Breeding Bird Communities Research Articles

Diversity/dominance diagrams show that fire disrupts the evenness in Mediterranean pinewood forest bird assemblages

Breeding bird communities were studied by line-transect in burnt pinewood and unburnt pinewoods, during three years subsequently to a fire event, in a coastal woodland of Mediterranean central Italy. We analyzed data following a diversity/dominance approach that ranks the species in order of their abundance, to obtain rank/abundance diagrams (‘Whittaker plots’). Although it is generally accepted that fire may induce structural changes in forest communities of breeding birds, we observed more evident effects when considering the assemblage of forest-specialist species. When considering the whole community of birds, ordinate intercepts of the regression between rank and relative abundance of species were not significantly different between unburnt and burnt plots in any of the three years of study. However, when considering only the forest-related species, there was a significant difference between unburnt and burnt plots in all the years of study. Evenness showed lower values that were explicited by the diversity/dominance diagrams (lower collocation of the curves of burnt pinewoods if compared to unburnt ones). Overall, the patterns observed in this study suggest that the effects of fire disturbance were more evident at the ecological level than at the taxonomic-level assemblages. The gradual decline of the more sensitive species due to fires and the proportional increase of edge/generalist species may induce a species turnover in burnt woods with cascade and relaxation effects which could be evidenced by diversity/dominance diagrams. Consequently, it is useful to separate the effects of fires at community-level and at assemblage-level when studying bird communities in areas subjected to fires.

Forested Buffer Strips and Breeding Bird Communities in Southeast Alaska

Abstract: Forested buffer strips are used to mitigate fragmentation and habitat loss and are a common feature in management of riparian landscapes. Low‐elevation, old‐growth coastal forests are a rare riparian habitat that can benefit from similar conservation measures. We evaluated the effectiveness of postlogging, forested buffer strips for forest‐dwelling birds in the coastal temperate rainforest of southeast Alaska, USA. Our objective was to compare bird composition and density among forested buffer strips of differing widths and controls at the stand and landscape scales. We applied a 2‐stage sampling design stratified by forested buffer width and randomly selected 24 managed and 18 control sites to sample over 2 breeding seasons. We estimated abundance of birds using the paired‐observer, variable‐circular plot method. We modeled combined effects of buffer width and vegetation and landscape characteristics on bird density at 2 spatial scales. Species richness and diversity were greatest in the narrowest buffers, but species composition in the largest buffers (≥400 m) was most similar to that in control blocks. Abundance of 3 of 10 common species differed across forested buffer treatments and controls. Densities of red‐breasted sapsucker (Sphyrapicus ruber) and Pacific‐slope flycatcher (Empidonax difficilis) were positively related to buffer width, whereas density of ruby‐crowned kinglet (Regulus calendula) was negatively associated with buffer width. Parameter estimates for buffer width effects at both spatial scales were similar within species. We found few habitat and landscape variables that clearly affected density of our focal species, and among species no predictor variables affected density in a similar fashion. We recommend retaining forested buffers ≥400 m to support composition and abundance of forest‐dwelling birds, particularly those species that rely on interior forest conditions. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):674‐681; 2008)

Breeding bird community composition in different successional vegetation in the montane coniferous forests zone of Taiwan

To examine the relationship between forest succession following fire and the composition of bird communities, we investigated the vegetation structure, bird population density, foraging behavior and guild structure in bamboo grasslands (11 years since the last fire), pine savanna (41 years), pine woodland (58 years), old-growth hemlock forest (never burned), and old-growth spruce forest (never burned) in the Tatachia area of central Taiwan. Canopy height, total foliage cover, tree density, total basal area of tree, total basal area of snags, foliage height diversity, and tree species richness all increased with successional age. However, shrub cover peaked in intermediate successional stages. The vertical profile of foliage cover was more diverse in later successional forests, which had more breeding bird species and ecological guilds. All the breeding bird species recorded in early and intermediate stages were also found distributed in the late successional forests. Because Taiwan has high precipitation and humidity, and most forest fires in Taiwan are caused by human activities, forest fires and large areas of early successional vegetation were probably rare in the mountain areas of Taiwan prior to the arrival of humans. Therefore, bird species have not had enough time to adapt to areas with early or intermediate successional vegetation. Moreover, late successional forests host all the major plant species found in the early and intermediate stages and have higher foliage height diversity index, which was positively correlated with the bird species richness and bird species diversity index in this study. As a result, all breeding bird species and guilds in the area can be found in late successional forests. Efforts for conserving avian diversity in Taiwan should focus on protecting the remaining native old-growth forests.

Comunidades nidificantes de aves en pastos supraforestales pirenaicos. Su evolución a lo largo del año

Bird density has been studied along areas with different features in supraforest pastures from two locations in Central Western Pyrenees, Aisa and Borau mountain passes (County of Huesca). Censuses, which have been taken all through the year, report on the formation of breeding bird communities and on those which exploit the studied environments during the postbreeding period. A stronger stability is noticeable in those areas which are higher than 2.000 m above sea level. There, breeding species are mostly highlanders and occurs a lack of strong population fluctuations of arthropods that prevents the invasion by consumers during the postbreeding period. Conversely, in lower areas prevail birds from the forest edge or deforested areas over the highland birds, except for the active large rocky places. In these places, highland birds include the Mediterranean highland factor (paleoxeromontanas).

Breeding Bird Communities Across an Upland Disturbance Gradient in the Western Lake Superior Region

Upland breeding bird communities were sampled from 225 points in 15 survey routes in the coastal region of western Lake Superior to examine relationships to human land use. Eighty-four species were detected and 50 were abundant enough to be included in data analysis. Monotonic quadratic regression models were constructed for these 50 species by using species counts as the dependent variable and the proportion of human conversion of the landscape (residential, agriculture, and commercial/industrial land uses) within each study area as the independent variable. Twenty-seven bird species had significant regressions (P < 0.05), 18 of which generally avoided areas developed by humans and 9 of which were attracted to development. Detrended correspondence analysis using counts of these 27 bird species was used to investigate multivariate, community responses to development. The first DCA axis was interpreted as a gradient from urban avoiding to urban exploiting bird species and was strongly correlated with land cover variables related to human development. Our results advance the idea that breeding bird communities can be used as indicators of ecological condition and can diagnose potential causes for changes in these conditions. Further, our study points out the usefulness of bird monitoring data in regional planning efforts that incorporate goals for maintaining native biological diversity.

Considerations for Monitoring Breeding Birds in Great Lakes Coastal Wetlands

One goal in indicator development is to implement long-term monitoring that will track the relative condition of the indicator over time. Among the first steps in establishing a monitoring program is to develop a sampling design that adequately characterizes the indicator to be monitored as well as the cost-effectiveness of the program. We used breeding bird data collected in Lake Superior and Lake Michigan coastal wetlands (riverine, lacustrine, barrier-protected) to determine: 1) how to select individual wetlands for sampling, 2) optimum number of sample points per wetland, 3) optimal daily sampling period, 4) how many times to sample, and 5) the costs associated with implementing a monitoring program for breeding bird communities of wetlands across the Great Lakes. We found that wetlands selected for sampling should represent the range of wetlands sizes available for monitoring and that the most cost-effective strategy would be to sample a maximum of three points, even in the largest wetlands. Because surveys conducted in the morning recorded a much higher (P < 0.001) number of species and individuals, we recommend that morning surveys should be conducted. Increasing number of wetlands sampled should be the first priority because sample precision is more improved at a higher cost ratio than by adding counts to the same wetland. Multiple visits to wetlands should be considered only after maximizing the number of individual wetlands visited with money available for surveys. We calculated that the average costs would be approximately 50.00 USD/year (2001 dollars) to monitor one wetland using one morning survey for breeding birds

Breeding bird communities of upland hardwood forest 12 years after shelterwood logging

Abstract We studied the relationship between the effects of shelterwood logging on forest structure and long-term abundance, diversity, and richness of breeding bird communities in an upland hardwood forest at Land Between The Lakes (LBL), Kentucky and Tennessee. Breeding bird communities (point counts in 1987–1989, 1999) and forest vegetation structure (1987–1988, 1999), the year prior to, 1 and 2 years after, and 12 years after shelterwood logging were compared between logged and uncut (>40 years since logging) forest sites. Shelterwood sites had significantly greater mid-story canopy. General avian community trends demonstrated an initial increase in diversity and density the year following logging, and decreased diversity and density in 1999. Uncut sites showed a general decline in diversity in 1989 and 1999. The influence of shelterwood logging varied among taxa and among foraging guilds. Specifically, the ground-gleaning guild was significantly more diverse on uncut sites than on shelterwood sites. We attribute this greater diversity to a more complex and diverse forest understory with greater opportunity for foraging. Logging did not significantly influence diversity, evenness, or richness of the nesting guilds. We examined four priority species of concern (as designated by Partners in Flight): Wood Thrush (Hylocichla mustelina), Worm-eating Warbler (Helmitheros vermivorus), Kentucky Warbler (Oporonis formosus), and Hooded Warbler (Wilsonia citrina). Of these, population densities of Wood Thrush were significantly lower on logged sites than on uncut sites while worm-eating warblers were higher on logged sites. The Kentucky Warbler and Hooded Warbler did not occur on logged sites. Higher densities of birds in our study sites compared to regional surveys suggest LBL is an important local area for breeding bird communities.

The Swiss agri-environment scheme promotes farmland birds: but only moderately

Agricultural production is intensive in the Swiss lowlands, where about half of farmland bird species are on the Red List. A nationwide agri-environment scheme was launched in 1993 to improve biodiversity on farmland. To qualify for subsidies, farmers have to use at least 7% of their farmland as ecological compensation areas (ECAs). We evaluated the effect of the ECAs on three levels. The national Swiss Bird Index for farmland birds shows a decline from 1990 to 2004. On a regional level, we monitored breeding bird communities on 23 study areas twice, with an interval of 4 years. Endangered species were largely absent and species richness was low. Between 1998 and 2002 and 1999 and 2003, respectively, common species showed a slight increase, whereas endangered species continued to decline. On a local level, it was expected that ECAs would have an effect on density and distribution of bird territories. The percentage area covered by ECAs had no influence on the population density of open farmland indicators nor on landscape indicators. A stepwise forward multiple regression model showed that “ECA-hedges” were significantly more often occupied by indicator species than hedges not financially supported by the agri-environment scheme. The Common Redstart Phoenicurus phoenicurus is an indicator species of traditional orchards. It occupies large traditional orchards with a high percentage covered by ECAs within 50 m of the edges more often than in the absence of ECAs. In two experimental study areas, ECAs of high ecological quality covered an exceptionally high proportion of farmland. In Laconnex in south-western Switzerland, many species benefit from these extra ecological improvements not part of the official agri-environment scheme. The Whitethroat Sylvia communis for example increased more than tenfold within 12 years to an actual density of 12 territories/km2, Stonechats Saxicola torquatus reached more than 8 territories/km2 and the Melodious Warbler Hippolais polyglotta also showed a remarkable increase. In the experimental study area “Widen” in north-eastern Switzerland, Yellowhammer Emberiza citrinella and Red-backed Shrike Lanius collurio doubled in numbers between 1998 and 2003, but not in the control area. We conclude that ECAs do have some positive effects on the breeding distribution of selected indicator bird species. However, the effects are moderate which is due the low quality of the ECAs.

Habitat change and woodland birds in Britain: implications for management and future research

There is increasing evidence that changes in habitat structure in the form of reduced understorey and loss of open habitats, both probably a result of increases in shading and deer browsing, may be responsible for causing recent changes in the composition of breeding bird communities in many lowland British woods and forests. In contrast, management of upland coniferous forests may prevent the attainment of mature and old‐growth structures which would benefit community development in these new ecosystems. We suggest that the key challenge for woodland conservation policy is to create larger areas of both young‐growth and old‐growth habitat. These objectives need not necessarily conflict with each other, or with other multipurpose forestry objectives, provided that they inform strategic plans and are targeted at appropriate locations and scales. In the lowlands, the current large stock of middle‐aged, often unmanaged and species‐poor woodland provides an opportunity to restore or create new woodland habitats of high biodiversity value. The development of woodfuel markets may effectively increase the amount of young‐growth but it is unclear exactly what habitat structures might be created. In the uplands, allowing more natural development of native woodland in mosaics with other habitats may provide opportunities for both old‐ and young‐growth species. For the foreseeable future, deer impacts will continue to be widespread and probably increasingly severe in many areas. In view of the uncertainty about the implications of climate change for woodland ecosystems, a strong case can be made for attempting to buffer valued wildlife communities against damaging effects by creating and maintaining high structural diversity at a range of scales and increasing the area of woodland.

Homogenisation processes and local effects on avifaunal composition in Italian towns

We tested whether urbanization homogenizes breeding bird communities. We compared the similarity of breeding bird communities among different urban sectors: town centres, inner periphery, outer periphery and scarcely built areas, at regional and local scale in 26 Italian towns. If urbanization causes homogenisation, the similarity of bird communities between different towns should be higher in the more urbanised sectors. We obtained data on presence of bird species in each square of the grid of urban atlases. We used the frequency of each species in each urban sector to calculate a similarity index. The similarity of the avifauna between towns was lowest in scarcely built areas and highest in the inner periphery. For each urban sector, the similarity indices between towns were negatively correlated with differences in both latitude and altitude between towns. The values of regression coefficient increased from the centre to the less urbanised sectors although the scarcely built area did not show the highest values. The frequency of a specialist group, the Mediterranean species, was negatively correlated with latitude only in the least urbanised sector. These results indicate that urbanization promotes homogenisation of biological communities. However, the similarity of avifauna between sectors in each town was higher than the similarity between different towns for the same sector. These and other findings suggest that local factors play an important role for the composition of urban bird communities.

Loss of Diversity in Bird Communities After Regulation of Riverine Meanders: How Strong is the Compensatory Effect of Mature Growth on Fishpond Dams?

Alterations to riverine ecosystems and the establishment of new man-made habitats along rivers have been accompanied by changes in vegetation composition and structure, which affect the birds inhabiting riparian stands. We examined the differences between bird communities inhabiting the relict growth of river meanders and those inhabiting secondary plantations along the Rivers Otava and Blanice (Czech Republic). In addition, we investigated whether the well-developed oak plantations on artificial fishpond dams, which are common in the studied landscape, might compensate for the loss of bird diversity following river regulation. Breeding bird community and habitat attributes were studied on 30 fixed-width line transects and analysed using Multivariate Redundancy Analysis. Relict meanders were the most structurally diversified habitat type, with the highest species diversity and the great richness of forest birds. In contrast, secondary plantations were the simplest stands with the poorest communities inhabited by more farmland species. Fishpond dams, though resembling the meanders more so than secondary stands, were found to be insufficient compensation for river meanders in regard to avian diversity. Supporting diverse plantations of softwood tree species and widening the narrow belts along river banks are highlighted as ways of managing riparian stands that are beneficial to birds.

Brown-headed Cowbird, &lt;em&gt;Molothrus ater&lt;/em&gt;, Parasitism and Abundance in the Northern Great Plains

The Brown-headed Cowbird (Molothrus ater) reaches its highest abundance in the northern Great Plains, but much of our understanding of cowbird ecology and host-parasite interactions comes from areas outside of this region. We examine cowbird brood parasitism and densities during two studies of breeding birds in the northern Great Plains during 1990–2006. We found 2649 active nests of 75 species, including 746 nonpasserine nests and 1902 passerine nests. Overall, &lt;1% of nonpasserine nests and 25% of passerine nests were parasitized by Brown-headed Cowbirds. Although the overall frequency of cowbird parasitism in passerine nests in these two studies is considered moderate, the frequency of multiple parasitism among parasitized nests was heavy (nearly 50%). The mean number of cowbird eggs per parasitized passerine nest was 1.9 ± 1.2 (SD; range = 1–8 cowbird eggs). The parasitism rates were 9.5% for passerines that typically nest in habitats characterized by woody vegetation, 16.4% for grassland-nesting passerines, 4.7% for passerines known to consistently eject cowbird eggs, and 28.2% for passerines that usually accept cowbird eggs. The Red-winged Blackbird (Agelaius phoeniceus) was the most commonly parasitized species (43.1% parasitism, 49.6% multiple parasitism, 71.2% of all cases of parasitism). Passerine nests found within areas of higher female cowbird abundance experienced higher frequencies of cowbird parasitism than those found in areas of lower female cowbird abundance. Densities of female cowbirds were positively related to densities and richness of other birds in the breeding bird community.

Ordination of breeding birds in relation to environmental gradients in three southeastern United States floodplain forests

We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains: Cache River, Arkansas (AR), Iatt Creek, Louisiana (LA), and the Coosawhatchie River, South Carolina (SC), USA. We used 5-min point counts to sample birds in each study area each spring from 1995 to 1998, and measured ground-surface elevations and a suite of other habitat variables to investigate bird distributions and community characteristics in relation to important environmental gradients. In both AR and SC, the average number of Neotropical migrant species detected was lowest in semipermanently flooded Nyssa aquatica Linnaeus habitats and greatest in the highest elevation floodplain zone. Melanerpes carolinus Linnaeus, Protonotaria citrea Boddaert, Quiscalus quiscula Linnaeus, and other species were more abundant in N. aquatica habitats, whereas Wilsonia citrina Boddaert, Oporornis formosus Wilson, Vireo griseus Boddaert, and others were more abundant in drier floodplain zones. In LA, there were no significant differences in community metrics or bird species abundances among forest types. Canonical correspondence analyses revealed that structural development of understory vegetation was the most important factor affecting bird distributions in all three study areas; however, potential causes of these structural gradients differed. In AR and SC, differences in habitat structure were related to the hydrologic gradient, as indexed by ground-surface elevation. In LA, structural variations were related mainly to the frequency of canopy gaps. Thus, bird communities in all three areas appeared to be organized primarily in response to repeated localized disturbance. Our results suggest that regular disturbance due to flooding plays an important role in structuring breeding bird communities in floodplains subject to prolonged inundation, whereas other agents of disturbance (e.g., canopy gaps) may be more important in headwater systems subject to only short-duration flooding. Management for avian community integrity in these systems should strive to maintain forest zonation and natural disturbance regimes.

Consideration of Geography and Wetland Geomorphic Type in the Development of Great Lakes Coastal Wetland Bird Indicators

We examined how geographic distribution of birds and their affinities to three geomorphic wetland types would affect the scale at which we developed indicators based on breeding bird communities for Great Lakes coastal wetlands. We completed 385 breeding bird surveys on 222 wetlands in the US portion of the basin in 2002 and 2003. Analyses showed that wetlands within two ecoprovinces (Laurentian Mixed Forest and Eastern Broadleaf Forest) had different bird communities. Bird communities were also significantly different among five lakes (Superior, Michigan, Huron, Erie, and Ontario) and among three wetland types (lacustrine, riverine, barrier-protected). Indicator values illustrated bird species with high affinities for each group (ecoprovince, lake, wetland type). Species with restricted geographic ranges, such as Alder and Willow Flycatchers (Empidonax alnorum and E. traillii), had significant affinities for ecoprovince. Ten bird species had significant affinities for lacustrine wetlands. Analyses on avian guild metrics showed that Lake Ontario wetlands had fewer long-distant migrants and warblers than other lakes. Numbers of short-distant migrants and total individuals in wetlands were higher in the Eastern Broadleaf Forest ecoprovince. Number of flycatchers and wetland obligate birds were not different among provinces, lakes, or wetland type. One potential indicator for wetland condition in Great Lakes wetlands, proportion of obligate wetland birds, responded negatively to proportion of developed land within 1 km of the wetland. We conclude that, although a guild approach to indicator development ameliorates species-specific geographic differences in distribution, individual species responses to disturbance scale will need to be considered in future indicator development with this approach.

Forest bird response to partial cutting in lodgepole pine forests on caribou winter range in west-central British Columbia

Breeding birds were surveyed 1 year pre-harvest (1995) and 4 years post-harvest (1996–2001) to measure the response to partial cutting in old lodgepole pine (Pinus contorta Dougl.) forests on the Chilcotin Plateau of British Columbia. The irregular group shelterwood and group selection systems recommended to manage northern caribou (Rangifer tarandus caribou Gmelin) habitat did not negatively affect the breeding bird community. In some years within the post-harvest period, dark-eyed juncos (Junco hyemalis L.), red crossbills (Loxia curvirostra L.), yellow-rumped warblers (Dendroica coronata L.), and gray jays (Perisoreus canadensis L.) showed significant (α = 0.05) increases in use of the partial-cutting treatments compared with the no-harvest treatment. No species decreased significantly in any of the partial-cutting treatments. The increased observations of mostly common species resulted in significantly (α = 0.05) higher species richness, and increased frequency of observations for the bird community in some years in the partial cuts. Partial cutting of caribou habitat will maintain bird communities typical of mature to older lodgepole pine forests.

Breeding bird response to riparian forest management: 9 years post-harvest

We previously examined the 3-year response of breeding bird communities to timber harvest in riparian areas using two harvest techniques (full tree harvest (GPL) and cut-to-length (CTL)) along first- to third-order streams in northern Minnesota, USA. We revisited the same 12 sites 9 years post-harvest and compared community composition, total abundance, species richness, and the abundance of bird guilds on harvest plots randomly assigned to four treatments (three plots per treatment). Analyses revealed a significant response of the bird community to timber harvest in the riparian area. Nine years post-harvest, bird communities in the uncut riparian buffers were statistically indistinguishable from control bird communities. Differences in bird communities between CTL and GPL treatments detected 3 years post-harvest in buffers were no longer evident after 9 years. Breeding bird community composition in harvested buffers became more similar to uncut and control buffer communities in species composition. All treatment buffers continued to have more species and individuals than control buffers; these bird species had affinities for early-successional forests. No differences among forest interior species or ground-nesting birds were evident between treatments 9 years post-harvest.

The effects of fire on communities, guilds and species of breeding birds in burnt and control pinewoods in central Italy

Breeding bird communities in burnt and unburnt residual pinewoods were studied over 3 years by line-transect method, following a catastrophic fire event in Castelfusano (Rome, Central Italy; July 2000). We applied bootstrap procedures to evaluate whether the observed data were true or just produced by chance, and then examined the emerging patterns at three levels: community, guild and species levels. At the community level, fire acted on breeding bird communities by altering especially the total abundance patterns: the species abundance decreased in the burnt pinewood compared to the residual one, but other parameters were not significantly affected by fire. As a consequence of fire, the destruction and structural simplification of the canopy and shrubby component, as well as the increase of edge habitat and patchiness at landscape scale, induced a turnover in species between pinewoods. Species turnover was higher at the burnt than at the residual pinewoods, during all the 3 years of study. At the guild level, the forest species decreased strongly in terms of richness and abundance in the burnt pinewoods, contrary to the edge and open habitat species which increased in terms of richness, abundance and evenness. Edge species showed the highest turnover in burnt pinewood during the whole period of study. At species level, after an a priori subdivision (based on bibliographic search) of the various species in two ecological guilds (forest versus edge species), it was found that an a posteriori statistical analysis confirmed the expected trend, i.e. that the species which decreased significantly in burnt pinewood were essentially the forest species, whereas the species which increased were essentially the edge/open habitat ones. Overall, in order to investigate the effects of fire catastrophes on birds, the guild approach seems more exhaustive than the taxonomic community approach, where intrinsic confounding trends are present.

Classification of breeding bird communities along an urbanization gradient using an unsupervised artificial neural network

An unsupervised artificial neural network known as self-organizing mapping (SOM) was used to examine the influence of urbanization on the assembly patterns of breeding birds. From late March until mid June 2004, we monitored 52 breeding bird species at 367 sites and analyzed their assembly patterns by their environment (impervious, water, and vegetative areas; number of deciduous trees and coniferous trees; and volume of deadwood) in Seongnam City, South Korea. The data were computed with SOM, which allows two-dimensional visualization and classification of complex bird assembly patterns using a U-matrix. SOM made it possible for us to organize the study sites into five clusters according to the similarity of the breeding bird assembly patterns. Clusters IV and V had high values for total species richness, as well as the number of species in the tree canopy, cavity, and ground-nesting guilds and the tree canopy, ground, and wood-foraging guilds. These results coincide with the fact that clusters IV and V had the highest proportion of vegetative areas, the greatest number of deciduous trees, and the highest volume of deadwood. By contrast, clusters I and II had a high percentage of impervious areas (e.g. buildings and roads) and a low percentage of vegetative areas. Coincidentally, clusters I and II had lower values for total species richness and the number of species forming nesting and foraging guilds, except for building-nesting guild and water-foraging guild. Cluster III, which contained many coniferous trees and little deadwood, had fewer total species richness compared with clusters IV and V, despite the number of coniferous trees in that area, because the trees in cluster III were relatively young, having been planted after the 1970s and having been subjected to periodic thinning. The SOM allowed us to elucidate the relationships among several environmental variables and breeding bird assembly patterns. From the point of view of an urban bird researcher who deals extensively with areas undergoing urbanization, SOM appears to be a valuable tool for visualizing and analyzing a relatively large volume of data relatively easily.

DETERMINANTS OF LOCAL EXTINCTION AND TURNOVER RATES IN URBAN BIRD COMMUNITIES

Studying the effects of urbanization on the dynamics of communities has become a priority for biodiversity conservation. The consequences of urbanization are mainly an increased fragmentation of the original landscapes associated with a decrease in the amount of favorable habitats and an increased pressure of human activities on the remaining patches suitable for wildlife. Patterns of bird species richness have been studied at different levels of urbanization, but little is known about the temporal dynamics of animal communities in urban landscapes. In particular, urbanization is expected to have stronger negative effects on migratory breeding bird communities than on sedentary ones, which should lead to different patterns of change in composition. Using an estimation method accounting for heterogeneity in species detection probability and data collected between 2001 and 2003 within a suburban area near the city of Paris, France, we tested whether these communities differ in their local extinction and turnover rates. We considered the potential effects of patch size and distance to Paris' center as a measure of the degree of urbanization around the patches. As expected, local rates of extinction and turnover were higher for migratory than for sedentary species, and they were negatively related to patch size for migratory species. Mean species richness of the sedentary species increased during the study period and their local turnover rate was negatively related to the distance to the urban core, showing a trend to colonize the most urban patches. These results highlight the very dynamic nature of the composition of some local bird communities in fragmented habitats and help to identify factors affecting colonization and extinction.

Effects of Selective Logging on Breeding Bird Communities in Bottomland Hardwood Forests in Louisiana

Bottomland hardwood forests of the southeastern United States support a rich avifauna, including >20 species of conservation concern; understanding the impact of land use practices on these communities is critical to their conservation. Selective timber harvesting is a common management practice in southern bottomland hardwood forests, but little research has examined impacts >5 years after harvesting. We studied breeding bird communities in selectively harvested bottomland forests in northeastern Louisiana during 2003–2004. We conducted point counts in recently harvested stands (1–5 yr postharvest) and older harvests (12–18 yr postharvest); we paired each with a reference stand that had not been harvested for >30 years. Of 35 species with sufficient detections for analysis, we found evidence that abundances of 17 species differed among treatments. Three species were sensitive to creation of canopy openings by timber harvests, including 2 species of concern in the Mississippi Alluvial Valley, USA, prothonotary warbler (Protonotaria citrea) and Acadian flycatcher (Empidonax virescens). However, 4 species of concern often associated with densely vegetated canopy gaps were more abundant in older harvests than in reference stands: Swainson's warbler (Limnothlypis swainsonii), hooded warbler (Wilsonia citrina), white-eyed vireo (Vireo griseus), and Kentucky warbler (Oporornis formosus). As expected, a suite of species typically associated with shrub and forest-edge habitats was more abundant in recent harvests than in reference stands. We conclude that selective logging has a strong influence on bird abundances in both recent and older harvests in bottomland forests. With the exception of Acadian flycatcher, older harvests and reference stands supported similar abundances of the species typically found in closed-canopy bottomland forests. In addition, older harvests supported substantially higher abundances of gap-dependent species than other treatments. Our results should be useful to land managers and conservation planners evaluating short- and long-term effects of timber management practices on breeding birds in the Mississippi Alluvial Valley. However, measures of breeding productivity are necessary to evaluate more fully the habitat quality of harvested forests.