We studied the diet and prey delivery behavior of Burrowing Owls (Athene cunicularia hypugaea) during the breeding season in the southeastern Chihuahuan desert, Mexico. The diet of the Burrowing Owl included 8 orders, 13 invertebrate families, and 5 genera of mammals, gastropods, reptiles, and birds. By frequency, invertebrates (Orthoptera, Coleoptera, Hymenoptera, and Hemiptera) were the most common prey, with vertebrates making up a much smaller proportion. However, by biomass, owls consumed mainly vertebrates (56.7%). Among invertebrates, the families Tenebrionidae and Acrididae accounted for 33.2% of the total consumed biomass. Females delivered more prey items than males (55.6% and 44.4%, respectively). Our observations contribute to our knowledge of the ecology of this owl in a region where it has been little studied.

Heavy metals exposure has been linked to severe health problems. In Mexico, the Monterrey metropolitan area (MMA) is considered one of the most polluted industrial regions. Because birds have been used successfully as environmental biomonitors, the levels of lead, cadmium, and arsenic in feathers of Great-tailed grackles (Quiscalusmexicanus) from two sites within and one site outside the MMA were determined. One hundred birds were captured, samples were analyzed by atomic absorption spectrometry. Ciudad Universitaria had the highest mean values of lead and cadmium, 11.91 ppm d.w. and 1.66 ppm d.w., respectively. This was at least, 10- and 8-times higher than the two other sample sites. We believe that using Great-tailed grackles as bioindicators in conjunction with air pollutants sampling from meteorological stations in Monterrey City could help in making decisions when applying environmental remediation measures as well as in the selection of places for housing, school and work among others.

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.

The dietary niche breadth of the Burrowing Owl was determined (Athene cuniculariaMolina, 1782) in Llano La Soledad, Galeana, Nuevo Leon in northern Mexico, by considering prey type, numerical percentage, weight, weight percentage, frequency of occurrence percentage, and IRI percentage. The study compared data from three winters (2002–2003, 2003–2004, 2004–2005) by analyzing 358 pellets, identifying 850 prey items. Invertebrates constituted 90% of prey items, which mostly included insects (85%); beetles were the most common insects found in pellets (70%). Vertebrates made up 84% of consumed weight, of which 83% were mammals. Most of the mammals were cricetid rodents (41%). Niche breadth based on the numerical and weight percentage confirmed the Burrowing Owl as a generalist species with mean values per year ranging between 0.65 and 0.82. Additionally, there was a strong association between the weight of rodent species in winter. This association was mainly driven by changes in composition and frequency of these prey species during the second winter, probably caused by high annual rainfall. The second season also showed a statistically significant narrower niche (Ro = 0.96) and the smallest overlap (0.45vs. 0.76) among the three winters.

Capsule We studied the migratory movements and site fidelity of a male Long-billed Curlew using satellite telemetry in North America; the bird completed three migratory cycles and showed strong fidelity to stop-over, breeding, and wintering sites, not only on a geographical scale but also on a local scale across the years.

The long-billed curlew (Numenius americanus) is a species of international conservation concern. Effective long-term conservation measures for a species require knowledge of all aspects of the species' ecology within its range. We analyzed 210 pellets regurgitated by long-billed curlews that were collected at two sites in the Chihuahuan Desert in Mexico. From these pellets, we identified 34 prey items corresponding to three classes of invertebrates (10 orders, 18 families, and 9 morphospecies), one class of reptiles (one order and one family), one class of plants (one order, one family, and four morphospecies), as well as gastroliths. We selected three habitat types used by the curlews and conducted a prey availability analysis with pitfall traps and a sweep net; we estimated a biomass of 20.78 g of ground-dwelling invertebrates and 64.73 g of flying and foliage invertebrates for every 10 m2 during the winter season. Our results demonstrate that the long-billed curlew has high dietary flexibility and uses different habitats during its wintering stay in the Chihuahuan Desert in Mexico. One main threat was detected on wintering grounds: exposure to pesticides, which can lead to both physiological problems and the reduction of its main prey.