Marc-André Villard

SELECTING INDICATOR SPECIES TO MONITOR ECOLOGICAL INTEGRITY: A REVIEW

We review critical issues that must be considered when selectingindicator species for a monitoring program that aims to maintainor restore ecological integrity. First, we examine the pros andcons of different management approaches on which a conservationprogram can be based and conclude that ecosystem management ismost appropriate. We then identify potential indicators ofecological integrity at various levels of the ecosystem, with aparticular emphasis on the species level. We conclude that,although the use of indicator species remains contentious, it canbe useful if (1) many species representing various taxa and lifehistories are included in the monitoring program, (2) theirselection is primarily based on a sound quantitative databasefrom the focal region, and (3) caution is applied wheninterpreting their population trends to distinguish actualsignals from variations that may be unrelated to thedeterioration of ecological integrity. Finally, we present anddiscuss different methods that have been used to select indicatorspecies.

Patch characteristics and landscape context as predictors of species presence and abundance: A review1

AbstractAn increasing proportion of ecological studies examine landscape effects on the phenomena they address. We reviewed studies which simultaneously considered landscape-scale and patch-scale e...

Dynamics in Subdivided Populations of Neotropical Migratory Birds in a Fragmented Temperate Forest

To study the hierarchy of variables involved in the year-to-year dynamics in the distribution of Neotropical migratory birds, we compared observed numbers of local extinctions and recolonizations to those expected under six hypothetical mechanisms of settlement by returning spring migrants. These mechanisms were (1) random dispersal among forest fragments; (2) passive sampling of spring migrants according to fragment area; (3) dispersal among fragments between years according to the distance to the nearest fragment occupied the 1st yr; (4) resettlement of spring migrants according to the vertical structure of the vegetation in the fragments; (5) site fidelity of experienced breeders; (6) a combination of mechanisms 2, 3, 4, and 5. We selected four target species: Wood Thrush (Hylocichla mustelina), Black-and-white Warbler (Mniotilta varia), Ovenbird (Seiurus au- rocapillus), and Scarlet Tanager (Piranga olivacea). In 50 fragments of mature deciduous forest (3.0-129.8 ha, median = 11.8 ha) within a 10 X 10 km square, we recorded the presence of any target species and an abundance index in two successive breeding seasons. Absences were validated using song playbacks. Except for the random dispersal model, each hypothetical mechanism was simulated using logistic regressions on empirical data. Frequencies of population turnovers (local extinctions + recolonizations) were 16-28% between the two breeding seasons, varying with species. Observed numbers of population turnovers were best approximated by the combination model (model 6). Expected numbers of population turnovers were consistently higher than observed numbers for models 1-4, suggesting that between-year dynamics were constrained by some process(es). Our simu- lations suggest that site fidelity might be an important constraint on the distributional dynamics of these species, even when effects of fragment area and habitat on site fidelity are factored out. This finding has important implications for the response of Neotropical migrant birds to the fragmentation of their habitat.

REVIEW: Beyond the fragmentation debate: a conceptual model to predict when habitat configuration really matters

Summary 1. Research addressing the effects of habitat fragmentation on species, assemblages or ecosystems has been fraught with difficulties, from its conceptual foundation to statistical analyses and interpretation. Yet, it is critical to address such challenges as ecosystems are rapidly being altered across the world. 2. Many studies have concluded that effects of habitat loss exceed those of fragmentation per se, that is, the degree to which a given amount of habitat is broken apart. There is also evidence from different biomes and taxa that habitat configuration, that is, the spatial arrangement of habitat at a given time, may influence several landscape processes such as functional connectivity, edge and matrix effects, and thus population viability. 3. Instead of focusing attention on the relative influence of either habitat loss or fragmentation, we must identify portions of the gradient in habitat amount where configuration effects are most likely to be observed. Here, we suggest that all species are, to a certain degree, sensitive to landscape change and that, assuming a homogeneous matrix, habitat configuration will have a higher influence on species at intermediate values of habitat amount, where configuration has potentially the greatest variability. 4. On the basis of empirical studies and simulations, we expect that species that are relatively tolerant to fragmentation of their habitat will exhibit a wider band where amount and configuration interact compared to species less tolerant to fragmentation. 5. Synthesis and applications. Reducing habitat loss should be a top priority for conservation planners. However, researchers should also investigate the indirect impacts of habitat loss on biodiversity through fragmentation effects. This research aims to identify windows of opportunity where habitat configuration can mitigate to some extent the effects of habitat loss, particularly through the maintenance of functional connectivity.

GEOSTATISTICS AS A TOOL FOR EXAMINING HYPOTHESIZED DECLINES IN MIGRATORY SONGBIRDS

Data from the North American Breeding Bird Survey (BBS) indicate sig- nificant declines in the populations of several species of songbirds, including several Neo- tropical migrants. These declines have been attributed to habitat destruction and fragmen- tation on the breeding grounds, in strategic migratory stopover sites, and on the wintering grounds. Using BBS data from the 1967-1989 period and universal kriging, we produced maps of abundance change for two declining species of wood warblers to test hypothetical spatial scenarios of decline over entire breeding ranges. These species were the Cerulean Warbler (Dendroica cerulea) and the Prairie Warbler (D. discolor). We found considerable variability in the location of areas of decline when comparing successive 5-yr periods. In some comparisons, areas of decline were concentrated in the centers of abundance of these species, and in others, they were scattered throughout their range. We also found that the direction and intensity of population trends was quite sensitive to the methods used for calculating abundance. Our results indicate that, even for species where significant long- term declines have been reported, considerable variation exists in the direction of abundance change, both geographically and temporally. Although most of the long-term declines re- ported in particular species at local and regional scales are undeniable, gaps in our knowl- edge still prevent us from incorporating these trends into a global model of the annual cycle of Neotropical migrants.

Playbacks of mobbing calls of Black-capped Chickadees as a method to estimate reproductive activity of forest birds

Abstract Community-level indices of reproductive success are useful for measuring or monitoring demographic effects of habitat alteration on birds. We present a time-efficient method to estimate the relative reproductive activity of the forest songbird community. A recording of mobbing calls of Black-capped Chickadees (Poecile atricapillus) was broadcast at pre-selected stations during the breeding season. These calls attracted individuals of many bird species present in the vicinity, allowing visual detection of reproductive activity (e.g., adults carrying food or presumed pairs). In mature deciduous forests of northern New Brunswick, 50 bird species responded to the playbacks. Playbacks significantly increased the probability of visual observations of birds compared to silent observations conducted before broadcasting mobbing calls. In coniferous forests of central Québec, playbacks attracted 24 species and also provided a significantly greater opportunity to make visual observations of individual birds. In New Brunswick, mobbing playbacks facilitated more observations of reproductive evidence relative to point counts. Observation periods were brief and a 306-ha plot (1.75 × 1.75 km, 64 points spaced 250 m apart) could be surveyed by foot in less than 32 observer-hours. The proportion of individuals of a given species showing evidence of reproductive activity was used as an index of reproductive success. Black-throated Blue Warblers (Dendroica caerulescens) and Ovenbirds (Seiurus aurocapillus) had a reproductive index consistent with their true nesting success as derived from intensive nest monitoring on the same plots.

Setting conservation targets for managed forest landscapes.

Forests host a disproportionate share of the world’s biodiversity. They are increasingly being seen as a refuge for genetic diversity, native species, natural structures, and ecological processes yet intensive forestry threatens their value for biodiversity. The authors present concepts, approaches, and case studies illustrating how biodiversity conservation can be integrated into forest management planning. They address ecological patterns and processes taking place at the scale of landscape, or forest mosaics. This book is intended for students and researchers in conservation biology and natural resource management, as well as forest land managers and policy-makers. It presents case studies and examples from many forest regions of the world and addresses multiple components of biodiversity. With contributions from researchers who are familiar with forest management and forest managers working in partnership with researchers, this book provides insight and concrete tools to help shape the future of forest landscapes worldwide.

Tolerance to habitat fragmentation influences the colonization of new habitat by forest birds

We examined the relationship between the ability of bird species to persist in fragmented forests and their ability to colonize new forest habitat. Using a long-term data set on the colonization of a forest plantation, we tested the hypothesis that bird species tolerant to habitat fragmentation would detect and colonize the new habitat faster than intolerant species. The forest plantation under study is situated on an area of land reclaimed from the sea (a polder) in the central part of The Netherlands. We constructed an index of tolerance to habitat fragmentation and included it as a predictor variable in a set of three logistic regression models that compared the probability of colonization over four consecutive time periods. After controlling statistically for the effects of regional incidence, preferred habitat and life-history characteristics, there was a significant effect of tolerance to fragmentation on the ability of species to colonize the plantation, and a marginal effect on the timing of colonization. We then examined the effect of the same index of tolerance to fragmentation on colonization patterns over a larger spatial scale. Multivariate regression models showed that the proportion of three polders of different ages occupied by forest bird species was dependent upon the regional incidence of a species, its preferred habitat and its tolerance to fragmentation. The results support the hypothesis that species tolerant to habitat fragmentation detect and colonize new habitat faster than those intolerant to habitat fragmentation.

Effects of forest regeneration on songbird movements in a managed forest landscape of Alberta, Canada

Recent studies have shown that barrier effects exist even in relatively vagile species such as forest songbirds. The objectives of this study were to determine whether a 560 × 100 m riparian buffer strip of mature forest was used as a movement corridor by forest songbirds and, if so, to what extent corridor effects persisted as woody vegetation regenerated in the adjacent clearcut. Over a 4-yr period, juvenile movement rates decreased in the riparian buffer strip and increased in the regenerating clearcut. Adult movement rates increased in the riparian buffer strip in the first year after logging, then gradually decreased, while still increasing in the regenerating clearcut. However, both juvenile and adult movement rates were higher in the buffer strip than in an undisturbed control site. Results suggest that most adults we captured held territories in the vicinity of the net lanes,and that most of the juveniles captured were dispersing away from their natal territory. Four years after harvest, juvenile movement rates were higher in the regenerating clearcut than in the riparian buffer strip, but several species had not yet been captured or detected in the regeneration. Our results suggest that the use of the riparian buffer strip as a movement corridor decreased with forest regeneration for both adults and juveniles. However, the buffer strip still acted as a movement corridor for the following species: Philadelphia and Red-eyed Vireos, Red-breasted Nuthatch, and Ovenbird.

Putting Density Back into the Habitat‐Quality Equation: Case Study of an Open‐Nesting Forest Bird

Ecological traps and other cases of apparently maladaptive habitat selection cast doubt on the relevance of density as an indicator of habitat quality. Nevertheless, the prevalence of these phenomena remains poorly known, and density may still reflect habitat quality in most systems. We examined the relationship between density and two other parameters of habitat quality in an open-nesting passerine species: the Ovenbird (Seiurus aurocapilla). We hypothesized that the average individual bird makes a good decision when selecting its breeding territory and that territory spacing reflects site productivity or predation risk. Therefore, we predicted that density would be positively correlated with productivity (number of young fledged per unit area). Because individual performance is sensitive to events partly determined by chance, such as nest predation, we further predicted density would be weakly correlated or uncorrelated with the proportion of territories fledging young. We collected data in 23 study sites (25 ha each), 16 of which were located in untreated mature northern hardwood forest and seven in stands partially harvested (treated) 1-7 years prior to the survey. Density explained most of the variability in productivity (R(2)= 0.73), and there was no apparent decoupling between density and productivity in treated plots. In contrast, there was no significant relationship between density and the proportion of territories fledging >or=1 young over the entire breeding season. These results suggest that density reflects habitat quality at the plot scale in this study system. To our knowledge this is one of the few studies testing the value of territory density as an indicator of habitat quality in an open-nesting bird species on the basis of a relatively large number of sizeable study plots.