Brenda D. Smith-Patten

Long-term changes in the bird community of Palenque, Chiapas, in response to rainforest loss

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.

Predictors of Occupancy Trend Across Spatial Scale

Many explorations of extinction probability have had a global focus, yet it is unclear whether variables that explain the probability of extinction at large spatial extents are the same as those at small spatial extents. Thus, we used nearly annual presence-absence records for the most recent 40 years of a 110-year data set from Palenque, Mexico, an area with ongoing deforestation, to explore which of >200 species of birds have probabilities of extirpation that are likely to increase. We assessed associations between long-term trends in species presence (i.e., detection in a given year) and body size, geographic range size, diet, dependence on forest cover, taxonomy, and ecological specialization. Our response variable was the estimated slope of a weighted logistic regression for each species. We assessed the relative strength of each predictor by means of a model ranking scheme. Several variables associated with high extinction probability at global extents, such as large body size or small geographic range size, were not associated with occurrence of birds over time at our site. Body size was associated with species loss at Palenque, but occurrence trends of both very large and very small species, particularly the latter, have declined, or the species have been extirpated. We found no association between declining occurrence trend and geographic range size, yet decline correlated with whether a species depends on forest (mean occupancy trend =-0.0380, 0.0263, and 0.0186 for, respectively, species with high, intermediate, or low dependence on forest) and with complex combinations of diet and foraging strata (e.g., occurrence of canopy insectivores and terrestrial omnivores has increased, whereas occurrence of mid-level frugivores and terrestrial granivores has decreased). Our findings emphasize that analyses of local areas are necessary to explicate extirpation risk at various spatial extents.

Survey data matter: predicted niche of adult vs breeding Odonata

Assessing and categorizing habitat needs or population trends of organisms with complex life histories, such as Odonata, is challenging. All Odonata have aquatic nymphs and terrestrial adults. As a consequence, their use as indicators of ecosystem health or as umbrella species in conservation plans may be misleading if data from a particular life stage does not reflect actual residency at a freshwater site. We explored this question with an extensive data set for Odonata from Oklahoma, USA, to determine if ecological niches modeled from records of adults (i.e., lacking any evidence of breeding) differed from niches modeled for records indicating breeding (tandem pairs, ovipositing females, larvae, teneral [recently emerged adults], or exuviae [shed exoskeletons of larvae]) at surveyed sites. We predicted that models would be comparable if adult presence strongly indicates local breeding but would be dissimilar if adults occupy many more sites than those at which the species breeds. Our results supported the latter prediction. Adult models were broader geographically and had a wider, more equitable (higher evenness) balance of contributing environmental variables (niche dimensions) than did models for breeders, which tended to be more ecologically specialized. These findings suggest that surveys of adult Odonata, which are relatively easy to obtain because of organized efforts to encourage observations by citizen scientists, can paint a misleadingly broad picture of a species’ ecological niche. We recommend that evidence of breeding, especially presence of tenerals or exuviae, be used to outline ecological requirements when questions of conservation or population monitoring arise.

Odonata species of special concern for Oklahoma, USA

Assessment of conservation status is a necessary step before management plans can be formulated. Historically such assessments have a strong bias toward vertebrates, particularly endothermic terrestrial vertebrates (i.e. birds and mammals). Invertebrates, by contrast, tend to be ignored, and many insect groups, despite being species rich and reasonably well studied, such as the Odonata (damselflies and dragonflies), have not been assessed or have been assessed only at a broad geographic level (e.g. internationally or continentally). Assessment at a state level recognizes that states often are at the front of regional and local conservation and management planning and implementation. On the basis of our extensive surveys across the Great Plains state of Oklahoma in the central USA, as well as our compilation of thousands of museum specimens dating back to 1877, we were able to discern the status and distribution of each of the 161 species of odonates recorded in the state. In doing so we were able to assess a conservation rank, using NatureServe criteria, for each species. We conclude that nine species are critically imperiled (S1) in the state. These species require immediate conservation attention, initially at the level of intensive surveys to delineate the full extent of the geographic range in the state and to determine the population size and habitat needs. We categorized an additional 13 species as imperiled (S2) and placed 18 species on a “watch list” (S3). Species on these two lists will require field surveys as well, and regions of high occurrence of listed species ought to be targeted for such efforts and considered as set-asides for preservation of key members of the odonate fauna in the state.

Is extinction forever

Mistrust of science has seeped into public perception of the most fundamental aspect of conservation—extinction. The term ought to be straightforward, and yet, there is a disconnect between scientific discussion and public views. This is not a mere semantic issue, rather one of communication. Within a population dynamics context, we say that a species went locally extinct, later to document its return. Conveying our findings matters, for when we use local extinction, an essentially nonsensical phrase, rather than extirpation, which is what is meant, then we contribute to, if not create outright, a problem for public understanding of conservation, particularly as local extinction is often shortened to extinction in media sources. The public that receives the message of our research void of context and modifiers comes away with the idea that extinction is not forever or, worse for conservation as a whole, that an extinction crisis has been invented.