The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecif...The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.展开更多
Background: The early stage of forest succession following disturbance is characterized by a shift in songbird composition as well as increased avian richness due to increased herbaceous growth in the forest understor...Background: The early stage of forest succession following disturbance is characterized by a shift in songbird composition as well as increased avian richness due to increased herbaceous growth in the forest understory. However, regeneration of woody species eventually outcompetes the herbaceous understory, subsequently shifting vegetation communities and decreasing availability of vital foraging and nesting cover for disturbance-dependent birds, ultimately resulting in their displacement. These early stages following forest disturbance, which are declining throughout the eastern United States, are ephemeral in nature and birds depend on such disturbances for nesting and other purposes throughout their lives.Methods: We investigated the use of a two-stage shelterwood method to manage long-term persistence of seven early successional songbirds over a 13-year period in an upland hardwood forest within the southern end of the midCumberland Plateau in the eastern United States.Results: Canopy and midstory gaps created after initial harvest were quickly exploited by tree growth and canopy cover returned to these areas, accelerating the displacement of early-successional species. Woody stem densities increased substantially following stage two harvest as advanced tree regeneration combined with the re-opening of the overstory layer increased resource competition for early-successional plants in the understory. Carolina Wren(Thryothorus ludovicianus), Eastern Towhee(Pipilo erythrophthalmus), Indigo Bunting(Passerina cyanea), and Yellowbreasted Chat(Icteria virens) were characterized by immediate increases following initial harvest in 2001; while the American Goldfinch(Spinus tristis), Prairie Warbler(Setophaga discolor), and White-eyed Vireo(Vireo griseus) did not show an immediate response. Stage two harvest in 2011 rejuvenated vegetation which benefitted focal species, with six of seven species showing increases in densities between 2010 and 2012.Conclusion: The two-stage shelterwood method created conditions advantageous to early-successional birds by helping to re-establish understory vegetation through periodic disturbance to the canopy layer. This method provides evidence that early-successional species can be managed long-term(> 15 years) while using relatively small spatial disturbance through the two-stage shelterwood method.展开更多
Worldwide, wild birds play a vital role in the dispersal of ticks that harbour tick-borne pathogens, including Borrelia burgdorferi, the Lyme disease bacterium. Using PCR testing, we found 124 (31%) of 405 ticks (4 sp...Worldwide, wild birds play a vital role in the dispersal of ticks that harbour tick-borne pathogens, including Borrelia burgdorferi, the Lyme disease bacterium. Using PCR testing, we found 124 (31%) of 405 ticks (4 species), which were collected from 21 species of birds in far-western Canada, to be infected with B. burgdorferi. Transstadial transmission of B. burgdorferi occurred from larva to nymph, plus nymph to adult, in the avian coastal tick, Ixodes auritulus, collected from songbirds in British Columbia (B.C). Collectively, all 3 motile life stages (larva, nymph, adult) of this tick had an infection prevalence of 31% for B. burgdorferi, which suggests vector competency. A Pacific Wren was highly infested with I. auritulus immatures, and 20 (44%) of 45 ticks (2 nymphs, 43 larvae) were infected with B. burgdorferi. This heavy infestation shows the high potential to initiate a new population of ticks and to disseminate Lyme spirochetes. Epidemiologically, B. burgdorferi-infected I. auritulus larvae collected from the Spotted Towhee, Swainson’s Thrush, Pacific Wren, and Fox Sparrow suggest that these avian hosts act as reservoirs for B. burgdorferi. In this study, the western blacklegged tick, Ixodes pacificus, and Ixodes spinipalpis played a limited role in the enzootic transmission cycle of B. burgdorferi along coastal B.C. We document the first record of I. spinipalpis on a bird in Alberta. Because songbirds widely disperse Lyme disease vector ticks, primary health providers and the general public must be vigilant that outdoors people may be bitten by B. burgdorferi-infected ticks throughout far-western Canada.展开更多
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)for financial support through grants to D.J.M., D.R.N.,and A.E.M.N.the Animal Behaviour Society+1 种基金the American Ornithological Societythe Society of Canadian Ornithologists for research grants to S.L.D.
文摘The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.
基金funded by the Center for Forest Ecosystem Assessment(CFEA),USDA Forest Service,and Alabama A&M Universityadditional funding from the Alabama Ornithological Society and Birmingham Audubon Society
文摘Background: The early stage of forest succession following disturbance is characterized by a shift in songbird composition as well as increased avian richness due to increased herbaceous growth in the forest understory. However, regeneration of woody species eventually outcompetes the herbaceous understory, subsequently shifting vegetation communities and decreasing availability of vital foraging and nesting cover for disturbance-dependent birds, ultimately resulting in their displacement. These early stages following forest disturbance, which are declining throughout the eastern United States, are ephemeral in nature and birds depend on such disturbances for nesting and other purposes throughout their lives.Methods: We investigated the use of a two-stage shelterwood method to manage long-term persistence of seven early successional songbirds over a 13-year period in an upland hardwood forest within the southern end of the midCumberland Plateau in the eastern United States.Results: Canopy and midstory gaps created after initial harvest were quickly exploited by tree growth and canopy cover returned to these areas, accelerating the displacement of early-successional species. Woody stem densities increased substantially following stage two harvest as advanced tree regeneration combined with the re-opening of the overstory layer increased resource competition for early-successional plants in the understory. Carolina Wren(Thryothorus ludovicianus), Eastern Towhee(Pipilo erythrophthalmus), Indigo Bunting(Passerina cyanea), and Yellowbreasted Chat(Icteria virens) were characterized by immediate increases following initial harvest in 2001; while the American Goldfinch(Spinus tristis), Prairie Warbler(Setophaga discolor), and White-eyed Vireo(Vireo griseus) did not show an immediate response. Stage two harvest in 2011 rejuvenated vegetation which benefitted focal species, with six of seven species showing increases in densities between 2010 and 2012.Conclusion: The two-stage shelterwood method created conditions advantageous to early-successional birds by helping to re-establish understory vegetation through periodic disturbance to the canopy layer. This method provides evidence that early-successional species can be managed long-term(> 15 years) while using relatively small spatial disturbance through the two-stage shelterwood method.
文摘Worldwide, wild birds play a vital role in the dispersal of ticks that harbour tick-borne pathogens, including Borrelia burgdorferi, the Lyme disease bacterium. Using PCR testing, we found 124 (31%) of 405 ticks (4 species), which were collected from 21 species of birds in far-western Canada, to be infected with B. burgdorferi. Transstadial transmission of B. burgdorferi occurred from larva to nymph, plus nymph to adult, in the avian coastal tick, Ixodes auritulus, collected from songbirds in British Columbia (B.C). Collectively, all 3 motile life stages (larva, nymph, adult) of this tick had an infection prevalence of 31% for B. burgdorferi, which suggests vector competency. A Pacific Wren was highly infested with I. auritulus immatures, and 20 (44%) of 45 ticks (2 nymphs, 43 larvae) were infected with B. burgdorferi. This heavy infestation shows the high potential to initiate a new population of ticks and to disseminate Lyme spirochetes. Epidemiologically, B. burgdorferi-infected I. auritulus larvae collected from the Spotted Towhee, Swainson’s Thrush, Pacific Wren, and Fox Sparrow suggest that these avian hosts act as reservoirs for B. burgdorferi. In this study, the western blacklegged tick, Ixodes pacificus, and Ixodes spinipalpis played a limited role in the enzootic transmission cycle of B. burgdorferi along coastal B.C. We document the first record of I. spinipalpis on a bird in Alberta. Because songbirds widely disperse Lyme disease vector ticks, primary health providers and the general public must be vigilant that outdoors people may be bitten by B. burgdorferi-infected ticks throughout far-western Canada.
