For the ten communities studied here, a total of 769 (Additional file 2: Appendix II) bird species were reported in or near each communal territory, representing 24 orders and 89 families. These occur in approximately one per cent of the Mexican national territory within nine of the 12 types of vegetation described by Rzedowski [64] as follows: XSG = xerophilous scrub and grassland, COF = conifer forest, OF = oak forest, CF = cloud forest, TEF = tropical evergreen forest, TDF = tropical subdeciduous, deciduous, and thorn forest, ASV = aquatic and subaquatic vegetation, RWV = ruderal and weed vegetation.
According to Mexican law (NOM-059-SEMARNAT-2010), 165 bird species have official bird conservation status [34], whereas the International Union for Conservation of Nature lists 50 species as of special concern for conservation [35]. Other International conservation guidelines we considered were VV of The Partners in Flight ACAD Book [37] and the birds of conservation concern in the USFWS [65], which listed 378 and 148 species, respectively.
Of the 769 species present in our 10 Indigenous study sites, 122 are endemic, quasi-endemic, or semi-endemic; 429 are resident; 125 are winter migrants; five are summer migrants; 12 are transitory; five are accidental; and 193 have more than one distribution status. Of the same 769 species, 557 were of some cultural relevance, 439 were considered to be of special bird conservation status; and 678 were noted as of either cultural significance, conservation concern, or both. Of these, 328 species were noted for both cultural and biological value; 229 species had cultural value but lacked special biological concern, while 111 were rated as of special biological concern but were not mentioned for cultural value. Finally, 99 species presumed to occur within the life space of our 10 Mexican indigenous communities lacked cultural or biological significance (Fig. 2).
Of the total of 769 species recorded in the whole study areas, 225 were listed in just one community, 149 in two, 124 in three, 103 in four, 64 in five, 48 in six, 29 in seven, 14 in eight, 8 in nine, and 5 of the whole communities (Fig. 3).
The most frequently noted species included domesticates and species that are both widespread and notable. The least frequently noted are species of specialized habitats, notably marine species that feature in the avian universe of just one or a few communities, such as the Seri. Of the 769 species listed, 574 were permanent residents (though some, 145, also had migratory populations); 292 species were (partly or wholly) migratory, wintering in Mexico (breeding to the north), with 63 species migrating to Mexico to breed in summer (though some of these might also have resident and/or wintering populations); 45 were “transients” (though a few of these could also be resident or migrants); 10 were “oceanic” (mostly recognized by the Seri in Sonora); and 5 were considered “accidental”, that is, not of regular occurrence in Mexico (Fig. 4).
Of the 769 species under consideration, 435 had some “bird conservation status” (that is were listed on one or another list of species of special conservation concern). These included 382 on international lists and 251 on Mexican National lists; 237 species were listed on either the International or the National lists, but not both; 198 were listed on both International and National lists. With regard to “cultural values”, 557 were named (NR) in at least one community; of these, 323 were named in two or more communities; 438 species were cited for “material values” (MAT) by at least one community, while 226 of these were cited by two or more communities; “symbolic values” (SYMB) were noted for 292 species in at least one community, of which 121 were noted for their symbolic value in two or more communities; with respect to “ecological indicator values” (ECOL), 230 species were so valued in at least one community, with 65 of those so noted in two or more communities (Fig. 5).
Correspondence analysis
We applied a correspondence analysis to these data which indicated that two main axes explained 81.55% of the variation. This demonstrates a strong relationship (p < 0.0001) between the 10 bird species within the communities, bird conservation status, and cultural value.
In examining Fig. 6, we can see the 10 indigenous communities and the correlation between bird cultural values and conservation status, the relationship among them is indicated within a delineated ellipse conforming to three main groupings. Group 1 birds of the Maya (0.328, − 0.299) and Tzeltal (0.305, − 0.123) communities with the species that maintain a conservation status for both national (0.213, − 0.363) and international (0.176, − 0.112) threatened lists, as well as by their nomenclatural recognition (0.094, − 0.045). In group 2, there is a strong relation between ecological (− 0.583, 0.126) and material (− 0.267, − 0.083) cultural values of bird species with the communities of Northern Zapotec (− 0.070, − 0.230), Cuicatec (− 0.301, 0.082), Seri (− 0.078, 0.111), and Nahuatl (− 0.180, − 0.099). Group 3 brings together birds of the Tlahuica (0.004, 0.263), Pima (0.260, 0.254), South Zapotec (0.358, 0.302), and Kiliwa (0.093) communities connecting their endemic status (0.156, 0.228) to their symbolic (0.179, 0.419) use.
It is worth mentioning that all three groups formed in the correspondence analysis are determined by the cultural values that each community gives to its birds. There is also an important variation in the number of species with some conservation status in National and International lists. The fact that there are 435 species with some conservation status for the 769 registered in the ten localities implies that the communities do not have the same number of species with conservation status as are culturally valued. However, the global analysis of correspondence with the explained variation of 81.55% is a high value that shows the close relationship between the conservation value of bird species and the cultural values that each community gives them.
Relevance to public policy
As we have shown through this analysis, cultural values are strongly correlated with the perceptions of professional biologists regarding the extent to which bird species for each locality are threatened. We hope that documenting a strong correlation between scientific and local perceptions of significance will help motivate public policy to protect “Bioculturally Prominent Bird Species” (hereafter BPBS) and to move towards the conservation of species of special biocultural importance, not only birds but other biological groups as well. Here, we propose three possible categories of BPBS relevant to public policy as follows:
High BCPBS:
Those species are used by indigenous people in a multiplicity of ways and are involved in a wide range of social and cultural practices, both material and non-material. These include those appearing on any threatened list, but also those considered endemic. Examples are: West Mexican Chachalaca (Ortalis poliocephala), Long-tailed Wood-Partridge (Dendrortyx macroura), Banded Quail (Philortyx fasciatus), Blue-throated Mountain-gem (Lampornis clemenciae), Strickland's Woodpecker (Dryobates stricklandi), Gray-barred Wren (Campylorhynchus megalopterus), Bearded Wood-Partridge (Dendrortyx barbatus), Bumblebee Hummingbird (Selasphorus heloisa), among others.
Medium BCPBS:
Those species used by indigenous people in a multiplicity of ways, and species involved in a wide range of social and cultural practices, both material and non-material. These include those appearing on any threatened list, but not endemic. Examples are: Northern Emerald-Toucanet (Aulacorhynchus prasinus), Chestnut-coloured Woodpecker (Celeus castaneus), White-crowned Parrot (Pionus senilis), Brown-backed Solitaire (Myadestes occidentalis), Slaty-breasted Tinamou (Crypturellus boucardi), Spotted Wood-Quail (Odontophorus guttatus), Solitary Eagle (Buteogallus solitarius), Collared Forest-Falcon (Micrastur semitorquatus), among others.
BCPBS:
Species not necessarily listed on any threat list, but with a wide range of social and cultural uses, both material and non-material. Some examples are: Turkey Vulture (Cathartes aura), Barn Owl (Tyto alba), Gartered Trogon (Trogon caligatus), Green Kingfisher (Chloroceryle americana), White-tipped Dove (Leptotila verreauxi), Killdeer (Charadrius vociferus), Great Horned Owl (Bubo virginianus), and Northern Beardless-Tyrannulet (Camptostoma imberbe).
It is necessary to first instantiate public policy regarding BPBS at the local level, and then move to regional and state levels, given the high biological and cultural richness throughout the country. One significant problem in Mexico when considering the biocultural conservation of species is the existing lack of public policy, especially given that this is one of the most bioculturally diverse countries in the world. Other problems have been the influence of a history of neoliberal economics on land use in rural and Indigenous communities, which has increased poverty and material inequalities, and led to overall social polarization, over-extraction of natural resources and a high degree of social marginalization. All these factors have contributed to a “cascade effect”, not only in terms of biodiversity depletion but also in terms of social and cultural deprivation. Prohibition of Indigenous languages throughout Mexico from the nineteenth century onwards, when ethnic and linguistic identities were systematically suppressed and devalued, coupled with urban and international labour migration, religious change, new forms of education, and social benefit programmes (“Progresa”, “Oportunidades” and “Prospera”) reinforced by neoliberalism, are among the main sociocultural and economic changes that have impacted negatively on traditional knowledge. We can see this, for example, among Zapotec and Cuicatec indigenous groups in Oaxaca [30].
The erosion and loss of traditional knowledge are largely associated with a breakdown in the mechanisms for its transmission. This is linked to a reduction in the extraction of natural resources through the loss of adult male workers to migration, and little engagement in local commercial development. The social benefit programmes may create dependence on external products and discourage local production. Although the current government tries to support the cultural values of ethnic groups, a biocultural vision is strongly required. Environmental policy has been neglected. Not only does Mexico need economic support for social minorities, but it is necessary to ensure the conservation of Mexico’s natural capital and to reduce budget cuts in CONABIO, CONANP, PROFEPA, SEMARNAT, among other supportive organizations. For these reasons, there is an urgent need to demonstrate the importance of bioculturally informed conservation strategies that can rapidly and accurately assess rates of biodiversity loss in relation to the retention of traditional knowledge for different age and gender groups. This will allow us to understand how biological loss impacts traditional knowledge and therefore cultural diversity and vice versa. Important also is the impact of illegal wildlife trade. The Indigenous communities of Oaxaca are mostly reliant on self-consumption, and cultural codes generally specify the upper limits for both numbers of hunters and animals caught, but where such codes have been undermined and outcomes determined by the demand for protected species hunting become unsustainable [30]. This is another reason why we need to stress the importance of biocultural conservation. The research we carry out in Indigenous and rural communities requires a holistic approach where the local actors are considered not as objects of public policy and Mexican law, but active agents on whom ultimately depends the survival of biocultural diversity [31]. We propose the term Bioculturally Prominent Bird Species to suggest a new way of conceptualizing the relationship between humans and wider nature, which will have positive consequences for biocultural conservation. This concept is consistent with the recommendation of others to establish Biocultural Communitarian Protocols (BCP). BCPs are charters with rules and responsibilities, in which communities establish their customary rights over their natural resources and territory, according to customary, national and international laws [66]. But the concept also highlights the role of ethnobiologist in conservation policies as proposed by Hunn [42], Wyndham [43] Wolverton, Nolan and Ahmed [44] and Tidemann and Gosler [45]