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Summary The Sierra Madre Sparrow Xenospiza baileyi is an endangered Mexican endemic and a bunchgrassland specialist with a disjunct range: a relatively larger population in the south-eastern Trans-Mexican Volcanic Belt, and a smaller and poorly studied population in the Sierra Madre Occidental. In the latter, known distribution and abundance consists of four localities with a maximum of 28 individuals recorded in one of them. We surveyed the Sierra Madre Sparrow in 30 sites with suitable habitat, meadows or “bajíos” with bunchgrasses, in the municipalities of Durango, Pueblo Nuevo, San Dimas, and Canatlán in the Sierra Madre Occidental of Durango. We detected a total of 193 individuals in nine (30%) of the sites (392 ha), conducting intensive searches throughout them. Bunchgrasses in confirmed meadows were composed mainly of Muhlenbergia macroura, M. rigida, M. speciosa, M. rigens, and Piptochaetium fimbriatum. Total bunchgrass area within a meadow was a significant positive predictor of the Sierra Madre Sparrow presence, while total meadow area was not a significant predictor of its abundance. Seven of the confirmed localities were previously unknown, and two of them harboured 55% of the observed individuals: Ex Hacienda Coyotes (Pueblo Nuevo) and La Lobera (San Dimas). The estimated population size is at least four times higher than any previous record (28) or suggested (40–50) for the Sierra Madre Occidental and raises an opportunity and a challenge for conserving this genetically distinct population of the Sierra Madre Sparrow in the region.

Las estimaciones indican que 148 especies de aves en Norteamérica enfrentan amenaza alta o severa, pues sus poblaciones están disminuyendo. El gorrión de Baird (Centronyx bairdii) es una de las especies con declive poblacional, presenta plumaje monomórfico y su sexo no se puede determinar a simple vista. La determinación del sexo de las aves permite conocer su comportamiento social y proporción en la dinámica de sus poblaciones. Un método de clasificación es el de redes neuronales artificiales y se ha utilizado en diversos campos, como la clasificación de plantas y semillas y la diferenciación de especies productoras de madera. En el ámbito de la ornitología se ha utilizado poco. Por lo tanto, el objetivo de este estudio fue desarrollar una red neuronal artificial para diferenciar el sexo de los gorriones de la especie Centronyx bairdii, con datos zoométricos obtenidos en campo. La hipótesis fue que las redes neuronales artificiales pueden predecir el sexo de las aves de la especie Centronyx bairdii. La red neuronal construida a partir de los datos de peso, cuerda alar, longitud de cola, culmen, ancho del pico y profundidad del pico de 111 aves, permitió diferenciar el sexo de la especie con grado de certeza de 92.3%.

A major barrier to advancing ornithology is the systemic exclusion of professionals from the Global South. A recent special feature, Advances in Neotropical Ornithology, and a shortfalls analysis therein, unintentionally followed a long-standing pattern of highlighting individuals, knowledge, and views from the Global North, while largely omitting the perspectives of people based within the Neotropics. Here, we review current strengths and opportunities in the practice of Neotropical ornithology. Further, we discuss problems with assessing the state of Neotropical ornithology through a northern lens, including discovery narratives, incomplete (and biased) understanding of history and advances, and the promotion of agendas that, while currently popular in the north, may not fit the needs and realities of Neotropical research. We argue that future advances in Neotropical ornithology will critically depend on identifying and addressing the systemic barriers that hold back ornithologists who live and work in the Neotropics: unreliable and limited funding, exclusion from international research leadership, restricted dissemination of knowledge (e.g., through language hegemony and citation bias), and logistical barriers. Moving forward, we must examine and acknowledge the colonial roots of our discipline, and explicitly promote anti-colonial agendas for research, training, and conservation. We invite our colleagues within and beyond the Neotropics to join us in creating new models of governance that establish research priorities with vigorous participation of ornithologists and communities within the Neotropical region. To include a diversity of perspectives, we must systemically address discrimination and bias rooted in the socioeconomic class system, anti-Blackness, anti-Brownness, anti-Indigeneity, misogyny, homophobia, tokenism, and ableism. Instead of seeking individual excellence and rewarding top-down leadership, institutions in the North and South can promote collective leadership. In adopting these approaches, we, ornithologists, will join a community of researchers across academia building new paradigms that can reconcile our relationships and transform science. Spanish and Portuguese translations are available in the Supplementary Material.

The Common Black Hawk (Buteogallus anthracinus), a widespread neotropical raptor, has been known since the 1970s to nest as far north as western Texas, but few breeding records exist for the adjacent area of northcentral Mexico. In 2015 we located two active nest sites within the Maderas del Carmen Flora and Fauna Protection Area at northwestern Coahuila. The nest sites were in Pecan (Carya illinoiensis) and Arizona Pine (Pinus arizonica) trees, both near natural permanent water sources. Our recent nest site records along with others in eastern Coahuila suggest the existence of a corridor connecting Texas and Nuevo Leon populations, highlighting the importance of transboundary natural protected areas for species conservation.

Local winter abundance of grassland passerines is highly variable throughout the Chihuahuan Desert among years. The objective of this study is to determine if plant biomass in grasslands and precipitation are predictors of bird abundance in space and time through Chihuahuan Desert. We conducted avian surveys in 17 Grassland Priority Conservation Areas (GPCA) in northern Mexico and southwestern United States in the winters of 2007–2011. We used distance sampling on line transects to estimate annual winter bird density in all GPCAs. We used a hierarchical model of distance sampling to estimate the effect of summer precipitation and vegetative cover during the fall on bird density for 10 grassland species. We used the MODIS NDVI at a pixel resolution of 231.5 m as a measure of plant biomass. Grasshopper Sparrow, Baird's Sparrow, Savannah Sparrow, Vesper Sparrow, and Eastern Meadowlark showed a strict positive response to NDVI, while Horned Lark, Sprague's Pipit, Chestnut-collared Longspur and Lark Bunting did not show a strictly-positive response to NDVI. Our results provide a valuable tool for the conservation of declining migratory birds on their wintering grounds by identifying a wildlife-habitat relationship using a remotely-sensed and readily available index of vegetative growth.

In this study we focused on urban bird diversity across Mexico, a megadiverse country, with a special focus on the relative role of urban greenspaces and heavily-built sites. We considered a country-wide approach, including 24 different sized Mexican cities. Our aims were to describe the urban bird diversity in focal cities and further assess the relationships between it and the biogeographic region where cities are located, their size, elevation, and annual rainfall. Additionally, we evaluated differences in the functional composition of bird communities in both studied urban scenarios (i.e., urban greenspaces, heavily-built sites). Our results confirm that urban greenspaces are home to a large proportion of species when contrasted with heavily-built sites. While total species richness and species richness of greenspaces were related with the cities' biogeographic region -with higher species richness in the Neotropical region and Transition Zone-, the relationship did not hold true in heavily-built sites. We found that annual rainfall was negatively related to bird richness in heavily-built sites, suggesting that species from arid systems can be more tolerant to urbanization. Regarding the bird functional group assessment, results show a clear differentiation between the functional groups of greenspaces and those of heavily-built sites, with granivores and omnivores associated with the latter and a highly diverse array of functional groups associated with urban greenspaces.

We studied four active nests of Vireo atricapilla in the Sierra de la Paila, southeastern Coahuila, Mexico, during July–August 2012. We quantified duration and behavior of each parent at nests during 25 h 10 min of video at two of the nests. Three nests reached the nestling stage, but only one was successful. We observed only the female constructing one nest. During incubation, females stayed in the nest 54.9% of the time, males 40.1%; both were absent 5% of the recorded time. Primarily the male conducted feeding of nestlings, whereas only the female brooded nestlings. We also recorded two new nesting substrates for the species.

Assessing genetic diversity in species of conservation concern is a critical parameter to implement management plans that may increase their viability. Traditionally, genetic diversity has been assessed using neutral genes; nevertheless, recent perspectives have proposed that genetic variation under natural selection (adaptive genes) is more representative of the adaptive potential of a population or species. Toll-like receptors (TLR) are an innate immune gene family that binds to Pathogen Associated Molecular Patterns. These receptors evolved under positive selection and by coevolution; therefore, they represent adaptive genetic diversity. We designed and tested six pairs of primers that amplify TLR genes in seven grassland species, one of the most vulnerable North American bird groups. Analysis of the sequences showed that all were polymorphic and evolved under positive selection, with the exception of TLR3, which evolved neutrally. These primers may constitute a useful tool for conservation studies for grassland sparrow species.

Grassland bird populations have declined more than any other group of bird species in North America. Some species such as the grasshopper (Ammodramus savannarum) and Baird’s sparrows (Ammodramus bairdii) are of particular conservation concern, since they have shown negative trends in their population over the last 50 years. Their winter ecology has only begun to be studied recently and information is limited. The purpose of this study is to achieve the morphometric characterization of these two grassland species during the wintering season. The study is conducted in the Rancho Santa Teresa located in Villa Hidalgo, Durango, Mexico and the Ecological reserve “El Uno”, located in Janos, Chihuahua, Mexico. During winter 2013-2014, 135 birds were captured; banded and zoometric measurements were taken such as total body weight, wing chord, tail length, culmen, and beak depth and width. Two indices of body condition (BCI) are also calculated. All measurements and indices are compared per species and per sex. Both species are sexed with molecular techniques, determining 20 females and 18 males for A. bairdii and 41 females and 56 males for A. savannarum. All variables are significant different between species (p A. bairdii (p p p A. bairdii. The biometric data obtained in this study can be used as reference values wintering populations of both species.

Aquatic wild birds, especially waterfowl, have been long considered the main reservoirs of the avian influenza A virus; however, recent surveys have found an important prevalence of these viruses among land birds as well. Migration has been suggested as an important factor in the avian influenza virus dissemination. We aimed to estimate the prevalence of influenza A viruses in wild birds (waterbirds and land birds; resident and migratory) in eastern Mexico, where the three main North American migration flyways converge and where there was no previous information on this subject. We detected influenza with reverse transcription coupled with a PCR approach. Of the 534 birds sampled between 2010 and 2012, we detected the influenza A virus in a high proportion of birds (39%). Prevalence was particularly high in land birds (49%) when compared to aquatic birds (26%); there was no difference in overall prevalence between resident (39%) and migratory birds (39%). The high prevalence of the avian influenza virus in land birds was noteworthy in the innermost sampling areas in northern Mexico (Coahuila [82%] and Nuevo Leon [43%]).Alta prevalencia del virus de la influenza aviar entre aves acuáticas silvestres y aves terrestres de México. Las aves silvestres acuáticas, especialmente las aves anseriformes, han sido consideradas durante mucho tiempo los principales reservorios del virus de la influenza aviar A; sin embargo, muestreos recientes también han encontrado una importante prevalencia de estos virus entre las aves terrestres. Se ha sugerido que la migración es un factor importante en la diseminación del virus de la influenza aviar. El objetivo de este estudio fue estimar la prevalencia de los virus de la influenza A en aves silvestres (aves acuáticas y terrestres; residentes y migratorias) en el este de México, donde convergen las tres rutas migratorias principales de América del Norte y donde no había información previa sobre este tema. Se detectó al virus de influenza mediante transcripción reversa acoplada a PCR. De las 534 aves muestreadas entre los años 2010 y 2012, se detectó al virus de la influenza A en una alta proporción de aves (39%). La prevalencia fue particularmente alta en las aves terrestres (49%) en comparación con las aves acuáticas (26%); no se observó diferencia en la prevalencia general entre las aves residentes (39%) y las migratorias (39%). La alta prevalencia del virus de la influenza aviar en las aves terrestres fue notable en las áreas de muestreo hacia el interior del norte de México (Coahuila [82%] y Nuevo León [43%]).

We found two nests of the long-eared owl (Asio otus) in Reserva Ecologica el Uno, located in Janos municipality, Chihuahua, Mexico. Contents of nests were recorded, photographed, and monitored between 28 March and 10 June 2007. Nests were constructed on honey mesquites (Prosopis glandulosa) and contained three eggs and three nestlings, respectively. These nests represent the first confirmed breeding record for the state of Chihuahua and the second for Mexico (outside Baja California).

We confirmed a new nest predator for the Mexican endemic and endangered Sierra Madre Sparrow (Xenospiza baileyi). We found a Mexican dusky rattlesnake (Crotalus triseriatus) preying on three 6-day-old nestlings while their parents and a neighboring sparrow showed active defensive behavior. We also identified C. triseriatus as a new bird nest predator.

Understanding home range size and habitat preferences is an important component of monitoring species in steep decline. Sprague's Pipit (Anthus spragueii) is a declining grassland specialist with a substantial portion of its population wintering in the highly threatened grasslands of the Chihuahuan Desert. We radio-tagged and tracked 10 wintering pipits between 2014 and 2017 at 3 sites across northern Mexico to generate baseline home range estimates and habitat preferences on their wintering grounds. We found that mean home range and core-use area size with 95% and 50% kernel density estimators were 11.4 ha and 2.4 ha, respectively, almost twice as large as some other grassland specialist passerines. Two birds left the study area and one individual shifted its home range 1.3 km after 20 d of monitoring, indicating that some individuals are flexible in their space use strategies. Within their home ranges, pipits selected grasslands with more bare ground and less “other cover” (litter, duff, animal excrement, and rocks) than what was available on the landscape. We found no relationship at the microhabitat scale between pipits and grass height nor shrub cover and heights, which in previous studies have been shown to influence habitat selection at larger scales. These findings may reflect different habitat use, diet, and predator avoidance strategies than other grassland passerines that select for denser grass cover during winter in the Chihuahuan Desert and highlight the importance of structurally heterogeneous grasslands. For this reason, strategies to manage and conserve Chihuahuan Desert grasslands and its avifauna must consider the diverse habitat and area needs of grassland birds to be effective.

Background The long-eared owl (Asio otus) has a Holarctic distribution, including much of North America. This nocturnal species is considered to be extremely secretive, and poorly known in the Great Plains of the United States and Canada, as well as to México, where no previous studies on its diet have been conducted. Findings We analyzed 120 pellets collected during January 2007 in roosts in a 2-3 m height mesquite scrub within a grassland area of Reserva Ecológica El Uno, located in the Natural Protected Area Janos. We registered and identified three orders, four families, eight genera and ten species of mammals and two orders and one family of insects. Winter diet is dominated by mammals, especially rodents in both frequency and biomass. Cricetidae and Perognathus flavus were the most frequent family and species, respectively. On the other hand, when analyzing biomass, Sigmodon species were dominant, achieving almost 70% of the consumed biomass. Levin's standardized niche breath based on frequency was calculated as 0.40, while based on biomass was 0.38. Also, two previously unrecorded rodent species were identified as long-eared owl prey. Conclusion Although 18 different types of items were identified, the long-eared owl tends to be selective, with a single genera (Sigmodon) comprising almost 70% of its consumed biomass during winter. Perognathus flavus was also important in frequency (21%); however, it barely constitutes 2% of the consumed biomass. Resumen El búho orejas largas es una especie Holártica, que se distribuye en gran parte de Norteamérica y que ha sido poco estudiada, especialmente en las Grandes Planicies de Estados Unidos y en México, donde no existe un estudio previo sobre su dieta invernal. Se colectaron y analizaron 120 egagrópilas en la Reserva Ecológica El Uno, dentro del Área Natural Protegida Reserva de la Biósfera Janos. Se identificaron un total de 18 tipos de presa, pero la especie mostró selectividad por dos géneros/especies, ya que cerca del 70% de la biomasa consumida fueron especies del género Sigmodon, mientras que el 21% de las muestras contenían Perognathus flavus. Además, dos especies de roedores identificadas constituyen nuevos registros de presa para la especie.

Worthen's Sparrows (Spizella wortheni) are endemic to the Mexican Plateau and have been listed as globally endangered. The breeding biology of these sparrows is poorly understood, and nesting is only known to occur at three locations (Las Esperanzas, Nuevo Leon, and La India and Tanque de Emergencia, Coahuila). In June and July 2006, we searched for nests of Worthen's Sparrows and located three new breeding localities: La Carbonera and San Rafael in the state of Nuevo Leon, and San Jose del Alamito in the state of Coahuila. We subsequently sampled vegetation where nests were located and, on 26 August 2006, conducted surveys along 1-km transects at the three new breeding locations as well as at El Erial-La Casita, Nuevo Leon. We recorded the most Worthen's Sparrows at El Erial-La Casita (N= 33), followed by San Jose del Alamito (N= 9), San Rafael (N= 6), and La Carbonera (N= 3). No nests were located at El Erial-La Casita, but small groups of sparrows that included juveniles were observed. At the three breeding locations, shrub strata were dominated by tarbush (Flourensia cernua; San Jose del Alamito and La Carbonera) and Berlandier's wolfberry (Lycium berlandieri; San Rafael). Most (68%) recently recorded nests for this species have been found in tarbush. Historical and recent data (including our study) suggest that Worthen's Sparrows typically breed in grassland habitat where shrubs of some type are also present. Because conversion of land to agriculture continues to be a major threat to grasslands in northeastern Mexico, we recommend that conservation efforts be implemented to protect the known breeding areas of Worthen's Sparrow. RESUMEN El gorrion de Worthen (Spizella wortheni) es una especie endemica del altiplano mexicano y ha sido enlistada como en peligro de extincion. La biologia reproductiva de este gorrion es pobremente comprendida, y solo existen tres sitios donde esta comprobado que anidan actualmente (Las Esperanzas, Nuevo Leon, y La India y Tanque de Emergencia, Coahuila). En junio y julio del 2006 buscamos nidos del gorrion de Worthen y localizamos tres nuevas localidades reproductivas: La Carbonera y San Rafael en el estado de Nuevo Leon, y San Jose del Alamito en el estado de Coahuila. Subsecuentemente muestreamos la vegetacion donde los nidos fueron localizados y, el 26 de agosto del 2006 llevamos a cabo recorridos a lo largo de transectos de un kilometro en las tres nuevas localidades reproductivas asi como en El Erial-La Casita, Nuevo Leon. Registramos la mayoria de los gorriones de Worthen en El Erial-La Casita (N= 33), seguido por San Jose del Alamito (N= 9), San Rafael (N= 6), y La Carbonera (N= 3). Ningun nido fue localizado en El Erial-La Casita, pero pequenos grupos que incluian juveniles fueron observados. En las tres localidades reproductivas el estrato arbustivo estuvo dominado por hojasen (Flourensia cernua; San Jose del Alamito y La Carbonera) y tomatillo (Lycium berlandieri; San Rafael). Sesenta y ocho por ciento de todos los nidos recientemente reportados para esta especie han sido encontrados en hojasen. Datos historicos y recientes (incluyendo este estudio) sugieren que esta especie se reproduce tipicamente en pastizales donde arbustos de algun tipo estan presentes. La conversion de la tierra a agricultura es la mayor amenaza a los pastizales en el noreste de Mexico y por lo tanto esfuerzos de conservacion deben de ser implementados para proteger las areas reproductivas del gorrion de Worthen.

During an 18-month sampling effort along the Rio Sabinas in Coahuila, Mexico (December 2004–August 2006), we observed eight confirmed and three potentially new breeding records, nine new non-breeding records, and eight rare records of birds for Coahuila. We also identified the Rio Sabinas as a potential new breeding site in the state for five species. These data illustrate the considerable conservation value of this understudied area in northern Mexico.

Eared Quetzals (Euptilotis neoxenus), a threatened species, are one of the least studied trogons in Mexico. We monitored 29 Eared Quetzal nests in the Chihuahuan portion of the Sierra Madre Occidental from 1998 to 2003. All nests were in tree cavities, and the mean tree and nest cavity heights (N ? 14) were 16.9 =b 7.8 m and 11.4 zb 4.1 m, respectively. The mean clutch size was 2.8 ? 0.9 eggs (N = 28), the incubation period lasted 22 d (N = 1), and nestling periods ranged from 29 to 31 d (N = 5). Both adults incubated eggs and fed nestlings. Of 80 eggs, 70 hatched (87.5%) and 67 of 70 young fledged (95.7%). Twenty-five of 29 nests (86.2%) produced at least one fledgling. One nest was predated, and two failed when nest trees fell. Higher rates of nest pr?dation have been reported for other species of trogons. However, fewer potential predators, such as snakes and mammals, are present in the Sierra Madre than in tropical zones where most trogon species occur. In addition, antipredator behaviors, including nestlings with calls resembling a snake and nests with an unpleasant odor, may contribute to the high nesting success. The main limiting factors for Eared Quetzals in the northern Chihuahua may be competition for cavities with other secondary cavity-nesters, and the failure of nests when snags fall.

We document the first breeding record of Mountain Plovers (Charadrius montanus) in the state of Nuevo Leon, Mexico. On 9 July 2004, we located a nest with two eggs and one chick in a colony of Mexican prairie dogs (Cynomys mexicanus). Mean height of vegetation near the nest was 7.1 cm, and bare ground cover was 41.2% (30 m2 sampled). Although this record represents the second nesting for this species in Mexico, it is the first to document successful breeding.

ResumenSe analizó la representatividad del inventario de plantas arbustivas de un área natural protegida de Coahuila, México, con los siguientes objetivos: describir los tipos de sesgos de muestreo; definir la heterogeneidad ambiental de la reserva captada en las recolectas botánicas, y determinar el nivel de resolución espacial que respalda la información recolectada. Los sesgos fueron significativos (por distancia a carreteras, χ2=199.01; p