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Insectivorous Birds (insectivorous + bird)
Selected AbstractsVariable strength of top-down effects in Nothofagus forests: bird predation and insect herbivory during an ENSO eventAUSTRAL ECOLOGY, Issue 4 2009C. NOEMI MAZIA Abstract Predators are thought to play a key role in controlling herbivory, thus having positive indirect effects on plants. However, evidence for terrestrial trophic cascades is still fragmentary, perhaps due to variation in top-down forces created by environmental heterogeneity. We examined the magnitude of predation effects on foliar damage by chewing insects and mean leaf size, by excluding birds from saplings in ,dry' and ,wet'Nothofagus pumilio forests in the northern Patagonian Andes, Argentina. The experiment lasted 2 years encompassing a severe drought during the La Niña phase of a strong El Niño/Southern Oscillation event, which was followed by unusually high background folivory levels. Insect damage was consistently higher in wet than in dry forest saplings. In the drought year (1999), bird exclusion increased folivory rates in both forests but did not affect tree leaf size. In the ensuing season (2000), leaf damage was generally twice as high as in the drought year. As a result, bird exclusion not only increased the extent of folivory but also significantly decreased sapling leaf size. The latter effect was stronger in the wet forest, suggesting compensation of leaf area loss by dry forest saplings. Overall, the magnitude of predator indirect effects depended on the response variable measured. Insectivorous birds were more effective at reducing folivory than at facilitating leaf area growth. Our results indicate that bird-initiated trophic cascades protect N. pumilio saplings from insect damage even during years with above-normal herbivory, and also support the view that large-scale climatic events influence the strength of trophic cascades. [source] Heavy Extinctions of Forest Avifauna in Singapore: Lessons for Biodiversity Conservation in Southeast AsiaCONSERVATION BIOLOGY, Issue 6 2000Marjorie Castelletta In Southeast Asia, Singapore, a newly developing country, has had 95% of its native lowland rainforest cleared. Most of the rainforest was lost in the mid- to late-nineteenth century. We compared avifauna checklists from 1923, 1949, and 1998 to determine the extent of extinctions between 1923 and 1998 in Singapore. Of 203 diurnal bird species, 65 were extirpated in Singapore in the past 75 years. Four of these species were nonforest- dependent species, whereas 61 (94%) were forest bird species dependent on the primary or old secondary forest to survive. Twenty-six forest bird species became extinct between 1923 and 1949, whereas 35 forest species disappeared after 1949. We compared the body lengths, feeding guilds, and vertical feeding zones between extinct and extant forest bird species to determine whether extinction patterns were dependent on these characteristics. Larger forest bird species went extinct between 1923 and 1949. Body sizes, however, did not affect the loss of forest bird species between 1949 and 1998. We observed high losses of insectivorous birds; the insectivore-carnivore and insectivore-granivore guilds lost> 80% of the species present in 1923. The highest losses were among birds that fed in the canopy. None of the forest bird species are currently common (>100 individuals/species) within Singapore. Our study shows that more than half the forest avifauna became locally extinct after extensive deforestation. Based on this fact, the countries within Southeast Asia should reconsider their heavy deforestation practices. Resumen: Las consecuencias de la tala rápida del bosque lluvioso sobre la avifauna nativa son poco conocidas. En Asia sudoriental, Singapur, un país en desarrollo, un 95% de su bosque nativo de tierras bajas ha sido talado. La mayoríia del bosque se perdió entre mediados y finales del siglo diecinueve. En este trabajo comparamos las listas de avifauna de 1923, 1949 y 1998 para determinar la extensión de las extinciones en Singapur entre 1923 y 1998. Sesenta y cinco de las 203 especies diurnas de aves fueron extirpadas de Singapur en los últimos 75 años. Cuatro de estas especies fueron especies no dependientes del bosque, mientras que 61 (94%) fueron especies de aves del bosque (especies que dependen del bosque primario o secundario viejo para sobrevivir). Veintiséis de las especies de aves del bosque se extinguieron entre 1923 y 1949, mientras que 35 especies del bosque desaparecieron después de 1949. Comparamos las longitudes del cuerpo, los gremios de alimentación y las zonas de alimentación vertical entre especies de aves de bosque extintas y existentes para determinar si los patrones de extinción fueron dependientes de estas características. Las especies de aves grandes del bosque se extinguieron entre 1923 y 1949. Sin embargo, el tamaño del cuerpo no afectó la pérdida de especies del bosque entre 1949 y 1998. Observamos altas pérdidas de aves insectívoras; los gremios de insectívoros-carnívoros e insectívoros-granívoros perdieron> 80% de las especies que estaban presentes en 1923. Los números más altos de pérdidas fueron de aves que se alimentan en el dosel. Ninguna de las especies de aves del bosque es común en la actualidad (>100 individuos/especie) dentro de Singapur. Nuestro estudio muestra que más de la mitad de la avifauna del bosque se ha extinguido localmente después de una deforestación extensiva. Con base en este hecho, los países dentro de Asia Sudoriental deberían reconsiderar sus prácticas de intensa deforestación. [source] Interannual changes in folivory and bird insectivory along a natural productivity gradient in northern Patagonian forestsECOGRAPHY, Issue 1 2004C. Noemi Mazía Trophic regulation models suggest that the magnitude of herbivory and predation (top-down forces) should vary predictably with habitat productivity. Theory also indicates that temporal abiotic variation and within-trophic level heterogeneity both affect trophic dynamics, but few studies addressed how these factors interact over broad-scale environmental gradients. Here we document herbivory from leaf-feeding insects along a natural rainfall/productivity gradient in Nothofagus pumilio forests of northern Patagonia, Argentina, and evaluate the impact of insectivorous birds on foliar damage experienced by tree saplings at each end of the gradient. The study ran over three years (1997,2000) comprising a severe drought (1998,1999), which allowed us to test how climatic events alter top-down forces. Foliar damage tended to increase towards the xeric, least productive forests. However, we found a predictable change of insect guild prevalence across the forest gradient. Leaf miners accounted for the greater damage recorded in xeric sites, whereas leaf chewers dominated in the more humid and productive forests. Interannual folivory patterns depended strongly on the feeding guild and forest site. Whereas leaf-miner damage decreased during the drought in xeric sites, chewer damage increased after the drought in the wettest site. Excluding birds did not affect leaf damage from miners, but generally increased chewer herbivory on hydric and xeric forest saplings. Indirect effects elicited by bird exclusion became most significant after the drought, when total folivory levels were higher. Thus, interannual abiotic heterogeneity markedly influenced the amount of folivory and strength of top-down control observed across the forest gradient. Moreover, our results suggest that spatial turnovers between major feeding guilds may need be considered to predict the dynamics of insect herbivory along environmental gradients. [source] Nestedness in fragmented landscapes: birds of the box-ironbark forests of south-eastern AustraliaECOGRAPHY, Issue 6 2002Ralph Mac Nally Nestedness in biota as a function of species richness , biota of depauperate assemblages being non-random subsets of richer biotas , has been widely documented in recent years (see Wright et al. 1998, Oecologia 113: 1,20). Ordering sites by richness maximizes nestedness indices; however, ordering by other criteria such as area or isolation may be more ecologically interpretable. We surveyed birds in true fragments (35 in all), and in "reference areas" in large extant forest blocks (30 locations), of the same range of areas (10, 20, 40, 80 ha). The avifauna was divided into "bush birds", species dependent on forest and woodland, and "open country" species. We looked at nestedness in four data sets: "bush birds" in fragments and reference areas, and "all birds" in fragments and in reference areas. All data sets were significantly nested. Ordering by area in all cases was not significantly less nested than ordering by richness. Ordering by area in fragments was significantly greater than in reference areas, but the differences in standardized nestedness indices were small (<15%). We identified those birds that had distributions among fragments that conformed strongly with area, those that were more randomly distributed and some species that were more likely to occupy the smallest fragments. Among the latter was a hyperaggressive, invasive, colonial native species (noisy miner Manorina melanocephala). A suite of small, insectivorous birds were more likely to strongly conform with expected distributions in relation to area, which was consistent with observations of their vulnerability to the effects of the noisy miner in smaller fragments. [source] Bioaccumulation and trophic transfer of polychlorinated biphenyls by aquatic and terrestrial insects to tree swallows (Tachycineta bicolor)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2006Jonathan D. Maul Abstract Insectivorous passerines often bioaccumulate polychlorinated biphenyls (PCBs) via trophic transfer processes. Tree swallows (Tachycineta bicolor) frequently are used for estimating PCB bioaccumulation, yet the focus on specific trophic links between contaminated sediment and bird has been limited. Bioaccumulation of PCBs from sediment to tree swallows was examined with focus on trophic pathways by simultaneously examining PCBs in emergent aquatic and terrestrial insects and gut contents of nestlings. Total PCB concentrations increased from sediment (123.65 ± 15.93 ,g/kg) to tree swallow nestlings (2,827.76 ± 505.67 ,g/kg), with emergent aquatic insects, terrestrial insects, and gut content samples having intermediate concentrations. Biota-sediment accumulation factors (BSAFs) varied among congeners for tree swallow nestlings and for male and female Chironomus spp. For nestlings, the highest BSAF was for the mono- ortho -substituted congener 118. Nestling biomagnification values were similar for gut contents and female Chironomus spp., suggesting this diet item may be the main contributor to the overall PCB transfer to nestlings. However, gut content samples were highly variable and, on a PCB congener pattern basis, may have been influenced by other taxa, such as terrestrial insects. Considering dietary plasticity of many insectivorous birds, the present study suggests that a variety of potential food items should be considered when examining PCB accumulation in insectivorous passerines. [source] Effects of bird predation on arthropod abundance and tree growth across an elevational gradientJOURNAL OF AVIAN BIOLOGY, Issue 4 2010W. Scott Schwenk Considerable uncertainty surrounds the conditions under which birds can cause trophic cascades. In a three-year experiment, we studied the direct and indirect effects of insectivorous birds on arthropod abundance, herbivory, and growth of striped maple Acer pensylvanicum saplings in a northern hardwood forest of central New Hampshire, USA. We manipulated bird predation by erecting exclosures around saplings and directly manipulated herbivory by removing herbivores. We also examined how climate modifies these interactions by replicating the experiment at three locations along an elevational gradient. Effects of bird predation were variable. Overall, mean arthropod biomass was 20% greater on saplings within bird exclosures than on controls (p<0.05). The mean biomass of leaf-chewing herbivores, primarily Lepidoptera larvae, was 25% greater within exclosures but not statistically different from controls. To a lesser degree, mean herbivore damage to foliage within exclosures exceeded that of controls but differences were not significant. We also did not detect significant treatment effects on sapling shoot growth. The high understory vegetation density relative to bird abundance, and low rate of herbivory during the study (mean 5% leaf area removed, controls), may have limited the ability of birds to affect sapling growth. Climate effects operated at multiple scales, resulting in a complex interplay of interactions within the food web. Regional synchrony of climatic conditions resulted in annual fluctuations in herbivore abundance and tree growth that were shared across elevations. At the same time, local environmental variation resulted in site differences in the plant, herbivore, and bird communities. These patterns resulted in a mosaic of top,down strengths across time and space, suggesting an overall pattern of limited effects of birds on plant growth, possibly interspersed with hotspots of trophic cascades. [source] Seasonal diets of insectivorous birds using canopy gaps in a bottomland forestJOURNAL OF FIELD ORNITHOLOGY, Issue 1 2007Christopher E. Moorman ABSTRACT Little is known about how insectivorous bird diets are influenced by arthropod availability and about how these relationships vary seasonally. We captured birds in forest-canopy gaps and adjacent mature forest during 2001 and 2002 at the Savannah River Site in Barnwell County, South Carolina, and flushed their crops to gather information about arthropods eaten during four periods: spring migration, breeding, postbreeding, and fall migration. Arthropod availability for foliage- and ground-gleaning birds was examined by leaf clipping and pitfall trapping. Coleopterans and Hemipterans were used by foliage- and ground-gleaners more than expected during all periods, whereas arthropods in the orders Araneae and Hymenoptera were used as, or less than, expected based on availability during all periods. Ground-gleaning birds used Homopterans and Lepidopterans in proportions higher than availability during all periods. Arthropod use by birds was consistent from spring through fall migration, with no apparent seasonal shift in diet. Based on concurrent studies, heavily used orders of arthropods were equally abundant or slightly less abundant in canopy gaps than in the surrounding mature forest, but bird species were most frequently detected in gaps. Such results suggest that preferential feeding on arthropods by foliage-gleaning birds in gap habitats reduced arthropod densities or, alternatively, that bird use of gap and forest habitat was not determined by food resources. The abundance of arthropods across the stand may have allowed birds to remain in the densely vegetated gaps where thick cover provides protection from predators. SINOPSIS Se conoce poco de como la dieta de insectívoros está influenciada por la disponibilidad de artrópodos y de como estas interacciones varían estacionalmente. Capturamos aves en huecos o aberturas del docel de un bosque, adyacente a un bosque maduro durante el 2001 y el 2002 en Savannah River Site, Condado Garnwell, Carolina del Sur. A las aves le lavamos el buche para obtener información sobre los artrópodos utilizados como alimento durante la migración primaveral, durante la época reproductiva, post-reproductiva y durante la migración otoñal. Para determinar la disponibilidad de artrópodos en el follaje y en el suelo, usamos la técnica de cortar hojas con artrópodos y la de trampas de envases en el suelo. Los coleópteros y los hemípteros fueron utilizados como fuente de alimento, más de lo esperado tanto por aves que se alimentaron en el follaje como en los suelos, durante todos los periodos. Por su parte, los arácnidos y los himenópteros, fueron utilizados menos de lo esperado, basándose en la disponibilidad de estos durante todos los periodos de estudio. Las aves que se alimentaron en los suelos utilizaron homópteros y lepidópteros en mayor proporción que lo esperado, dada su disponibilidad, durante todos los periodos. Los artrópodos utilizados por las aves fueron consistentes desde la primavera hasta la migración otoñal, sin que hubiera desplazamiento o cambios estacionales en la dieta. Basado en estudios concurrentes, los ordenes de artrópodos más utilizados como alimento, estuvieron en similar o un poco más bajo en abundancia en los huecos del docel que en los alrededores de bosque maduro, pero las especies de aves se detectaron con mayor frecuencia en los huecos. Estos resultados sugieren que la alimentación preferencial de artrópodos por aves que se alimentan buscando insectos entre el follaje en habitats con huecos, reducen la densidad de artrópodos, o que el uso de los huecos o de bosque maduro no esta determinado por los recursos alimentarios. La abundancia de artrópodos a lo largo del rodal puede haber permitido que la aves permanecieran en los huecos o aperturas con alta densidad de plantas, en donde el follaje provee de protección contra los depredadores. [source] Light dependent shift in the anti-predator response of a pyralid mothOIKOS, Issue 2 2003A. Monica Svensson Male small china-mark moth Cataclysta lemnata (Pyralidae) swarming over shallow water show a flight activity that peaks during the afternoon but which sometimes is extended into the night. We exposed wild, naturally flying C. lemnata to simulated predator attacks consisting of a) bursts of ultrasound (26 kHz, simulating a bat) and b) a thrown stick (rapid movement, simulating a small bird), during day and night, respectively. We thus investigated the possibility that these moths are able to switch between defensive strategies as the predator regime shifts from insectivorous birds to bats in the evening. The defensive response differed qualitatively between day and night, as expected, but it was independent of the kind of stimulus. We thus demonstrate a previously unknown flexibility in the defensive strategy of moths. [source] Ranging behavior and habitat selection of terrestrial insectivorous birds in north-east Tanzania: implications for corridor design in the Eastern Arc MountainsANIMAL CONSERVATION, Issue 5 2010W. D. Newmark Abstract Understanding the ranging behavior and habitat selection of understory tropical birds is important for corridor design and enhancing functional connectivity in fragmented tropical landscapes. Here we report on the ranging behavior and habitat selection of three terrestrial insectivorous bird species, the spot-throat Modulatrix stictigula, Usambara thrush Turdus roehli and orange ground thrush Zoothera gurneyi, in the East (EUM) and West (WUM) Usambara Mountains in north-east Tanzania. Based on 5945 locations and 3676 bird radio-tracking hours conducted between 2001 and 2008 at four study sites in the EUM and WUM, we determined that the 95% kernel home range and 50% kernel core range for the spot-throat, Usambara thrush, and orange ground thrush are similar yet large (aggregate mean home range=10.3±1.1 ha; aggregate mean core range 1.5±0.4 ha); that these species are adverse to crossing non-forested openings , no bird was recorded over the course of the study to cross a non-forested opening >15 m; and that the most extinction-prone species in our study system, the spot-throat and Usambara thrush, preferentially used slightly disturbed and primary forest, respectively. These results indicate that maintaining continuous forest cover and minimizing forest disturbance in corridors in the Eastern Arc Mountains is important for enhancing their habitat suitability for these species. [source] Pest reduction services by birds in shade and sun coffee in JamaicaANIMAL CONSERVATION, Issue 2 2010M. D. Johnson Abstract The reduction of insect pests by birds in agriculture may provide an incentive for farming practices that enhance the conservation value of farms for birds and other wildlife. We investigated pest reduction services by insectivorous birds on a coffee farm in Jamaica, West Indies. Our results suggest that birds reduced insect pests on our study site. Infestation by the coffee berry borer Hypothenemus hampei, the world's most damaging insect pest in coffee, was significantly elevated on coffee shrubs from which birds were experimentally excluded from foraging. Overall, we estimated the economic value of the reduction of coffee berry borer by birds on the 18 ha farm to be US$310 ha,1 for the 2006 harvest season. These results provide additional evidence that birds can reduce numbers of economically damaging pests and enhance crop yields in coffee farms. Differences in the magnitude of pest reduction within the farm may have resulted from variation in shade management and surrounding habitats, and these factors merit further investigation. [source] Effects of surface fires on understorey insectivorous birds and terrestrial arthropods in central Brazilian AmazoniaANIMAL CONSERVATION, Issue 4 2003Torbjørn Haugaasen Understorey insectivorous birds are highly vulnerable to different forms of habitat disturbance in tropical forests. Here we examine the effects of an unprecedented surface fire on understorey insectivores and forest litter arthropods in a terra firme forest of central Brazilian Amazonia, and compare species and guild abundance both close to and far from the clearly distinguishable fireline separating burnt and unburnt forest. All six of the most abundant insectivorous foraging guilds examined were detrimentally affected by fire, with dead-leaf gleaners and professional ant-followers being the most heavily affected. While army ants were apparently absent from the burnt forest, results from pit-fall traps showed that wildfires had only a limited effect on the abundance of most leaf-litter invertebrates. The fireline appeared to be an abrupt barrier to many understorey insectivorous birds, and there was little evidence to suggest that primary forest species were recolonizing burnt forest up to 1 year after the fires. Factors affecting the capture frequency of insectivorous birds are discussed. [source] Arthropod prey of shelterbelt-associated birds: linking faecal samples with biological control of agricultural pestsAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2007Sagrario Gámez-Virués Abstract, The value of insectivorous birds as agents for biological control of arthropod pests has been little studied, especially in Australia. This paper reports on the extent to which arthropods from various pest and non-pest taxa feature in the diets of birds captured in farm shelterbelts in central western New South Wales. The parameters examined were the types of arthropod fragments in bird faeces and percentage volume and frequency of occurrence of each component. The faecal data were compared with samples of the arthropod fauna trapped in shelterbelts during the period the birds were captured. In 26 of 29 faecal samples, arthropod fragments were the predominant components, the most common being from Coleoptera, Hymenoptera (especially Formicidae), Orthoptera and Araneae. The recognisable pest taxa in faecal samples were Scarabaeidae and wingless grasshopper Phaulacridium vittatum (Sjöstedt) (Orthoptera: Acrididae). The results indicate that the native bird species common in farm shelterbelts preyed on a range of arthropod taxa including several that are pests of crops and pastures. Accordingly, conservation of birds in farmlands could contribute to suppression of arthropod pests. [source] Importance of colour in the reaction of passerine predators to aposematic prey: experiments with mutants of Pyrrhocoris apterus (Heteroptera)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2006ALICE EXNEROVÁ Persistent questions concerning the warning coloration of unpalatable insects address whether the bright aposematic colour itself or its combination with a species-specific dark pattern is the key factor in their protection against insectivorous birds, and how chromatic polymorphism originates and is maintained in aposematics. In the present study, these questions were tested experimentally, using the birds Parus major, Parus caeruleus, Erithacus rubecula, and Sylvia atricapilla as predators, and chromatically polymorphic firebug Pyrrhocoris apterus: red wild form, white, yellow, and orange mutants (all four of them with the same black melanin pattern, the mutants differing in colour of pteridine pigments only) and the nonaposematic brown-painted wild form as prey. The results show that a specific colour is essential for the birds to recognize the specific aposematic prey; the melanin pattern is not sufficient. White mutants were no better protected than nonaposematic firebugs; red wild-type and orange mutants were equally well protected against all bird species; and the reaction of birds to yellow mutants was species-specific. An evolutionary scenario of 'recurrent recessive mutations' is formulated to explain the origin of colour polymorphism in some aposematics. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 143,153. [source] Effects of Shade-Tree Species and Crop Structure on the Winter Arthropod and Bird Communities in a Jamaican Shade Coffee Plantation,BIOTROPICA, Issue 1 2000Matthew D. Johnson ABSTRACT I examined the effects of two farm management variables, shade-tree species and crop structure, on the winter (dry season) arthropod and bird communities in a Jamaican shade coffee plantation. Birds and canopy arthropods were more abundant in areas of the plantation shaded by the tree Inga vera than by Pseudalbizia berteroana. The abundance of arthropods (potential pests) on the coffee crop, however, was unaffected by shade-tree species. Canopy arthropods, particularly psyllids (Homoptera), were especially abundant on Inga in late winter, when it was producing new leaves and nectar-rich flowers. Insectivorous and nectarivorous birds showed the strongest response to Inga; thus the concentration of birds in Inga may be a response to abundant food. Coffee-tree arthropod abundance was much lower than in the shade trees and was affected little by farm management variables, although arthropods tended to be more abundant in dense (unpruned) than open (recently pruned) areas of the plantation. Perhaps in response, leaf-gleaning insectivorous birds were more abundant in dense areas. These results underscore that although some shade coffee plantations may provide habitat for arthropod and bird communities, differences in farm management practices can significantly affect their abundances. Furthermore, this study provides evidence suggesting that bird communities in coffee respond to spatial variation in arthropod availability. I conclude that /. vera is a better shade tree than P. berteroana, but a choice in crop structures is less clear due to changing effects of prune management over time. [source] | ||||||||||||||||||||||