Search

Neotropical shade-grown coffee systems are renowned for their potential to conserve avian biodiversity. Yet, little is known about food resources consumed by insectivorous birds in these systems, the extent of resource competition between resident and migratory birds, or how management of shade trees might influence diet selection. We identified arthropods in stomach contents from obligate and generalist insectivorous birds captured in mist-nets at five coffee farms in Chiapas, Mexico between 2001-2003. Overall stomach contents from 938 individuals revealed dietary differences resulting from changes in seasons, years, and foraging guilds. Of four species sampled across all management systems, Yellow-green Vireo (Vireo flavoviridis) prey differed depending on coffee shade management, consuming more ants in shaded monoculture than polyculture systems. Diets of obligate and generalist resident insectivores were 72% dissimilar with obligate insectivores consuming more Coleoptera and Araneae, and generalist insectivores consuming more Formicidae and other Hymenoptera. This suggests that obligate insectivores target more specialized prey whereas generalist insectivores rely on less favorable, chemically-defended prey found in clumped distributions. Our dataset provides important natural history data for many Nearctic-Neotropical migrants such as Tennessee Warbler (Leiothlypis peregrina; N = 163), Nashville Warbler (Leiothlypis ruficapilla; N = 69), and Swainson's Thrush (Catharus ustulatus; N = 68) and tropical residents including Red-legged Honeycreepers (Cyanerpes cyaneus; N = 70) and Rufous-capped Warblers (Basileuterus rufifrons; N = 56). With declining arthropod populations worldwide, understanding the ecological interactions between obligate and generalist avian insectivores gives researchers the tools to evaluate community stability and inform conservation efforts. [ABSTRACT FROM AUTHOR]

The rusty blackbird (Euphagus carolinus) is a species of conservation concern throughout its range because of rapid population decline. During winter, relatively large flocks are in suburban landscapes within the Georgia and South Carolina Piedmont Plateau of the southeastern United States. We studied radio‐tagged blackbirds within flocks that moved daily among 3 distinct patch types: pecan (Carya illinoinensis) and small‐seeded oak (Quercus spp.) groves, shallowly flooded forested wetlands, and residential areas landscaped with turf grass. The patch types used for foraging have varying availability of invertebrate and mast food. We investigated the relationship between daily observations of blackbird flocks and previous, current, and oncoming short‐term weather. Suburban landscapes with the appropriate configuration of shallow wetland, residential lawns, and mast grove patches within a 153–415‐ha area, the size of patch aggregations in this study, likely constitute high quality wintering areas for this species. Blackbird flocks were 1.6–1.8 times more likely to be observed foraging in wetlands with each 10°C increase in current temperature, 1.5 times more likely in wetlands for every 5 days with no previous precipitation, and 3.2 times more likely in wetlands with every 10 extra hours of oncoming cold weather. Blackbirds were 4.1–4.5 times less likely to be observed foraging in forested wetlands with every 5‐mm increase in current precipitation. Blackbirds were 2.2 times more likely to be observed in mast groves with every 5‐mm of oncoming precipitation. Radio‐tagged blackbirds used pecan groves for foraging in 2011 but not 2012, which was an overall warmer winter. Pecan groves may be a sporadically used component of a combination of foraging patches that are rarely near flooded forested wetlands or residential areas. Our results can be used to identify and conserve patch components used by rusty blackbird flocks during winter in suburban nature parks and greenways. © 2018 The Wildlife Society. Management for rusty blackbird flocks in anthropogenic landscapes should consider flocks use a combination of distinct patch types in relation to short‐term weather events. Patches of exotic resources such as earthworms and pecans likely allow small wetland fragments to be useful for wintering rusty blackbirds by providing abundant nutrient‐rich resources during weather conditions when wetland invertebrates are not available. [ABSTRACT FROM AUTHOR]

Subspecific genetic diversity is a source for ongoing evolutionary processes, can be predictive of a population's ability to respond to conservation challenges, and may represent the raw material for incipient speciation. As such, diagnosable subspecies are increasingly recognized as an important unit for conservation. Differentiating among subspecies can be particularly difficult in ecosystems characterized by recent phenotypic divergence, such as the tidal marshes of North America. These systems require approaches that can capture selective changes which occurred over only a few millennia as species adapted to new habitats following the Holocene glacial retreat. Here we test for genetic differentiation in morphologically distinct tidal-marsh-endemic subspecies of the swamp sparrow ( Melospiza georgiana) using nuclear microsatellites. This case study serves as a test approach for the quantification of conservation units for tidal marsh ecosystems. Though prior surveys of mtDNA variation showed no detectable phylogeographic structure, we found evidence of genetic differentiation in seven microsatellite loci between two M. georgiana subspecies. The most likely model of population structure suggested two clusters in western Maryland/Pennsylvania and Delaware/Chesapeake Bays, with a zone of uncertain population assignment in New Jersey. The microsatellite intergrade zone is broader than the known area of morphological intergrades. We show that microsatellites can be used to support a subspecific status for tidal-marsh taxa such as the swamp sparrow, where changing post-glacial environments likely selected for locally adapted traits while neutral genetic structure is weak. This approach thus allows for the identification and conservation of hot spots that foster ongoing evolutionary change. [ABSTRACT FROM AUTHOR]

ABSTRACT The rusty blackbird ( Euphagus carolinus) is a species of conservation concern throughout its range and the cause of the species' population decline is unknown. We studied diet composition of rusty blackbirds with stable isotope mixing models in suburban landscapes in the southeastern United States. We captured blackbirds in Georgia and South Carolina from 2009 to 2012, and estimated proportions of earthworm, other animals, pecan, and acorn incorporated into individual diets. On the Piedmont Plateau, terrestrial and aquatic earthworms constituted the largest proportion incorporated into the diet (39% ± 2.9; mean ± SD by site and year) and animals other than earthworms (mostly larval invertebrates Odonata and Diptera) constituted 27% ± 12.9. In contrast, on the Coastal Plain, which featured milder winters than the Piedmont, earthworms constituted a lower proportion (19% ± 1.2) of incorporated food items and animals other than earthworms comprised 62% ± 3.3% of the diet. Increased incorporation of earthworms in the diet was related to increased upcoming precipitation and daily maximum temperature. Rusty blackbirds incorporated more tree mast into their diet on the Piedmont Plateau than the Coastal Plain. Increased incorporation of tree mast was related to advancing cold temperature. Mast, including crushed pecans ( Carya illinoenensis) and pre-opened small-seeded red oak ( Quercus spp.) acorns, is a high-lipid dietary component of blackbirds wintering in colder climates, and is incorporated prior to extreme cold weather. Therefore, planting mast trees, especially lipid-rich pecan, could be used to augment resources in known rusty blackbird wintering hotspots. Maintaining shallowly flooded wetlands with a fluctuating water regime and residential lawns with abundant red oak ( Quercus spp.) leaf litter would promote acorn and invertebrate resources including earthworms. © 2015 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Bird habitat quality is often inferred from species abundance measures during the breeding and non-breeding season and used for conservation management decisions. However, during the non-breeding season age and sex classes often occupy different habitats which suggest a need for more habitat-specific data. Rusty Blackbird (Euphagus carolinus) is a forested wetland specialist wintering in bottomland hardwood forests in the south-eastern U. S. and belongs to the most steeply declining songbirds in the U.S. Little information is available to support priority birds such as the Rusty Blackbird wintering in this threatened habitat. We assessed age and sex distribution and body condition of Rusty Blackbirds among the three major habitats used by this species in the Lower Mississippi Alluvial Valley and also measured food availability. Overall, pecan groves had the highest biomass mainly driven by the amount of nuts. Invertebrate biomass was highest in forests but contributed only a small percentage to overall biomass. Age and sex classes were unevenly distributed among habitats with adult males primarily occupying pecan groves containing the highest nut biomass, females being found in forests which had the lowest nut biomass and young males primarily staying in forest fragments along creeks which had intermediate nut biomass. Males were in better body condition than females and were in slightly better condition in pecan groves. The results suggest that adult males occupy the highest quality habitat and may competitively exclude the other age and sex classes. [ABSTRACT FROM AUTHOR]

Aim Bill size is positively correlated with average air temperature in several avian taxa. The conventional explanation for this pattern is that the poorly insulated surface area of the bill functions to dissipate excess heat in hot climates or retain heat in cold climates (Allen's rule). We hypothesize that the applicability of Allen's rule depends upon the season of critical thermal stress, which may vary by location and species. We previously found that bill size increases with high summer temperature in song sparrows ( Melospiza melodia) of California, supporting the hypothesis that larger bills are an adaptation to release dry heat and minimize evaporative water loss in a hot, dry environment. Song sparrows in eastern North America face a different climatic regime, in which summers are warm but moist, and winters are cold. We predicted that this climate region would select for smaller bills to minimize heat loss. Location From coastal Delaware and Maryland to the Allegheny Plateau of the eastern USA. Methods We measured body size and bill morphology of 274 song sparrow individuals across a climatic gradient and geographical gradient. We used linear regression models to test for effects of geographical location and 30-year means of minimum winter and maximum summer temperatures and annual rainfall on bill size. Results Bill size was best predicted by, and positively correlated with, cold winter temperatures and distance from the Atlantic coast. Body size did not change substantially with distance from the coast, indicating that the pattern of bill size was not a result of allometry. Coastal birds had bills larger than predicted by a linear effect of minimum temperature. Main conclusions Collectively, these results support the hypothesis that variation in bill size reflects selection for winter heat retention rather than for summer heat dissipation. Bill size may be shaped by physiological responses to regional climates, and the season of critical thermal stress may vary geographically, even on relatively small spatial scales. [ABSTRACT FROM AUTHOR]

Copyright of Auk: Ornithological Advances is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Condor: Ornithological Applications is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plantations of non-native, fast-growing trees are increasing in the tropics and subtropics, perhaps with negative consequences for the native avifauna. We studied bird diversity in 4 types of plantations in South China to determine which plantation types are especially detrimental, and compared our findings with studies in nearby natural forests to assess the magnitude of the negative impact. A total of 57 species was recorded. The mean capture rate of understory birds was 1.7 individuals 100-net-h-1. Bird richness and capture rate were lower in plantations than in nearby natural forests. Babblers (Timaliidae), primarily forest-dependent species in South China, were particularly under-represented in plantations. Species richness, composition and bird density, particularly of understory birds, differed between plantation types. Plantations of Schima, which is native to South China, had the highest species richness according to point count data. Plantations of Acacia (non-native) supported the highest understory species richness and produced the highest capture rate of understory birds, probably because of their complex structure and high arthropod abundance. If bird diversity is to be considered, we strongly recommend that future re-afforestation projects in South China should, as far as possible, use mixed native tree species, and especially Schima, ahead of the other species. [ABSTRACT FROM AUTHOR]

The Winter Food Limitation Hypothesis (WFLH) states that winter food abundance is a dominant source of population limitation of migratory birds. Evidence is accumulating that long-distance migratory birds wintering in tropical climates have high overwinter survival probabilities and that winter food limitation mainly affects their fitness nonlethally by limiting energetic reserves necessary for successful reproduction. In contrast, the relative roles of direct mortality vs. indirect effects caused by food limitation have not been investigated thoroughly on short-distance migratory birds wintering in temperate zones, where they face thermal challenges. We performed the first test of the WFLH for a temperate migratory bird in the wild on the Swamp Sparrow (Melospiza georgiana), with a replicated plot-wide food supplementation experiment. In contrast to tropical, but consistent with other temperate-wintering migrants, Swamp Sparrows on unmanipulated plots showed relatively low apparent survival across the winter. Following food addition, birds (1) immigrated to experimental plots, which subsequently supported --50% higher abundances, (2) experienced increases of within-season apparent survival of 8-10%, depending on age/sex class, and (3) had higher-scaled mass index values, all supporting winter food limitation. The last two findings are interrelated because birds with higher scaled mass had higher survival probabilities, further supporting direct effects of winter food limitation. Food limitation of fat reserves might also have indirect effects on reproductive success by limiting migration timing and survival during migration. Increases in scaled mass were higher in females, suggesting that they are disproportionately affected by food limitation, possibly through competition. Based on Robust Design Modeling, we found no support for emigration prior to food addition, indicating that our estimates of mortality are unbiased. [ABSTRACT FROM AUTHOR]

Female sparrows prefer bigger bills, causing the evolution of distinctly different bill sizes for males and females. The size and shape of a bird’s bill has historically been viewed only as an adaptation for eating, but in at least one species of sparrow, bill size differences echo female mating preferences better than diet. Older males have larger bills, so females who mate with larger billed males get the advantage of more experienced mates that have proven their ability to survive.The evolutionary origins of sexual dimorphism are credited to both natural and sexual selection. Sexual dimorphism in feeding structures, however, provides some of the clearest examples of ecologically driven dimorphism. Studies of bird bills have significantly aided these claims, but bird bills are also commonly used in pair formation behaviors, and thus their morphology could be subject to sexual selection. We tested 4 hypotheses of the evolution of sexual dimorphism using the feeding structure of a sexually dimorphic and a nondimorphic subspecies of the swamp sparrow, Melospiza georgiana. The increased bill volume of males was not explained by simple allometric relationships, ecological niche divergence between the sexes, or correlations with territory defense. Male bill volume was positively selected by female mate choice, as relative male bill volume predicted both the presence of and degree of cuckoldry. Further, male bill volume increased with age, and females may thus receive benefits by choosing larger billed males for social (direct benefits) or extrapair (indirect benefits) mates. It is clear from this example that sexual selection can play a role in the evolution of sexually dimorphic feeding structures, even in bird bills, which are a classic system for ecologically driven sexual dimorphism. [ABSTRACT FROM PUBLISHER]

Speciation is promoted when traits under divergent selection also contribute to non-random mating. For example, divergent selection on bill morphology in birds can influence song because of the role of bills in song production (ecomorphological constraints). Since song is used by females to find appropriate mates, divergent selection on bills through its impact on song can promote non-random mating. However, because song in songbirds is learned, divergence in song between populations could be the result of cultural influences (cultural evolution). In this study, we use an experimental approach to address the relative influence of ecomorphological constraints and culture on song divergence in swamp sparrow subspecies (Melospiza georgiana). As with other songbirds, swamp sparrows are subject to cultural influences that may explain differences in song between subspecies (cultural evolution). However, ecological conditions promote larger bill size in the coastal subspecies of swamp sparrows rendering males unable to perform the broad-band, rapid songs that inland females prefer potentially contributing to non-random mating between sub-species. To determine the impact of ecomorphological constraints on song learning, we trained hand-raised swamp sparrows from divergent populations with an identical set of tutor songs from a foreign inland population. Males from both populations learned species typical songs. We found that inland males produced learned songs with better vocal performance than coastal males suggesting that observed differences in specific features of song are influenced more by morphological constraints than cultural drift. Further, we found that inland males reproduced tutor songs more accurately than coastal males suggesting that coastal males tried but were less able to accurately reproduce physically challenging songs. These results support the current model for how motor constraints influence song production and may demonstrate a mechanism by which natural selection can influence signal evolution and population divergence through divergent selection on bills. [ABSTRACT FROM AUTHOR]

Tidal marshes present profound adaptive challenges to terrestrial vertebrates. For example, North American sparrows have relatively longer and thinner bills and darker dorsal plumage in coastal saltmarshes than in interior marshes. Bay-capped wren- spinetail ( Furnariidae; Spartonoica maluroides) show a strong association with South American saltmarshes. We hypothesized that bay-capped wren- spinetail have similar morphological adaptations to North American sparrows to the saltmarsh environment, which would be indicative of the generality of selection on these traits in the coastal saltmarsh ecosystem. We captured individuals of S. maluroides from coastal saltmarshes and interior marshes. Populations were compared based on morphology and molecular markers. We found significant phenotypic differences in bill shape and plumage coloration (melanism) between S. maluroides populations from coastal and inland marshes. The low levels of genetic variation, weak geographical structure and shallow divergences, based on mitochondrial DNA and microsatellite data, suggest that coastal populations had a recent demographic expansion. Our results are consistent with the pattern of morphological divergence found between North American Emberizids. The possibility of convergent evolutionary adaptations between saltmarsh North American Emberizids and South American Furnariids suggests that there are strong selective pressures associated with saltmarsh environments on the beak, leading to adaptations for food acquisition, and on plumage coloration for better camouflage for predator avoidance (melanism). © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 78-91. [ABSTRACT FROM AUTHOR]

Environments undergo short-term and long-term changes due to natural or human-induced events. Animals differ in their ability to cope with such changes which can be related to their ecology. Changes in the environment often elicit avoidance reactions (neophobia) which protect animals from dangerous situations but can also inhibit exploration and familiarization with novel situations and thus, learning about new resources. Studies investigating the relationship between a species’ ecology and its neophobia have so far been restricted to comparing only a few species and mainly in captivity. The current study investigated neophobia reactions to experimentally-induced changes in the natural environment of six closely-related blackbird species (Icteridae), including two species represented by two distinct populations. For analyses, neophobic reactions (difference in number of birds feeding and time spent feeding with and without novel objects) were related to several measures of ecological plasticity and the migratory strategy (resident or migratory) of the population. Phylogenetic relationships were incorporated into the analysis. The degree of neophobia was related to migratory strategy with migrants expressing much higher neophobia (fewer birds feeding and for a shorter time with objects present) than residents. Furthermore, neophobia showed a relationship to diet breadth with fewer individuals of diet generalists than specialists returning when objects were present supporting the dangerous niche hypothesis. Residents may have evolved lower neophobia as costs of missing out on opportunities may be higher for residents than migrants as the former are restricted to a smaller area. Lower neophobia allows them approaching changes in the environment (e.g. novel objects) quickly, thereby securing access to resources. Additionally, residents have a greater familiarity with similar situations in the area than migrants and the latter may, therefore, initially stay behind resident species. [ABSTRACT FROM AUTHOR]

. 1. Neotropical organisms have evolved in an environment of relatively low temporal variation in food availability, but when neotropical forests are converted to agriculture, the temporal patchiness of food resources is increased. Plant species with a continuous (i.e. steady-state) flowering/fruiting phenology are unique to the tropics and may more evenly distribute food resources temporally in agroecosystems. 2. Here, we test the effects of an experimentally planted supplemental steady-state floral resource, Hamelia patens Jacq., on bee diversity and pollination services in coffee agroforests. In addition, we evaluate effects of the steady-state resource during low-density and mass coffee blooms. 3. Malaise trap data indicated that bee species density was significantly higher in coffee agroforests with the supplemental steady-state floral resources [11.89 ± 1.62 (SE)] compared to those without (8.88 ± 1.10). 4. The steady-state floral resource had a negative impact on native bee visits to coffee flowers and a positive impact on Apis mellifera visits to coffee flowers (e.g. during low-density blooms agroforests with steady-state resources had 76% fewer native bee and 130% more A. mellifera visits to coffee flowers). Although coffee initial fruit set rates were higher across all agroforests during low-density blooms (0.74 ± 0.03) compared to the mass bloom (0.59 ± 0.03), steady-state floral resources did not affect initial fruit set rates ( Z = −1.05, P = 0.29). 5. Our results suggest that plants with a steady-state phenology can provide more reliable resources for bees, supporting the conservation of wild bees in agroforests. However, steady-state flowering may draw native bees away from the focal crop, especially during low-density flowering. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hypothesis is tested that birds in hotter and drier environments may have larger bills to increase the surface area for heat dissipation. California provides a climatic gradient to test the influence of climate on bill size. Much of California experiences dry warm/hot summers and coastal areas experience cooler summers than interior localities. Based on measurements from 1488 museum skins, song sparrows showed increasing body-size-corrected bill surface area from the coast to the interior and declining in the far eastern desert. As predicted by Newton's convective heat transfer equation, relative bill size increased monotonically with temperature, and then decreased where average high temperatures exceed body temperature. Of the variables considered, distance from coast, average high summer temperature, and potential evapotranspiration showed a strong quadratic association with bill size and rainfall had a weaker negative relationship. Song sparrows on larger, warmer islands also had larger bills. A subsample of radiographed specimens showed that skeletal bill size is also correlated with temperature, demonstrating that bill size differences are not a result of variation in growth and wear of keratin. Combined with recent thermographic studies of heat loss in song sparrow bills, these results support the hypothesis that bill size in California song sparrows is selected for heat dissipation. [ABSTRACT FROM AUTHOR]

We estimated mercury exposure and bioaccumulation in sparrow feathers to determine variation among age groups, between sparrow species, and between feather types. Results of feather mercury studies in piscivorous birds indicate that mercury concentrations tend to increase with age and differ between feather types; however, data for insectivorous birds are lacking. We estimated mercury exposure of two insectivorous and sympatric tidal marsh sparrows: coastal plain swamp sparrow ( Melospiza georgiana nigrescens), and seaside sparrow ( Ammodramous maritimus). Tidal marshes have favorable conditions for mercury methlyation, thus it is likely that tidal marsh sparrows are exposed to methylmercury. We found no difference in mercury concentrations between males and female birds of both species. Adult swamp sparrow feather mercury concentrations did not differ among adult age groups; therefore, mercury was not found to increase with age in sparrows at the site. Hatch-year birds had significantly greater feather mercury concentrations compared with adult birds for both species. Mercury concentrations in adult seaside sparrows were twice as high as those in adult swamp sparrows suggesting species-specific variation, although concentrations in hatch-year sparrow species did not differ. Mercury concentrations differed between feather types in adults of both species. The first primary feather of both species had at least three times greater mercury concentrations than the outer tail feather possibly reflecting varying depuration rates with feather type. [ABSTRACT FROM AUTHOR]

Background: Research on variation in bill morphology has focused on the role of diet. Bills have other functions, however, including a role in heat and water balance. The role of the bill in heat loss may be particularly important in birds where water is limiting. Song sparrows localized in coastal dunes and salt marsh edge (Melospiza melodia atlantica) are similar in size to, but have bills with a 17% greater surface area than, those that live in mesic habitats (M. m. melodia), a pattern shared with other coastal sparrows. We tested the hypotheses that sparrows can use their bills to dissipate ''dry'' heat, and that heat loss from the bill is higher in M. m. atlantica than M. m. melodia, which would indicate a role of heat loss and water conservation in selection for bill size. Methodology/Principal Findings: Bill, tarsus, and body surface temperatures were measured using thermal imaging of sparrows exposed to temperatures from 15-37°C and combined with surface area and physical modeling to estimate the contribution of each body part to total heat loss. Song sparrow bills averaged 5-10°C hotter than ambient. The bill of M. m atlantica dissipated up to 33% more heat and 38% greater proportion of total heat than that of M. m. melodia. This could potentially reduce water loss requirements by approximately 7.7%. Conclusions/Significance: This >30% higher heat loss in the bill of M. m. atlantica is independent of evaporative water loss and thus could play an important role in the water balance of sparrows occupying the hot and exposed dune/salt marsh environments during the summer. Heat loss capacity and water conservation could play an important role in the selection for bill size differences between bird populations and should be considered along with trophic adaptations when studying variation in bill size. [ABSTRACT FROM AUTHOR]

Physiological factors are rarely proposed to account for variation in the morphology of feeding structures. Recently, bird bills have been demonstrated to be important convective and radiant heat sinks. Larger bills have greater surface area than smaller bills and could serve as more effective thermoregulatory organs under hot conditions. The heat radiating function of bills should be more important in open habitats with little shade and stronger convective winds. Furthermore, as a means of dumping heat without increasing water loss through evaporation, bills might play a particularly important thermoregulatory role in heat loss in windy habitat where fresh water is limited. North American salt marshes provide a latitudinal gradient of relatively homogeneous habitat that is windy, open, and fresh-water limited. To examine the potential role of thermoregulation in determining bill size variation among ten species or subspecies of tidal marsh sparrows, we plotted bill size against maximum summer and minimum winter temperatures. Bill surface areas increases with summer temperature, which explained 82-89% of the variance (depending upon sex) when we controlled for genus membership. Latitude alone predicted bill surface area much more poorly than summer temperature, and winter temperatures explained < 10% of the variance in winter bill size. Tidal marsh sparrow bill morphology may, to a large degree, reflect the role of the bill in expelling excess body heat in these unbuffered, fresh-water-limited environments. This new example of Allen's rule reaffirms the importance of physiological constraints on the evolution of vertebrate morphologies, even in bird bills, which have conventionally been considered as products of adaptation to foraging niche. [ABSTRACT FROM AUTHOR]

Insectivorous Western Bluebirds (Sialia mexicana) occupy vineyard nest boxes established by California winegrape growers who want to encourage avian conservation. Experimentally, the provision of available nest sites serves as an alternative to exclosure methods for isolating the potential ecosystem services provided by foraging birds. We compared the abundance and species richness of avian foragers and removal rates of sentinel prey in treatments with songbird nest boxes and controls without nest boxes. The average species richness of avian insectivores increased by over 50 percent compared to controls. Insectivorous bird density nearly quadrupled, primarily due to a tenfold increase in Western Bluebird abundance. In contrast, there was no significant difference in the abundance of omnivorous or granivorous bird species some of which opportunistically forage on grapes. In a sentinel prey experiment, 2.4 times more live beet armyworms (Spodoptera exigua) were removed in the nest box treatment than in the control. As an estimate of the maximum foraging services provided by insectivorous birds, we found that larval removal rates measured immediately below occupied boxes averaged 3.5 times greater than in the control. Consequently the presence of Western Bluebirds in vineyard nest boxes strengthened ecosystem services to winegrape growers, illustrating a benefit of agroecological conservation practices. Predator addition and sentinel prey experiments lack some disadvantages of predator exclusion experiments and were robust methodologies for detecting ecosystem services. [ABSTRACT FROM AUTHOR]

The article discusses a study to find out why island passerine birds have bigger bills than their cousins on mainland areas. It suggests that this could be due to the lesser diversity of avian species on islands compared to their mainland counterparts. It reports that this theory is contradicted by the discovery that emberizid sparrows located in the salt marshes of North America also have bigger bills. In 2010, the research concluded that proximity to salt water produces birds with bigger bills, and that this is not confined only to islands.

The article presents a study which investigates the implications on aging rusty blackbirds of the prebasic and previously undescribed prealternate molt at Whitehorse, Yukon Territory. It says that a Friedman test was used in the study to compare molt intensity in feather and a Kruskal-Wallis test to test the molt intensity variation of the aging rusty blackbirds. The result of the study shows that presence of the pale-eye ring can be used to identify the age of aging birds along with the chin.

The article offers a study on stable hydrogen isotopes in feathers of rusty blackbirds (Euphagus carolinus) in Mississippi Alluvial Valley and coastal South Carolina and Virginia, and in museum specimens from 1879 to 1990 to determine a migratory connectivity. It says that modern and historical isotopic analyses show a difference in the breeding origins of birds wintering in those regions. Moreover, it suggests that wildlife management should be tailored on both breeding and wintering grounds.

The article presents the findings of a study of the International Rusty Blackbird Working Group on the factors that influenced the decline in population of Rusty Blackbird. According to survey, the rates of population decline range from nearly 5-12% annually. It says that while the bird relies on wooded wetlands, the loss or destruction of these habitats is a major factor. It adds that global warming and environmental contamination in the boreal zone may have affected the breeding populations.

Conditions favoring population divergence in trophic features, such as the low levels of species richness and interspecific competition found on islands, can be similar to conditions that increase their sexual dimorphism or overall variance. Male emberizid sparrows of tidal marshes have undergone parallel evolution of large bills. We tested for parallel increases between dimorphism and overall variation in bill size by comparing three groups totaling 30 sparrow subspecies: tidal-marsh sparrows, nontidal relatives of tidal-marsh taxa, and representative sparrow taxa. Bill size (and not other features) showed the following patterns in tidal-marsh sparrows compared to nontidal relatives or sparrows at large: (1) an increase; (2) a greater increase in males than females; (3) an increase in sexual dimorphism; and (4) greater variation in females. A high degree of sexual dimorphism in bill size is consistent with the hypothesi that low levels of interspecific and high levels of intraspecific competition select for intraspecific niche divergence. Alternatively, increased sexual selection in tidal-marsh sparrows, vis-à-vis high densities and hence increased male-male competition, may account for the. differentially large increase in bill size in males. Relaxed natural selection due to high ecosystem productivity and low interspecific competition may explain why, in tidal-marsh sparrows, female bills have diverged less than males and show higher levels of variability at larger sizes. Both the niche divergence and sexual selection hypotheses depend upon processes, particularly increases in population density, that are simjlar to those often reported for island passerines. However, the low species diversity and increased intraspecific competition of salt marsh faunas is probably a result of abiotic constraints on colonization (tides and salinity) rather than the isolating distances of island biotas. Thus, both a shift in bill size and increases in its dimorphism and variability may be favored by high productivity and abiotic constraints. [ABSTRACT FROM AUTHOR]

1. The abundance and predictability of food resources have been posited as explanations for the increase of animal species richness in tropical habitats. However, the heterogeneity of natural ecosystems makes it difficult to quantify a response of animal species richness to these qualities of food resources. 2. Fruit-frugivore studies are especially conducive for testing such ecological theories because fruit is conspicuous and easily counted. Fruit-frugivore research in some locations has demonstrated a relationship between animal abundance and fruit resource abundance, both spatially and temporally. These studies, which typically use fruit counts as the variable of fruit abundance, have never documented a response of species richness at the community level. Furthermore, these studies have not taken into account factors influencing the detection of an individual within surveys. 3. Using a combination of nonstandard approaches to fruit-frugivore research, we show a response of bird species richness to fruit resources. First, we use uniform and structurally similar, one-ha shade-grown coffee plots as replicated experimental units to reduce the influence of confounding variables. Secondly, we use multi-season occupancy modelling of a resident omnivorous bird assemblage in order to account for detection probability in our analysis of site occupancy, local immigration and local emigration. Thirdly, we expand our variable of fruit abundance, Fruit Energy Availability (FEA), to include not only fruit counts but also fruit size and fruit quality. 4. We found that a site’s average monthly FEA was highly correlated (0·90) with a site’s average bird species richness. In our multi-season occupancy model 92% of the weight of evidence supported a single model that included effects of FEA on initial occupancy, immigration, emigration and detection. 5. These results demonstrate that fruit calories can broadly influence the richness of a neotropical bird community, and that fluctuations of FEA explains much of the site occupancy patterns of component species. This study shows that in depauperate, managed landscapes fruit resource abundance supports more species and fruit constancy allows for higher levels of avian persistence, an important practical concept for conservation planning. [ABSTRACT FROM AUTHOR]

The evolutionary stability of signals varies due to interactions between sexual and natural selection. A tidal-marsh sparrow, Melospiza georgiana nigrescens, possesses darker pigmentation than an inland-marsh sparrow, M. g. georgiana. Studies of feather-degrading bacteria and convergent evolution among salt-marsh vertebrates suggest this dark coloration is due to environmental selection. Sexually dichromatic swamp sparrow crowns, however, may be additionally under sexual selection. We investigated ties between two plumage patches (rusty cap and black forehead) and two behaviors (male-male aggression and parental care) in the coastal and inland subspecies to test the effect of sexual versus natural selection on badge evolution. Across both subspecies the extent of rusty feathers in the cap patch was correlated positively with parental care and negatively with aggression, and the extent of black feathers in the forehead patch was correlated positively with aggression. Males with larger forehead patches produced more offspring along the coast, while males with larger cap patches did so inland. The date of the first nesting attempt for both subspecies correlated with cap patch extent, suggesting a similar role for female choice. Natural selection likely accounts for darker coastal females. Coastal male head color, however, is darker due to increased selection for larger forehead patches via intrasexual competition, yet it remains largely rusty due to female choice for larger cap patches. Increased sexual dichromatism among coastal plain swamp sparrows thus provides a clear example of the interplay between sexual and natural selection in subspecies divergence. [ABSTRACT FROM AUTHOR]

Theory on trophic interactions predicts that predators increase plant biomass by feeding on herbivores, an indirect interaction called a trophic cascade. Theory also predicts that predators feeding on predators, or intraguild predation, will weaken trophic cascades. Al- though past syntheses have confirmed cascading effects of terrestrial arthropod predators, we lack a comprehensive analysis for vertebrate insectivores-which by virtue of their body size and feeding habits are often top predators in these systems-and of how intra-guild predation mediates trophic cascade strength. We report here on a meta-analysis of 113 experiments documenting the effects of insectivorous birds, bats, or lizards on predaceous arthropods, herbivorous arthropods, and plants. Although vertebrate insectivores fed as intra-guild predators, strongly reducing predaceous arthropods (38%), they nevertheless suppressed herbivores (39%), indirectly reduced plant damage (40%), and increased plant biomass (14%). Furthermore, effects of vertebrate insectivores on predatory and herbivorous arthropods were positively correlated. Effects were strongest on arthropods and plants in communities with abundant predaceous arthropods and strong intraguild predation, but weak in communities depauperate in arthropod predators and intraguild predation. The naturally occurring ratio of arthropod predators relative to herbivores varied tremendously among the studied communities, and the skew to predators increased with site primary productivity and in trees relative to shrubs. Although intraguild predation among arthropod predators has been shown to weaken herbivore suppression, we find this paradigm does not extend to vertebrate insectivores in these communities. Instead, vertebrate intraguild predation is associated with strengthened trophic cascades, and insectivores function as dominant predators in terrestrial plant-arthropod communities. [ABSTRACT FROM AUTHOR]

Background: Adaptive divergence between populations in the face of strong selection on key traits can lead to morphological divergence between populations without concomitant divergence in neutral DNA. Thus, the practice of identifying genetically distinct populations based on divergence in neutral DNA may lead to a taxonomy that ignores evolutionarily important, rapidly evolving, locally-adapted populations. Providing evidence for a genetic basis of morphological divergence between rapidly evolving populations that lack divergence in selectively neutral DNA will not only inform conservation efforts but also provide insight into the mechanisms of the early processes of speciation. The coastal plain swamp sparrow, a recent colonist of tidal marsh habitat, differs from conspecific populations in a variety of phenotypic traits yet remains undifferentiated in neutral DNA. Methods and Principal Findings: Here we use an experimental approach to demonstrate that phenotypic divergence between ecologically separated populations of swamp sparrows is the result of local adaptation despite the lack of divergence in neutral DNA. We find that morphological (bill size and plumage coloration) and life history (reproductive effort) differences observed between wild populations were maintained in laboratory raised individuals suggesting genetic divergence of fitness related traits. Conclusions and Significance: Our results support the hypothesis that phenotypic divergence in swamps sparrows is the result of genetic differentiation, and demonstrate that adaptive traits have evolved more rapidly than neutral DNA in these ecologically divergent populations that may be in the early stages of speciation. Thus, identifying evolutionarily important populations based on divergence in selectively neutral DNA could miss an important level of biodiversity and mislead conservation efforts. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the patterns of seasonal abundance and social segregation of coastal plain swamp sparrows in Delaware. The study uses a systematic survey on the abundance of coastal plain as well as interior swamp sparrows and aims to address seasonal patterns of their occurrence and their response to the onset of freezing temperatures. It outlines the results of the study and reveals that the species preferentially interact with similar birds.

The abundance of epiphytes has been assumed to be important in explaining the high diversity of tropical canopy arthropods. In this study we assessed the possible role that the presence of epiphytes may have on the diversity and abundance of canopy insects in an experimental study conducted in a coffee plantation in Coatepec, Veracruz, Mexico. Epiphytes were removed from trees in one of two plots in two sites of the coffee plantation. In each plot we collected insects from three Inga jinicuil trees by knockdown insecticide fogging. Insects were sorted to morphospecies, counted and measured. Trees with epiphytes had significantly higher numbers of species and individuals and insects larger than 5 mm were also more species-rich and abundant in trees with epiphytes. The magnitude of the enhancement was surprisingly large with the epiphyte plot samples having on average 90% more individuals and 22% more species than plots without epiphytes. These differences were even greater for large (>5 mm) insects (184% and 113% respectively). Our results support the tenet that epiphytes provide valuable resources to arthropods, which we have illustrated for canopy insects in shade trees of coffee plantations. [ABSTRACT FROM PUBLISHER]

Mangrove ecosystems are found globally along tropical and subtropical coastlines. They exhibit a steep environmental gradient between inland and marine systems, providing a unique, selective environment that shapes local morphological, physiological, and behavioral adaptations. In the first global assessment of terrestrial vertebrate species that are restricted to mangrove ecosystems, we found 48 bird, 14 reptile, I amphibian, and 6 mammal species endemic to mangroves, the majority of which are found in Asia and Australia. We also found that more than 40% of assessed mangrove-endemic vertebrates are globally threatened. Clearly, additional research is needed to better understand mangrove-endemic vertebrates in order to conserve them. Future research should focus on global inventories, intercontinental comparative work, and the ecology of mangrove-endemic vertebrates. [ABSTRACT FROM AUTHOR]

The article examines the link of the feather color of the pale montane Southern Swamps Sparrow Melospiza georgiana georgiana and the dark Coastal Plain Swamp Sparrow with their adaptive response to differences in the occurrence and abundance of bacilli in habitats that differ in salinity. Results show a greater number of Swamp Sparrows with feather-degrading bacteria in their plumage in salt marshes than in freshwater fens. The study observes the resistance of the Coastal Plain Swamp Sparrows' dark plumage to feather degradation by salt-tolerant bacilli.

Over the past two decades, the combination of molecular and field methods has revealed considerable variation in the level of extrapair fertilizations among socially monogamous birds. Models predicting extrapair young range in scale from a single population to multiple Orders, and there is no single, unifying theory for these reproductive tactics. We investigated proximate explanations of extrapair fertilizations in two subspecies of the swamp sparrow, Melospiza georgiana georgiana and Melospiza georgiana nigrescens, across a range of social and environmental conditions. The presence of extrapair young was best predicted by the size of two male plumage badges (one correlated with parental care and one with territorial aggression) relative to the badge size of their immediate neighbors, the interaction of these two measures, mean territory size, and the maximum size of the aggression badge among neighbors. The size of the male’s parental care badge (relative to neighbors) was negatively correlated with the probability of lost paternity. The relative size of the aggression badge was positively correlated with the presence of extrapair young when the parental care badge was small and negatively correlated when the badge was large. Controlling for these crown measures, males with larger territories were less likely to suffer losses in paternity. There was no effect of breeding density, breeding synchrony, their interaction, subspecies, or weather during the fertile period on the presence of extrapair young. These results suggest that female preference for males that provide more parental care (or preference for genes that convey this trait) plays a dominant role in extrapair interactions among swamp sparrows. Models based on female assessments of relative mate quality offer a promising explanation of patterns in extrapair fertilizations among bird species. [ABSTRACT FROM AUTHOR]

Aim Comparisons of the biotas in the Palaearctic and Nearctic have focused on limited portions of the two regions. The purpose of this study was to assess the geographic pattern in the abundance, species richness, and importance of different migration patterns of the boreal forest avifauna of Eurasia from Europe to East Asia as well as their relationship to climate and forest productivity. We further examine data from two widely separated sites in the New World to see how these conform to the patterns found in the Eurasian system. Location Boreal forest sites in Russia and Canada. Methods Point counts were conducted in two to four boreal forest habitats at each of 14 sites in the Russian boreal forest from near to the Finnish border to the Far East, as well as at two sites in boreal Canada. We examined the abundance and species richness of all birds, and specific migratory classes, against four gradients (climate, primary productivity, latitude, and longitude). We tested for spatial autocorrelation in both dependent and independent variables using Moran’s I to develop spatial correlograms. For each migratory class we used maximum likelihood to fit models, first assuming uncorrelated residuals and then assuming spatially autocorrelated residuals. For models assuming unstructured residuals we again generated correlograms on model residuals to determine whether model fitting removed spatial autocorrelation. Models were compared using Akaike’s information criterion, adjusted for small sample size. Results Overall abundance was highest at the eastern and western extremes of the survey region and lowest at the continent centre, whereas the abundance of tropical and short-distance migrants displayed an east–west gradient, with tropical migrants increasing in abundance in the east (and south), and short-distance migrants in the west. Although overall species richness showed no geographic pattern, richness within migratory classes showed patterns weaker than, but similar to, their abundance patterns described above. Overall abundance was correlated with climate variables that relate to continentality. The abundances of birds within different migration strategies were correlated with a second climatic gradient – increasing precipitation from west to east. Models using descriptors of location generally had greater explanatory value for the abundance and species-richness response variables than did those based on climate data and the normalized difference vegetation index (NDVI). Main conclusions The distribution patterns for migrant types were related to both climatic and locational variables, and thus the patterns could be explained by either climatic regime or the accessibility of winter habitats, both historically and currently. Non-boreal wintering habitat is more accessible from both the western and eastern ends than from the centre of the boreal forest belt, but the tropics are most accessible from the eastern end of the Palaearctic boreal zone, in terms of distance and the absence of geographical barriers. Based on comparisons with Canadian sites, we recommend that future comparative studies between Palaearctic and Nearctic faunas be focused more on Siberia and the Russian Far East, as well as on central and western Canada. [ABSTRACT FROM AUTHOR]

We tested three hypotheses of clutch size variation in two subspecies of the swamp sparrow ( Melospiza georgiana georgiana and M. g. nigrescens). Swamp sparrows follow the pattern of other estuarine endemics, where clutch size is smaller among tidal salt marsh populations ( M. g. nigrescens) than their closest inland relatives ( M. g. georgiana). Our results support predation risk and temperature, but not adult survival, as explanations of this pattern in swamp sparrows. Coastal nests were twice as likely to fail as inland nests, and parental activity around the nest site was positively related to clutch size at both sites. When brood size was controlled for, coastal adults visited nests less often and females vocalized less frequently during visits than inland birds, which may decrease nest detectability to predators. Coastal parents waited longer than inland birds to feed offspring in the presence of a model nest predator, but there was no difference in their response to models of predators of adults, as would be expected if coastal birds possessed increased longevity. Additionally, coastal females laid more eggs than inland females over a single season, following a within-season bet-hedging strategy rather than reducing within-season investment. Coastal territories experienced ambient air temperatures above the physiological zero of egg development more often, and higher temperatures during laying correlated with smaller clutches and increased egg inviability among coastal birds. Similar effects were not seen among inland nests, where laying temperatures were generally below physiological zero. Both subspecies showed an increase in hatching asynchrony and a decrease in apparent incubation length under high temperatures. Coastal individuals, however, showed less hatching asynchrony overall despite higher temperatures. Both air temperatures during laying and predation risk could potentially explain reduced clutch size in not only coastal plain swamp sparrows, but also other tidal marsh endemics. [ABSTRACT FROM AUTHOR]

Copyright of Conservation Biology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Agroecology and conservation must overlap to protect biodiversity and farmer livelihoods. Coffee agroecosystems with complex shade canopies protect biodiversity. Yet, few have examined biodiversity in coffee agroecosystems in Asia relative to the Americas and many question whether coffee agroecosystems can play a similar role for conservation. We examined vegetation, ant and bird diversity, coffee yields and revenues, and harvest of alternative products in coffee farms and forests in SW Sumatra, Indonesia near Bukit Barisan Selatan National Park (BBS). BBS is among the last habitats for large mammals in Sumatra and >15,000 families illegally cultivate coffee inside of BBS. As a basis for informing management recommendations, we compared the conservation potential and economic outputs from farms inside and outside of BBS. Forests had higher canopy cover, canopy depth, tree height, epiphyte loads, and more emergent trees than coffee farms. Coffee farms inside BBS had more epiphytes and trees and fewer coffee plants than farms outside BBS. Tree, ant, and bird richness was significantly greater in forests than in coffee farms, and richness did not differ in coffee farms inside and outside of BBS. Species similarity of forest and coffee trees, ants, and birds was generally low (<50%). Surprisingly, farms inside the park were significantly older, but farm size, coffee yields, and revenues from coffee did not depend on farm location. Farmers outside BBS received higher prices for their coffee and also more often produced other crops in their coffee fields such that incentives could be created to draw illegal farmers out of the park. We also discuss these results with reference to similar work in Chiapas, Mexico to compare the relative contribution of coffee fields to conservation in the two continents, and discuss implications for working with farmers in Sumatra towards conservation plans incorporating sustainable coffee production. [ABSTRACT FROM AUTHOR]

Insectivorous birds reduce arthropod abundances and their damage to plants in some, but not all, studies where predation by birds has been assessed. The variation in bird effects may be due to characteristics such as plant productivity or quality, habitat complexity, and/or species diversity of predator and prey assemblages. Since agroforestry systems vary in such characteristics, these systems provide a good starting point for understanding when and where we can expect predation by birds to be important. We analyze data from bird exclosure studies in forests and agroforestry systems to ask whether birds consistently reduce their arthropod prey base and whether bird predation differs between forests and agroforestry systems. Further, we focus on agroforestry systems to ask whether the magnitude of bird predation (1) differs between canopy trees and understory plants, (2) differs when migratory birds are present or absent, and (3) correlates with bird abundance and diversity. We found that, across all studies, birds reduce all arthropods, herbivores, carnivores, and plant damage. We observed no difference in the magnitude of bird effects between agroforestry systems and forests despite simplified habitat structure and plant diversity in agroforests. Within agroforestry systems, bird reduction of arthropods was greater in the canopy than the crop layer. Top-down effects of bird predation were especially strong during censuses when migratory birds were present in agroforestry systems. Importantly, the diversity of the predator assemblage correlated with the magnitude of predator effects; where the diversity of birds, especially migratory birds, was greater, birds reduced arthropod densities to a greater extent. We outline potential mechanisms for relationships between bird predator, insect prey, and habitat characteristics, and we suggest future studies using tropical agroforests as a model system to further test these areas of ecological theory. [ABSTRACT FROM AUTHOR]

Unique components of tropical habitats, such as abundant vascular epiphytes, influence the distribution of species and can contribute to the high diversity of many animal groups in the tropics. However, the role of such features in habitat selection and demography of individual species has not been established. Understanding the mechanisms of habitat selection requires both experimental manipulation of habitat structure and detailed estimation of the behavioral and demographic response of animals, e.g., changes in movement patterns and survival probabilities. Such studies have not been conducted in natural tropical forest, perhaps because of high habitat heterogeneity, high species diversity, and low abundances of potential target species. Agroforestry systems support a less diverse flora, with greater spatial homogeneity which, in turn, harbors lower overall species diversity with greater numerical dominance of common species, than natural forests. Furthermore, agroforestry systems are already extensively managed and lend themselves easily to larger scale habitat manipulations than protected natural forest. Thus, agroforestry systems provide a good model environment for beginning to understand processes underlying habitat selection in tropical forest animals. Here, we use multistate, capture-recapture models to investigate how the experimental removal of epiphytes affected monthly movement and survival probabilities of two resident bird species (Common Bush-Tanager [Chlorospingus ophthalmicus] and Golden-crowned Warbler [Basileuterus culicivorus]) in a Mexican shade coffee plantation. We established two paired plots of epiphyte removal and control. We found that Bush-Tanagers were at least five times more likely to emigrate from plots where epiphytes were removed compared to control plots. Habitat-specific movement patterns were not detected in the warbler. However, unlike the Golden-crowned Warbler, Common Bush-Tanagers depend upon epiphytes for nest sites and (seasonally) for foraging. These dispersal patterns imply that active habitat selection based on the presence or absence of epiphytes occurs in C. ophthalmicus on our study area. Survival rates did not vary with habitat in either species. Interestingly, in both species, survival was higher in the nonbreeding season, when birds were in mixed-species flocks. Movement by Common Bush-Tanagers into areas with epiphytes occurred mostly during the breeding season, when mortality-driven opportunity was greatest. [ABSTRACT FROM AUTHOR]

Copyright of Condor is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the Neotropics, crops that are grown in agroforestry systems with shade trees support high levels of bird diversity compared with crops grown without shade (Estrada & Coates-Estrada 2005, Faria et al. 2006). Several experiments in shaded coffee farms have explored how insectivorous birds reduce herbivore numbers and their damage to plants and have simultaneously approached ecological questions that are applied (e.g. biological control) and basic (e.g. tri-trophic interactions) (Borkhataria et al. 2006, Greenberg et al., Perfecto et al. 2004). Here we used exclosures to test whether birds lower the densities of herbivorous insects and reduce insect damage to cocoa (Theobroma cacao L., Sterculiaceae) foliage in shaded farms of western Panama. Although bird predation has been shown to reduce insect damage to crops in other systems (Mols & Visser 2002), we provide the first test for shade-grown cocoa. [ABSTRACT FROM PUBLISHER]

Copyright of Conservation Biology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Theobroma cacao plantings, when managed under the shade of rainforest trees, provide habitat for many resident and migratory bird species. We compared the bird diversity and community structure in organic cacao farms and nearby forest fragments throughout mainland Bocas del Toro, Panama. We used this dataset to ask the following questions: (1) How do bird communities using cacao habitat compare to communities of nearby forest fragments? (2) To what extent do Northern migratory birds use shaded cacao farms, and do communities of resident birds shift their abundances in cacao farms seasonally? (3) Do small scale changes in shade management of cacao farms affect bird diversity? Using fixed radius point counts and additional observations, we recorded 234 landbird species, with 102 species that were observed in both cacao and forest fragments, 86 species that were only observed in cacao farms, and 46 species that were restricted to forest fragments. Cacao farms were rich in canopy and edge species such as tanagers, flycatchers and migratory warblers, but understory insectivores were nearly absent from cacao farms. We observed 27 migratory species, with 18 species in cacao farms only, two species in forest only, and seven species that occurred in both habitats. In cacao farms, the diversity of birds was significantly greater where there was less intensive management of the canopy shade trees. Shade tree species richness was most important for explaining variance in bird diversity. Our study shows that shaded cacao farms in western Panama provide habitat for a wide variety of resident and migratory bird species. Considering current land use trends in the region, we suggest that action must be taken to prevent conversion away from shaded cacao farms to land uses with lower biodiversity conservation value. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)