PRIMER REGISTRO DE UNA ABERRACIÓN MARRÓN PARA EL CORMORÁN NEOTROPICAL NANNOPTERUM BRASILIANUM DE MÉXICO

En esta nota, reportamos un caso de aberración del plumaje en el cormorán neotropical Nannopterum brasilianum. Se registró la presencia de un color atípico en el plumaje de un individuo observado en un humedal del norte de México. El ave presentaba una aberración marrón, en la que el color negro original fue sustituido por tonos marrón claro y beige pálido. Observamos el ave alimentándose junto a otros cormoranes con una coloración normal y no mostró comportamientos diferentes. La documentación de fenotipos aberrantes es importante para determinar su frecuencia y patrones geográficos de aparición, especialmente en aves acuáticas con distribuciones geográficas extensas como N. brasilianum. Esta observación representa el primer reporte de aberración de plumaje marrón en esta especie

Effect of annual rainfall and temperature on the selection of habitat and overwintering home range of grassland birds

Objective: To determine the effect of annual precipitation and winter temperature on habitat and winter home range size of two grassland birds in a native grassland of northern Durango, Mexico. Design/methodology/approach: Using telemetry techniques over four consecutive winters (2016-2019), we estimated the home range size (HR; by Kernel method), of Centronyx bairdii and Ammodramus savannarum. Likewise, we estimated the cover of grass, bush, grass, bare ground, dead vegetation, animal excrement and counted the seeds available in the soil (biomass, gr/m2) of the habitat. We compared these dependent variables with non-parametric statistics, with the minimum and maximum annual precipitation (mm) and temperature (°C) of the site. Results: The grassland sparrows used sites with equal coverage of grass, herbaceous plants, shrubs, bare ground, and others (Kruskal-Wallis, p≤0.05). In general, annual rainfall has no effect on the structure and vegetation cover. HR was negatively correlated (Sperman, p≤0.05) with annual rainfall for C. bairdii (rs=-0.90, n=45) and for A. savannarum (rs=-0.80, n=33). When the maximum temperature was higher, both species had a smaller HR. In contrast, when the minimum temperature was low, the HR increased for C. bairdii and decreased for A. savannarum. Study limitations/implications: We demonstrate the importance of considering quantifying the largest number of variables when research is required on the selection and use of grassland bird habitat. Findings/conclusions: This study allows us to increase our knowledge about the winter ecology of grassland birds and demonstrates that environmental variables such as annual rainfall and temperature influence habitat selection of C. bairdii and A. savannarum.Objective: To determine the effect of annual precipitation and winter temperature on the habitat and size of the overwintering home range of two grassland birds in a native grassland in northern Durango, Mexico. Design/ Methodology/ Approach: Using telemetry techniques during four consecutive winters (2016-2019), we estimated the size of the home range (HR; by the Kernel method) of Centronyx bairdii and Ammodramus savannarum. Likewise, the coverage of grassland, scrubland, bare soil, dead vegetation, and animal excrement was estimated and the seeds available in the soil (biomass, g m-2) of the habitat were counted. We correlated these dependent variables with non-parametric statistics, to the minimum and maximum annual rainfall (mm) and temperature (°C) of the site. Results: Grassland sparrows used sites with equitable cover of grass, herbaceous plants, shrubs, bare soil and others (Kruskal-Wallis, p≤0.05). Overall, annual precipitation has no effect on structure and vegetation cover. The HR was negatively correlated (Spearman, p≤0.05) with the annual precipitation for C. bairdii (rs=-0.90, n=45) and for A. savannarum (rs=-0.80, n=33). When the maximum temperature was higher, both species had lower HR. In contrast, when the minimum temperature was low, the HR increased for C. bairdii and decreased for A. savannarum. Study Limitations/ Implications: We demonstrated the importance of considering quantifying the greatest number of variables when research is required on the selection and use of grassland bird habitat. Findings/ Conclusions: This study allowed us to increase our knowledge about the winter ecology of grassland birds and demonstrated that environmental variables such as annual precipitation and temperature influenced the habitat selection of C. bairdii and A. savannarum

Desert bighorn sheep in Mexico

The management of bighorn sheep in Mexico is not based on empirical data. We conducted phone interviews and a literature review to determine published information on desert bighorn sheep in Mexico. Most information on bighorn sheep was published prior to 1983 and focused on population size and structure. We concluded that desert bighorn sheep in Mexico are in need of further research. To provide better management to bighorn sheep, research needs to focus on basic life history strategies (e.g., minimum viable population size, diet, habitat relationships, movements, predation, diseases, and metapopulation dynamics). Bighorn sheep in Mexico have been scarcely studied. We conducted a habitat use study in Rancho el Plomito, Sonora, Mexico from April 1997 to December 1998 and the data were used to determine causes of sexual segregation. Vegetation associations were not used according to their availability. Segregated females formed larger groups, were closer to escape terrain and occupied more rugged areas than males. Sexual segregation exhibited by desert bighorn sheep in Rancho el Plomito may result from different energetic and reproductive strategies for males and females. Females tend to optimize conditions suitable for rearing offspring and males maximize body condition. Bighorn sheep in Mexico are important game animals and are confined to scattered populations (Villa 1.959). Little research has been conducted on desert bighorn sheep and consequently the species is listed in appendix II of CITES (i.e., vulnerable) (Valdez 1997). Tarangb and Krausman (1997) emphasized food selection as a fundamental research topic for the species in Mexico. We conducted a study of diet composition in Sonora, Mexico from April 1997 to December 1998. We identified 41 plant species consumed by desert bighorn sheep. The mean annual diet was composed of browse, forbs, succulents, and grasses. Composition of forage categories in diets of males and females was similar. The coefficient of overlap (Morisita 1959) of diets of male and female bighorns for seasons indicated significant overlap. Sexual segregation of desert bighorn sheep in Sonora, Mexico was not related to forage selection (i.e., botanical composition, forage quality), and suggested that other factors (i.e., physiographic characteristics) were responsible for this segregation

TRACKS INDEX AND VEGETATION CHARACTERISTICS OF THE HABITAT OF Mazama temama (KERR 1792) IMMERSED IN THE CAÑÓN DE RÍO BLANCO NATIONAL PARK, VERACRUZ, MEXICO

Background. The red temazate deer (Mazama temama, Artiodactyla: Cervidae) is a deer with ecological, cultural and economic importance, but its density and habitat characteristics in National Parks are unknown. Objective. To estimate the track index as an indirect measure of density and describe the vegetation characteristics of the habitat of M. temama in the town of Zapoapan, Parque Nacional Cañón del Río (PNCRB), Veracruz, Mexico. Methodology. During January to October 2021, eight transects were established to record tracks, phototraps were installed to determine their presence, and Canfield lines were used to describe the vegetation in areas with the presence of the species. Results. Twenty-three tracks of M. temama were recorded: nine tracks (39%), six excreta (26%), three foraging tracks (13%), three stalls (13%) and two photocaptures (8%), equivalent to an index tracks of 0.57 individuals/ha or 2.2 ha/individual, low density compared to other reports of the species. The habitat presented a richness of 19 species of plants, the shrubs being more abundant (36%) than the herbaceous and arboreal (represented by 32% each); the tree layer was dominant in terms of height and diameter. Implications. These results suggest that the habitat does not have sufficient diversity of resources to maintain a dense population of M. temama. Conclusion. The population density of M. temama in the PNCRB was low associated with a restricted carrying capacity in the study area, so actions must be taken towards the conservation and sustainable use of the population of this species