, the oxygen isotope analysis found that all but one of the macaws had spent its life in the Casas Grandes area. The exceptional macaw had an oxygen isotope ratio suggesting a more humid, low-lying environment, so it was likely traded up from somewhere in Mesoamerica. This suggests that the macaws were indeed being bred at Casas Grandes, although trade relationships with Mesoamerican communities did involve the acquisition at least occasionally of additional birds.
This is all very interesting for understanding Casas Grandes, but what I find most intriguing about the paper is the possibility of using the same techniques on macaw bones from other parts of the Southwest, especially Chaco and other sites pre-dating Casas Grandes. This paper seems to show pretty conclusively that macaw breeding was going on at Casas Grandes, but it’s still a very open question whether that was an innovation or the continuation of an earlier Southwestern tradition. I think the Mimbres area is the best place to look for earlier macaw breeding, although obviously Chaco is a possibility as well. The exact techniques used in this paper would really only be useful for determining if macaws were bred in captivity and if they came from Mesoamerica or somewhere in the Southwest, but the addition of strontium analysis would allow more precise identification of breeding areas within the Southwest, if indeed there were any earlier than Casas Grandes.
Somerville, A., Nelson, B., & Knudson, K. (2010). Isotopic investigation of pre-Hispanic macaw breeding in Northwest Mexico Journal of Anthropological Archaeology, 29 (1), 125-135 DOI: 10.1016/j.jaa.2009.09.003