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Universidad Autónoma de Nuevo León (2014)

Aves de pastizal invernando en áreas agrícolas y pastizales naturales del Noreste de México

Allen Bobadilla, Jorge

Titre : Aves de pastizal invernando en áreas agrícolas y pastizales naturales del Noreste de México

Auteur : Allen Bobadilla, Jorge

Université de soutenance : Universidad Autónoma de Nuevo León

Grade : Maestría en Ciencias con acentuación en Manejo de Vida Silvestre y Desarrollo Sustentable UANL, 2014.

Grasslands are the most impacted biome by human activities worlwide. In Northeastern Mexico, this ecosystem is mainly distributed within the Chihuahuan Desert ecorregion, where a 70% loss has been estimated. These desert grasslands are critical for wintering migratory grassland birds that nest in the Great Plains of North America. The objective of this study is to determine the use and density of the grassland birds in agricultural áreas of southern Nuevo León y Coahuila, and compare them with natural grassland areas of the GPCA El Tokio y Valle Colombia. One-hundred an eight and 104 1 km-transects were done to record birds and vegetation on two wintering season (2010 and 2011) in the agricultural áreas ; 61 in E Tokio and 36 in Valle Colombia. In agricultural áreas, a total of 66 species were observed, 16 of which are grassland obligates. In El Tokio, 60 species were registered, 15 grassland especialists, and 54 and 16 in Valle Colombia. Species richness, corrected by rarefaction with EstimateS 8.2 was slightly higher in agricultural tan natural grasslads areas. When estimating density with program Distance 6.0, Eremophila alpestris (2.8 inds/ha - 0.34 inds/ha) and Passerculus sandwichensis (0.682 - 2.039 inds/ha) showed the highest densities in agricultural areas, during 2010 and 2011, respectively. The significant diference of both species between seasons was the result of years with below and above average anual precipitation, that in conjunction with fertilizers on the ground, changed composition and structure of vegetation. In agricultural areas, during 2010, bare ground dominated estimations with a 59.63% mean, followed by forbs (16.59%) and grasslands (12.52%). On the secod season, mean percentage of bare ground decrease significantly (36.66%), while forbs (27.72%) and other coverage such as loose vegetation (20.13%), increased significantly. In the GPCA, densities variated as well but were more stable, with E. alpestris (2.199 and 1.402 inds/ha) dominating in El Tokio ; and P. sandwichensis (0.160 y 0.077 inds/ha) and Pooecetes gramineus (0.039 y 0.113) in Valle Colombia. Similarly, vegetation variables did not show a significant diference between years in natural grasslad areas. On the other hand, several grassland species were more sensitive to agricultural areas use and were marginally recorded using them, such as : Athene cunicularia (8), Asio flammeus (3), Anthus spragueii (3), Peucaea cassini (2), Ammodramus savanarum (3) and Ammodramus bairdii (1) ; or not observed at all, like Charadrius montanus. Also, within agricultural areas some species protected under Mexican law (NOM-059-SEMARNAT-2010) were registered such as : Buteo regalis, Falco mexicanus, A. flammeus, A. cunicularia and Spizella wortheni, this latter endemic. In such conditions, it is indispensable to evaluate the effect of the use of agricultural areas which can result attractive hábitats due to food, water, perching and refuge sites availability, but can also turno out to be ecological traps where predation, pesticide exposure and man-made structure collisions are of greater risk to the species that use them.

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