With increased human populations and subsequent pressure to develop or farm land, the rate of fragmentation of tropical rainforests has accelerated in the past several decades. How native organisms respond to such fragmentation has been the subject of intense study in temperate ecosystems and at several tropical sites in Central and South America, but there has been little study of this phenomenon in Mexico, the country bridging the Neotropics and temperate North America. A reason for this neglect is an apparent lack of long-term data; however, such data can be obtained from ''non-traditional'' sources, such as birders and tour leaders. We make innovative use of such data, combining them with more traditional data (e.g., museum specimens) to create a record of occurrence for Palenque, Mexico, from 1900 to 2009, including a near-continuous presence-absence record since 1970. We analyzed these data using logistic regression and, importantly, recent statistical advances expressly for sighting records. As recently as the 1960s Palenque's forest was contiguous with that of Selva Lacandona to the east, but the protected area surrounding the famous ruins is now a forested island. As a result, various species formerly known from the site have disappeared, including species both large (Crax rubra, Penelope purpurascens, and Ara macao) and small (Notharchus hyperrhynchos, Malacoptila panamensis, Microrhopias quixensis, and Pachyramphus cinnamomeus). By contrast, several species of open areas or second growth have apparently colonized the area (e.g., Thryothorus modestus, Mimus gilvus, Euphonia affinis). Some species turnover has occurred within particular families, such as Columbidae, Trochilidae, and Troglodytidae. Losses and declines we documented at Palenque correspond with those reported from other sites in Mesoamerica, suggesting the soundness of our approach and the general vulnerability of certain species. Compilation and analysis of sighting record data holds great promise for tracking trends in many regions and across many taxa for which long-term census data are lacking.

Sierra Madre Sparrows (Xenospiza baileyi) are among the least known of all bird species in Mexico. Recent surveys have discovered previously unknown populations and the current known distribution of Sierra Madre Sparrows consists of two populations separated by >800 km. We used available distributional information to develop ecological niche models that (1) predict much of the distribution potential of the species, (2) establish that the broad disjunction separating the two populations has ecological correlates that appear to be important to the distributional of these sparrows, and (3) illustrate the extremely restricted ecological distribution of the species. We used two sets of climatic and topographic variables, with one including all 22 variables available and the second with only six variables that were positively related to quality of distributional models. Although indications of differences between the two sets of populations were found based on the full 22‐dimensional environmental dataset, such a highly dimensional analysis is vulnerable to over‐fitting; models based on the reduced dataset indicated that the two populations occur in areas with similar ecological conditions. Our models also suggest that southern population of Sierra Madre Sparrows covers most of their potential range in that region. The potential range of the northern population, however, extends beyond known points of occurrence. To clarify the distribution of Sierra Madre Sparrows and evaluate their status and conservation opportunities, detailed searches for additional populations in areas identified by the model are needed.

The primary lowland rainforest around the Mayan ruins of Palenque, in the state of Chiapas, Mexico, has been the focus of much study. The second growth and the mosaic of pasture and farmland surrounding the protected area of Palenque National Park also have received some attention by researchers and visitors. Until now though, a complete avifaunal list for this area had not been compiled. In our judgment, 353 species have been recorded reliably, a hundred more than previously reported. An additional 27 species have been reported at the site on multiple occasions but for which we feel there is no definitive evidence. There are 202 regular breeders, most of them resident, and 87 migrants that winter or pass through regularly. Relative capture rates for understorey birds indicate that Phaethornis longirostris and Henicorhina leucosticta are most often caught, and some rarely seen birds, such a Geotrygon montana, are less rare than previously thought. In a state in which habitat destruction is routine, in which national parks are increasingly becoming forested islands, we need baseline data such as these to get a clearer idea of what occurs there if we are to understand anthropogenic effects on forests.

Studies of species diversity, macroecology, and conservation are usually based on lists of species, but lists found in the scientific literature vary in completeness. The use of such data sets can produce misleading results, making it necessary to test species lists for completeness before undertaking an analysis. Species-richness estimators are useful for judging the completeness of species lists but have limitations. To add rigor to studies based on species lists, we propose that species lists should test for " omnipresent" taxa-species, genera, and families that occur throughout the region concerned-and for a minimum number of species and families. As a case study, we compared species assemblages in diverse habitats in Mexico and found that seven families and two genera of land birds are omnipresent in mainland Mexico (excluding treeless areas) and that the most depauperate assemblage known contains 35 species from 21 families. We concluded that a list of land birds from Mexico that lacks any of these omnipresent taxa or that contains fewer than 35 species or 21 families is incomplete. Similar analyses can be done for other taxa and other parts of the world. Tests for omnipresent taxa and for a minimum number of species and families can be used in combination with other existing criteria, such as species-richness functions, to better evaluate the completeness of species lists. Realistic results may be produced in macroecological and conservation studies only if they are based on reasonably complete species lists.Evaluación para Determinar si las Listas de Especies para Conservación y Macroecología son Completas: Caso de Estudio de Aves Terrestres Mexicanas Resumen: Los estudios sobre diversidad, macroecología y conservación emplean listas de especies, pero en la literatura científica y en los bancos de datos suelen estar mezcladas listas completas e incompletas de especies. El uso de datos heterogéneos puede generar resultados engañosos y es recomendable reconocer y eliminar las listas incompletas antes de llevar a cabo un análisis. Los estimadores de riqueza de especies son útiles para juzgar cuán completa es una lista determinada, pero éstos tienen limitaciones. Para agregar rigor a los estudios basados en listas de especies proponemos que las listas sean evaluadas con criterios adicionales: se pueden reconocer listas incompletas cuando faltan taxones "omnipresentes" (especies, géneros y familias que ocurren en la totalidad de la región) y si contienen menos de un cierto número mínimo de especies y familias. Por ejemplo, estudiamos ensamblajes de aves en diversos hábitats de México y encontramos que siete familias y dos géneros de aves terrestres son omnipresentes en México (excluyendo islas y hábitats desprovistos de árboles) y que la comunidad con menor riqueza conocida tiene 35 especies de aves pertenecientes a 21 familias. Concluimos que cualquier lista de aves terrestres de México que le falte algunos de estos taxones omnipresentes o tenga menor número de especies o familias se puede reconocer rápidamen...