Individual and environmental determinants of reproductive success in male tree swallow (Tachycineta bicolor) (original) (raw)
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Austral Ecology, 2007
Forestry operations in jarrah forests of southwestern Australia use two types of selective logging, gaps which remove 85-95% of basal area and shelterwoods which remove 40-60% of basal area.These operations create considerable lengths of forestry edge (edges between logged and unlogged forest) each year, but their impact on the avifauna of the jarrah forest is unknown. Changes in bird density were examined along edges created by forestry operations in jarrah forests using a BACI design experiment. Bird densities were estimated on 1-ha plots that were surveyed three times per season, in three seasons both before and after logging. There was no evidence of edge effects at the community level; overall bird density and species richness did not changes along forestry edges. Scarlet robin (Petroica multicolor) abundance increased significantly along both gap and shelterwood edges, relative to controls. Apart from a probably spurious increase in density along gap edges by red-winged fairy-wrens (Malurus elegans), no other species showed a significant change in density along edges. There was also no difference in responses to gap and shelterwood edges, despite gaps removing more basal area than shelterwoods, suggesting that response to forestry edges in the jarrah forest may be threshold dependent, rather than increasing with increasing intensity of logging operations. Comparisons with other studies examining density changes along forestry edges in southwestern Australia suggest that density changes observed in this study are short-term in nature. The limited density change in avifauna along forestry edges is probably because selective logging practices were examined instead of clear-felling. Studies in the literature indicate that this pattern is likely to be true for many forest ecosystems.
sekj.org
Nest predation in ground nesting black grouse (Tetrao tetrix) inhabiting managed boreal forests is arguably the single most important cause of nesting failure. Little is known, however, about indirect effects of other factors, such as maternal or environmental properties, and to what extent maternal and habitat qualities interact with varying levels of predator densities. Using an information-theoretical approach, we studied maternal and environmental determinants of daily nest survival rates under variable predator densities of 210 individual black grouse hens in central Finland. Environmental determinants were far more important than maternal ones, and the effects were more apparent at higher predator densities. Keeping predator densities constant, daily nest survival rates increased with nest conspicuousness and increasing tree density, and were higher in undrained areas. While there was no difference between adults and juveniles, hens that invested more in egg size were more successful. Therefore, environmental factors and, to a lesser extent, maternal properties, indirectly affect nesting success especially when predator density is high. Modern forestry practices such as clear cutting and drainage are commonly linked to increased densities of predators such as foxes. Our results suggest that the nesting success of black grouse may further be indirectly affected by the same practices, the overall impact being a balance between the negative (e.g. drainage, clear-cutting) and the positive (reforestation, producing dense young forest stands) effects.
Residual Tree Retention Ameliorates Short-Term Effects of Clear-Cutting on Some Boreal Songbirds
Ecological Applications, 2001
Retention of residual trees in ''cutblocks,'' logged blocks of forest, has been proposed as a method to conserve songbirds in landscapes fragmented by clear-cut logging. We examined songbird communities in the boreal mixed-wood forest of Alberta, Canada, to investigate the effect on songbird abundance of (1) logging and (2) retaining variable densities of residual trees in cutblocks (10-133 trees/ha or basal area of 0.50-10.65 m 2 ). We surveyed songbirds in logged and forested, aspen-dominated, mixed-wood stands in the year before, the year after, and three years after logging. We analyzed changes in abundance of 27 common songbird species: 23 present in the forest prior to logging and four that appeared after logging. Ten species declined with logging and were termed ''forest species.'' Ten more species did not change with logging and were called ''habitat generalists.'' The seven species that increased with logging were called ''cutblock species.'' When the effect of residual tree retention was examined in terms of basal area (rather than density) of residual trees, more songbird species were found to be both positively and negatively affected by residual tree retention, despite the fact that the two tree measures were highly correlated. In the first year after logging, four bird species (two forest, one generalist, and one cutblock) increased, and none decreased with increasing residual tree retention in cutblocks. In the third year after logging, again four species increased with increasing retention, but these were different species than in the first year after logging (one forest and three generalist species). Furthermore, four cutblock species decreased with increasing retention. Based on these findings, we conclude that retention of residual trees may be beneficial to some species, although conservation of unlogged reserves is also important. Most importantly, we recommend that research be continued to examine a larger range of tree retention and longer term effects on the avifauna.
Conservation Biology, 2003
A critical step in understanding the relationship between forest management and bird populations is conducting studies that employ rigorous experimental designs, relate forest management to avian demography, and explore relationships at expanded temporal and spatial scales. The Missouri Ozark Forest Ecosystem Project (MOFEP) is a long-term, large-scale manipulative experiment that is testing the effects of evenaged (i.e., clearcutting) and uneven-aged (i.e., selection cutting) forest management on a suite of response variables in Missouri oak-hickory forests. We report on the short-term effects of these management systems on the density and reproductive success of birds by evaluating 5 years of preharvest and 3 years of postharvest data from MOFEP. Densities of mature forest species declined 24-69% on the control (i.e., no timber harvest) sites during post-treatment years, confounding interpretation of treatment effects. Densities of both Kentucky Warblers ( Oporornis formosus ) and Worm-eating Warblers ( Helmitheros vermivorus ) increased in treatment sites relative to control sites. Conversely, even-aged management negatively affected Ovenbird ( Seiurus aurocapillus ) density. Treatment significantly and positively affected density of four of the six early successional species. Densities of Indigo Bunting ( Passerina cyanea ) and Yellow-breasted Chat ( Icteria virens ) were significantly higher in both even-aged and uneven-aged treatments, whereas densities of Prairie Warbler ( Dendroica discolor ) and White-eyed Vireo ( Vireo griseus ) were significantly higher in even-aged treatments than in the controls. Nest success rates averaged 29% for all species and did not change significantly from preto post-treatment years. Mature forest bird populations declined as trees were removed, but significant changes in nest predation and brood parasitism did not occur. In addition, openings associated with timber removal provided habitats for early successional species. We suggest that a mixed strategy of timber management may be necessary to support the full range of breeding birds in this region.
The Effects of Forest Management on Cavity-Nesting Birds in Northwestern Washington
The Journal of Wildlife Management, 1985
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Large-scale drainage and breeding success in boreal forest grouse
Journal of Applied Ecology, 2007
The breeding success of Finnish grouse has been in decline for decades. While it has been shown that fragmentation and modern forestry practices such as clear-cutting affect the viability of grouse populations, little is known about effects of large-scale drainage. The drainage network in Finland has increased dramatically during the past decades. By 1988, 6 million ha of bog ecosystems had been drained. This is likely to have had a profound direct and indirect effects on grouse productivity. Because ditches persist in time, large-scale drainage may therefore have strong potential for affecting the long-term breeding success of three forest grouse species in Finland.
How can forest management benefit bird communities? Evidence from eight years of research in Ireland
Irish Forestry, 2012
An extensive programme of research on the breeding bird assemblages of Irish forests has been undertaken since 2001 to improve our understanding of the ways in which forest management can influence bird populations. Data on bird communities were collected from 115 sites across the island of Ireland. The sites included monoculture plantations at various stages of the forest cycle, commercially mature mixed species plantations, native woodlands and open non-forest habitats. Although this work comprised several discrete studies, the overarching aim was to investigate ways in which commercial forest plantations could be managed to improve their value for birds. The bird communities of some open habitats, including low intensity agricultural land and peatland, can be negatively affected by afforestation, but afforestation has the potential to have a more positive impact on the bird communities of intensively managed grasslands. Bird assemblages of native oak (Quercus spp.) and ash (Fraxinus excelsior L.) woodlands are more diverse than those of commercially mature conifer plantations and provide a reference against which to compare plantation forests. The inclusion of native broadleaved trees in conifer plantations can be beneficial for bird populations, at least in part due to diversification of forest vegetation structure. Shrub cover, which is associated with higher bird species richness, is prominent in pre-thicket plantation forests, particularly in the second rotation. The loss of understorey structure after canopy closure leads to a less diverse bird assemblage in the mid to late stages of the forest cycle. In general, forest management practices that promote growth of non-crop vegetation and presence of deadwood, thereby enhancing structural complexity, increase the quality of forest habitats for bird communities. In this paper we provide a summary of the findings from the first eight years of these studies, and discuss their application in achieving "Sustainable Forest Management".
Landscape-level effects of forest management on bird species in the Ozarks of southeastern Missouri
2002
This study was designed as an experiment to test how bird populations in an extensively forested landscape respond to small (group and single-tree selection) and large (clearcut) openings. Our objectives are to test the landscape-level effects of even-aged and uneven-aged forest management relative to no-harvest management on population density and reproductive success for forest-interior and early-successional bird species. Pre-treatment data were gathered during the period 1991 through 1995, treatments were applied in 1996 and early 1997, and post-treatment data have been collected \ from 1997 through the present. Immediately following treatment, populations of forest-interior species declined on all study sites. Posttreatment, forest-interior species responded both positively and negatively to the even-aged and uneven-aged treatments. For earlysuccessional species, changes in density were positive in response to both even-aged and uneven-aged treatment types. Neither nest predation rates nor nest parasitism rates increased following treatment. From a landscape-level perspective, our findings indicate that the short-term effects of even-aged management are mixed, positive and negative, for forest-interior species and that the response by early-successional species is greater for even-aged than for unevenaged management.