The Sierra Madre Sparrow (Xenospiza baileyi) is an endemic species of Mexico that is threatened with extinction. Its distribution is reported in two areas: One in the Transvolcanic Belt of central Mexico (La Cima) near Mexico City and the other in the Sierra Madre Occidental in northwestern Mexico (Ejido Ojo de Agua El Cazador) near the city of Durango, in the state of Durango. The habitat is the same in these two areas, and consists of sub-alpine grassland that is located in shallow valleys or shallows. In our case, "El Bajío la Cantera" of approximately 55 hectares, is mostly used in rainfed agriculture, protected from livestock grazing with wire fences, which in turn represents protection for remnants of grassland where they are the birds. "El Bajío la Cantera" belongs to Ejido 12 de Mayo, Municipality of San Dimas, Durango, where 28 males were detected singing along a 500 meter transect. This finding represents the population of the healthiest Sierra Madre Sparrow currently known, so it would be necessary to document their population trend over time. This information can help to evaluate and propose the creation of a special protection area for the species that involves joint government actions and ejidatarios tending to conserve the habitat during the reproductive season in order to increase and / or maintain the size of the population.
During the winter of 2009 grassland birds were monitored in the region of Cuchillas de la Zarca to estimate the association between Ammodramus bairdii Audubon 1844, focal species of grassland and bird species belonging to the trophic guild of grassland granivorous birds (n = 25 ). The study area was divided into monitoring quadrants (n = 16) where 96 transects for bird monitoring were conducted, recording 16,635 individuals of which only 32.9% were in the trophic guild of grassland granivorous birds. The association between A. bairdii and other species was estimated from the nonparametric statistical index of Kendall's coefficient of concordance (W) and the p value, through permutation analysis (n = 10,000), finding positive and significant associations (p ≤ 0.05) of the target species for study with Sturnella magna, Passerculus sandwichensis and Ammodramus savannarum, species that share habitat preferences of natural grassland in good condition, slightly grazed and with little tolerance to the shrub cover. The association W ranged from 0.072 and 0.749. These results can recognize this region as an important area for the conservation of obligate grassland birds during winter, suggesting establish training programs to better utilize this resource by means of cattle activity.
La región de Cuchillas de la Zarca es considera como un área prioritaria para la conservación de pastizales reconocida por CONABIO la cual alberga una gran cantidad de aves migratorias durante el invierno. En este estudio calculamos el tamaño del ámbito hogareño, los patrones de movimiento y estructura de la vegetación de dos especies de pastizal el gorrión de Baird (Centronyx bairdii) y el gorrión chapulinero (Ammodramus savannarum). Durante el invierno 2013 - 2014 colocamos 33 transmisores; de los cuales se obtuvieron un total de 1440 registros de detección. El análisis de los datos espaciales permitió definir que la especie Centronyx bairdii (n = 20) recorre en promedio mayor distancia (203.13 m ± DE 187.07) y ocupa mayor área (4.82 ha ± 1.86 IC 95 %) que Ammodramus savannarum (n = 13, 134.31 m ±DE 106.3 y 4.38 ± 2.35 IC 95 %). El análisis de la vegetación permitió suponer que Centronyx bairdii prefiere sitios con mayor cobertura de pasto (66.76 ± 0.6) a diferencia de Ammodramus savannarum que prefirió sitios con pastizal más alto (36.06 ± 0.6). Las medidas geoespaciales y la estructura de la vegetación calculadas en este estudio pueden utilizarse como valores de referencia de ambas especies y pueden aportar conocimiento y entendimiento de su estadía no reproductiva.
El registro de las aberraciones en la coloración del plumaje en aves es importante porque permite conocer la frecuencia y las condiciones en que esto ocurre en las poblaciones silvestres, lo cual contribuye en el conocimiento de este tema. Para el caso particular en este estudio, se reporta la observación de dos ejemplares de ganso frente blanca (Anser albifrons), con leucismo parcial, en el humedal de Los Álamos, municipio de Durango, México, a 25 km al noreste de la ciudad de Durango. No se observó aislamiento en los individuos observados, pues formaban parte de una parvada de ejemplares de la misma especie con coloración normal, lo cual resultó de gran valor en este reporte. Éste es el primer registro de leucismo para esta especie en México.
Understanding habitat preferences of grassland birds declining is important for their conservation. Currently, the use of remote sensing technology to describe the habitat of grassland birds is a novel tool in Mexico which may allow for more accurate assessments of grassland habitat. High-resolution photographs and a protocol established by Bird Conservancy of the Rockies that uses ocular estimation was used in order to estimate vegetation cover within areas where individual sparrows of the genus Ammodramus were recorded in two sites located in Durango. Forty location points were randomly selected from detections (n = 1881) recorded from the follow-up of 33 individuals of A. bairdii and 23 of A. savannarum, by telemetry. Vegetation metric was obtained and from high-resolution photographs we created an orthomosaic with supervised classification in 4 classes of vegetation cover (%). At each bird location point, the percentage of each vegetation cover class within a 5 m radius area around the point was estimated. We did not find a significant difference between vegetation cover obtained by a high-resolution photographs or ocular estimations (p≤0.05) by species. Both species were found in areas with grass cover similar to those reported using different methods (61.24±4.07%, 62.78±4.24%). These results indicate that the use of remote sensing provide favorable information for the characterization of grassland bird's habitat.Grasshopper sparrow, Baird sparrow, remote sensing, supervised classification, vegetation.RESUMEN Comprender la preferencia del hábitat de aves de pastizal que declinan sus poblaciones es importante para su conservación. Actualmente el uso de sensores remotos para describir el hábitat de aves en México es reciente y brinda estudios en menor tiempo y costo. El objetivo del trabajo fue describir la cobertura del suelo en áreas con gorriones del género Ammodramus en dos sitios de pastizal de Durango, con el protocolo de Bird Conservancy of the Rockies e imágenes de alta resolución. Se seleccionaron 40 puntos de localización aleatoriamente a partir de detecciones (n=1881) registradas del seguimiento de 33 individuos de A. bairdii y 23 de A. savannarum, mediante telemetría. Se obtuvo una métrica de vegetación y un ortomosaico con clasificación supervisada en 4 clases, donde se insertaron los puntos de localización, realizando un buffer de 5 metros de radio y generando porcentajes de clases. Ambas técnicas se correlacionan y demuestran ser útiles para cuantificar las variables observadas (p≤0.05); no existen diferencias significativas entre especies, ya que usan lugares con cobertura de pasto similares a los reportados en otros estudios (61.24±4.07%, 62.78±4.24%). Estos resultados muestran que la tecnología geoespacial tiene gran potencial para la descripción del hábitat de aves de pastizal.gorrión Chapulinero, gorrión de Baird, teledetección, clasificación supervisada, vegetación.
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