No abstract

No abstract

The transformation of natural systems into urban cities represents a radical habitat modification and one that generates species-specific effects on bat communities. Cities present heterogeneous mosaics of urban conditions, which the bats can inhabit differentially by utilizing their intrinsic characteristics. We expected bat species richness, number of abundant species and feeding guilds to be positively impacted by an increased degree of suitability for bats in certain areas interspersed in the city. We also expected that the number of dominant species would follow an inverse pattern, with some species being fostered in less suitable areas for bats. We determined the levels of suitability for the presence of bats in urban-based basic geostatistical units (BGUs) in the Neotropical city of Morelia, in Michoacán state, Mexico. We identified three levels of suitability for bats, low, medium and high, using the percentage of arboreal vegetation and constructed and open areas in the BGUs. We monitored the bat assemblage monthly over an annual cycle using autonomous ultrasonic recorders to assess the abundance of each species at each suitability level. Across all three suitability levels throughout the year, we found a high dominance of three insectivorous bat species that forage in open areas. Diversity measures supported our predictions, agreeing with bat flight and foraging functional traits. These results highlight the importance of city features in driving bat diversity and how urban planning that fails to consider key city features, such as arboreal areas in the city, may reduce suitability for bats, leading changes in diversity.

One strategy animals perform to cope scarcity of food resources is to shift in number of individuals according towards areas with available resources. This strategy can be more marked in species that are constrained by high energetic requirements such as hummingbirds. We aim to determine the extent to which the availability of food resources could be predictor of hummingbird numbers within and across hummingbird species in a temperate forest of central Mexico. We anticipate fluctuations in the number of hummingbirds grouped by species is best explained by monthly fluctuations in flowering resources species compared to pooled data. Our results indicate all seven hummingbird species fluctuate monthly in number across the year, which corresponds to monthly fluctuations of plant species they feed upon. The Basilinna leucotis and the Salvia elegans were present and interact in the study area almost all year-round, guiding the abundance pattern of both plants and hummingbirds in the study site. Generalized Linear Mixed Models indicate that although considering the abundance of the number of flowers for all plant species together could explain the fluctuation in all hummingbird species pooled together, considering both plant species and hummingbird species separately can provide a better explanation for changes in bird abundance. The model that analyzed species indicate that the interaction between the year-round species B. leucotis and S. elegans recorded the highest significant size effect. Our results highlight the fact that abundant species guiding abundance patterns could obscure by-species hummingbird trends and the processes guiding their patterns of abundance. We point out the need for performing adequate analytical approaches that can detect important biological interactions, and the likelihood of changes in habitat changing the pattern observed.RESUMENUna estrategia los colibríes usan para lidiar con la escasez de alimento es realizar cambios en número de individuos a zonas con recursos disponibles. Esta estrategia es más marcada en especies que son limitadas por altos requerimientos energéticos como los colibríes. Nuestro objetivo fue determinar el grado con el cual la disponibilidad de alimento puede ser un predictor de número de individuos en un bosque templado del Centro de México. Anticipamos fluctuaciones en número de colibríes agrupados por especies serían mejor explicadas por fluctuaciones mensuales en recursos florales al comparar con datos combinados. Nuestros resultados indican que las siete especies de colibríes fluctuaron mensualmente en números a lo largo del año de acuerdo a fluctuaciones mensuales de las especies de plantas que ellos se alimentan. Basilinna leucotis y Salvia elegans estuvieron presente e interactuaron en la zona de estudio casi todo el año, guiando el patrón de abundancia tanto de colibríes como de plantas. Los Modelos Lineales Generalizados Mixtos indicaron que aunque considerar la abundancia del número de flores para todas las especies juntas podría explicar la fluctuación en todas las especies juntas, considerar las especies de colibríes y de plantas por separado provee una mejor explicación para los cambios en abundancia de aves. El modelo analizando especies indicó que la interacción entre las especies anuales B. leucotis y S. elegans tuvieron el tamaño del efecto significativo más alto. Nuestros resultados destacan el hecho de que especies abundantes guiando el patrón de abundancia podrían obscurecer tendencias especificas por especie y los procesos guiando su patrón de abundancia. Indicamos la necesidad de usar enfoques analíticos adecuados que puedan detectar interacciones biológicas importantes, así como la probabilidad de que cambios en el hábitat pueden cambiar el patrón observado.Palabras claveBosque templado, abundancia estacional, uso del hábitat, asociación colibrí-comida, fluctuaciones temporales en abundanciaLay summaryHummingbirds, as many animals with high energy requirements, might cope with food resources shortage using different strategiesOne strategy to face food shortage is the local shifting in number of individuals.We used monthly surveys of hummingbirds and flowering plants in a temperate forest of central Mexico to evaluate the association of resources availability, seasonality, species identity, and vegetation condition on hummingbird abundance.All seven hummingbird species fluctuate in number across the year, which matches to fluctuations of plant species they feed upon.Hummingbird species Basilinna leucotis and the plant species Salvia elegans are the most abundant and largely guide the general abundance pattern.Both plant and hummingbird species separately are better explanting changes in hummingbirds’ abundance than species abundance combined.Abundant species may guide the plant and hummingbird abundance patterns, which complicates understanding underlying processes per species for the whole community.Given the current trends of habitats modification and the fact that habitat condition may influence the presence of key plant species for hummingbirds, we need to protect habitats where these key food plant species for hummingbirds are, particularly if they are specific to habitats