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Map of the Colorado River Delta. The location of the wetlands is indicated by the numbers: 1, Rio Hardy; 2, Ciénega de Santa Clara; 3, El Doctor (Source: Glenn et al. 1996).
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Motivated by the finding of consistent declining population trends in migrant landbird species in the northeastern United States, there emerged numerous studies throughout the 1990’s dealing with the breeding biology of Neotropical migratory species (Terborgh 1992, Hagan & Johnston 1992, Rappole 1995, Martin & Finch 1995). More recently, attention...
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The Egyptian Vulture Neophron percnopterus is globally endangered and its population shows a decreasing trend. Within Turkey, the largest breeding population is found in the Beypazarı region north of Ankara. In the breeding season of 2020, we identified 109 occupied nest sites and breeding activities were recorded in 90 of them (breeding propensity...
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The socioeconomic development model of Brazilian cities has caused serious environmental problems. In addition, the development of agriculture and livestock causes the fragmentation and loss of Cerrado habitat, second largest Brazilian biome. In this scene, it is necessary to carry out actions aimed understanding at the importance of recovery and c...
http://dx.doi.org/10.5007/2175-7925.2012v25n2p165
Dentre os impactos ambientais, a fragmentação dos hábitats para uso agrícola e pecuário, tem provocado a descaracterização natural dos ambientes e como consequência, o atropelamento da fauna silvestre nas rodovias. Foram realizadas vistorias semanais ao longo da rodovia RS-135 (km 08 ao 34), entre...
RESUMEN
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Citations
... Para los bosques de altura del Parque Nacional Zoquiapan en el Estado de México, Ugalde-Lezama et al. (2009 mostraron que la diversidad de aves respondía a la diversidad estructural y al grado de perturbación de la vegetación, en términos de la distribución vertical de las aves; mencionan también que la comunidad de aves en bosques de pino en mejor estado de conservación presentó mayor riqueza específica que la existente en un bosque perturbado en el mismo parque. Villaseñor-Gómez (2006, 2008 realizó un análisis de los patrones de uso de hábitat (tipos de vegetación) de las aves invernantes en el estado de Sonora, detectando 80% de las 243 especies registradas en sitios de vegetación ribereña, que fue el tipo de vegetación más importante para la riqueza y abundancia de aves a nivel regional. Un aspecto común en todos estos trabajos es el reconocimiento de la necesidad de conservar la diversidad ecológica de paisaje, por la contribución que tienen tanto los tipos de vegetación original como las vegetaciones sucesionales, en términos de las especies de aves que constituyen la diversidad regional. ...
El conocimiento del uso de hábitat de las especies animales intenta comprender la estructura y dinámica de las comunidades y es útil para la evaluación e implementación de acciones de conservación en hábitats y especies que lo ameritan. Con el fin de comprender los patrones de uso de hábitat de las especies de aves del Distrito Minero El Oro-Tlalpujahua, obtuvimos información a través de conteos de búsqueda intensiva para evaluar la amplitud de nicho de las especies, la composición de comunidades, sus similitudes y diferencias, la caracterización de las mismas a través del análisis de gremios alimentarios desde las perspectivas taxonómica (gremios-especies) y funcional (gremios-biomasa), y la definición de especies sensibles. A través de 210 conteos distribuidos en siete unidades ambientales (2017-2019), se registraron 183 especies de aves. La mayor diversidad de aves se encontró en los bordes de pastizal y matorrales, y los campos agrícolas fue la unidad menos diversa. El análisis de las comunidades definió cuatro grupos de hábitats: a) bordes – bosques –vegetación ribereña, b) matorrales – pastizales; c) cuerpos de agua y d) campos agrícolas, cada uno con su conjunto de especies distintivas. De acuerdo a la amplitud de nicho, 28 especies fueron exclusivas de un tipo de hábitat y en contraste, 11 fueron generalistas. La composición de las comunidades y la estructura taxonómica de 16 gremios diferentes, sugiere una importante influencia de la fisonomía vegetal y el grado de perturbación ecológica. El análisis funcional sugiere un arreglo diferente; la contribución de nectarívoros, frugívoros e insectívoros, unifica a bosques, vegetación ribereña, campos agrícolas y matorrales, mientras que pastizales, bordes y cuerpos de agua se ubican de forma independiente por la contribución de gremios acuáticos e insectívoros aéreos. Los carroñeros, carnívoros y omnívoros contribuyen similarmente a la constitución de los ensambles en todos los hábitats. Veinticuatro especies sensibles se registraron en cuerpos de agua, y 23 en matorrales, lo que destaca su importancia en términos de conservación.
... Bioaccumulation of these elements is known to cause negative effects at the neurological (lethargy), physiological (chronic stress and changes in DNA structure), behavioral (decrease of appetite), and reproductive level (low production of eggs in birds) (Festa et al. 2003, Seewagen 2009, Chapa-Vargas et al. 2010, contributing to the decline of biodiversity at contaminated sites. The rivers of Santa Cruz, San Pedro and Colorado in Sonora, Mexico, which receive flows from copper mines, are very important sites for breeding and wintering birds, despite the negative impacts of their low water quality (Sprouse 2005, Villaseñor-Gómez 2006; they have not been studied in detail. Little is known on the effects of potentially toxic elements in tailing residual soils and their bioavailability. ...
Birds contribute to the stability of ecosystems and represent a tool used to evaluate a variety of anthropogenic impacts. The area known as El Oro-Tlalpujahua Mining District in central Mexico was subjected to significant environmental impacts as a result of ore extraction, including profound habitat transformations, landscape changes, and the accumulation of potentially toxic elements in their tailings (favoring its bioavailability and dispersion). After more than 60 years without extractive activities, there is no knowledge on extant remaining impacts on biological communities. Assuming the presence of negative impacts on birds, we compared the composition and abundance of bird communities in two locations, representing a site without exposure to tailings (S1) and another one with tailings deposition (S2). From June 2014 to June 2015, we recorded 2828 individuals of 108 avian species in 369 point counts (S1 = 91, S2 = 95). The Chao1 indicator suggested we recorded 96% of the species present. We found a high similarity in the general composition and abundance of bird species between communities (> 85%). However, there were significant differences in the abundances of 18 species (9 of them higher in the control site); these differences might result from differential effects of potentially toxic elements on functional groups (such as feeding guilds), resource availability, as well as other factors not accounted for. Historically, mining activities in the area generated significant changes in the structure and composition of the forest, and disrupted ecological processes. Despite the fact that current conditions appear favorable to the relative stability of the bird community, specific physiological effects on some species of birds sixty years after the cessation of mineral extraction could occur. Further studies on physiological performance and the effects of potentially toxic elements on local birds could unveil unknown effects at the individual level.
... However, human-disturbed landscapes may have impacts on migratory songbird survival that are not linked to food availability, such as an increase in predator abundance or diversity, which could increase stress-levels, costly predator-avoidance behaviors, or rates of depredation [74,75]. Indeed, Villaseñor [76] described significantly higher stress levels for migratory birds using disturbed and fragmented riparian habitats in Mexico compared with intact riparian forests, although the physical condition and abundance of individuals were similar to those of the conspecifics in less disturbed habitats. Furthermore, while coffee landscapes have been shown to provide good quality habitat to overwintering migrants, as measured by consistent gains in weight over the winter season [17], this work remains to be done for hardwood and oil palm plantations. ...
Tropical forests in the Americas are undergoing rapid conversion to commercial agriculture, and many migratory bird species that use these forests have experienced corresponding populations declines. Conservation research for migratory birds in the tropics has focused overwhelmingly on shade coffee plantations and adjacent forest, but both cover types are now in decline, creating an urgent need to evaluate conservation opportunities in other agricultural systems. Here we compare how a community of 42 Neotropical migratory bird species and a subset of five conservation-priority species differ in usage and habitat associations among a secondary forest baseline and four expanding commercial plantation systems in Guatemala: African oil palm, teak, rubber, and mixed-native hardwoods. We found that mixed-native hardwood plantations supported the highest richness and diversity of all migrants and that the three hardwood plantation types generally outperformed oil palm in richness and diversity metrics. Despite this, oil palm supported high abundance of several common and widespread species also experiencing range-wide population declines and may therefore play an important role in conserving common species. Mature secondary forest hosted low abundance and diversity of the full migratory community, but high abundance and richness of conservation priority migrants along with native hardwood and teak plantations. Likewise, the percentage of forest cover on the landscape was positively associated with priority migrant abundance and richness but negatively associated with the abundance of migrants in general, highlighting how individual species within the broad group of Neotropical migratory landbirds respond differently to anthropogenic changes in land use. Across all cover types, the retention of tall overstory trees increased the abundance, richness, and diversity of all migrants, which indicates that vertical structural diversity and remnant trees are important habitat features for birds in agricultural landscapes. Our findings show that conservation opportunities exist in hardwood and oil palm plantations, though the species likely to benefit from conservation action will vary among plantation types. For the subset of conservation priority migrants, our results suggest that conservation efforts should combine strategies that retain and restore secondary forest, promote the adoption of native hardwood and teak plantations, and promote the retention of tall, remnant trees in agricultural landscapes.
... Groundwater levels can also affect surface runoff, possibly narrowing the river channel; a negative correlation has been found between channel width and the percentage of agricultural land use along the river sides, in several rivers in Sonora [11]. Alteration of groundwater levels and surface runoff can prevent the establishment of obligate-riparian species such as Salix gooddingii and Populus fremontii [12], sometimes causing the complete loss of riparian vegetation or its replacement by drought tolerant desert species like Prosopis sp. or Acacia sp.; these changes in composition can have several consequences on the ecosystem: loss of local biodiversity [13], increase the susceptibility to invasive species [3,14], loss of riparian native corridors [15,16] and decrease in vegetation indices values [17]. Riparian ecosystems are often considered hotspots for ecosystem services [18][19][20]. ...
... Previous land use and vegetation classification studies in the area have found that agriculture and cattle ranching are the activities that contribute the most to land cover dynamics [8], which is consistent with the present study given that those activities were present in all of the study sites and are determinant to the disturbance degree of riparian habitats. Different indices that evaluate ecological parameters in riparian habitats have been used in many places in Mexico [15,[58][59][60], all of them use vegetation parameters such as composition, cover and species density to estimate riparian habitat condition. The ADI proposed in this study includes composition and human activities mainly but not cover. ...
Transformation or modification of vegetation distribution and structure in arid riparian ecosystems can lead to the loss of ecological function. Mexico has 101,500,000 ha of arid lands, however there is a general lack of information regarding how arid riparian ecosystems are being modified. To assess these modifications, we use eight sites in the San Miguel River (central Sonora) to analyze (1) riparian vegetation composition, structure and distribution using field sampling and remote sensing data from Unmanned Aerial Vehicles (UAV); (2) productivity (proxies), using vegetation indices derived from satellite data; and (3) variability posed by riparian vegetation and vegetation adjacent to riparian habitats. The development of a simple yet informative Anthropogenic-disturbance Index (ADI) allowed us to classify and describe each study site. We found sharp differences in vegetation composition and structure between sites due to the absence/presence of obligate-riparian species. We also report significant difference between EVI (Enhanced Vegetation Index) values for the dry season among vegetation types that develop near the edges of the river but differ in composition, suggesting that land cover changes form obligate-riparian to facultative-riparian species can lead to a loss in potential productivity. Finally, our tests suggest that sites with higher disturbance present lower photosynthetic activity.
... Sand mining observed in the study area might also pose a threat to the existence of these native species, as it obstructs the flow of surface water, which is an essential requirement to retain soil moisture for their germination and establishment . Several studies have demonstrated that a decline in native riparian species negatively affects the richness and diversity of avian species in the study area (Arizmendi et al. 2008;Edward et al. 2008;Hinojosa-Huerta 2006;Villasenor-Gomez 2006). ...
The study aims to examine tree species richness, and composition and diversity of riparian forests across forest and agro-ecosystem landscapes observed along the river Cauvery of southern India. Riparian forest was sampled in a belt transect of size 100 x 50 m, at each of the 80 sampling plots scattered over a 318 km length along the river Cauvery. Total of 177 tree species belonging to 52 families, representing 2930 individuals, were recorded. Differences occurred between the forest and agro ecosystem landscape in terms of species richness, family richness and number of individuals observed, with a decrease in agro-ecosystem compared to forest landscape. Species similarity was low between the forest and agro-ecosystem landscapes. The Shannon-Wiener diversity index was higher for forest landscape (5.6) with more evenness in distribution. In the forest landscape, high importance value indices (IVI) were obtained for Terminalia arjuna, Pongamia pinnata, Hopea parviflora. In the agro-ecosystem, species Pongamia pinnata, Ficus benghalensis, Salix tetraspermae exhibited high IVI. Expansion of agricultural activities and other biotic pressures might have led to the variation in species composition between the forest and agro-ecosystem. Also, it has led to the decline in ripicole and evergreen species such as Hydnocarpus pentandra, Elaeocarpus tuberculatus, Madhuca neriifolia, Palaquium ellipticum, Myristica dactyloides, etc., consequently affecting the associated biodiversity of the river in the agro-ecosystem. Country needs to enact a permanent policy to protect and conserve riparian buffers to avoid further degradation and loss of biodiversity in the unregulated areas along the river.
... Prior to our efforts, data on birds in this region of Sonora were limited to accounts of notable species near Sahuaripa, records from highland forests east of Sahuaripa, and observations obtained along the Aros, Bavispe, and Yaqui Rivers (Clark 1984;Brown 1988;Rodríguez-Estrella and Brown 1990;Russell and Monson 1998;O'Brien et al. 2006). More generally, data on birds in many lowland vegetation communities in western Mexico are still limited in seasons other than winter (Hutto 1980(Hutto , 1992Villaseñor-Gómez 2006. ...
We assessed the status and richness of birds in a remote region of northwest Mexico and provided the first description of a bird community in foothills thornscrub vegetation across the full annual cycle of seasons. Our efforts were part of a broad program to describe biodiversity and conservation value of the Northern Jaguar Reserve. This large private reserve was recently proposed for federal protection, in part, because it supports the northernmost breeding population of jaguars (Panthera onca) and extensive riparian woodlands along the largest free-flowing river in western Mexico. The reserve and surrounding region are dominated by foothills thornscrub, which is a vegetation community that covers a vast transition zone between tropical forest and desert-scrub in northwest Mexico but is not represented in the federal system of Natural Protected Areas. Bird species richness was similar to that found in other protected areas in western Mexico. Over seven years, we observed 214 species of birds and estimate that 241 species are present (95% CI = 225–257). Community composition was temporally dynamic; 49% of species were winter residents or passage migrants, 31% were permanent residents, and 15% were summer residents. We observed 10 species that were breeding or wintering north of the previously described limits of their geographic ranges. We observed 13 species of conservation concern in Mexico, including the Bald Eagle (Haliaeetus leucocephalus) and Military Macaw (Ara militaris) that occur at the extreme southern and northern edges of their breeding ranges, respectively. High environmental variation and unique biogeographic and physiographic settings in this region promote high bird species richness and high conservation value.
Unveiling factors that determine abundance and distribution of endangered wildlife species has important implications for their conservation across international boundaries. For instance, the Western Distinct Population (as defined by the U.S. Fish and Wildlife Service) of the yellow-billed cuckoo Coccyzus americanus (Linnaeus, 1758) has disappeared in most of the species’ range across western United States and southwestern Canada but little is known about the conservation status at the southern edge of its breeding distribution in Mexico. To fill this information gap, we estimated abundance and occupancy rates of yellow-billed cuckoos using a standard broadcast call survey protocol. We used Bayesian spatial count models to estimate cuckoo population density at survey sites. We used Bayesian hierarchical models to estimate the effects of geography, climate, and vegetation on occupancy rates while accounting for imperfect detection. Mean cuckoo count per transect for all sites was C ¯ = 9.00 ± 0.45 cuckoos. Overall cuckoo density was D ¯ ¯ = 13.18 cuckoos/km² (SD( D ¯ ) = 5.61 cuckoos/km²). Overall cuckoo occupancy in Sonora was ψ ¯ = 0.538 (95% credible interval (ψ) = 0.488–0.600), but showed strong geographic variation. Relatively high occupancy levels suggest yellow-billed cuckoo populations in Sonora may be robust, but they are largely reliant on declining high-tree cover.
Resumen Documentamos el primer registro fotográfico más al sur y para aguas interiores de México de la negreta ala blanca (Melanitta fusca). El 12 de diciembre de 2013 observamos una hembra adulta de esta especie en la laguna de Refugio Salcido del municipio de Durango, ubicada a 15 km de la ciudad de Durango; aproximadamente a 1,450 m al sureste del límite de distribución invernal. Palabras clave: Mergini. First record of the White-winged Scoter (Melanitta fusca) in inland waters of Mexico Abstract We document the southern most photographic record and the first in Mexican inland waters of the White-winged Scoter (Melanitta fusca). On December 12, 2013 we observed an adult female of this species in the Laguna de Refugio Salcido, in the municipality of Durango, located 15 km from the city of Durango, on; at about 1,450 m southeast of its winter distribution.
