Small endotherms frequently experience fluctuations in ambient temperature ( T a ) and food availability that challenge the maintenance of energy balance. Many species cope with these conditions by entering torpor, a reversible physiological state characterized by reductions in metabolic rate and body temperature ( T b ). Although T a , body mass ( M b ), and food availability are known to influence torpor expression, how environmental conditions interact with the energetic state of individuals to regulate torpid metabolism remains poorly understood. We experimentally manipulated energy intake and measured metabolic responses across a range of T a to evaluate how M b , energy intake, and T a influence torpid metabolic rate in the big brown bat ( Eptesicus fuscus ). Torpid metabolic rate during cooling increased with M b and T a but decreased with increasing energy intake. In addition, the influence of energy intake on torpid metabolic rate depended on T a , with the strongest reductions occurring at lower T a s. Minimum torpid metabolic rate also differed between energetic treatments and was influenced by an interaction between M b and energetic state. Energy-supplied individuals reached lower minimum torpid metabolic rates than energy-restricted bats, suggesting that energetic condition modulates the physiological limits of metabolic suppression. Together, these results reveal two complementary levels of torpor regulation in E. fuscus : dynamic metabolic responses during cooling shaped by M b , T a , and energy intake, and intrinsic limits to metabolic suppression determined by body size and energetic state. Our findings highlight the joint roles of environmental and physiological factors in shaping torpor expression in heterothermic mammals.

Urbanisation acts as a non-random filter of biodiversity, often resulting in less diverse communities dominated by a subset of species with particular traits. These patterns have led to the expectation that urban environments may promote biotic homogenisation, yielding taxonomically or functionally similar communities across cities, relative to their surrounding natural ecosystems. Here, we evaluated whether the non-random filtering of biodiversity by urbanisation results in the homogenisation of bird communities across three environmental conditions (i.e. natural ecosystems, urban greenspaces, urban sites) in three biogeographically distinct Mexican cities. Assuming an urban-driven filtering process (i.e. an overall decline in native species richness from natural ecosystems into the urban matrix, with possible additions of exotic species), we formulated scenario-based expectations to disentangle urban filtering from biotic homogenisation, predicting whether filtering results in locally distinct urban communities, or additionally, convergent filtering across cities drives cross-city homogenisation. We quantified taxonomic and functional richness (alpha diversity) and compositional dissimilarity (beta diversity) across natural ecosystems, urban greenspaces and urban sites to evaluate whether only filtering occurred or if such process has additionally led to context-dependent convergence in community composition across cities, which could indicate homogenisation. We analysed taxonomic and functional approaches using incidence- and abundance-based metrics to assess compositional variation within and among cities. We recorded 131 bird species, of which only a handful were shared across urban conditions in all three cities. Bird communities showed strong taxonomic and functional differentiation among cities, with greater similarity within the studied environmental conditions per city region than across cities, indicating that urbanisation filters species locally, with no clear evidence of cross-city convergence in community composition. Our findings indicate that urbanisation filters species locally, simplifying communities, yet avian assemblages remain more similar within the three environmental conditions per city region than across the three surveyed cities in Mexico. Notably, widespread and abundant urban-associated species contribute to increased similarity within urban assemblages but do not result in cross-city convergence. This challenges the notion that urbanisation causes homogenisation (at least across the three studied Mexican cities and their surrounding natural ecosystems, which belong to highly distinct biogeographic regions) and highlights the predominant influence of regional species pools and local environmental contexts in shaping urban avifaunas.

Nectar-feeding birds have low nitrogen requirements that tend to be paired with low protein dietary ingestion. As a result, they must acquire and efficiently use proteins for maintenance, growth, and reproduction, thereby avoiding being limited by this nutrient. While these birds regularly consume arthropods, particularly during periods of low nectar availability, little is known about their intake and regulation of nutrients other than sugar and water. In this study, we used a nutritional geometry approach to examine protein's role in nutrient and energy balance in hummingbirds. We conducted free-choice feeding trials with solutions varying in protein (0.2%-2%) and sucrose (5%-30%) concentrations to compare the nutritional strategies of Broad-billed (Cynanthus latirostris) and Berylline (Saucerottia beryllina) Hummingbirds. Results show that daily and cumulative protein and sucrose intake per unit of metabolic mass were significantly higher in C. latirostris than in S. beryllina. During the first days, both species presented similar accumulated feeding trajectories with nearly identical protein:sucrose ratios. However, as trials proceeded, their slopes diverged, emphasizing a higher protein intake in C. latirostris. These species-specific intake patterns are consistent with differences in protein tolerance and nutrient-handling constraints under the offered diets. We suggest that such differences could contribute to contrasting ecological strategies in the wild (e.g., residency vs. local movements) when floral resources decline, a hypothesis that requires comparative and field-based testing. Overall, this study is the first to explore protein and sugar ingestion in hummingbirds, offering new insights into how nutrient-handling abilities reflect the ecology of nectar-feeding birds.

Increasing temporal and spatial coverage of bird inventories is urgent in changing tropical ecosystems. Camera trapping, traditionally focused on surveying mammals, has been pointed out as a potential tool to complement standard bird surveys. However, few standard bird surveys and camera trapping comparisons have been made in tropical biodiversity hotspots. We conducted camera trapping and point count surveys of bird species in eighteen 1 km2 landscape units along a deforestation gradient in the Lacandon forest in M & eacute;xico. We compared the two methods based on the estimates they produced of bird species richness, composition, body mass, and conservation status. We recorded 2.6 times more species by point counts than by camera trapping. There was no correlation between the number of species recorded by the two methods, and the similarity in species composition was low. Body mass was higher in species recorded by camera trapping only in medium levels of deforestation. Camera trapping has little potential to replace standard bird survey methods, such as point counts, for documenting bird species diversity. However, in some circumstances, it can be a valuable tool to help document the presence of some bird species by monitoring them throughout the day.

Land use change from wildlands to urban and productive environments can dramatically transform ecosystem structure and processes. Despite their structural and functional differences from wildlands, human-modified environments offer unique habitat elements for wildlife. In this study, we examined how migratory birds use urban, productive, and wildland environments of a highly anthropized region of Western Mexico known as “El Bajío”. We used Generalized Linear Models to compare species richness, abundance, and the functional traits of migratory bird assemblages among these three environments. Results revealed differences in species richness, composition, and the functional traits of migratory birds among environments. Regardless of wildlands showing medium to high levels of human disturbance, they presented the highest species richness and abundance of migratory birds, with urban environments presenting the lowest values. Insectivorous and granivorous birds were dominant in the migratory bird assemblages of the three environments. The migratory bird assemblages of productive environments had more grassland granivorous birds. In contrast, insectivorous birds with dense habitat preferences and short culmen lengths dominated the urban bird assemblage. Migratory bird assemblages in productive and urban environments showed similar species richness and abundance of insectivorous birds, but they differ in their composition. Our results reveal that urban trees allowed cities to function as simplified forests, showing that the urban environment has the untapped potential to support complex assemblages of migratory birds. To promote migratory birds in human-modified landscapes, we must maintain complex vegetation areas that allow birds with diverse functional traits to overwinter in urban and productive environments.

the terms Due to the environmental and economic costs caused by invasive bird species, it is crucial to document their initial stages of invasion and manage them before control efforts become unfeasible. In this study, we conducted extensive sampling in search of the African collared dove ( Streptopelia roseogrisea) ) in three regions of Mexico: The Northwest, "El El Baj & iacute;o" " (central Mexico), and the Southeast. We documented five records of this species in two northwestern states (Sonora and Baja California) and analyzed additional sightings from citizen science and scientific literature to evaluate its presence and geographic distribution in Mexico. Streptopelia roseogrisea has been reported in nine Mexican states (32 records), with its first record occurring in 2000 in Tijuana, Baja California. The species is invading Mexico on two fronts: from populations established in the southern United States expanding southwards into northern Mexico, and individuals escaped/released from captivity invading central Mexico. Additionally, we used temperature and precipitation data to determine its climatic niche in Mexico. We compared it with the climatic niches of the United States populations and with the climatic space of its original distribution range in Africa and the Arabian Peninsula. We found that the climatic niche of the Mexico and the Southern United States populations is similar, and did not overlap with the climatic space present in its original geographic distribution. This suggests that niche models based on the climate of its original distribution could fail to predict the invasibility of this species in North America. Although S. roseogrisea does not seem to constitute a high-risk invader, it is important to document its early invasion process and take action before it spreads throughout the country, as it recently happened with the Eurasian collared-dove (S. S. decaocto). ).

Arthropods are hummingbirds’ principal source of nitrogen, fatty acids, and micronutrients. Despite the nutritional importance of arthropods for hummingbirds, our understanding of the factors influencing their consumption and their relative role as an energy source remains limited. Here, we aimed to describe the use of arthropods by a hummingbird ensemble in a seasonal temperate mountain ecosystem in West Mexico during one annual cycle. We compared arthropod capture attempt rates among six different humming species. Also, we investigated the impact of seasonal variation in food availability on the arthropod capture attempt rates of the White-eared Hummingbird (Basilinna leucotis), the sole species observed foraging for arthropods in all seasons. We found that hummingbirds ingested arthropods from different orders (Araneae, Hemiptera, Psocoptera, Hymenoptera, and Diptera), with arthropod capture attempt rates varying wildly among species. The arthropod capture attempt rates of the White-eared Hummingbird showed a significant positive correlation with arthropod availability, peaking during the warm-dry season when floral nectar was scarce and arthropod availability was high. Our data show that arthropod ingestion is crucial for some hummingbird species, mainly when nectar availability is limited or absent in the environment.

Context Slash-and-burn agriculture generates landscape mosaics composed of different land uses. Ecological theory postulates that in these mosaics, the structure of species assemblages depends on both local- and landscape-scale factors, but their relative role remains poorly known.Objectives Understanding the relative importance of local and landscape variables for bird assemblages in landscape mosaics of the Mayan tropical forest, Mexico.Methods We evaluated the effect of two local variables (land use type and tree basal area) and two landscape variables (old-growth forest cover and human proximity) on bird abundance and diversity, separately assessing forest and non-forest birds. As species extirpation may accelerate when forest loss exceeds certain limits (extinction thresholds), we assessed forest loss effects with linear and nonlinear models.Results We recorded 1867 birds from 118 species in four land-use types (old-growth forest, secondary forest, burned lands, and agricultural lands). Land-use type and surrounding old-growth forest cover better predicted bird abundance and diversity than tree basal area and human proximity. Agricultural lands showed the lowest abundance and diversity of forest species, but the highest abundance and diversity of non-forest species. We found no support for the extinction threshold hypothesis. Yet, independently of the land use, old-growth forest loss decreased the diversity of forest species and increased the abundance and diversity of non-forest species. Human proximity also decreased total bird abundance, especially because of the loss of forest species.Conclusions Our findings highlight the key role played by old-growth forests for preserving bird assemblages in landscape mosaics exposed to slash-and-burn agriculture.

Mexico City is one of the most polluted cities in the world, and one in which air contamination is considered a public health threat. Numerous studies have related high concentrations of particulate matter and ozone to several respiratory and cardiovascular diseases and a higher human mortality risk. However, almost all of those studies have focused on human health outcomes, and the effects of anthropogenic air pollution on wildlife species is still poorly understood. In this study, we investigated the impacts of air pollution in the Mexico City Metropolitan Area (MCMA) on house sparrows ( Passer domesticus ). We assessed two physiological responses commonly used as biomarkers: stress response (the corticosterone concentration in feathers), and constitutive innate immune response (the concentration of both natural antibodies and lytic complement proteins), which are non-invasive techniques. We found a negative relationship between the ozone concentration and the natural antibodies response ( p = 0.003). However, no relationship was found between the ozone concentration and the stress response or the complement system activity ( p > 0.05). These results suggest that ozone concentrations in air pollution within MCMA may constrain the natural antibody response in the immune system of house sparrows. Our study shows, for the first time, the potential impact of ozone pollution on a wild species in the MCMA presenting the Nabs activity and the house sparrow as suitable indicators to assess the effect of air contamination on the songbirds.

Understanding the factors underlying bird invasions is crucial for their management. Here, the invasion processes of Mexico by the European Starling (Sturnus vulgaris) and the Eurasian Collared-Dove (Streptopelia decaocto) are analyzed. A 30 x 30 km grid-cell map with the presence/absence of both species was generated using citizenscience data to describe their invasion patterns in time and space from their first records until 2016. Binomial Generalized Linear Models were used to determine the invasion probabilities of both species. Geographic Information was used to determine the climatic variables that better explain their presence (abiotic factors) and the number of phylogenetically closely-related species (biotic factors). A bioclimatic model was used to test if the role that climatic variables play to determine the invasion success of birds at the global scale holds at regional scales. This model related the invasion probabilities of each species with biotic and abiotic factors. The main findings are: (1) Both species have expanded from established populations in the US, and new introductions by bird-trade. (2) European Starlings invaded the country slower than Eurasian Collared-Doves. (3) European Starlings invaded areas with dry and temperate climates, while Eurasian Collared-Doves invaded most of the country, being positively affected by temperature and precipitation. (4) Invasion probabilities of both species were not constrained by phylogenetically closely-related species richness. This study indicates that for exotic invasive birds that exploit agricultural areas, biotic factors do not provide invasion resistance of megadiverse countries such as Mexico.

Los gatos y perros domésticos son las mascotas preferidas del hombre, por lo que se han convertido en especies invasoras y los carnívoros más abundantes del planeta. A pesar de su buena relación con nuestra especie, tienen un impacto ecológico negativo con consecuencias para las políticas de conservación. Los efectos que estos animales tienen sobre la fauna silvestre han sido estudiados principalmente en países con baja biodiversidad de vertebrados (EUA, Nueva Zelanda y Europa), y salvo por algunos trabajos realizados en Australia, Brasil, y México, no contamos con información sobre sus efectos en países con alta biodiversidad. Los efectos negativos que ambas especies tienen sobre la biodiversidad incluyen la depredación y competencia con fauna nativa, su hibridación con especies filogenéticamente cercanas o poblaciones silvestres de su propia especie, y la transmisión de enfermedades a la fauna silvestre y a los humanos. La falta de información sobre los efectos de depredadores introducidos a nivel continental y la falsa idea de que los gatos y perros son ambientalmente inocuos, vuelve crucial aumentar la investigación sobre estas especies en países megadiversos para proponer estrategias de manejo que fomenten la conservación de fauna nativa.

Domestic cats and dogs are the most beloved human pets. As a result, they have become globally invasive species and are the most abundant carnivores in the world. Although they have a good relationship with humans, domestic cats and dogs have a negative ecological impact with significant consequences for conservation policies worldwide. The effects of these animals on wildlife have been studied only in a few countries, with most studies carried out in countries or regions with low vertebrate biodiversity (USA, New Zealand, and Europe). Except for a few studies carried out in Australia, Brazil and Mexico, we have no information on the effects of these predators in megadiverse countries. The main negative environmental effects of both species include predation of vertebrates and invertebrates, competition for food and space with native fauna, hybridization with phylogenetically close species or wild populations of their species, and transmission of diseases to wildlife and humans. The lack of information on the effects that introduced predators have at continental scales and the false perception of the human population that cats and dogs do not adverse impacts on the environment difficult their management and control. It is crucial to increase the number of studies of these two species in megadiverse countries to propose adequate management strategies that promote the conservation of native fauna.

Cities function as ecological systems composed of a geosphere, a biosphere and an anthroposphere, interacting with each other and generating various selection pressures on urban organisms. Odonates (damselflies and dragonflies) are frequent inhabitants of urban areas, showing no clear or unique responses to urbanization. Thus, we defined an urbanization gradient using a habitat integrity index (HII) calculated for 19 sites in central Mexico, and investigated: a) changes in species richness and abundance along the urbanization gradient; and, b) the relationship between presence of waste of anthropic origin, chemical conditions of water, macrophyte cover, and odonate species richness, abundance and community composition. We analyzed the data for the whole odonate community, as well as for dragonfly and damselfly communities separately in each site. We found higher damselfly species richness and abundance in sites with low urbanization than in sites with high urbanization, and no differences in dragonfly communities along the gradient. We found a positive relationship between dragonfly species richness and abundance and waste percentage and macrophyte cover, and a negative relationship with dissolved solids in water. Our results indicated that odonate communities were fairly tolerant to urbanization and dragonflies were less affected than damselflies. However, we suggest that during design and restructuring of cities, the care and conservation of water bodies and all the life forms that inhabit there, be considered.

Human disturbance might be perceived as a threat by animals and interfere in their vital activities. Urbanisation generates changes in habitat structure that allows only a low number of species to adapt, which results in a decrease of species richness and an increase of the abundance of a few dominant species. To survive in urbanised areas, animals need to be highly tolerant to human approximation. One key characteristic of successful invasive species is their high behavioural plasticity. This plasticity could translate to higher chances of surviving in urbanised areas and becoming tough competitors for native species. The Eurasian collared-dove is a successful invader in Europe, it arrived to México during the nineties and has been spreading in the country since. We compared its tolerance to human approximation to that of the already well-established feral pigeon and other native species in agricultural and urban sites. We found the Eurasian collared-dove is less tolerant to humans than the feral pigeon, but more tolerant than native species. Also, we observed that birds showed higher tolerance to humans in urban areas than in agricultural sites, regardless of the species. Interestingly, feral pigeons restrained their distribution to human settlements, and acting as a counterpart, common ground doves were only found in rural sites. However, the Eurasian collared-dove was present also in agricultural areas, which could suggest the Eurasian collared-dove represents a higher threat than the feral pigeon for native species in our study area. We highlight the importance to further understand the behavioural traits that could promote the Eurasian collared-dove invasion to better design management plans for dove diversity in urban areas.

Nearctic-Neotropical migratory birds are threatened by land-use change throughout their complex annual cycles. While urbanization is an essential driver of land-use change, it is unclear how it affects migrant birds. Although migratory birds are more diverse in non-urban patches of native vegetation than in urban areas, neotropical cities can host diverse assemblages of overwintering migrant birds. Migratory birds in neotropical cities tend to be closely associated with urban green areas (UGAs). However, how their presence and abundance are affected by the habitat elements of UGAs and the urban matrix of neotropical cities is poorly understood. In this study, we compared the migratory bird species richness and abundances among UGAs and the urban matrix of the southern section of the megacity of Mexico City and native vegetation sites outside the city. Our results show that UGAs in neotropical cities provide habitats capable of maintaining complex overwintering migratory bird assemblages with local trees as critical features. We also assess the role that UGAs' characteristics play in determining migrant bird assemblages. We conducted bird censuses and measured habitat traits to determine how migrant bird assemblages are related to the habitat features of our study sites. We measured local, buffer, and spatial habitat features of each UGA. We found 23 overwintering migrant species in the three habitats, with 22 present within UGAs. Both UGAs and urban matrix sites had higher estimated species richness of migrant birds than non-urban native vegetation sites located outside the city. Only local features of UGAs affected migrant birds. While tree abundance in UGAs was positively associated with migratory bird species richness, the proportion of tree coverage was positively related to bird abundance. Our results show that UGAs in neotropical cities can maintain complex overwintering migratory bird assemblages, with trees being the most critical habitat feature. As a result, UGA management focused on maintaining trees and increasing their numbers can improve habitat conditions for migratory birds overwintering in neotropical cities.

Understanding how biological communities respond to human-caused landscape disturbances is urgently needed to identify optimal spatial scenarios for preserving biodiversity in anthropogenic landscapes. Forest loss is increasingly cited as a major disturbance in these landscapes, but its impact on biodiversity in mountain regions with high endemism is not well understood. Here we evaluated how bird species diversity responds to forest loss in ‘La Montaña’ mountain region of Guerrero State, Mexico. We separately assessed the complete bird assemblage, and the diversity and spatial distribution of three different ecological groups (forest-specialists, habitat-generalists, and disturbance-adapted species) in the whole landscape mosaic. We found that the diversity of the complete assemblage decreased linearly with forest loss. However, species responses to forest loss differed among ecological groups, with the diversity of forest-specialist and habitat-generalist species increasing in more forested landscapes, and the diversity of disturbance-adapted species following the opposite pattern. Similarly, the proportion of sites occupied by forest-specialist birds decreased with forest loss, but site occupancy by habitat-generalist and disturbance-adapted birds was independent from forest cover. Our findings highlight that the optimal landscape scenarios for preserving bird biodiversity in general and forest species in particular, are those that maintain as much forest cover as possible.

Emerging diseases in wildlife pose challenges for conservation due to their usually rapid spread and high cause of mortality. The transmission of these diseases is a complex ecological process that involves interactions between groups of individuals, particularly in gregarious species. White-nose syndrome, caused by the fungus Pseudogymnoascus destructans, is increasingly infecting species of vespertilionid North American bats causing, in some cases, high population mortality. In this study, we modeled ecological niches projected as potential distributions for three strains of P. destructans (Asian, European and North American) and a group of species of verpertilionid bats in North America. Our model showed that the ecological niches of North American and Asian fungi strains are projected to expand into new geographic areas, with statistical significance between the two strains. In addition, our model identified the presence of all three strains of fungi in areas where the fungus has previously been documented as well as new suitable climatic areas for the establishment of P. destructans in North America: large regions of the central USA and highlands of Mexico in the Peninsula of Baja California, the Sierra Madre Occidental and Oriental, and Transvolcanic Mexican Belt. Our models identified 10 species of vespertilionid bats distributed similarly to P. destructans. Bats had a high risk of infection with WSN and a strong likelihood of dispersing the fungus.

Migratory birds can be familiar winter visitors of Neotropical cities. However, of the regional migrant species bird pool, only a few species are abundant in urban areas. Their presence inside cities has been positively related to green urban areas with high tree cover. However, urban elements like artificial lights can also attract them to cities. Habitat quality that enables energetic refueling for migrant birds is crucial in all their annual migratory stages. While some Nearctic cities offer a high-quality refueling habitat for migrant birds, we lack this information for Neotropical cities where migratory birds winter. In this study, we evaluate whether the urban green areas of a Neotropical city act as high-quality habitats for two abundant species of migratory warblers: Setophaga coronata and Leiothlypis ruficapilla. We assessed this by capturing birds inside three urban green areas and comparing their abundances, population structure, and individual quality (scaled-mass index—SMI) with individuals spending winter in natural vegetation habitats outside the city. We found that both species do not show differences in SMI between urban and non-urban sites. We also found that Setophaga coronata had a higher capture rate in urban than non-urban sites, while Leiothlypis ruficapilla had similar capture rates in both habitats. Our findings indicate that the urban green areas of cities can act as suitable quality habitat during winter for two abundant migrant birds. Our results indicate that cities can have a higher conservation potential for a declining and sensitive group such as the Nearctic-Neotropical migratory birds than previously thought. We also point out the need to acknowledge that migratory species can be urban dwellers.