Raymond J. O'Connor

PREDICTING EXTINCTIONS AS A RESULT OF CLIMATE CHANGE

Widespread extinction is a predicted ecological consequence of global warming. Extinction risk under climate change scenarios is a function of distribution breadth. Focusing on trees and birds of the eastern United States, we used joint climate and environment models to examine fit and climate change vulnerability as a function of distribution breadth. We found that extinction vulnerability increases with decreasing distribution size. We also found that model fit decreases with decreasing distribution size, resulting in high prediction uncertainty among narrowly distributed species. High prediction uncertainty creates a conservation dilemma in that excluding these species under-predicts extinction risk and favors mistaken inaction on global warming. By contrast, including narrow endemics results in over-predicting extinction risk and promotes mistaken inaction on behalf of individual species prematurely considered doomed to extinction.

Egg Weights and Brood Reduction in the European Swift (Apus apus)

Although all species of birds have characteristic egg weights (Lack 1968), there exist intraspecific differences which may reflect genotypic differences among females or phenotypic adjustment of egg size to season, food supply, laying order, clutch size or other factors (Kear 1965). This variation has received considerable attention in poultry, where egg size has long been known to influence chick quality, as judged by hatching size and survival (review in Landauer 1967), but only recently has received attention from field biologists (Parsons 1970, 1975b, Schifferli 1973, Murton et al. 1974). This paper is concerned with size variation and its adaptive significance in the eggs of the European Swift (Apus apus). Since swifts feed on flying insects, they may have difficulty in finding food, particularly in cold, wet or windy weather (Lack and Lack 1951, Lack 1956), and they consequently lay unusually small eggs for their body size (Lack 1968:286). A study of a species with such specialized habits seemed more likely to reveal the adaptive significance of egg size variation than is the case with poultry. I report here the results of such a study.

THE SCOPE AND TREATMENT OF THREATS IN ENDANGERED SPECIES RECOVERY PLANS

The recovery of threatened and endangered species is complicated by the number, severity, and tractability of the threats facing each species. We investigated the nature and the treatment of threats in recovery plans for 181 threatened and endangered species. We examined the types of threats facing species, as well as the degree to which threats were understood and addressed. We found that >85% of all species faced at least four out of nine distinct types of threats. The most common threats were those related to resource use, exotic species, construction, and the alteration of habitat dynamics. Recovery plans lacked basic information about the magnitude, timing, frequency, or severity of 39% of all threats facing the 181 species. Likewise, 37% of all threats were not directly addressed with recovery tasks. Threats from pollution were more poorly understood than other threats, and threats from exotics were better addressed than other types of threats. Finally, we found that threats that were better understood were assigned recovery tasks more often than threats that were more poorly understood. Thus our results suggest that a lack of basic understanding of the nature of the threats facing threatened and endangered species may, in part, be undermining our recovery efforts.

Quantifying the impacts on biodiversity of policies for carbon sequestration in forests

Abstract There is currently a great deal of interest in the use of afforestation (conversion of non-forest land to forest) to reduce atmospheric concentrations of carbon dioxide. To date, economic analyses have focused on the costs of forest carbon sequestration policies related to foregone profits from agricultural production. No studies have examined additional costs or benefits associated with impacts on biodiversity. The main objective of this paper is to estimate the changes in farmland and forest bird populations that are likely to occur under an afforestation policy. Econometric models of land use are used to simulate the response of private landowners to subsidies for tree planting on agricultural land. We evaluate subsidies that achieve conversion of 10% of the total agricultural land in each of three U.S. states (South Carolina, Maine, and southern Wisconsin). Bird density estimates are derived for 615 species with data from the national Breeding Bird Survey. Percentage changes in agricultural and forest land for each county are applied to county-level estimates of bird densities for farmland and forest birds. Despite considerable spatial variation in agricultural land conversion rates and farmland bird distributions within these states, statewide losses of farmland birds were relatively uniform at 10.8–12.2%. Increases in forest bird populations, however, varied substantially between states: 0.3% in Maine, 2.5% in South Carolina, and 21.8% in southern Wisconsin. Surprisingly, a net loss in total bird populations results in all three states (−2.0% in Maine, −2.3% in South Carolina, and −1.1% in southern Wisconsin), despite the prevailing wisdom as to bird-rich forests. The loss is due to the coincidence of centers of high farmland bird richness and low forest bird richness with areas economically suited to conversion. Additional gains in forest species may result, however, if afforestation within the economically optimal counties is concentrated to fill in existing forest fragments presently suffering avian losses to edge predators. Our results thus show that assessments of the biological consequences of afforestation for carbon sequestration must consider both current land cover and the distributional patterns of organisms as well as the policys conversion goal.

Using multiple taxonomic groups to index the ecological condition of lakes.

Biological indicators of communitiestypically reflect a common environmental signalreflecting the general condition of the ecosystem, as well asindividual signals by indicators differentiallysensitive to particular environmental conditions. Wedescribe here a method of integrating and interpretingsuch indicators from 19 New England lakes for fivetaxonomic groups (diatoms, benthos, zooplankton, fish,and birds). Our approach provides a systematicstandardized way to integrate multiple metrics fromdifferent taxonomic groups by addressing four elementscrucial to analyzing data from multiple indicators: covariate control, re-scaling of data, standardizing the sign of responses, and dimensional reduction. We evaluated the biologicalmetrics against individual environmental stressors andagainst multivariate physicochemical metricscharacterizing general anthropogenic stress among thelakes. The method detected a response to variationin the gross environmental condition of the lakes thatwas correlated across taxa and metrics. In addition,a differential response to near shore conditions wasdemonstrated for fish. The success of the approach inthis study lends support to its general application toecological monitoring involving complex data sets.

Morphometric analysis of pollen grains for paleoecological studies: classification of Picea from eastern North America

Little is known about the paleoecological histories of the three spruce species (white spruce, Picea glauca; black spruce, P. mariana; and red spruce P. rubens) in eastern North America, largely because of the difficulty of separating the three species in the pollen record. We describe a novel and effective classification method of distinguishing pollen grains on the basis of quantitative analysis of grain attributes. The method is illustrated by an analysis of a large sample of modern pollen grains (522 grains from 38 collections) of the three Picea species, collected from the region where the three species co-occur today. For each species X we computed a binary regression tree that classified each grain either as X or as not-X; these three determinations for each grain were then combined as Hamming codes in an error/uncertainty detection procedure. The use of Hamming codes to link multiple binary trees for error detection allowed identification and exclusion of problematic specimens, with correspondingly greater classification certainty among the remaining grains. We measured 13 attributes of 419 reference grains of the three species to construct the regression trees and classified 103 other reference grains by testing. Species-specific accuracies among the reliably classified grains were 100, 77, and 76% for P. glauca, P. mariana, and P. rubens, respectively, and 21, 30, and 22% of the grains by species, respectively, were problematic. The method is applicable to any multi-species classification problem for which a large reference sample is available.

Hierarchical correlates of bird assemblage structure on northeastern U.S.A. lakes.

We investigated the factorsstructuring lake shore bird assemblages of thenortheastern U.S.A. using data collected from 158 lakesbetween 1992 and 1994. The assemblage data wereaggregated and standardized to produce assemblagecompositions consisting of proportions of individualsemploying different foraging, dietary, and migratorystrategies. The assemblage data were then re-expressedusing compositional analysis techniques and subjectedto regression tree analysis to identify environmentalcorrelates over a range of scales. Regionally, humandensity in the watershed was the most importantpredictor for the foraging, dietary, and migratorycompositions. A combination of anthropogenic andnon-anthropogenic factors likely contributed to thesebroad-scale associations because land use was largelyconfounded with climate and geomorphology. Morelocally, associations with lake shoreresidential-urban development were identified as beingimportant for the foraging and dietary compositions,as were associations with lake shore wetlands, butonly contingent there being little human developmentpresent locally and regionally. Assemblages wereassociated with increasing local and regional humandevelopment such that: hawking, aerial foraging, andground gleaning individuals increased relative tohover-and-gleaners, foliage gleaners, and barkgleaners; omnivores increased relative toinsectivores; and residents increased relative toneotropical migrants. The observed changes in birdcommunity structure were consistent with declines inforest interior species relative to edge species inresponse to forest fragmentation and suggest thatanthropogenic factors have played a prominent role instructuring lake shore bird assemblages of this region.

HOW WELL DO CONSISTENTLY MONITORED BREEDING BIRD SURVEY ROUTES REPRESENT THE ENVIRONMENTS OF THE CONTERMINOUS UNITED STATES

Abstract We investigated the degree to which consistently monitored Breeding Bird Survey (BBS) routes represented environmental conditions across the United States. Using 388 models of individual species distributions, we identified eight environmental variables to which birds were particularly sensitive. The nonproportional sampling of these variables would therefore have relatively large impacts on large-scale studies using BBS data. We then used a sampling grid to compare the distribution of these variables in grid cells with and without consistently surveyed BBS routes. We made comparisons nationally, within BBS-defined physiographic regions, and within U.S. states. Not surprisingly, given the geographic variation in the intensity of route coverage, areas with BBS routes differed from those without at a national scale. In general, higher elevations and drier climates were poorly represented by BBS routes, and northeastern deciduous forests were overrepresented. In contrast, we found few large differences within most BBS-defined physiographic regions and within most states. However, there were a few large differences in a small number of regions and states, many of which had relatively few BBS routes. We conclude that the weighting factors supplied by the BBS will likely address most differences in sampling densities at a national scale. However, for studies not using these weights, studies investigating specific subsets of the BBS data, and studies that include states with relatively few BBS routes, we strongly suggest resampling analyses to determine any bias incurred by uneven sampling and, if necessary, the subsequent development of study-specific weighting factors. ¿Cuán Bien Representan las Rutas Consistentemente Censadas por el Conteo de Aves Reproductivas los Ambientes de Estados Unidos? Resumen. Investigamos el grado en que las rutas censadas anualmente por el Conteo de Aves Reproductivas (BBS, por sus siglas en inglés) representan las condiciones ambientales en los Estados Unidos. Utilizando 388 modelos de distribución individual de especies, identificamos ocho variables ambientales a las cuales las aves fueron particularmente sensibles. El muestreo no proporcional de estas variables podría tener un fuerte impacto sobre estudios a gran escala que utilizan los datos del BBS. Luego utilizamos una grilla de muestreo para comparar la distribución de estas variables en las celdas de la grilla con y sin rutas consistentemente monitoreadas por el BBS. Realizamos comparaciones a nivel nacional, dentro de las regiones fisiográficas definidas por el BBS y dentro de los estados. De manera no sorprendente, dada la variabilidad geográfica en la intensidad de cobertura de las rutas, las áreas con rutas del BBS difirieron de aquellas sin rutas a nivel nacional. En general, las elevaciones más altas y los climas más secos estuvieron pobremente representados por las rutas del BBS, y los bosques deciduos del noreste estuvieron sobre-representados. De manera contrastante, encontramos pocas diferencias dentro de las regiones fisiográficas definidas por el BBS y dentro de los estados. Sin embargo, hubo algunas diferencias considerables en un pequeño número de regiones y de estados, muchos de los cuales tenían relativamente pocas rutas del BBS. Concluimos que los factores de peso que el BBS provee probablemente dan cuenta de la mayoría de las diferencias en las densidades de muestreo a una escala nacional. Sin embargo, para los estudios que no utilizan estos pesos, los estudios que investigan subconjuntos específicos de datos del BBS y para los estudios que incluyen estados con relativamente pocas rutas del BBS, sugerimos con énfasis un análisis de re-muestreo para determinar cualquier sesgo que pueda presentarse debido al muestreo desigual, y si es necesario, el desarrollo subsiguiente de factores de peso específicos para el estudio.

Atlas of climate change effects in 150 bird species of the Eastern United States

NOTE: Instructions for navigating this publication can be found on the front cover. This atlas documents the current and potential future distribution of 150 common bird species in the Eastern United States. Distribution data for individual species were derived from the Breeding Bird Survey (BBS) from 1981 to 1990. Regression tree analysis was used to model the BBS data as functions of contemporary climate and elevation variables and the current distribution of 68 tree species that occurred in the bird models. The model for each bird species is described. These models were projected onto two scenarios of global climate change. Depending on the global climate model used, as many as 78 bird species are projected to decrease in abundance by at least 25 percent, while as many as 33 species are projected to increase in abundance by at least 25 percent.

RECOVERY PLAN REVISIONS: PROGRESS OR DUE PROCESS?

Revisions allow the recovery planning process for threatened and endangered species to be flexible and responsive to new information or changes in the status of a species. However, the Endangered Species Act defines neither firm criteria that trigger revision of recovery plans nor clear guidelines about how plans should be revised. Consequently, the effect of revisions in the recovery planning process is unknown. We examined how species and recovery plan attributes influenced the likelihood that a plan would be revised and how the content of plans changed with revision. Vertebrate species with designated critical habitat were nearly four times more likely to have their recovery plans revised than were invertebrates or plants without designated critical habitat. Nonetheless, recovery priorities assigned by the U.S. Fish and Wildlife Service (USFWS) did not influence the likelihood of plan revision. Paired comparisons between original and revised versions suggested that knowledge of species biology and status had improved, and that recognition of threats had increased since the original plans were written. However, these improvements did not lead to recovery criteria or monitoring actions that were more clearly justified. We recommend that recovery plan authors strive to maximize benefits from improved biological information by defining management actions and goals that are more biologically justified. We also urge the USFWS to establish a consistent priority system for recovery plan revisions that affords consideration to listed species of all taxa and emphasizes revisions for those species most likely to benefit.