During the years 1561–1565, a research group of Mexican scholars collected information in Tlatelolco on a large number of bird species. They were writing a regional work on Mexican birds that would eventually be part of a comprehensive encyclopedia about the Spanish colony of New Spain (Mexico). While gathering data on the great-tailed grackle, they were told by their expert consultants and collaborators that this bird was not native to the area but had instead been introduced there by Aztec Emperor Auitzotl before the Spanish Conquest (Haemig 2012).

Sometime during the years 1486–1502, Auitzotl (also spelled Ahuitzotl) commanded that great-tailed grackles be brought to the Valley of Mexico from Aztec provinces in the Huastec (Teenek) and Totonac regions of Mexico (Haemig 1978, 2011). After the grackles were transported to the Valley of Mexico and released there, the Aztecs made two additional human interventions to ensure establishment of these exotic birds: (1) supplemental feeding and (2) protection from human harassment and predation (Haemig 1978, 2011). Nurtured and guarded by Mexico’s most powerful ruler and his people, the grackles soon established themselves in their new home, multiplied and spread to other areas (Haemig 1978, 2011).

The research group that collected this information was led by Bernardino de Sahagún, an academic clergyman who had studied at the University of Salamanca in Spain (Anderson 1982). The other members of the research group, all native Mexican scholars, were either graduates and/or faculty members of the Royal College of the Holy Cross (El Imperio Colegio de la Santa Cruz) (Sahagún [1577] 1982; Haemig 2012). This College, located in Tlatelolco, was an elite European-style school that was a center for advanced learning and research in New Spain (Haemig 2012).

When Sahagún’s research group were told the details of Auitzotl’s introduction of the great-tailed grackle, they wrote them down in the Aztec language into a document now known as the Manuscript of Tlatelolco (Appendix A.1) Although the account they recorded does not specifically say that it is based on eye-witness-testimony, we cannot exclude that possibility. The account quotes the words of Aztec people guarding the introduced great-tailed grackles, suggesting eyewitness testimony (Appendix A.2) and/or use of a pre-Hispanic pictorial manuscript that was itself based on one or more eyewitness sources (Appendix A.3). In addition, the research group later revealed that the city where they were then working (Tlatelolco), was one of the sites where Auitzotl had introduced the great-tailed grackles 59-79 years earlier (Haemig 2011).

Nevertheless, to further verify the authenticity of the account, Sahagún’s research group had it peer reviewed by bird experts in another city where Auitzotl introduced the great-tailed grackle: the Aztec capital Tenochtitlan (Haemig 2011, 2012). After successfully passing this peer review, the research group wrote the historical account into a document now known as the Manuscript of 1569, which is regarded as the finished Aztec language version of their work (Appendix A.4). During the 1570s, the research group copied the Aztec texts of the entire great-tailed grackle account, together with a Spanish translation that included the scholia (i.e. glosses, explanations, critical comments, grammatical explanations, Appendix A.5) into the encyclopedia known today as the Florentine Codex (Appendix A.6). The complete bilingual texts of the historical account from the Florentine Codex read as follows:

Aztec Text (English Translation): It is named teotzanatl [divine, genuine, or marvelous grackle, see Appendix A.7] because it did not live here in Mexico in times of old. Later, in the time of the ruler Auitzotl it appeared here in Mexico. For he commanded that they be brought here from [the provinces of] Cuextlan [and] Totonacapan. It was made known especially that those which came here were to be fed. But when they multiplied, they scattered, they traveled everywhere, they ate everywhere. They eat lizards. And when they were still esteemed, no one might throw stones at them. If anyone stoned them, they chided one another; the common folk said to one another, “What are you doing over there? Do not shout at, do not stone the lord’s birds!” (Sahagún [1577] 1963, p. 50).

Spanish Text: Llámanse teotzanatl que quiere decir ave rara, o tzanatl preciosa: Porque no son naturales desta tierra: No ha muchos años que vinieron a estas partes; cuando era señor Auitzotl vinieron a estas partes de México, por su mandado fueron traídas de las provincias de Cuextlan y Totonacapan. Y entonce tenían cargo de dar las de comer. Y como comenzaron a multiplicarse derramáronse por todas las comarcas de México. Estas comen lagartijas y otras sabandijas semejantes. A los principios nadie las usaban matar, ni tirar: porque estaba vedado por el señor. (Sahagún [1577] 1979, Volume 3, Book 11, folios 53v-54r).

Comparing the Florentine Codex’s chapter on birds to the texts of the earlier Manuscript of Tlatelolco, we find that the Codex contains over thirty new bird accounts that are not present in the Manuscript of Tlatelolco, as well as significant new information on many birds already present in the latter (e.g. Itzquauhtli, Mixcoaquauhtli, Itztlhotli, Chiqujmoli, Chachalacametl). These many changes to the bird chapter, which appear both before and after the account of Auitzotl’s introduction of the great-tailed grackle, were added by the peer reviewers in Tenochtitlan. They confirm Sahagún’s statement that the Tenochca (people of Tenochtitlan, Appendix A.8) “amended and added many things to the twelve books” at that time (Sahagún [1577] 1982, p. 55), and also leave little doubt that the Tenochca scrutinized the grackle account (Appendix A.9). That the Tenochca were familiar with the male great-tailed grackle is proven by the fact that this bird is specifically mentioned as a size model in the Florentine Codex’s account of the Chachalacametl (Sahagún [1577] 1963, 1979), which was written in Tenochtitlan.

That the grackle account successfully passed the peer review process in Tenochtitlan is shown by the following facts: (1) The details of the introduction of the great-tailed grackle, as told in the Aztec and Spanish texts of the Florentine Codex (above), are not significantly different from those of the Manuscript of Tlatelolco (Haemig 2011, 2012), (2) No alternate account of the great-tailed grackle was added to the manuscript in Tenochtitlan, as was done for several bird accounts from Tlatelolco that the Tenochca judged unsatisfactory (e.g. Atotolin, Atapalcatl, Itzquauhtli, Mixcoaquauhtli, Tolcomoctli). (3) The account lacks warning phrases (Haemig 2012) that the research group used to alert the reader to doubtful information such as fables.

The account of Auitzotl’s introduction of the great-tailed grackle is thus a peer-reviewed historical account, collected and authenticated by a professionally-trained research group within a human lifetime of the grackle translocation (Haemig 2012). The existence of this peer-reviewed historical account means that the evidence for Auitzotl’s introduction of the great-tailed grackle is considerably better than what exists for many birds currently thought to have been translocated by humans (See examples in Long 1981; Lever 2005; Blackburn et al. 2009).

A significant part of Remsen and Cardiff’s critique of the historical account consists of distorted and inaccurate descriptions. They caricature the Florentine Codex as “a friar’s 1577 collection of animal stories”, belittle the peer-reviewed historical account as “folklore”, and call the highly-civilized and literate Aztecs “primitive peoples”.

Remsen and Cardiff’s (1990) caricature of the Florentine Codex gives the impression that this work is hopelessly out-of-date, written by a non-scholar, and contains no useful scientific information. Like most caricatures, it is inaccurate because it omits many important details and trivializes others. For example, while it is true that Sahagún was a (Franciscan) friar, Remsen and Cardiff neglect to mention that he was also a serious scholar, teacher and leader of a distinguished academic research group (Lopez Austin 1974; Anderson 1982; Nicolau d’Olwer 1987; Leon-Portilla 2002). In 1536, Sahagún helped found the Royal College of the Holy Cross (described above) in Tlatelolco. While working at this college, Sahagún taught the brightest children of the former native nobility and mentored several who went on to became distinguished scholars.

Later, during a twenty year period (1558–1577), Sahagún directed the General History Project, which cumulated in the writing of a peer-reviewed encyclopedia (the Florentine Codex) that contained a wealth of important new information about Mexico that was unknown to science. Comparing him to other friars of his time, Anderson, (1982, p. 41) wrote: “While Sahagún clearly reflected the views and methods of his time and of his order, he nevertheless stands absolutely unique…Even when compared with his ablest contemporaries he excelled any of them in his ability to organize, train, use, and direct effectively a team of emerging native scholars.”

Remsen and Cardiff’s caricature also leaves the false impression that the Florentine Codex was written by one person. In reality, this encyclopedia was produced by a group of scholars in collaboration with indigenous experts in the various topics studied. While Sahagún was the leader of the project, much of the research and fieldwork was done by four distinguished trilingual scholars: Martin Jacobita, Antonio Valeriano, Alonso Vegerano, and Pedro de San Buenaventura (Sahagún [1577] 1982). Because Sahagún was the only member of the research group that was a clergyman, it is inaccurate and misleading to characterize the authorship of the Florentine Codex as a “friar’s” work.

Third, the Florentine Codex is far more than a “collection of animal stories.” Covering a wide variety of topics, it contains the first scholarly descriptions of flora and fauna for many species in the New World. In the prologue to Book Eleven of the Florentine Codex, where the account of Auitzotl’s introduction of the great-tailed grackle is found, Sahagún ([1577] 1982, p. 87) summarizes the contents of this volume as follows: “In it, recorded in the Mexican language, are the better known and most utilized animals, birds, fish, trees, herbs, flowers, and fruits which exist in all this land - their characteristic properties and traits, exterior and interior.”

The account of Auitzotl’s introduction of the great-tailed grackle is found in Chapter Two of Book Eleven. This chapter focuses on birds and describes many species. Included are not only physical descriptions and names but also other information, such as habitat, song, nesting habits, eggs, behavior and interactions with humans. Thus, among other things, Chapter Two of Book Eleven is a serious scholarly attempt to summarize the better known and most utilized birds of the Spanish colony of New Spain. Because its Aztec texts were finished in 1569, three years before Francisco Hernandez came to New Spain, it may be the earliest-known regional avifaunal work on the birds of Mexico.

As shown in the previous section, the Florentine Codex’s bird chapter is a regional avifaunal work. Regional works on birds review and summarize the existing state of knowledge of birds in a given area, and so are usually based at least partially on the work of others. Important historical information, such as the introduction of exotic bird species, is often mentioned in regional works and is almost never based on the direct observations of the authors themselves (e.g. Berger 1972; Cramp et al. 1977-1996; AOU 1998). It is therefore astonishing to read that Remsen and Cardiff (1990, p. 973) criticize the historical account because, in their words, it comes from “Aztec informants (and not the friar’s direct observations)”.

Although Peer (2011) gave credence to Remsen and Cardiff’s argument by uncritically quoting it, he failed to note that Remsen and Cardiff themselves use indirect sources and so could be accused of imposing a double standard. For example, a year before Remsen and Cardiff (1990) criticized “the friar” for reporting the great-tailed grackle’s introduction without directly observing it, Remsen reported in a regional work on Bolivian avifauna that two bird species of that county were introduced (Remsen and Traylor 1989). Like Sahagún’s research group, Remsen and Traylor (1989) did not directly observe the introduction of these two exotic species by humans, but had instead obtained their knowledge of these birds’ introduced status indirectly, from sources which they knew to be reliable.

Six years after criticizing “the friar”, Remsen et al. (1996) published another regional work, this time on vireo migration in Louisiana. In that paper, Remsen and Cardiff stated that some of the data they used were not based on their own direct observations but instead came from amateur bird watchers. They explained, “Some previously unpublished observations were obtained from the card file of unusual bird sightings reported to the regional editors of Audubon Field Notes - American Birds - National Audubon Society Field Notes (Remsen et al. 1996, p. 123).”

Because Remsen and Cardiff use indirect information that they judge to be reliable, it is hard to understand why they object to Sahagún’s research group doing the same. More important, it is quite common in scientific work to use reliable indirect information. For example, most modern-day scientific papers have a section titled “References” or “Literature Cited” where the authors cite sources that contributed indirectly to the work. Most also have a section titled “acknowledgements”, where unpublished sources that contributed indirect information, such as museums, databases, other researchers, etc. are thanked. While direct observations are the ideal, they are not always necessary nor even possible. In the present case, Sahagún’s research group was not able to travel back in time to Auitzotl’s reign to witness the grackle introduction directly, and so had to depend upon interviews and/or pictorial manuscripts. Needless to say, all good data, whether direct or indirect, gain more credibility when they are peer reviewed by experts, as was the account of Auitzotl’s introduction of the great-tailed grackle (Haemig 2012).

Some critics have suggested that the Aztecs confused, or may have confused, a natural invasion of great-tailed grackles for an introduction (Remsen and Cardiff 1990; Christensen 2000; Peer 2011). However, none of these critics have presented evidence that such confusion happened or that a natural invasion occurred during Auitzotl’s reign.

In an earlier paper (Haemig 2012), I showed why it is highly unlikely that the historical account is the result of confusion. The investigative methods used by Sahagún’s research group were designed to avoid, detect and correct any possible confusion. For example, the research group consulted and collaborated with native experts that had reputations for integrity. If any of their consultants and collaborators in Tlatelolco had really become confused, it is likely that the research group would have discovered the confusion when the account was peer reviewed in Tenochtitlan. Furthermore, many details of the grackle translocation are given in the account. If confusion had really occurred, one would expect to find differences in the various details in the texts from the two cities. Instead, there were no substantive differences between the Aztec and Spanish texts written before and after peer review (Haemig 2011, 2012).

Remsen and Cardiff (1990) argued that since other bird species colonized the Mexican Highlands without human help, the great-tailed grackle must also have done so. They wrote, “the Mexican Plateau region inhabited by the grackle is also inhabited by disjunct, highland populations of other normally lowland species…for which a hypothesis of human introduction is untenable (p. 973).” Therefore, they concluded, the great-tailed grackle’s distribution was “readily explained within the context of broader distribution patterns, and that there is no need to invoke human intervention (p. 973).”

Remsen and Cardiff’s argument is based on the assumption that similar distributions are the result of similar dispersal histories. However, this is not always true. Consider the following examples: Europe and North America, like the highlands and lowlands of Mexico, have many bird species in common. Some are native to both continents, while others are native to one continent and introduced on the other (Table 1). If we follow Remsen and Cardiff’s reasoning that the presence of species native to both areas rules out the possibility of there also being birds native to one of the areas but introduced in the other, we would erroneously conclude that the starling (Sturnus vulgaris), house sparrow (Passer domesticus) and mute swan (Cygnus olor) invaded North America naturally. Likewise, the presence of naturally-occurring neotropical birds in Florida, like the mangrove cuckoo (Coccyzus minor), snail kite (Rostrhamus sociabilis), shiny cowbird (Molothrus bonariensis) and smooth-billed ani (Crotophaga ani) does not prove that other neotropical birds there, such as the spot-breasted oriole (Icterus pectoralis), were not introduced by humans.

Remsen and Cardiff (1990), as well as Christensen (2000) and Peer (2011), cite the great-tailed grackle’s modern invasion of areas in the United States (Wehtje 2003) as evidence to support the natural invasion hypothesis. However, this fact does not disprove Auitzotl’s introduction of the great-tailed grackle, and can just as easily be used to support the introduction hypothesis because it confirms a claim made by the historical account: that the introduced grackles multiplied and spread to other areas.

Finally, I must comment on Remsen and Cardiff’s oft-quoted argument that “there is no need to invoke human intervention” because the great-tailed grackle’s presence in the “Mexican Plateau region” is “readily explained within the context of broader distribution patterns” (p. 973). I find this argument to be unpersuasive. Remsen and Cardiff are in essence telling us to ignore good evidence (a credible historical account) because it threatens their favorite hypothesis.

Remsen and Cardiff (1990) concluded their critique of the historical account by attacking its source. Noting that the account came from indigenous peoples, they argued that such peoples cannot be trusted because they sometimes make errors. Remsen and Cardiff explained:

“Although the plausibility and detail of the latter [the historical account] are intriguing, we regard such folklore with distrust. Our personal experience with South American indigenous peoples as well as with “educated” peoples is sprinkled with cases of amusing, but obviously erroneous, explanations of past and present natural phenomena, in spite of detailed and accurate knowledge of natural history in other cases (Remsen and Cardiff 1990, p. 973).”

I know of no other case in the introduced species literature where a credible historical account documenting bird introduction (and even identifying the person responsible for the introduction) has been questioned using negative stereotypes of folk groups. I also find it amazing that Remsen and Cardiff (1990) categorize indigenous peoples separately from “educated” peoples as though indigenous peoples are never educated.

Over the years, I have met other individuals who dispute the historical account because it comes from indigenous sources. Seldom, if ever, does anyone accuse Europeans, or their descendants, of confusing natural invasions with introductions. Yet, as soon as American Indians are identified as the source of information, critics tell us that the information cannot be trusted, that the Aztecs might have been confused - in spite of the fact that the historical account was collected and verified by professionally-trained scholars (Lopez Austin 1974; Haemig 2012). The old falsehood that American Indians are more easily confused than others and cannot keep their facts straight has been a powerful, enduring myth in the Americas, one used for centuries to cover up crimes against native peoples such as treaty violations, war provocations, genocide and land theft, and to argue that surviving Indians need colonial authorities to manage their lands, resources and histories. As professional scientists, we need to recognize that prejudices such as these can hinder the search for truth.