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Las aves son uno de los grupos de vertebrados más importantes en el funcionamiento de los ecosistemas al cumplir con importantes funciones como la polinización o dispersión de semillas. Sin embargo, las comunidades y sus poblaciones se pueden ver afectadas por cambios en los ecosistemas. Estas modificaciones pueden ser reflejo de los diferentes usos de la tierra, por lo que es importante analizar cómo las áreas con diferentes usos de suelo y coberturas influyen en las comunidades de aves. Para este estudio, realizamos muestreos de aves de febrero a junio de 2017 utilizando redes de niebla en cuatro sitios con distintas condiciones de uso: un sitio con vegetación conservada (Reserva de la Biósfera de Calakmul), dos acahuales, uno agrícola, otro forestal y un sitio ganadero. La diversidad de las comunidades fue diferente en cada uno de los sitios muestreados, se identificó que las comunidades de aves en los acahuales y la Reserva de la Biósfera de Calakmul son más similares a las del sitio ganadero. El gremio de los semilleros y las aves generalistas fueron más abundantes en el sitio ganadero. El 39% de las especies estuvo presente en la reserva de Calakmul, que fue el sitio con la comunidad más diversa (D1= 36.38); el sitio ganadero estuvo dominado por un menor número de especies (D2= 3.88). Los análisis multivariados mostraron que el tipo de vegetación presente en los sitios influye en la abundancia de familias y especies de aves (Dev= 373.1, p= 0.001). La presencia de especies compartidas entre los acahuales y la Reserva de la Biósfera de Calakmul demuestra la importancia en la conservación y regeneración de acahuales ya que son estados de transición que ayudan a recuperar especies presentes en las selvas maduras y que se encuentren bajo alguna categoría de riesgo.

There is increasing recognition that ecosystems and their services need to be managed at landscape scale and greater. The development of landscape-scale conservation strategies need to incorporate information from multiple sources. In this study, we combine various research tools to link landscape patterns with production units and systems in the Usumacinta River Basin, and inform the discussion of key questions around decision-making related to conservation action and policy in Southern Mexico. A typology based on policy-relevant farmer characteristics (land tenure, farm size, source of income, farming system) differentiated between farmers (traditional vs. cattle ranching) with different motivations that determine how management affects landscape configuration. Five main types of traditional farming systems were identified that combine different forms of land use and vary in their degree of land intensification. Major fragmentation and decrease in connectivity coincided spatially with floodplains dominated by large-scale commercial farms that specialize in livestock production. Traditional practices within large units with low-sloped high quality land were also seen to be intensive; however the presence of trees was notable throughout these units. Policies that promote livestock farming are among the principle causes motivating deforestation. Land intensification by traditional farmers decreased as the landscape became increasingly rugged. Traditional farmers are the focus of initiatives developed by the Biological Corridor project which seeks to increase forest cover and landscape connectivity. These initiatives have shown high levels of rural participation (10,010 farmers benefited from 27,778 projects involving 95,374 ha of land) and acceptance (producers carried out more than one project and several types of projects during the first eight years of work). Strong action is still required to take on the segment of large-scale ranchers. Changes in the structure of land tenure over the past decade are highlighted that could have a profound impact on conservation policies and programs.

Ticks of the family Ixodidae are potential transmitters of pathogens to vertebrates, including birds that because of their mobility are important hosts and dispersers of ticks. Knowing the interactions can help identify potential emerging sites of tick-borne diseases. Abundance of ticks were assessed on birds captured between February and June 2017 at four sites with different land use in the Calakmul region. Ticks from the captured birds were stored individually in 70% ethanol in tubes for later identification using a stereoscope and taxonomic keys. Of 406 birds captured in 82 species, 2.7% were parasitized by ticks, mostly nymphs and larvae of Amblyomma spp. Only the Passeriformes order was parasitized, most parasitized birds were resident species. The higher number of parasitized individuals was found in the forestry successional vegetation. In total 14 ticks of the family Ixodidae were collected. This is the first study we know that analyzed the abundance of ticks on wild birds in Mexico, and new hosts of ticks of the genus Amblyomma spp. were reported.

Quantifying patterns of deforestation and linking these patterns to potentially influencing variables is a key component of modelling and projecting land use change. Statistical methods based on null hypothesis testing are only partially successful for interpreting deforestation in the context of the processes that have led to their formation. Simplifications of cause-consequence relationships that are difficult to support empirically may influence environment and development policies because they suggest simple solutions to complex problems. Deforestation is a complex process driven by multiple proximate and underlying factors and a range of scales. In this study we use a multivariate statistical analysis to provide contextual explanation for deforestation in the Usumacinta River Basin based on partial pattern matching. Our approach avoided testing trivial null hypotheses of lack of association and investigated the strength and form of the response to drivers. As not all factors involved in deforestation are easily mapped as GIS layers, analytical challenges arise due to lack of a one to one correspondence between mappable attributes and drivers. We avoided testing simple statistical hypotheses such as the detectability of a significant linear relationship between deforestation and proximity to roads or water. We developed a series of informative generalised additive models based on combinations of layers that corresponded to hypotheses regarding processes. The importance of the variables representing accessibility was emphasised by the analysis. We provide evidence that land tenure is a critical factor in shaping the decision to deforest and that direct beam insolation has an effect associated with fire frequency and intensity. The effect of winter insolation was found to have many applied implications for land management. The methodology was useful for interpreting the relative importance of sets of variables representing drivers of deforestation. It was an informative approach, thus allowing the construction of a comprehensive understanding of its causes.

We evaluated the impacts of land-cover changes of evergreen cloud forests on the distribution of quetzals in the four mountain regions of Chiapas, Mexico. The land-cover changes were estimated comparing satellite images of 1970 and 2000. We also simulated the amount of remnant forests 50 years in the future. The past and the current distributions of quetzals were based on literature records and recent field surveys. Our results showed that in 1970 the forests occupied 973 km 2 , and in 2000, 312 km 2 , and annual loss from 3.34 to 6.85%. Our simulation suggests that 50 years from now, only one region will maintain evergreen cloud forests. In addition, we documented literature reports of 39 forests inhabited by quetzals, but in 2001 there remained 11 smallisolated forests. In order to guarantee the survival of this species, conversation efforts must be made to protect the quetzal and its habitat throughout the entire Mesoamerica region. # 2003 Elsevier Ltd. All rights reserved.