Avian Community Composition and Foraging Behavior in Response to Commercial Thinning and Habitat Structure PDF Download

Author: Kelly A. Williams-Sieg
Publisher:
ISBN:
Category : Bird communities
Languages : en
Pages :

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Author: Martin L. Cody
Publisher: Princeton University Press
ISBN: 0691209332
Category : Science
Languages : en
Pages : 334

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Professor Cody's monograph emphasizes the role of competition at levels above single species populations, and describes how competition, by way of the niche concept, determines the structure of communities. Communities may be understood in terms of resource gradients, or niche dimensions, along which species become segregated through competitive interactions. Most communities appear to exist in three or four such dimensions. The first three chapters describe the resource gradients (habitat types, foraging sites, food types), show what factors restrict species to certain parts of the resource gradients and so determine niche breadths, and illustrate the important role of resource predictability in niche overlap between species for resources they share. Most examples are drawn from eleven North and South American bird communities, although the concepts and methodology are far more general. Next, the optimality of community structure is tested through parallel and convergent evolution on different continents with similar climates and habitats, and the direct influence of competitors on resource use is investigated by comparisons of species--poor island communities to species-rich mainland ones. Finally, the author discusses those sorts of environments in which the evolution of one species--one resource set is not achieved, and where alternative schemes of resource allocation, often involving several species that act ecologically as one, must be followed.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 404

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Author: Wendy K. Gram
Publisher:
ISBN:
Category : Birds
Languages : en
Pages : 242

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After the breeding season, many bird species move to different habitats or alter their social behavior for the nonbreeding season. High densities of neotropical migrant species funnel into Mexico, Central America, and the West Indies, but relatively little is known about the wintering strategies of these migrants or the permanent resident species. I documented the distribution of migrant species in four habitats in the El Cielo Biosphere Reserve in southern Tamaulipas, Mexico, and studied the structure of mixed-species flocks which consisted of both migrant and Mexican resident species. I used point count surveys and mist nets to determine the distribution of migrant species among tropical semi-deciduous forest (300 m altitude), cloud forest (1100 m altitude), humid oak-pine forest (1200 m altitude), and dry pine-oak forest (1800 m altitude) in the Sierra Madre Oriental mountains. Forty-one species of migrants and 136 species of Mexican residents were observed during the winters of 1993-1995; migrant species represented from 22% to 29% of the species detected in point counts and captured in mist nets. Habitats at higher elevations with temperate-like forests and at lower elevations with tropical forests supported the greatest number and highest abundance of migrant species. Migrants showed some flexibility in habitat use, particularly compared to resident species. Mixed-species flocks, particularly insectivorous foraging flocks, were prevalent during the nonbreeding season in northern Mexico. Flocks in the dry pine-oak forest averaged the most individuals and species per flock. Participants in mixed-species flocks did not appear to be a random collection of species, and niche partitioning by foraging behavior was ubiquitous among flock members. Ruby-crowned kinglet, a migrant species, and crescent-chested warbler, a Mexican resident species, were nuclear flock species in one habitat and follower flock species in another habitat; their foraging behavior also changed among habitats and with different flockmates. Patterns of foraging behavior in mixed-species flocks were consistent with models of competition and habitat selection, but I could not separate the effects of these processes in this system. Survival during the nonbreeding season is critical in maintaining populations; continued studies of winter community structure are important for understanding large-scale population dynamics.

Author:
Publisher:
ISBN:
Category : Agricultural conservation
Languages : en
Pages : 404

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"The bibliography is a guide to recent scientific literature covering effects of agricultural conservation practices on fish and wildlife. The citations listed here provide information on how conservation programs and practices designed to improve fish and wildlife habitat, as well as those intended for other purposes (e.g., water quality improvement), affect various aquatic and terrestrial fauna"--Abstract.

Author: Cecilia Lea Barham Noyes
Publisher:
ISBN:
Category : Birds
Languages : en
Pages : 152

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Effects of habitat and season on guild structure of avian communities were examined for islands in the estuary zone of the Columbia River, Oregon. Bird species were classified into guilds according to their major food item, typical foraging substrate, and foraging behavior. Variation in community structure indices (number of guilds, guild diversity, evenness, bird density, and biomass) among habitats and seasons were analyzed with multivariate analysis of variance and discriminant function analysis. Cluster analysis was used to examine patterns of guild distribution among habitats and seasons. Four habitat-bird community associations (tree-shrub, upland, beach-low marsh, and high marsh) were described based on results from this study. High guild evenness within tree-shrub habitats during the breeding season (spring and summer) distinguished tree-shrub bird communities from communities within the 3 other habitats. Relatively stable bird density within tree-shrub habitats was attributed to high vegetation heterogeniety and later successional stage of tree-shrub habitats. Seasonal variation of community structure indices was greatest within upland habitats. Comparison of seasonal patterns in number of guilds, guild evenness, bird density, and guild composition between tree-shrub and upland habitats suggested greater stability of food resource productivity, availability, and diversity within tree-shrub habitats. Differences in avian community structure between the 2 terrestrial seral stages (tree-shrub and upland) were ascribed to differences in successional stage and vegetation complexity. High avian biomass distinguished bird communities of beach-low marsh habitats and was probably related to high productivity typical of estuary systems. Seasonal variation of community structure, primarily a winter reduction in bird density, was least definitive in beach-low marsh habitats. Lack of winter reduction in number of guilds and seasonal changes in guild composition suggested low winter density was related to reduced availability of food resources as affected by tidal inundation, low temperatures, and ice on the river. Bird communities associated with the high marsh habitat were characterized from all other bird community-habitat associations by greater number of guilds. Less extensive tidal inundation, greater vegetation complexity and more edge effect in the high marsh habitat than in beach-low marsh habitats seemed to affect greater occurrence of terrestrial associated guilds. Results of this study indicated description of avian community structure on the basis of food-resource defined guilds was useful in interpreting how environmental (habitat and season) variation may affect bird communities. Validity of inferences from this study requires more detailed analysis of the bird communities and their habitats. Thus, the guild approach as used in this research is most appropriate for preliminary examination of communities, indicating areas where more specific study should increase understanding of the structure and functioning of avian communities.

Author: Jennifer M. Weikel
Publisher:
ISBN:
Category : Cavity-nesting birds
Languages : en
Pages : 204

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There is limited information on how to manage young forests of the Pacific Northwest to benefit wildlife populations. Commercial thinning is becoming more important in young forests both as a tool for timber management and to hasten the development of old-forest characteristics. There is some evidence that many species of birds in the Pacific Northwest, including many species of cavity-nesting birds, respond positively to thinning. It is not known why the abundance of many species of cavity-nesting birds respond positively to thinning I studied habitat use of cavity-nesting birds in young thinned and unthinned forests of the northern Coast Range of Oregon. I examined effects of two intensities of commercial thinning on the abundance of cavity-nesting birds using an experimental approach with one year of pre-treatment and two of post-treatment data for four species of cavity-nesting birds. No species examined was negatively affected by moderate intensity thinning, but one species had a severe negative response to heavy intensity thinning. The abundance of one species was positively influenced by thinning. I studied the foraging ecology of four species of cavity-nesting birds and characterized the types of structures used for foraging. Large-diameter hardwoods; large-diameter, well decayed snags and logs; and large-diameter conifers were all important foraging resources for the four species examined. Thinning for old-forest characteristics will likely have a positive impact on populations of cavity-nesting birds in the long term. There may be little negative short-term effects of thinning on cavity-nesting birds. I suggest a patchy approach to thinning with patches of unthinned and heavily thinned areas intermixed in a landscape dominated by moderately thinned areas. This mix should help to balance the short-term and long-term effects of thinning on all species of cavity-nesting birds. Patches of hardwoods, large-diameter snags, and large-diameter logs should be retained when thinning to provide suitable foraging resources for cavity-nesting birds.

Author: Christina Galitsky
Publisher:
ISBN:
Category : Biodiversity
Languages : en
Pages : 58

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Both fine scale patterns of vegetation and coarser scale landscape patterns affect bird community composition and structure. However, the relative importance of the drivers at these two spatial scales continues to be debated. Here, we show how the factors that drive avian diversity and community structure depend on context, including the particular environment studied, the response variables analyzed, and the groups of species examined. We explored the relative roles of landscape pattern and stand structure and composition in defining bird communities in 44 remnant oak stands in the Willamette Valley, Oregon. We focused on two key questions--are bird communities influenced more by landscape patterns (at the matrix and patch levels) or stand composition and structure, and in what contexts are each of these spatial scales more important. We conducted point counts to determine avian abundance, richness, and evenness and categorized birds into functional groups based on diet and foraging tactics. We then used canonical correspondence analysis and generalized linear models to analyze overall community patterns, functional group diversity, synanthropic and non-synanthropic species diversity, and the abundance of individual species of concern. Both local and landscape factors significantly influenced each group of avian species for every measure of diversity we tested, but their relative importance varied markedly. Local factors explained four times more variance than landscape factors for overall species diversity and double the variance for two functional groups. For the other functional groups, landscape factors were up to ten times more important. We found the same high variability for individual species, depending on the species evaluated. When we evaluated factors more specifically at the landscape level, we found that the surrounding matrix was much more important than patch variables for each group of birds we tested. However, we also found that patch size influenced some groups and individual species much more than others, and some not at all. Understanding the degree to which species respond to local environmental conditions and landscape patterns is an essential part of optimizing scarce conservation resources and our results indicate that such an understanding will need to be put into very specific context.

Author: Timothy T. McMahon
Publisher:
ISBN:
Category : Birds
Languages : en
Pages : 470

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Author: Brenda C. McComb
Publisher: CRC Press
ISBN: 1420007637
Category : Nature
Languages : en
Pages : 338

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In recent years, conflicts between ecological conservation and economic growth forced a reassessment of the motivations and goals of wildlife and forestry management. Focus shifted from game and commodity management to biodiversity conservation and ecological forestry. Previously separate fields such as forestry, biology, botany, and zoology merged