Population density of the western burrowing owl (Athene cunicularia hypugaea) in Mexican prairie dog (Cynomys mexicanus) colonies in northeastern Mexico
© The Author(s) 2016
Received: 1 November 2015
Accepted: 29 July 2016
Published: 26 August 2016
The western burrowing owl (Athene cunicularia hypugaea) occurs throughout western North America in various habitats such as desert, short-grass prairie and shrub-steppe, among others, where the main threat for this species is habitat loss. Range-wide declines have prompted a need for reliable estimates of its populations in Mexico, where the size of resident and migratory populations remain unknown.
Our objective was to estimate the abundance and density of breeding western burrowing owl populations in Mexican prairie dog (Cynomys mexicanus) colonies in two sites located within the Chihuahuan Desert ecoregion in the states of Nuevo Leon and San Luis Potosi, Mexico. Line transect surveys were conducted from February to April of 2010 and 2011. Fifty 60 ha transects were analyzed using distance sampling to estimate owl and Mexican prairie dog populations. We estimated a population of 2026 owls (95 % CI 1756–2336) in 2010 and 2015 owls (95 % CI 1573–2317) in 2011 across 50 Mexican prairie dog colonies (20,529 ha).
The results represent the first systematic attempt to provide reliable evidence related to the size of the adult owl populations, within the largest and best preserved Mexican prairie dog colonies in Mexico.
KeywordsChihuahuan Desert Distance sampling Grassland Mexican prairie dog Mexico Population Western burrowing owl
Published data from owl populations vary within the range of distribution in North America. For example, in the 1990's population estimates of this species in Canada and the United States of America (USA) ranged from as low as 2000–20,000 to as high as 20,000–200,000 individuals . In Canada, the populations have declined abruptly and even disappeared from British Columbia and Manitoba . Previous reports indicate a wide variation of population trends ranging from stable in some areas in the USA and Canada, to reduced, extirpated or increasing in others [2, 7–16].
Local density estimates a range of 13–31 owls/km2 in Canada (Manitoba, Alberta, Saskatchewan and British Columbia) and the USA (Arizona, California, Colorado, Idaho, Iowa, Kansas, Minnesota, Montana, Nebraska, New Mexico, North and South Dakota, Oklahoma, Oregon, Texas, Utah and Washington) during the western burrowing owl breeding season indicating variation in the density estimates [1, 7, 9, 14, 17–26]. In Mexico, the federal government classifies the western burrowing owl under the category of special protection . Habits of the western burrowing owl such as summer diet, prey selection, movement of juveniles, selection of nesting sites and threats remain poorly known. Densities estimated during the breeding season in 2002 in Mexico include 14.1 owls/km2 near Mexicali , 3.2 pairs/km2 in Yaqui-Mayo Valley, Sonora, 4.5 pairs/km2 in Valle del Fuerte, Sinaloa, and 4.7 pairs/km2 in Valle de Culiacan, Sinaloa . Winter season density estimates in central Mexico include 11 owls/km2 in Guanajuato  and 5.2 owls/km2 in Nuevo Leon .
Based on the problems and the lack of knowledge mentioned above, in this study we estimate the abundance and density of western burrowing owls in colonies of Mexican prairie dog in northeastern Mexico. Density/abundances of western burrowing owls and their association with Mexican prairie dog colonies provide relevant conservation information to ensure the long-term persistence of both species. In addition, this study can be integrated across North America to establish baseline range-wide population estimate(s) to improve our understanding of the recent range-wide shifts in owl populations.
Our study sites were located in Nuevo Leon (NL) and San Luis Potosi (SLP) within the Chihuahuan Desert ecoregion  (Fig. 2) that is part of the physiographic region known as the Mexican Plateau within the Mexican states of Coahuila, Zacatecas, NL and SLP. The semi-arid climate features temperatures ranging from 6 to 25 °C with an annual average of 16 °C . Average precipitation totals 427 mm .
Previously, studies in NL have been conducted in the areas known as Llano de la Soledad (23°53′N, 100°42′W) and Compromiso (23°53′N, 100°42′W). These areas maintain the largest Mexican prairie dog populations, including those at Martha (25°0′N, 100°40′W), Concha (25°1′N, 100°35′W), and Hediondilla (24°57′N, 100°42′W). Western burrowing owls of SLP were studied in Llano del Manantial (24°7′N, 100°55′W) and Gallo (24°12′N, 100°54′W) in the municipality of Vanegas.
The Llano de la Soledad has been provided with several conservation designations by the NL government such as State Natural Protected Area , and Important Site for Bird Conservation . This site hosts several vulnerable, endemic and migratory species [50, 51]. The dominant vegetation in Mexican prairie dog colonies is characterized by halophytic grassland and consists largely of Muhlenbergia villiflora, Muhlenbergia repens, Pleuraphis mutica, Sporobolus airoides, Frankenia gypsophila and Dalea gypsophila. Other coexisting plant communities include microphyllus vascular plants and rosette shrubs [31, 52–56].
From 50 colonies of prairie dogs existing in NL and SLP, nine were selected for sampling. These colonies were selected based on the following characteristics: spatial continuity of the community and a lack of fragmentation, conservation status of the site, vegetation type that was homogeneous enough to contain at least one complete transect. The sampled colonies covered about 55 % of the area available for all colonies of Mexican prairie dogs in the southern Chihuahuan Desert. Sampling was conducted between February and April in both 2010 and 2011. The transect line method was used . Fifty transects (each 2 km long × 0.3 km wide and ≥0.5 km apart from each other) were traveled using the remote sampling method by the observer as described below to estimate the density of adult owls . The number (n) of transect routes for each area was: Soledad (n = 28) and Compromiso (15), Marta (2) and Concha (2) in NL; Manantial (2) and Gallo (1) in SLP. We walked each transect at a constant rate using a global positioning system (GPS) to ensure a straight survey line. Owls were detected visually or with binoculars. Then, the perpendicular distance from the transect line route was measured using a laser rangefinder (15–815 m, Leica Rangemaster 900, Optics Planet, Inc. Northbrook, IL, USA). To meet the assumptions of distance sampling, only adult owls were recorded on the ground outside the burrows or without movement [58, 59]. If the bird under observation moved because of the presence of the observer, registering the perpendicular distance was performed at the original site without the observer leaving their sighting transect travel line. Those adult owls flying with an unknown initial location were not documented. To reduce bias and avoid an overestimation of population density, only adult owls were recorded. Considering the extreme desert climate, personal observations made during previous years and different criteria of previous authors related to the activities of owls, the field observations were conducted from 0600 to 1200 h [20, 23, 60, 61].
We used program DISTANCE ver. 6.0 to obtain western burrowing owl density estimates from distance sampling . DISTANCE calculates density and abundance using modeling detection probability as a function of the perpendicular distance to the transect in a series of monotonic models. Several standard detection functions (uniform, half-normal, or hazard-rate) with cosine series adjustment were evaluated using the Akaike information criterion (AIC). We used the AIC to select the model with the most parsimonious detection function in DISTANCE [58, 59, 63]. We pooled all data to estimate a single detection function (probability of detection, g (x), at a given distance (x) from the transect) because we did not anticipate effects of environmental features on detection, such as age (adult) and factor STATE (levels: NL and SLP). We considered serial adjustments of one to three parameters. We did not truncate the data because the frequencies of long distances observations were better maintained in this manner .
Overall estimates of western burrowing owl density (and their SE) at the nine sampled colonies (9620 ha) were obtained by pooling detection distance data by year. These estimates were then multiplied by the total area of the 50 colonies of the Mexican prairie dog described for the southern part of the Chihuahuan Desert to provide yearly estimates of owl population size through the range of Mexican prairie dog: 38 in NL (19,802 ha) and 12 in SLP (727 ha) . On average, 55 % of the surface reported for the Mexican prairie dog colony complex was sampled .
Density and population size
Western burrowing owl population density between 2010 and 2011 in Mexican prairie dog colonies in NL and SLP, Mexico
Estimated density (owl/ha)
95 % ICd
95 % ICe
Applying the overall yearly estimates of western burrowing owl density to the entire area of the 50-colony complex of prairie dogs in NL and SLP resulted in a population size of 2026 (CV 0.173) in 2010 and 2015 (CV 0.213) in 2011. For colonies in NL, an average population size of 1747 (CV 0.178) was obtained in 2010 and 1464 (CV 0.218) for 2011, while in SLP, population estimates were between 190 (CV 0.312) and 341 (CV 0.322) for each year.
To date, many density estimates have been made for the western burrowing owl in Canada and the USA, with quite variable results [1, 6, 7, 9, 11–15, 20–23, 25, 26]. The resulting variation in the population sizes can be attributed to the size of sample area, methodology, analytical precision, timing, observer skill, and so on; these have contributed to an inexact picture of the density of the western burrowing owl populations [6, 15]. Therefore, a comparison of our results with those of the USA and Canada could be difficult.
During the last 30 years, the North American Breeding Bird Survey has estimated a negative trend for the western burrowing owl population for Canada and the USA. Similarly, the United States Geological Survey (2014) has reported the same negative trend in the Chihuahuan Desert region .
Even though Mexico has not established systematic surveys that allow the establishment of a population trend, some studies (the present one included) can form the basis to achieve this goal of documenting population trends in the future.
In NL and SLP, the average density of breeding pairs (9.8 ind/km2) in 2010 and 2011 is greater than that reported by Macias-Duarte in Sonora (6.4 ind/km2) and similar to the Sinaloa average (9.2 ind/km2) . However, in Baja California, Itubarria-Rojas reported an average of 14.1 ind/km2, which is a value higher than that determined by the present study . This difference could be caused by the habitat quality among sites as reported in NL and SLP where burrow competition is related to the abundance of prairie dogs per colony or Baja California where the owls use irrigation canals to create burrows.
Our overall estimates of population size for western burrowing owls reveal the relative importance of Mexican prairie dog colonies to owl population viability. No previous data related to population size estimates in owls is available for the study area. However, the precision of these estimates must be taken with caution because of the variability between sites. However, we believe the extrapolation is correct because we sampled over 55 % of the current area with the active prairie dog colonies in both states. The range of the western burrowing owl in northeastern (NL, SLP, and Coahuila) Mexico includes viable colonies of Mexican prairie dogs. These areas provide an optimal habitat for the prairie dogs to feed on grasses and this contributes to a low height of herbaceous plants and allows the owls greater visual access to the foraging area. This species uses prairie dog colonies as a place for nesting, protection against climatic factors (extreme temperatures, flooding by rain, and strong winds). The owls also respond to alarm calls by prairie dogs, alerting them to the presence of predators. The western burrowing owl colonies in Mexico have declined from 88 colonies to 53, equivalent to a loss of 37 % in 10 years (1992–2003) [37, 38].
Many of the problems in northeastern Mexico that involve the western burrowing owl are directly related to loss of habitat from agriculture, but some direct mortality has been caused by collisions with vehicles. However, another possible cause of morbidity and mortality could be the direct or incidental (by bioaccumulation) exposure to pesticides used in neighboring areas.
These results represent the first systematic effort to address the conservation status of the western burrowing owl populations in Mexican prairie dog colonies located in northeastern Mexico. This geographic area is considered to contain the largest preserved Mexican prairie dog colonies in the country and deserves attention from the scientific and conservation communities. Furthermore, these results contribute new information to our understanding of the population dynamics of this kind of species across North America, and highlight the urgent need to preserve grasslands, particularly those in the southern part of the Chihuahuan Desert, which harbor many bird species cataloged as threatened or endangered.
USA: United States of America; NL: Nuevo Leon; SLP: San Luis Potosi.
km: kilometers; ind/km2: individual per square kilometer; ha: hectare; n: number of line transects; m: meters; mm: millimeter; °C: celsius; hr: hours.
gx: probability of detection; x: given distance; ± SE: standard error; CV: coefficient variation; p: probability; AIC: akaike information criterion; IC: confidence intervals.
N: north; W: western; GPS: global positioning system.
GRA conceived of and designed the study, collected the data and performed data analysis. AOK, AMD, AGV and JIGR contributed to study design and provided advice for data collection and analysis. All authors participated in drafting the manuscript. All authors read and approved the final manuscript.
We are grateful to Pronatura Noreste Asociacion Civil for Cynomys ludovicianus photo (Fig. 2) and their facilities for hospitality throughout the sampling period.
The authors declare that they have no competing interests.
Availability of data and materials
All protocols were performed according to the ethical guidelines adopted by the ethic committee of the Facultad de Ciencias Biologicas of the Universidad Autonoma de Nuevo Leon, as well by the current environmental Mexican laws. Only field observations were made. There was no animal handling. However in order to comply with the Mexican regulations we have a permit (SGPA/DGVS/01588/10), granted by the Secretaria del Medio Ambiente y Recursos Naturales/Subsecretaria de Gestion para la Proteccion Ambiental/Direccion General de Vida Silvestre.
This research was funded with resources from the Universidad Autonoma de Nuevo Leon through the support program for Scientific and Technological Research (PAICyT).
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Macias-Duarte A, Conway CC. Distributional changes in the western burrowing owl (Athene cunicularia hypugaea) in North America from 1967 to 2008. J Raptor Res. 2015;49:75–83.View ArticleGoogle Scholar
- ACA. Commission for Environmental Cooperation. In: North America conservation action plan (Athene cunicularia hypugaea). Commission for Environmental Cooperation. Printed in Canada; 2005. p. 1–55. http://www.cec.org Accessed 15 Apr 2009.
- Clark RJ. A review of the taxonomy and distribution of burrowing owl (Speotyto cunicularia). J Raptor Res. 1997;9:14–23.Google Scholar
- Coulombe HN. Behavior and population ecology of the burrowing owl, Speotyto cunicularia, in the Imperial Valley of California. Condor. 1971;73:162–76.View ArticleGoogle Scholar
- Howell GR, Webb S. A Guide to the birds of Mexico and Central America. Oxford University Press; 1995. pp. 364.Google Scholar
- James PC, Espie RHM. Current status of the burrowing owl in North America: an agency survey. J Raptor Res. 1997;9:3–5.Google Scholar
- COSEWIC. Assessment and update status report on burrowing owl Athene cunicularia in Canada. Committee on the status of endangered wildlife in Canada. Ottawa; 2006. pp. 31.Google Scholar
- Desante DF, Ruhlen ED, Adamany SL, Butron KM, Amin S. A census of burrowing owls in central California in 1991. In: Lincer J, Steenhof K, editors. The burrowing owl, its biology and management including the proceedings of the first international burrowing owl symposium; 1997.Google Scholar
- Desmond MJ, Savidge JA. Factors influencing burrowing owl (Speotyto cunicularia) nest densities and numbers in western Nebraska. Am Midl Nat. 1996;136:143–8.View ArticleGoogle Scholar
- Clayton KM, Schmutz JK. Is the decline of burrowing owls Speotyto cunicularia in prairie Canada linked to changes in great plains ecosystems? Bird Conserv Int. 1999;9(2):163–85.View ArticleGoogle Scholar
- Arrowood PC, Finley CA, Thompson C. Analyses of burrowing owl populations in New Mexico. J Raptor Res. 2001;35(4):362–70.Google Scholar
- Korfanta NM, Ayers LW, Anderson SH, McDonald DB. A preliminary assessment of burrowing owl status in Wyoming. J Raptor Res. 2001;35:337–43.Google Scholar
- Sheffield SR, Howery M. Current status, distribution, and conservation of the burrowing owl in Oklahoma. J Raptor Res. 2001;35:351–6.Google Scholar
- Murphy RK, Hasselbland DW, Grondahl CD, Sidle JG, Martin RE, Feed DW. Status of the burrowing owl in North Dakota. J Raptor Res. 2001;35:322–30.Google Scholar
- Klute DS, Green TM, Howe WH, Jones ST, Shaffer JL, Sheffield SR, Zimmerman TS. Status assessment and conservation plan for the western burrowing owl in the United States. US Department of Interior, Fish & Wildlife Service, Biological Technical Publication FWS/BTP-R6001-2003, Washington, D.C.; 2003.Google Scholar
- Sauer JR, Hines J E, Fallon JE, Pardieck KL, Ziolkowski DJ. Link the North American breeding bird survey, results and analysis 1966–2013. Version 01.30.2015 USGS Patuxent Wildlife Research Center, Laurel. USA; 2014.Google Scholar
- Butts KO, Lewis JC. The importance of prairie dog towns to burrowing owls in Oklahoma. Proc Okla Acad Sci. 1982;62:46–52.Google Scholar
- Enriquez-Rocha P, Rangel-Salazar DW. Presence and distribution of Mexican owls: a review. J Raptor Res. 1993;27:154–60.Google Scholar
- Trulio L. Burrowing owl demography and habitat use at two urban sites in Santa Clara County, California. J Raptor Res. 1997;9:84–9.Google Scholar
- Conway CJ, Simon JC. Comparison of detection probability associated burrowing owl survey methods. J Wildl Manag. 2003;67(3):501–11.View ArticleGoogle Scholar
- Desante DF, Ruhlen ED, Rosenberg DK. Density and abundance of burrowing owls in the agricultural matrix in the Imperial Valley. Stud Avian Biol. 2004;27:116–9.Google Scholar
- Manning JA. Burrowing owl population size in the Imperial Valley, California: survey and sampling methodologies for estimation. Final report to the Imperial irrigation district, Imperial, California, USA; 2009. http://www.iid.com/Modules/ShowDocument.aspx?documentid=8172. Accessed 15 Apr 2009.
- Tipton HC, Doherty PF, Dreitz VJ. Abundance and density of mountain plover (Charadrius montanus) and burrowing owl (Athene cunicularia) in eastern Colorado. Auk. 2009;126:493–9.View ArticleGoogle Scholar
- Berardelli D, Desmond JM, Murray L. Reproductive success of burrowing owls in urban and grassland habitats in southern New Mexico. Wilson J Ornithol. 2010;122(1):51–9.View ArticleGoogle Scholar
- Crowe D, Longshore K. Population status and reproduction ecology of the western burrowing owl (Athene cunicularia hypugaea) in Clark Contry, Nevada. Report final 2005.USGS-582-P. United States Geological Survey; 2010. pp. 31.Google Scholar
- Wilkerson RL, Sigel RB. Distribution an abundance of western burrowing owls (Athene cunicularia hypugaea) in southeastern California. Southwest Nat. 2011;56(3):378–84.View ArticleGoogle Scholar
- NOM-059-SEMARNAT-2010. Protección ambiental-Especies nativas de Mexico de flora y fauna silvestres-categorias de riesgo y especificaciones para su inclusion, exclusion o cambio-lista de especies en riesgo. DIARIO OFICIAL DE LA FEDERACION; 2010. http://www.profepa.gob.mx/innovaportal/file/435/1/NOM_059_SEMARNAT_2010.pdf. Accessed 30 Dec 2010.
- Itubarria-Rojas H. Estimacion de abundacia y afinidad de habitat del tecolote llanero (Athene cunicularia) en el Valle de Mexicali California y Sonora, Mexico. Universidad Autonoma de Guadalajara. Facultad de Ciencias Quimicas y Biologicas. Tesis de licenciatura. Guadalajara, Jalisco, Mexico; 2002. pp. 36.Google Scholar
- Macias-Duarte A. Change in migratory behavior as possible explanation for burrowing owl population declines in northern latitudes. The University of Arizona. School of Natural Resources and the Environmental. PhD Thesis. USA; 2011. pp. 145.Google Scholar
- Valdez-Gomez HE, Holroyd GL. The burrowing owl, habits and distribution center in western Mexico. Boletin de la Sociedad de Ciencias Naturales de Jalisco. 2000;1:57–63.Google Scholar
- Cruz-Nieto MA. Ecologia invernal de la lechuza llanera (Athene cunicularia), en los pastizales ocupados por los perritos llanero Mexicano (Cynomys mexicanus), Nuevo Leon, Mexico. Universidad Autonoma de Nuevo Leon. Facultad de Ciencias Biologicas. Laboratorio de Ornitologia. San Nicolas de los Garza. Tesis Doctorado en Ciencias; 2006. pp. 118.Google Scholar
- Desmond MJ, Savidge JA, Eskridge KM. Correlations between burrowing owl and black-tailed prairie dog declines: a 7-year analysis. J Wild Manag. 2000;64(4):1067–75.View ArticleGoogle Scholar
- Griebel RL, Savidge JA. Factors related to body condition of nestling burrowing owls in Buffalo Gap National Grassland, South Dakota. Wilson J Ornithol. 2003;115:477–80.Google Scholar
- McNicolle JL. Burrowing owl (Athene cunicularia) nest site selection in relation to prairie dog colony characteristics and surrounding land-use practices in Janos, Chihuahua, Mexico. Las Cruces, New Mexico, New Mexico State University. Ms Thesis. USA; 2005. pp. 54.Google Scholar
- Ruiz-Ayma G. Exito reproductive, entrega de presas y dieta del tecolote (Athene cunicularia hypugaea) en el complejo de la colonias de perrito de la pradera Mexicano (Cynomys mexicanus) en Galeana, Nuevo Leon, Mexico. Universidad Autonoma de Nuevo Leon. Facultad de Ciencias Biologicas. Tesis Maestria en Ciencias. Mexico; 2009. pp. 85.Google Scholar
- Ceballos GOG. Los mamiferos silvestres de Mexico. Ed. Fondo de Cultura Economica de España; 2009. pp. 986.Google Scholar
- Carrera MMA. Situacion actual, estrategias de conservacion y bases para recuperacion del perrito llanero mexicano (Cynomys mexicanus). Universidad Autonoma de Mexico. Tesis Maestria en Ciencias. Mexico; 2008. pp. 72.Google Scholar
- Scott-Morales L, Estrada E, Chavez-Ramirez M, Cotera M. Continued decline in geographic distribution of Mexican prairie dog (Cynomys mexicanus). J Mammal. 2004;85(6):1095.View ArticleGoogle Scholar
- Green GA, Anthony RG. Nesting success and habitat relationships of burrowing owl in the Columbia Basin. Oregon Condor. 1989;91:347–54.View ArticleGoogle Scholar
- Haug EA, Millsap BA, Martell MS. Burrowing owl (Speotyto cunicularia). In: Poole A, Gill F, editors, The birds of North America, No. 61. Academy of Natural Sciences, Philadelphia, and American Ornithologists’ Union, Washington, DC; 1993. pp. 20.Google Scholar
- Sheffield SR. Current status, distribution, and conservation of the burrowing owl (Speotyto cunicularia) in Midwestern North America. 1997. In: Duncan JR, Johnson DH, Nicholls TH, editors. Biology and conservation of owls of the Northern Hemisphere, USDA Forest Service, General Technical Report NC-190. North Central Forest Experiment Station, St. Paul, Minnesota;1997. pp. 399–407.Google Scholar
- Wellicome TI. Effects of food on reproduction in burrowing owl (Athene cunicularia) during three stages of the breeding season. University of Alberta. Edmonton. PhD Thesis. Canada; 2000. pp. 113.Google Scholar
- Holroyd GR, Rodriguez RE, Sheffield S. Conservation of the burrowing owl in western North America, challenges and recommendations. J Raptor Res. 2001;35(3):399–407.Google Scholar
- McDonald D, Korfanta M, Lantz SJ. The burrowing owl (Athene cunicularia): a technical conservation assessment Wyoming, USDA Forest Service, Rocky Mountain Region; 2004.Google Scholar
- CONABIO. Comision Nacional para el Conocimiento y Uso de la Biodiversidad. Mexico; 2008. http://www.conabio.gob.mx/informacion/metadata/gis/ecort08gw.xml?_xsl=/db/metadata/xsl/fgdc_html.xsl&_indent=no. Accessed 26 Sept 2009.
- CONAGUA. Comisión Nacional del Agua. Consulta base de datos. Distrito Federal, Mexico. http://www.smn.cna.gob.mx/es/emas. Accessed 15 Sept 2009.
- Instituto Nacional De Estadística Geografia e Informatica. Conjunto de datos vectoriales de la carta de uso del suelo y vegetacion, escala 1:250,000, Serie III. INEGI. Mexico; 2005.Google Scholar
- Periodico Oficial. Monterrey, N. L., Gobierno Constitucional del Estado Libre y Soberano de Nuevo Leon, Mexico. Tomo CXXXIX; 2002.Google Scholar
- WHSRN. Designación de sitio en categoria de importancia internacional para la conservacion de aves playeras de la red hemisferica de reservas para aves playeras. 2005. http://www.whsrn.org/site-profile/llano-de-la-soledad. Accessed 03 Dec 2014.
- Macias-Duarte A, Panjabi AO, Pool D, Youngberg E, Levandoski G. Wintering grassland bird density in Chihuahuan Desert grassland priority conservation areas, 2007–2011. Rocky Mountain Bird Observatory, Brighton, CO, RMBO Technical Report INEOTROP- MXPLAT-10-2; 2011. pp. 164.Google Scholar
- Del Coro-Arizmendi, Marquez VL. Areas de importancia para la conservacion de las aves, CONABIO & Fondo Mexicano para la Conservacion de la Naturaleza; 2000. http://www.conabioweb.conabio.gob.mx/aicas/doctos/NE-36.html. Accessed 03 Dec 2010.
- Johnston MC. Past and present grassland of southern Texas and northeastern Mexico. Ecology. 1963;44:456–66.View ArticleGoogle Scholar
- Rojas MP. Generalidades sobre la vegetacion del estado de Nuevo Leon y datos acerca de su flora. Facultad de Ciencias. Mexico D.F, Universidad Nacional Autonoma de Mexico; 1965. pp. 124.Google Scholar
- Rivera RE. Caracterizacion y productividad invernal de tres areas de pastizal habitat para la lechuza llanera (Athene cunicularia) en el Municipio de Galeana, Nuevo Leon; Mexico. Universidad Autonoma de Nuevo Leon. Facultad de Ciencias Biologicas. Tesis licenciatura. México; 2006. pp. 72.Google Scholar
- Garcia RAM. Habitat reproductivo del gorrion de Worthen (Spizella wortheni) en cuatro localidades del noreste de Mexico. Universidad Autonoma de Nuevo Leon. Facultad de Ciencias Biologicas. Tesis licenciatura. México; 2008. pp. 71.Google Scholar
- Martinez RLM. Caracterizacion de los sitios de anidación del gorrion de Worthen (Spizella wortheni) en los estados de Nuevo Leon y Coahuila de Zaragoza, Mexico. Universidad Autonoma de Nuevo Leon. Facultad de Ciencias Biologicas. Tesis licenciatura. México; 2009. pp. 47.Google Scholar
- Ralph CJ, Geupel GR, PYLE P, Martin TE, Desante DF, Milá B. Manual de metodos de campo para el monitoreo de aves terrestres. General Technical Report PSW–GTR–159, USDA Forest Service, Albany; 1996.Google Scholar
- Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L. Introduction to distance sampling. 3rd ed. Oxford: Oxford University Press; 2001. p. 466.Google Scholar
- Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L. Introduction to distance sampling. 4th ed. Oxford: Oxford University Press; 2004. p. 435.Google Scholar
- Manning JA. Factors affecting detection probability of burrowing owls in southwest agroecosystem environments. J Wild Manag. 2011;75:1558–67.View ArticleGoogle Scholar
- Manning JA, Kaler RSA. Effects of survey methods on burrowing owl behaviors. J Wild Manag. 2011;75:525–30.View ArticleGoogle Scholar
- Thomas L, Buckland ST, Rexstad EA, Laake JL, Strindberg S, Hedley SL, Bishop JRB, Marques TA, Burnham KP. Distance software: design and analysis of distance sampling surveys for estimating population size. J Appl Ecol. 2010;47:5–14.View ArticlePubMedPubMed CentralGoogle Scholar
- Burnham KP, Anderson DR. Model selection and multimodel inference: a practical information-theoretic approach. 2nd ed. New York: Springer; 2002. p. 448.Google Scholar
- MCulloch CE, Searle SR, Neuhaus JM. Generalized, linear and mixed models. 2nd ed. Wiley: New York; 2008.Google Scholar
- Ruizayma G, Olallakerstupp A, Maciasduarte A, Antonio G, Gonzalezrojas JI. Data from: population density of the burrowing owl (Athene cunicularia hypugaea) in Mexican prairie dog (Cynomys mexicanus) colonies at northeastern México. BMC Ecol. http://dx.doi.org/10.5061/dryad.pm362.