This post was contributed by John A. Moretti, co-author of a recent paper in The Wilson Journal of Ornithology on the occurrence of Thick-billed Parrot remains at archaeological sites in the Southwest.
The American Southwest conjures images of giant saguaro cacti, Gila monsters, and vast deserts. This landscape and ecology are a starkly different from the tropical forests and savanna of Central and South America, but preserved within the iconic ancient Native American pueblos of the American Southwest are the skeletons of Scarlet Macaws. Genetic and isotopic data show that the over 100 individual Scarlet Macaws found at sites such as Wupatki and Chaco Canyon were imported from Mesoamerica. Those highly intelligent, brightly colored birds appear to have held ritual significance for Southwestern cultures, and their transport into the region was part of an ancient cultural exchange of both objects and ideas. Scarlet Macaws are the most common member of the parrot clade (i.e., Psittacidae) in archaeological sites within the present-day United States, but other species, including Military Macaws, Thick-billed Parrots, and even a rare few parakeets also occur. Those species are generally regarded by archaeologists as exotic objects, transported into the region from present-day Mexico—but could one of them have originated much closer?
I am a paleontologist interested in changes in the diversity and distribution of vertebrate species in western North America throughout the Quaternary Period. Archaeological sites such as those of the American Southwest are rich sources of the remains of past animals. Archaeologists study those remains to understand the behaviors of past people. To me, however, those same remains provide important evidence of the distribution of extant taxa prior to the major changes that accompanied European settlement, the Industrial Revolution, and modern environmental and climatic degradation. By studying those faunal samples, I can contribute to the development of a natural history perspective that helps all of us understand faunal communities of the past and present. Those records shed light on the evolution of species and ecosystems as well as their response to changes in climate, environments, and vegetation. In turn, those interactions in the past help us predict future outcomes and improve conservation strategies.
Several years ago, I was working at the Museum of Texas Tech University while I finished my Master’s degree and was tasked with reviewing samples of unidentified faunal remains from an archaeological site in New Mexico. That site, Bonnell, was a small Native American village dating to between 1200 and 1400 C.E. in the foothills of the Sacramento Mountains. Bonnell was excavated from 1950 to 1956 by Jane Holden Kelly and others from Texas Tech. Although reports were published in the mid 1980s describing the cultural and faunal materials collected from Bonnell, several bags of bones remained unidentified and uncatalogued in the collections of the Anthropology Division. My task was to sort through the samples and report anything significant. Overall, the work was mundane and repetitive; most bones were unidentifiable, and those that could be assigned to a taxon came from deer or rabbits, common food items of past peoples.
After going through repetitive bags of deer and rabbit bone scraps, I was surprised when, one day, I emptied the next bag and found a small, stocky foot bone of a bird. I instantly recognized that the bone, a tarsometatarsus, represented a psittacid. Many years earlier I had been intrigued by the Scarlet Macaws of the American Southwest and learned the basic anatomy of the psittacid skeleton. The tarsometatarus is one of the most easily recognizable elements because it forms the distinctive zygodactyl (two toes pointed forward, two backward) foot structure common to all parrots, macaws, and parakeets. I immediately started excitedly digging through the relevant literature and found that no psittacid remains had been reported previously from Bonnell, or even eastern New Mexico. I pulled all of the identified, cataloged bones from Bonnell to check for any other psittacid elements but could not find any. This was a new record and I was already pondering how to write it up.
To determine what type of psittacid the Bonnell specimen represented, I studied the form of the tarsometatarsus in modern specimens of parrots, macaws, and parakeets in the collections of the Smithsonian National Museum of Natural History and the University of Kansas Biodiversity Institute and National History Museum. That work documented the morphology of the tarsometatarsus in 21 extant species from the Western Hemisphere and revealed traits capable of distinguishing between individual genera. Applying that morphological dataset to the tarsometatarsus from Bonnell demonstrated that the specimen came from Rhynchopsitta pachyrhyncha – the Thick-billed Parrot.
Thick-billed Parrots are pine cone specialists native to the Sierra Madre Occidental of western Mexico. These are not tropical parrots. For example, Thick-billed Parrots will eat snow when free water is unavailable! They inhabit mature, old-growth conifer forest and conifer-oak woodland high in the mountains. The pine nut crops that the parrots depend on are highly variable across space and time. Accordingly, Thick-billed Parrots are highly mobile and the large, gregarious flocks range widely during daily and seasonal foraging as they track pine-cone production. The narrow, specialized diet of these birds restricts their geographic distribution, but so does their behavior of nesting in old, large, dead trees. As logging and deforestation altered old growth forests throughout North America, the species declined and, today, the Thick-billed Parrot is highly endangered.
Skeletons and isolated bones of Thick-billed Parrots have shown up in archaeological sites in the United States before. Seeking to provide some geographic context to the new record from Bonnell, I reviewed the literature and determined that these parrots have occured at nine other archaeological sites, all in Arizona and New Mexico. No one had ever assembled a full list of archaeological occurrences of Thick-billed Parrots in the U.S., and as I examined the list of 10 sites, I began to suspect that there were important clues explaining the geographic distribution that had been overlooked by earlier workers.
Five of the ten sites with Thick-billed Parrot bones were in or near montane conifer forest with species of pine and fir that the parrots are known to consume. Was it possible that the parrots were not imported across long distances as long suspected, but instead were captured in the high elevation forests of the American Southwest? That regional procurement hypothesis has long been discounted, and I began to discount it too as I realized that the remaining five sites were all located in desert habitats, no place for a montane parrot.
As I continued to dig through publications, however, I turned up important data and started to connect dots scattered widely throughout the archaeological and ornithological literature. I soon recognized that each of the five sites located in desert habitats had direct links to distant mountain forests. At Una Vida, Pueblo Bonito, Wupatki, and Snaketown, ancient people used large, mature pine and Douglas fir trees as structural timbers to build complex, monumental-scale dwellings. Procuring that timber required extensive networks of logging, transport, and trade spanning dozens of kilometers operating over centuries, and timber was not the only material being transported from mountain forests back to the population centers in the desert. The presence of bones from tassel-eared squirrels and Clark’s Nutcracker, both montane conifer forest specialists, at some of these sites demonstrates a link between desert and mountain forest habitats and between logging and hunting. The final site, Buena Vista Ruin, contained no record of montane conifer timber, game, or other materials. Still, the site, located in the desert flood plain of the Gila River, was linked to habitats reaching far up the slopes of the nearby Pinaleno Mountains by a contemporaneous network of irrigation canals, agricultural fields, and rural communities. Each of the ten sites, then, were either located in or exhibited direct links to montane conifer forests in Arizona and New Mexico.
Many of the same ten sites contained remains of Scarlet Macaws and other evidence of Mesoamerican influence, and despite the clear connections between the archaeological sites and regional montane conifer forest habitats, we have no direct evidence that parrots were present in those forests in the ancient past. However, the literature contains records of wild and re-introduced Thick-billed Parrots visiting, foraging, and even breeding in many of the same mountain forests associated with the ten archaeological sites. The most striking examples come from Wupatki, near Flagstaff, Arizona, and Buena Vista Ruin, in southeastern Arizona. Thick-billed Parrot remains dating to 1095-1185 C.E. were found at Wupatki, just east of the San Francisco Mountains, and Spanish explorers observed flocks of parrots just to the west of the San Francisco Mountains in 1583. In the 1980s, a flock of wild-caught Thick-billed Parrots confiscated from the illegal pet trade were released in extreme southeast Arizona and made annual migrations across the state, spending the summer of 1987 in the San Francisco Mountains. Those re-released parrots visited the Pinaleno Mountains above Buena Vista Ruin in 1986-1987, an area where wild flocks had foraged in the 1910s. Actually, wild flocks visited montane conifer forests throughout southern Arizona and southeastern New Mexico on a near-annual basis from 1898 to at least 1938, with sightings occurring as late as 1964. The release of confiscated birds in Arizona in the late 1980s was prompted by those wild occurrences earlier in the 20th century and the associated hypothesis that the wild flocks represented seasonal breeding populations.
The wild flocks of the twentieth century and the behavior of the re-released individuals show that these forests offer suitable habitat for Thick-billed Parrots. Moreover, those occurrences indicate that Arizona and New Mexico were once part of the species’ natural range. The twentieth-century flocks were hunted extensively and likely also suffered from deforestation, with both factors presumably influencing their eventual extirpation. The archaeological occurrences, linked to many of the same forests, present compelling evidence indicating that Arizona and New Mexico have been part of the range of Thick-billed Parrots for millennia. Many of the archaeological occurrences appear to date to relatively wet intervals set within cycles of megadrought, suggesting that the parrots were present in the American Southwest when pinecone crops were abundant. The montane forests of Arizona and New Mexico may, then, represent portions of the range of the Thick-billed Parrot that become critical during periods of pinecone crop scarcity or failure elsewhere. Accordingly, those habitats may be act as a sort of safety net essential to the long-term survival of species.
Still, our knowledge of the past is incomplete, and the full picture is difficult to resolve. The case I present for the regional procurement of Thick-billed Parrots within the American Southwest is largely based on circumstantial evidence. Nonetheless, the evidence I describe in my paper makes it clear that Thick-billed Parrots cannot and should not be interpreted in the context of Scarlet Macaws just because they are both psittacids. The ecology of the two species is completely different, and the available evidence demonstrates that there is no necessity to presume that Thick-billed Parrots had to be imported from present-day Mexico. Instead, viewed from the lens of Thick-billed Parrot ecology and natural history, that evidence suggests that the species is native to the region.
This whole project was a lot of fun for me, full of twists and turns, ups and downs, and persistent discoveries. I certainly never imagined that the mundane task of reviewing bags of unidentified bones could have led to this. I learned a great deal as I tracked Thick-billed Parrots across space and time, and my paper presents a new perspective on parrot natural history, a perspective that should help us better understand the last remaining parrot species native to the United States.
Learn more about the Museum of Texas Tech University at depts.ttu.edu/museumttu.