Article

Bird community composition across an Andean tree‐line ecotone

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Few studies have found strong evidence to suggest that ecotones promote species richness and diversity. In this study we examine the responses of a high‐Andean bird community to changes in vegetation and topographical characteristics across an Andean tree‐line ecotone and adjacent cloud forest and puna grassland vegetation in southern Peru. Over a 6‐month period, birds and vegetation were surveyed using a 100 m fixed‐width Distance Sampling point count method. Vegetation analyses revealed that the tree‐line ecotone represented a distinctive high‐Andean vegetation community that was easily differentiated from the adjacent cloud forest and puna grassland based on changes in tree‐size characteristics and vegetation cover. Bird community composition was strongly seasonal and influenced by a pool of bird species from a wider elevational gradient. There were also clear differences in bird community measures between tree‐line vegetation, cloud forest and puna grassland with species turnover (β‐diversity) most pronounced at the tree‐line. Canonical Correspondence Analysis revealed that the majority of the 81 bird species were associated with tree‐line vegetation. Categorizing patterns of relative abundance of the 42 most common species revealed that the tree‐line ecotone was composed primarily of cloud forest specialists and habitat generalists, with very few species from the puna grassland. Only two species, Thlypopsis ruficeps and Anairetes parulus, both widespread Andean species more typical of montane woodland vegetation edges, were categorized as ecotone specialists. However, our findings were influenced by significant differences in species detectability between all three vegetation communities. Our study highlights the importance of examining ecotones at an appropriate spatial and temporal scale. Selecting a suitable distance between sampling points based on the detection probabilities of the target bird species is essential to obtain an unbiased picture of how ecotones influence avian richness and diversity.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Changes in vegetation at the forest-tundra ecotone (treeline), an ecotone caused by complex changes at a latitudinal or altitudinal gradient, have been extensively documented (Payette et al. 2001;Harper et al. 2011), in response to the growing concern that global climate change may adversely affect these important areas (Grace et al. 2002). However, the impact of treeline ecotones on other key organisms like passerine songbirds remains relatively unstudied (Terborgh 1985;Archaux 2004;Lloyd et al. 2011;Kent et al. 2013), and boreal ecotone communities are especially understudied. ...
... These studies do not examine the vegetation-habitat concept nor do they explicitly examine ecotones. Other studies have examined these concepts, but this is the first study, to the best of our knowledge, to do so across a boreal treeline ecotone (see Terborgh 1985;Archaux 2004;Lloyd et al. 2011;Kent et al. 2013 for nonboreal treeline examples) and to consider the potential impacts of global climate change (see Conservation impli- Table 2). Stress <0.15 for both years. ...
... Furthermore, while some species were clearly associated with the treeline (Figs. 4A and 4B), similar to Lloyd et al. (2011), they are clearly not treeline specialists. The birds in this study are all quite common across North America (e.g., American Robin), and the ecotone is far too narrow in these mountains to promote speciation; in all likelihood, these birds were simply using the area along the elevational gradient with their preferred floristics and physiognomy. ...
Article
Full-text available
We examined the factors structuring bird communities across a complex sub-arctic treeline in the Mealy Mountains, Labrador, Canada. Using point counts of bird abundance in 2007 and 2008, we show that changes in vegetation driven by elevation are strongly correlated with avian community structure in this treeline ecotone system. Overall, avian diversity was higher in the forest compared to other habitat classes (krummholz, deciduous shrub, and alpine). There were strong correlations between avian diversity and vegetation richness as well as structure among and within habitat class in 2008. Numerous habitat types (subset of habitat class) were correlated with avian composition although some species were clearly habitat generalists. Contrary to expectation, avian species composition was associated with physiognomy (vegetation structure) in alpine and deciduous shrub, and with neither physiognomy or floristics (vegetation species composition) in krummholz and forest. Given the strong impact of elevation on vegetation and the demonstrated influence on bird communities, we note that for bird species whose near-southernmost populations are found in the Mealy Mountains, climate change is likely to have a strong negative effect if alpine tundra habitat is lost. Further, forest bird species are likely to benefit from the increased tree cover as treeline moves poleward and upward.
... The tree line of Manu National Park, in the southern Peruvian Andes, has a very similar landscape to Unchog. Lloyd et al. (2012) found out a distinctive community of plants and birds, different from puna grasslands and the cloud forest. Bird pollinators that are expected in tree line zones include a dozen hummingbirds such as Great Sapphirewing Pterophanes cyanopterus, Sword-billed Hummingbird Ensifera ensifera and species of the genus Coeligena, Eriocnemis and Heliangelus, the last two restricted to the elfin forest. ...
... The Coppery Metaltail Metallura theresiae was the most dominant flower visitor in this ecosystem, so it could be the most effective pollinator (Willmer, 2011). In other tree line ecosystems in the central Andes, the small hummingbirds Tyrian Metaltail Metallura tyrianthina and Amethyst-throated Sunangel Heliangelus amethysticollis are dominant (Gonzalez, 2008;Lloyd et al., 2012;Toloza-Moreno et al., 2014) but in Unchog, M. theresiae has taken over the tree line and these other hummingbirds stay in lower elevations. The diversification of Metallura hummingbirds was recent (Garcia-Moreno et al., 1999), hummingbirds have their beta-diversity associated with elevation (Weinstein et al., 2014). ...
Article
Full-text available
Nectarivorous birds (hummingbirds, flowerpiercers, and conebills) and their floral resources in an elfin forest of the central Andes of Peru (Unchog, Carpish Mountains) are described. This forest is well-known for its concentration of endemic species, mainly birds. We recorded the nectarivorous birds, vascular plants and the interactions among them between 2011-2014. The birds were recorded by direct observations and mist nets. Plants were evaluated with Gentry plots and occasional collection. A total of 26 nectarivorous bird species have been reported in this forest, however from our observations we detected from this assemblage 17 bird species that feed in plants' nectar. A total of 27 plant species were visited by the birds. The nectarivorous birds were hummingbirds (Trochilidae, 12 species), flowerpiercers (Thraupidae, 4 species) and a conebill (Thraupidae: 1 specie). The plants were from 16 families and 14 orders. One species of hummingbird, Metallura theresiae, is endemic to Peru. On plants, Greigia macbrideana, Puya pseudoeryngioides, Centropogon isabellinus, Miconia alpina and Brachyotum lutescens are endemic to Peru. We comment on the species reported in previous expeditions and in the current checklists. Since this forest is important for its large number of endemic species, we comment on its current threats and the importance of accounting for ecological interactions to conserve montane forests. Resumen Se describen las aves nectarívoras (colibríes, pinchaflores y picoconos) y sus recursos florales en un bosque achaparrado de los Andes centrales peruanos (Unchog, Cordillera Carpish). Este bosque es bien conocido por su concentración de especies endémicas, principalmente aves. Registramos a las aves nectarívoras, plantas vasculares y sus interacciones entre el 2011 al 2014. Las aves fueron registradas por observaciones directas y redes de neblina. Las plantas fueron evaluadas con parcelas de Gentry y colecta ocasional. Un total de 26 especies nectarívoras han sido reportadas en este bosque, sin embargo, en nuestras observaciones detectamos 17 especies de aves que se alimentan del néctar de las plantas. Un total de 27 especies de plantas fueron visitadas por las aves. Las aves nectarívoras fueron colibríes (Trochilidae, 12 especies), pinchaflores (Thraupidae, 4 especies) y un picocono (Thraupidae: 1 especie). Las plantas fueron de 16 familias y 14 órdenes. Una especie de colibrí, Metallura theresiae, es endémica del Perú. Sobre plantas, Greigia macbrideana, Puya pseudoeryngioides, Centropogon isabellinus, Miconia alpina y Brachyotum lutescens son endémicas del Perú. Comentamos sobre las especies reportadas en expediciones previas y en listas actuales. Puesto que este bosque es importante por su gran número de especies endémicas, comentamos acerca de las amenazas actuales y en la importancia de considerar las interacciones ecológicas para la conservación de los bosques montanos.
... Here, we extend these studies to investigate the drivers of species' interactions and network structure in a bird–flowering plant network in ''elfin'' forests located within the high Andes of Peru (Brack & Mendiola, 2000). Elfin forests, like other highland sites, are characterized by flowering plants adapted largely for bird pollination, as cold temperatures and often wet conditions limit insect abundance and activity (Dalsgaard et al., 2009; Lloyd et al., 2012). In mainland Americas these forests, while dominated by hummingbirds of various sizes and bill morphologies, also are frequented by Diglossa flowerpiercers (Ramirez et al., 2007). ...
... We recognize that not all birds are equally captured by mist-nets (e.g., Remsen & Good, 1996), and thus estimates may be biased. Nonetheless, in montane forest mist-netting is widely used as a recommended method for bird assessment (Lloyd et al., 2012; Maglianesi et al., 2014). As for plants, we combined the results among sites to characterize the bird community and bird–flower observations. ...
Article
Full-text available
Biological constraints and neutral processes have been proposed to explain the properties of plant–pollinator networks. Using interactions between nectarivorous birds (hummingbirds and flowerpiercers) and flowering plants in high elevation forests (i.e., “elfin” forests) of the Andes, we explore the importance of biological constraints and neutral processes (random interactions) to explain the observed species interactions and network metrics, such as connectance, specialization, nestedness and asymmetry. In cold environments of elfin forests, which are located at the top of the tropical montane forest zone, many plants are adapted for pollination by birds, making this an ideal system to study plant–pollinator networks. To build the network of interactions between birds and plants, we used direct field observations. We measured abundance of birds using mist-nets and flower abundance using transects, and phenology by scoring presence of birds and flowers over time. We compared the length of birds’ bills to flower length to identify “forbidden interactions”—those interactions that could not result in legitimate floral visits based on mis-match in morphology. Diglossa flowerpiercers, which are characterized as “illegitimate” flower visitors, were relatively abundant. We found that the elfin forest network was nested with phenology being the factor that best explained interaction frequencies and nestedness, providing support for biological constraints hypothesis. We did not find morphological constraints to be important in explaining observed interaction frequencies and network metrics. Other network metrics (connectance, evenness and asymmetry), however, were better predicted by abundance (neutral process) models. Flowerpiercers, which cut holes and access flowers at their base and, consequently, facilitate nectar access for other hummingbirds, explain why morphological mis-matches were relatively unimportant in this system. Future work should focus on how changes in abundance and phenology, likely results of climate change and habitat fragmentation, and the role of nectar robbers impact ecological and evolutionary dynamics of plant–pollinator (or flower-visitor) interactions.
... but decreased thereafter (Fig. 4). This abrupt change coincides with the tree-line effect on community composition 33,34 . The blue food webs, conversely, showed a consistent linear decrease with elevation. ...
Article
Full-text available
While aquatic (blue) and terrestrial (green) food webs are parts of the same landscape, it remains unclear whether they respond similarly to shared environmental gradients. We use empirical community data from hundreds of sites across Switzerland and a synthesis of interaction information in the form of a metaweb to show that inferred blue and green food webs have different structural and ecological properties along elevation and among various land-use types. Specifically, in green food webs, their modular structure increases with elevation and the overlap of consumers’ diet niche decreases, while the opposite pattern is observed in blue food webs. Such differences between blue and green food webs are particularly pronounced in farmland-dominated habitats, indicating that anthropogenic habitat modification modulates the climatic effects on food webs but differently in blue versus green systems. These findings indicate general structural differences between blue and green food webs and suggest their potential divergent future alterations through land-use or climatic changes.
... The area that we call a transition habitat can be considered an ecotone between 2 habitat types because it contains the vegetation of 2 habitats found next to each other (Odum 1959): peatlands and puna grasslands. Because ecotones tend to promote higher species richness and diversity (Baker et al. 2002, Lloyd et al. 2012, we may expect this to happen in the transition habitat in the High Andean region. ...
Article
Full-text available
The High Andean peatlands are peat-accumulating wetlands dominated by cushion-forming plants and are embedded in a matrix of puna grasslands above 4,000 m. These ecosystems are an essential source of water and evergreen vegetation for wild and domestic animals and are considered sensitive to environmental alterations. We studied the birds' habitat and microhabitat preference in peatlands and their surrounding grasslands in the Cordillera Real, Bolivia. We established 3 parallel transects around 12 peatlands: (1) in peatland, (2) at 100200 m from the peatland edge, considered as the transition habitat between peatlands and grasslands, and (3) in puna grasslands at >500 m from the peatland edge. We quantified bird abundance, species richness, and the availability of 8 microhabitats along 36 transects. We recorded 934 individuals of 34 species and found higher bird species richness and abundance in peatlands than in surrounding grasslands and transition habitats. We found that 26% of bird species were exclusive to peatlands. While most bird species common in peatlands were almost nonexistent in other habitats, most species associated with grasslands were also found in proximity to peatlands. A canonical correspondence analysis showed that bird species were associated with one or more microhabitats. The high abundance, bird species richness, and diet types in peatlands is probably related to the high primary productivity of peatlands and year-round availability of water. Degradation of these peatlands may reduce the abundance of regional bird communities, not only peatland specialists but also species in surrounding habitats.
... Species interactions are thought to be particularly important in shaping Andean community turnover: For example, Andean birds are often highly specialized on particular habitats and resources (13,34), and competitive exclusion is thought to further limit and reinforce range boundaries (7,(35)(36)(37). However, parasitism has received less attention as a driver of turnover compared to competition (35,37) and bird-plant mutualisms (36,38,39). One important group that could affect bird turnover is the hemosporidians (Apicomplexa: Haemosporida), a diverse clade of vector-borne parasites in the genera Haemoproteus, Parahaemoproteus, Plasmodium, and Leucocytozoon (40,41). ...
Article
Full-text available
Significance Interactions between hosts and parasites can reciprocally limit the ranges of individual species. But to what extent do they affect composition of communities? In the Andean biodiversity hot spot, we tested why host and parasite communities vary over spatial and temporal scales. Variation in rainfall was the predominant predictor of turnover for both hosts and parasites. However, the effects of species interactions were asymmetric: Parasite communities were strongly predicted by host communities, but not vice versa. Against conventional wisdom, climatic effects on parasite turnover were primarily local while biotic effects predominated regionally. Using our predictive models, we mapped faunal dissimilarity, illustrating hot spots of turnover that can guide conservation of host and parasite biodiversity.
... In Monteverde, Costa Rica on the drier Pacific slope there were 165 species of birds, while on the wetter Caribbean slope there were 315 species . Lloyd et al. (2012) studied avian richness in Kcosñipata Valley, Department of Cusco, southern Peru and detected about 50 species within the MCF. Compared with the tree-line and puna grassland vegetative communities, MCF had the highest bird diversity during both the dry and wet seasons; during the dry season the species richness of birds was slightly higher. ...
Chapter
Full-text available
... The effects of the MHDE on ecosystems have yet to be fully resolved, but increased aridity may have fostered more frequent and larger fires, causing grasslands to expand to replace woodlands or shrublands (Sylvester et al., 2014). One habitat that may have been adversely affected were Polylepis woodlands, an endemic fire-sensitive Andean tree that forms monodominant stands above treeline (Fjeldså and Kessler, 1996) providing essential habitat for high Andean woodland specialists including plants, birds, mammals, and insects (Cahill and Matthysen, 2007;Fjeldså, 1993;Lloyd et al., 2012;Yensen and Tarifa, 2002). Wet microrefugia (Mosblech et al., 2011;Rull, 2009) where the effects of the drought and fire were minimized, may have been an essential component allowing the survival and post-drought recovery of these groups. ...
Article
We present a 12,6700-yr limnological history of Lake Miski, a high-elevation lake in a wet section of the Peruvian Andes. While many shallow Andean lakes dried up during the mid-Holocene, loss-on-ignition, magnetic susceptibility, and diatom analysis showed that Lake Miski was a constant feature in the landscape. Overall, fluctuations in the fossil diatom communities of Lake Miski tracked changes in insolation, but this was not the only mechanism influencing observed variability. We identify periods when insolation and interactions with the Pacific Ocean may have played a role in structuring local climate and diatom assemblages. The true mid-Holocene Dry Event (MHDE) is manifested in this record between 8000 and 5000 cal BP, but the carbonate stratigraphy and the diatom community indicated that although the level of the lake decreased, it never completely dried out, instead there was higher availability of planktic habitat and stronger mixing than in much of the Holocene. High rates of biological change observed during the late-Holocene in other records from Peru associated with human amplification of climatic signals were not observed in Lake Miski, as this lake may have been too wet and remote to be strongly influenced by human activity. Because of the presence of a woodland microrefugium, Lake Miski was suggested to have been an unusually climatically stable and wet location during the regional drying associated with the MHDE. Our new limnological information provides additional insights relating to this discussion. The presence of the observed woodland apparently withstood fluctuations that induced state changes in the lake and diatom flora, underscoring that microrefugia do not equate to ‘unchanging’ hydrologies or climates.
... Polylepis (Rosaceae) is an endemic tree genus in the high Andes, forming upper high-elevation treelines often disconnected from the lower-elevation cloud-forest treelines by puna grasslands [1,2]. These high-elevation forests are an essential element of the Andean landscape, harboring a significant part of high-mountain biodiversity [3]. Their patchy distribution, though probably of anthropogenic origin, may also reflect the habitat suitability of topographic positions varying in, e.g., moisture or thermal regimes, as well as in land-use intensity. ...
Article
Full-text available
The patchy distribution of high-Andean treeline forests has provoked discussion about the relative importance of anthropogenic and climatic causes of this pattern, both of which vary with topography. We aimed to understand the topographic controls on the distribution of Polylepis subsericans treeline forests in the Andes of southern Peru, and the changes in these controls along an elevational gradient. We mapped Polylepis forests in the Cordillera Urubamba, Cusco, using high-resolution aerial images and related forest cover to topographic variables extracted from a digital terrain model (30-m resolution). The variables were selected based on their expected biological relevance for tree growth at high elevations. We constructed logistic regression models of forest cover, separately for each of five 100-m elevational belts. To deal with spatial autocorrelation, models were based on randomized 10% subsampling of the data with 1000 repetitions. The results suggest a consistent shift in topographic preference with elevation, with forests at lower elevations showing a preference for topographically protected sites near rivers and forests at higher elevations being increasingly restricted to north-facing and well-drained sites. Our study offers the first indication of the ability of Andean treeline forests to benefit from the topographic heterogeneity of the high-Andes. Providing that dispersal and establishment are possible, local relocation between microsites could help these forests to persist regionally in spite of changing climatic conditions.
... We were able to find species utilising concomitantly the grassland and the edge. The within beta diversity is higher at these habitats (sites are more distant in the ordination space), which suggests that the grassland areas near the edge presenting shrub layer can provide more spatial heterogeneity that can be used by a more diversified assemblage of birds, including forest generalist species (LLOYD et al., 2011). In that sense, small forest patches or even isolated individuals of the commonly bush Baccharis uncinella (Asteraceae) could be a food source or shelter for a wider array of species (ANJOS & BOÇON, 1999), like the appearance of the species S. diadematus and P. ventralis in the grassland. ...
Article
Full-text available
The present study evaluates differences in alpha and beta diversity and guild structure of bird assemblages along the ecotone between grassland and Araucaria forest in Southern Brazil. Birds were sampled by point counts (radius of 25 m) disposed in the grassland, in the grasslandforest edge, and in the forest interior, grouped in three blocks. Grassland presented low bird richness and abundance, and the bird composition and guild structure in grasslands were different from the edge and the forest interior. Grassland showed more granivores, while forest interior presented more omnivores, insectivores and insectivores/ frugivores. Notwithstanding, there was an overlap on the occurrence of some forest bird species in the edge and grassland, evidencing that the grassland plant structure composed of small forest patches and shrubs could facilitate bird movements, which, in turn, could influence forest expansion dynamics over the grassland.
... Due to the high elevation and extreme conditions, these regions have different habitats compared to the neighboring lowlands and cloud forest (Szumik et al., 2012). Inhabitants of these regions are well-adapted to the environment, and have therefore become isolated from other taxa in adjacent regions (Lloyd et al., 2010). This lack of species overlap is especially evident in avian taxa (Fjeldså et al., 2012). ...
Article
Hosts-parasite interactions are plentiful and diverse, and understanding the patterns of these interactions can provide great insight into the evolutionary history of the organisms involved. Estimating the phylogenetic relationships of a group of parasites and comparing them to that of their hosts can indicate how factors such as host or parasite life history, biogeography, or climate affect evolutionary patterns. In this study we compare the phylogeny generated for a clade of parasitic chewing lice (Insecta: Phthiraptera) within the genus Columbicola to that of their hosts, the small New World ground-doves (Aves: Columbidae). We sampled lice from the majority of host species, including samples from multiple geographic locations. From these samples we sequenced mitochondrial and nuclear loci for the lice, and used these data to estimate phylogenetic trees and population networks. After estimating the appropriate number of operational taxonomic units (OTUs) for the lice, we used cophylogenetic analyses to compare the louse phylogeny to an existing host phylogeny. Our phylogenetic analysis recovered significant structure within the louse clade, including evidence for potentially cryptic species. All cophylogenetic analyses indicated an overall congruence between the host and parasite trees. However, we only recovered a single cospeciation event. This finding suggests that certain branches in the trees are driving the signal of congruence. In particular, lice with the highest levels of congruence are associated with high Andean species of ground-doves that are well separated altitudinally from other related taxa. Other host-parasite associations are not as congruent, and these often involved widespread louse taxa. These widespread lice did, however, have significant phylogeographic structure, and their phylogenetic relationships are perhaps best explained by biogeographic patterns. Overall these results indicate that both host phylogeny and biogeography can be simultaneously important in influencing the patterns of diversification of parasites.
... In any case, the field is clearly dominated by the study of plant communities, and mainly focusing on vascular plants (41.5% of representative literature; e.g., [17][18][19]). The analysis of species turnover along altitudinal gradients in animals exploits some species-rich groups of arthropods, particularly insects (24.5%), mostly beetles and butterflies (e.g., [20][21][22][23]), or some emblematic groups of vertebrates, mainly birds (6.6%; e.g., [15,24]). Soil community ecologists have paid attention to species turnover in elevation gradients for bacteria (2.8%; e.g., [25][26]) and fungi (5.7%; e.g., [27]). ...
Article
Full-text available
Our perception of diversity, including both alpha- and beta-diversity components, depends on spatial scale. Studies of spatial variation of the latter are just starting, with a paucity of research on beta-diversity patterns at smaller scales. Understanding these patterns and the processes shaping the distribution of diversity is critical to describe this diversity, but it is paramount in conservation too. Here, we investigate the diversity and structure of a tropical community of herbivorous beetles at a reduced local scale of some 10 km2, evaluating the effect of a small, gradual ecological change on this structure. We sampled leaf beetles in the Núi Chúa National Park (S Vietnam), studying changes in alpha- and beta-diversity across an elevation gradient up to 500 m, encompassing the ecotone between critically endangered lowland dry deciduous forest and mixed evergreen forest at higher elevations. Leaf beetle diversity was assessed using several molecular tree-based species delimitation approaches (with mtDNA cox1 data), species richness using rarefaction and incidence based diversity indexes, and beta-diversity was investigated decomposing the contribution of species turnover and nestedness. We documented 155 species in the area explored and species-richness estimates 1.5–2.0x higher. Species diversity was similar in both forest types and changes in alpha-diversity along the elevation gradient showed an expected local increase of diversity in the ecotone. Beta-diversity was high among forest paths (average Sørensen's dissimilarity = 0.694) and, tentatively fixing at 300 m the boundary between otherwise continuous biomes, demonstrated similarly high beta-diversity (Sørensen's dissimilarity = 0.581), with samples clustering according to biome/elevation. Highly relevant considering the local scale of the study, beta-diversity had a high contribution of species replacement among locales (54.8%) and between biomes (79.6%), suggesting environmental heterogeneity as the dominant force shaping diversity at such small scale, directly and indirectly on the plant communities. Protection actions in the Park, especially these addressed at the imperative conservation of dry forest, must ponder the small scale at which processes shape species diversity and community structure for inconspicuous, yet extraordinarily diverse organisms such as the leaf beetles.
Article
Aim To determine the palaeoecological influences of climate change and human land use on the spatial distribution patterns of Polylepis woodlands in the Andes. Location Tropical Andes above 2,900 m between 2°S and 18°S of latitude. Methods Pollen and charcoal data were gathered from 13 Andean lake sediment records and were rescaled by the maximum value in each site. The rescaled pollen data were used to estimate a mean abundance and coefficient of variation to show woodland expansions/contractions and woodland fragmentation over the last 20,000 years. The rescaled charcoal was displayed as a 200‐year moving median using 500‐year bins to infer the influence of fire on woodland dynamics at landscape scale. Pollen and charcoal were compared with speleothem, clastic flux and archaeological data to assess the influence of moisture balance, glacial activity and human impact on the spatial distribution of Polylepis woodlands. Results Woodland expansion and fire were correlated with precipitation changes and glacier dynamics from c. 20 to 6 kcal bp (thousands of calibrated years before present). Charcoal abundances between 20 and 12 kcal bp were less common than from 12 kcal bp to modern. However, human‐induced fires were unlikely to be the main cause of a woodland decline centred at 11 kcal bp, as woodlands recovered from 10.5 to 9.5 kcal bp (about twofold increase). Charcoal peaks analogous to those that induced the woodland decline at 11 kcal bp were commonplace post‐9.5 kcal bp but did not trigger an equivalent woodland contraction. An increase in the coefficient of variation after c. 5.5 kcal bp suggests enhanced fragmentation and coincided with the shift from logistic to exponential growth of human populations. Over the last 1,000 years, Polylepis became hyper‐fragmented with over half of sites losing Polylepis from the record and with coefficients of variation paralleling those of glacial times. Main conclusions Polylepis woodlands formed naturally patchy woodlands, rather than a continuous vegetation belt, prior to human occupation in the Andes. The main factors controlling pre‐human woodland dynamics were precipitation and landscape heterogeneity. Human activity led to hyper‐fragmentation during the last c. 1,000 years.
Chapter
Vegetation classification and mapping are important tools for addressing natural resource management, ecosystem restoration, and other contemporary ecological issues. Though classical set theory is most often applied for mapping problems, natural landscapes are often expressed as fuzzy sets. Where contrast among map categories or geometric objects is often weak in ecological contexts fuzzy approaches offer the advantage of identifying and utilizing the degree of membership among multiple possibilities, enabling opportunities for alternative outputs and for the careful analysis of error structure. In this chapter, fuzzy systems are explored for purposes of describing ecological features, for interpretation and mapping of those features, and for analyzing the uncertainty of spatial information. Some ecological applications that lend themselves to fuzzy logic are discussed along with examples of the effective use of fuzzy techniques for mapping and analysis, with explanations of the advantages of fuzzy approaches over crisp methods. Finally, in a look to future, I discuss advanced classifier methods, some Web-based solutions, and the potential for applying fuzzy systems to interactively generate user-defined map products, neutral of á priori ecological classification, according to the precise needs of natural resource managers and researchers.
Article
South America has undergone many dramatic changes during the past 60 million years, which has had a major impact on the patterns of biological speciation and diversity in the region. Birds have been particularly affected, and major geologic events have been an important factor in generating avian diversity in the New World. Here we investigate the impact of two geologic events, Andean uplift and the Panamanian land bridge formation, on the speciation and diversification patterns of birds in the New World using a broadly dispersed clade, the small New World ground doves (Aves: Columbidae). Using complete species-level sampling for the clade (barring 2 possibly extinct species), we used sequences of 4 mitochondrial genes and 1 nuclear gene to infer a phylogenetic tree for the group. To address historical biogeographic questions, we estimated divergence times and reconstructed ancestral ranges. The phylogenetic analysis resulted in a well-supported tree. Divergence time estimates and historical biogeographic reconstruction indicated a South American origin for the clade, with several speciation events coinciding with either Andean uplift events or the land bridge formation. These results indicate how major geologic events affected the diversification of this group of birds, and lead to a broader understanding of the impact of these events on patterns of speciation in New World birds.
Article
Full-text available
Rio Abiseo National Park includes three main basins, one of which Montecristo was surveyed for this study. The basin runs west to east in the northern part of the Park. The upper elevations (2300--4200 m) includes 174 species. Most of the species (55%) were terrestrial. The most diverse ecological zone was the montane rain forest from 3100 m upwards to timberline (~25 km2), which contained 109 pteridophyte species.
Article
Full-text available
A comprehensive, but simple-to-use software package for executing a range of standard numerical analysis and operations used in quantitative paleontology has been developed. The program, called PAST (PAleontological STatistics), runs on standard Windows computers and is available free of charge. PAST integrates spreadsheettype data entry with univariate and multivariate statistics, curve fitting, time-series analysis, data plotting, and simple phylogenetic analysis. Many of the functions are specific to paleontology and ecology, and these functions are not found in standard, more extensive, statistical packages. PAST also includes fourteen case studies (data files and exercises) illustrating use of the program for paleontological problems, making it a complete educational package for courses in quantitative methods.
Article
Full-text available
Point count distance sampling surveys were conducted at three sites in the Cordillera Vilcanota to determine whether variation in high-Andean species richness, diversity and abundance was a reflection of Polylepis habitat quantity. Bird community and abundance measures revealed that there was considerably variation in bird species richness, diversity and mean encounter rates between large, medium, and small forest patches. Densities of Polylepis-dependent bird species (including five globally-threatened and eight restricted-range species) were greater in larger forest patches and differed significantly between different patch size categories. Density estimates for matrix-dependent species were higher in smaller Polylepis patches indicating that the matrix exerts an influence on bird species composition and abundance in remnant Polylepis forests, particularly smaller patches. Comparison of lowland forest habitat specialists using three categories of rarity revealed that between 19-22% of all Polylepis-dependent species were intrinsically rare within larger forest patches, and a greater number (34-74%) were rare in smaller forest patches. Population estimates for all species, in particular for all threatened species, were extremely low, numbering ≤ 10 individuals at nine of the ten sites examined. The results suggest that declines in the densities of certain Polylepis birds may be predictable following habitat loss and that these patterns of rarity should govern population recovery goals through appropriate habitat restoration strategies. Such strategies are urgently required and must be designed to prevent further habitat loss, and to increase Polylepis habitat quantity to boost threatened bird populations in the Cordillera Vilcanota.
Book
Full-text available
This book is available for purchase, The 1993 version is available on the page at http://distancesampling.org/whatisds.html
Article
Full-text available
We used a bird-song simulation system to experimentally assess the effects of habitat, vegetation structure, and background noise on detection probability in aural avian point counts. We simulated bird songs of seven species in two habitats (mixed pine–hardwood forest and deciduous forest) and two leaf conditions (leaves on and leaves off) with two levels of background noise (~40 dB and ~50 dB). Estimated detection probabilities varied greatly among species, and complex interactions among all the factors existed. Background noise and the presence of leaves on trees decreased detection probabilities, and estimated detection probabilities were higher in mixed pine–hardwood forest than in deciduous forest. At 100 m, average estimated detection prob-abilities ranged from 0 to 1 and were lowest for the Black-and-white Warbler (Mniotilta varia) and highest for the Brown Thrasher (Toxostoma rufum). Simulations of expected counts, based on the best logistic model, indicated that observers detect between 3% (for the worst observer, least detectable species, with leaves on the trees and added background noise in the deciduous forest) and 99% (for the best observer, most detectable species, with no leaves on the trees and no added background noise in the mixed forest) of the total count. The large variation in expected counts illustrates the importance of estimating detection probabilities directly. The large differences in detection probabilities among species suggest that tailoring monitoring protocols to specific species of in-terest may produce better estimates than a single protocol applied to a wide range of species.
Article
Full-text available
Spot-mapping of territories was used to document the restriction of nineteen bird species to thickets of bamboo (Guadua weberbaueri) in lowland forests in southeastern Peru. These species were defined as bamboo specialists. An additional seven species showed a preference for such thickets, but also used other habitats. These results correspond with previous, qualitative descriptions of the habitat preferences of bamboo specialists. At least four specialists are restricted to thickets throughout their entire geographic range (obligate bamboo specialists); another nine specialists may use other habitats sparingly away from southeastern Peru (near-obligate bamboo specialists); the remaining six species are frequent users of habitats lacking bamboo away from southeastern Peru (facultative bamboo specialists). The nonbamboo habitats used by the 13 near-obligate and facultative specialists are predominantly dense habitats with low canopy cover, including treefall gaps and early successional vegetation along rivers. The obligate and nearobligate specialists generally have small geographic ranges centered in southwestern Amazonia; a few have sister taxa in southeastern Brazil that are also bamboo specialists suggesting a common evolutionary history. The facultative specialists are generally more widespread. Bamboo specialists are more abundant in bamboo habitats than are other bird species in more generalized habitats.
Article
Full-text available
1.Distance sampling is a widely used technique for estimating the size or density of biological populations. Many distance sampling designs and most analyses use the software Distance. 2.We briefly review distance sampling and its assumptions, outline the history, structure and capabilities of Distance, and provide hints on its use. 3.Good survey design is a crucial prerequisite for obtaining reliable results. Distance has a survey design engine, with a built-in geographic information system, that allows properties of different proposed designs to be examined via simulation, and survey plans to be generated. 4.A first step in analysis of distance sampling data is modelling the probability of detection. Distance contains three increasingly sophisticated analysis engines for this: conventional distance sampling, which models detection probability as a function of distance from the transect and assumes all objects at zero distance are detected; multiple-covariate distance sampling, which allows covariates in addition to distance; and mark–recapture distance sampling, which relaxes the assumption of certain detection at zero distance. 5.All three engines allow estimation of density or abundance, stratified if required, with associated measures of precision calculated either analytically or via the bootstrap. 6.Advanced analysis topics covered include the use of multipliers to allow analysis of indirect surveys (such as dung or nest surveys), the density surface modelling analysis engine for spatial and habitat modelling, and information about accessing the analysis engines directly from other software. 7.Synthesis and applications. Distance sampling is a key method for producing abundance and density estimates in challenging field conditions. The theory underlying the methods continues to expand to cope with realistic estimation situations. In step with theoretical developments, state-of-the-art software that implements these methods is described that makes the methods accessible to practising ecologists.
Article
Full-text available
Most bamboos are semelparous. Their synchronous masting events occur on a cycle of 3-120 yr and represent an extremely pulsed resource for granivorous birds. Although many bird species feed occasionally on bamboo seeds, there are constraints to specializing on such a fluctuating resource and few bird species are known to specialize on bamboo seeds. Three of these bird species are endemic to the Atlantic forest of South America: the purple-winged ground-dove Claravis godefrida, buff-fronted seedeater Sporophila frontalis, and Temminck's seedeater Sporophila falcirostris. All three species are irregularly recorded in the province of Misiones, Argentina. We compared the temporal and spatial patterns of records of these birds in Misiones to masting events of the five common bamboos: yatevó Guadua trinii, takuaruzú Guadua chacoensis, takuapí Merostachys claussenii, pitinga Chusquea tenella, and takuarembó Chusquea ramosissima. All bird records coincided with times and places where Guadua bamboos (G. trinii and G. chacoensis) were known or estimated to have seeds. None of the bird species occurred during masting events of Merostachys or Chusquea, unless Guadua was also masting. We discuss relevant ecological and morphological features of the birds that might bear on their association with Guadua bamboos and that might be key to their conservation.
Article
Full-text available
Distance sampling (DS) and territory mapping (TM) are globally applied bird survey techniques. However, specifically designed studies comparing results of both methods in different habitats in the framework of a scientific experiment have rarely been conducted. To provide a more generalized guidance for the field surveyor, here we evaluated estimates of bird abundances and number of bird species in four different habitats (broad-leaved forest, coniferous forest, open woodland and farmland) in central Germany. Abundances were estimated in parallel by TM and DS in 2006 and 2008, following standard protocols. Detection probability differed significantly among habitats and species. Density estimates by DS were in total 24% lower than those estimated by standardized TM. While the number of bird species detected with both methods was approximately the same, the estimated abundances of 15 bird species showed significant differences. Increasing the number from two to four and five registrations to count a territory by using TM decreased the density on average about 28 and 42%, respectively. Using standardized TM resulted in an overestimation of abundances of species showing a high detection probability. In contrast, DS estimated very high densities for species that had a very low detection probability. In fact, a highly negative correlation was found between the density estimated by DS and the detection probability. Using standardized TM and setting a fixed number of registrations before a location qualifies for a bird territory cannot compensate for the large differences in species detectability. Instead, the number of registrations required to count a territory should be adjusted to differences in detection probabilities and seasonal activity. From our results we can recommend a mean of four registrations if eight visits were conducted to count a territory. However, the lack of any statistically-based quality assessment reduces the serious usability of TM for estimating densities for science-based management application, whereas, the clear advantage of DS is that it provides error estimates and considers differences in species detectability. Distance Sampling (DS) und Revierkartierung gehören zu den verbreitetsten Erfassungsmethoden von Vogelbeständen weltweit. Bisher gibt es kaum Studien bei denen im Rahmen eines wissenschaftlichen Experiments beide Methoden parallel durchgeführt und die Ergebnisse verglichen wurden. Ziel der im Jahr 2006 und 2008 im Hohen Vogelsberg, Hessen durchgeführten Untersuchung war es deshalb, jeweils die Artenanzahl und die Abundanzen von Vögeln sowohl mit DS als auch mit der Revierkartierung in vier unterschiedlichen Lebensräumen (Laubwald, Nadelwald, Halboffenland und Offenland) standardisiert zu erfassen und zu vergleichen. Die Erfassungswahrscheinlichkeit unterschied sich deutlich zwischen den Lebensräumen und zwischen den Vogelarten. Die Dichten, die mit Hilfe von DS erfasst wurden, fielen im Durchschnitt um 24% niedriger aus im Vergleich zu den mit der Revierkartierung ermittelten Dichten. Während die Anzahl der ermittelten Arten bei beiden Methoden in etwa gleich war, zeigten die Abundanzen von 15 Arten signifikante Unterschiede. Bei der standardisierten Revierkartierung wurde ein Revier nur dann gezählt, wenn mindestens zwei Registrierungen der Art erfolgten. Steigert man die Anzahl der notwendigen Mindestregistrierungen auf vier bzw. fünf reduzierte sich die Dichte im Durchschnitt um 28% bzw. 42%. Die standardisierte Revierkartierung führte zu einer Überschätzung der Bestände von Vogelarten mit einer hohen Erfassungswahrscheinlichkeit. Im Gegensatz hierzu wurden mit DS sehr hohe Dichten für Arten mit geringer Erfassungswahrscheinlichkeit ermittelt. Dies verdeutlicht die festgestellte negative Korrelation zwischen Dichte und Erfassungswahrscheinlichkeit. Die Verwendung der Revierkartierung mit einer fixen Anzahl von Mindestregistrierungen zur Zählung eines Reviers wird den unterschiedlichen Erfassungswahrscheinlichkeiten zwischen den verschiedenen Vogelarten nicht gerecht. Daher empfiehlt sich ein artspezifisches Vorgehen unter Berücksichtigung der Erfassungswahrscheinlichkeit und der saisonalen Aktivität. Unsere Ergebnisse zeigen, das zur Wertung eines Reviers im Durchschnitt vier Registrierungen eines Vogels bei acht Begehungen notwendig sind, um realistischere Abundanzen zu erhalten. Das Fehlen jeglicher statistischer Angaben zur Bestimmung der Erfassungsgüte bei der Revierkartierung reduziert deren Eignung, um wissenschaftlich fundierte Aussagen zu erhalten. DS bietet dagegen den großen Vorteil, dass es zu jeder berechneten Abundanz Konfidenzintervalle und den jeweiligen Fehler liefert. KeywordsBird census–Detection probability–Number of registrations–Habitat type–Survey design
Article
Full-text available
Little of Brazil's remaining Atlantic forest is protected, so it is important to assess how well the region's wildlife can persist in areas/habitats outside reserves. We studied bird diversity and abundance during 546 point counts in the Sooretama/Linhares reserve, 200 point counts in 31 forest fragments (10–150 h), and 50 point counts in Eucalyptus plantations, within 7 km of the reserve. Only eight bird species were recorded in Eucalyptus, and this impoverishment, as compared to some Eucalyptus plantations elsewhere in Brazil may be a result of intensive clearance of understory vegetation. Species diversity in forest fragments was significantly lower than in the reserve. Twelve, mostly non-forest or edge species, were significantly commoner in the fragments, but nineteen species were frequent in the reserve but rare or absent in forest fragments. These included two Pyrrhura parakeets, a Brotogeris parakeet, a trogon Trogon, a jacamar Galbula, woodpeckers Piculus and Campephilus, Myrmotherula antwrens, and Hemithraupus and Tachyphonus tanagers. Bird species richness at points in forest fragments did not decline with fragment size, distance from the reserve, or forest quality. However, forest in fragments was more heavily degraded than forest within the reserve and poor forest quality may be the cause of declines in some species. Whilst protection of forest within reserves is a priority, management of forest fragments may aid conservation of some threatened species.
Article
Full-text available
Gene flow and morphological divergence were measured among 12 populations of a common species of rainforest passerine. Populations in the forest and the ecotone (the transition zone between the African rainforest and savanna) are morphologically divergent, despite high gene flow, and morphological differences between habitats are as large as those found between related species. in contrast to past theories of rainforest speciation, which emphasize geographic isolation, these results suggest that natural selection may play an important role in generating rainforest biodiversity. Because ecotone habitats may be a source of evolutionary novelty, greater attention should be paid to their conservation in order to preserve the processes that may be important to maintain rainforest diversity.
Article
Full-text available
Both local and regional habitat characteristics influence species richness and community structure. The scale at which communities are studied, however, affects the detection of relationships between habitat characteristics and patterns of habitat selection, species diversity, and species composition, and may obscure observation of differences in how species perceive the scale of environmental variation. To determine how environmental variation at different scales is related to species occurrence and richness, I analyze mist net sampling data on several guilds of forest understory birds. Bird capture, vegetation, and physical environment data come from 23 0.5-ha study sites in primary and secondary forest in Amazonian Ecuador. The percentages of primary forest within concentric circles around each site form forest imbeddedness measures (FIMs), which are evaluated using satellite imagery. Variation in FIM size represents different measurement scales for determining forest cover. Primary forest cover is also analyzed in successively larger tori surrounding sites and is used, after variable reduction with Principal Components Analysis, to summarize variation in forest cover around sites. Linear regression, surface trend analysis, and ordination help to quantify how variation in guild composition and species richness is explained by forest cover, vegetation structure, and physical environment. Species composition is related to variation in primary forest cover, primarily within 200-600 m of study sites. Canonical Correspondence Analysis (CCA) indicates that nectarivores, shrub-layer frugivores, and ant-following birds are captured in areas with relatively low primary forest cover. In contrast, shrub-layer insectivores, shrub-layer omnivores, and birds probing dead foliage for large insects tend to be captured in areas of relatively high primary forest cover. The species richness of insect gleaners, ant followers, and omnivores is statistically related to the percent cover of primary forest within hundreds of meters from the study sites. This suggests that some mechanisms that influence guild composition act over substantial distances. Nonetheless, the small radii of FIMs related to the species richness of dead-leaf probers suggests that local conditions and variation in forest cover over short (<200 m) distances directly or indirectly influence species richness of some primary forest birds. The significant relationship between temperature variation among capture sites and species richness of ant-following birds suggests that these species choose among habitats in a temperature range at which physiological constraints operate, either directly on the birds themselves or on the ants they follow. Species richness within the nectarivores, in contrast, shows no relationship with large-scale variation in primary forest cover. The radius of the FIM most closely associated with species richness differs among guilds, which suggests variation in the scale at which forest cover is associated with guild structure, as well as variation in the strength of the association. Differences in the scale of relationships between environment and species richness among guilds suggest that the mechanisms that influence both species' habitat use and community structure differ among guilds. A single mechanism, operating at a single scale, is inconsistent with these patterns.
Article
Full-text available
The original publication is available at http://www.springer.com/ The scattered and dwindling Polylepis woodlands of the high Andean global hotspot have been identified as being of particular importance to biodiversity conservation, and yet little is known of the make-up of their faunal communities, how these vary across landscapes, and how well species might tolerate matrix/edge habitats. We examined the bird communities and vegetation characteristics of Polylepis woodlands and the surrounding matrix habitats at three sites in the Cordillera Vilcanota, southern Perú (3,400–4,500 m). The vegetation structure of woodlands varied significantly across the three sites but all were dominated by two Polylepis tree species, with mossy ground cover. Matrix habitats were treeless and dominated by ground-level puna grass-steppe or boulder scree vegetation. Bird species richness and diversity, encounter rates and the number of globally-threatened and restricted-range bird species were consistently higher in the Polylepis forests, than in matrix habitat. We used canonical correspondence analysis (CCA) to identify habitat gradients across the landscape, and to classify bird species according to their association with Polylepis, the matrix or Polylepis-matrix interface. There were few matrix-restricted bird species, but around half the bird community, including fourteen threatened or restricted-range species, were Polylepis-dependant. Many of these species had very narrow niches. The Polylepis-matrix interface was dominated by species traditionally considered invasive ecological generalists. Our study illustrates the overriding importance of Polylepis interior habitats, indicating that conservation strategies for high Andean birds must focus on patch size maintenance/enlargement, enhancement of within-patch habitat quality, and efforts to safeguard connectivity of suitable habitat across what is essentially an inhospitable puna/scree matrix.
Article
Full-text available
The eastern slope of the tropical Andes and adjacent Amazonian lowlands are home to some of the world's richest biotas. Here we report on recent surveys and inventories of mammal and bird faunas in Peru's Manu National Park and Biosphere Reserve and compile these records with prior literature, museum specimens, and unpublished records to produce updated lists for both taxa. The lists of 222 species of mammals and 1005 species of birds recorded along an elevational transect in the Manu Biosphere Reserve are the largest for any similarly sized area in the world. Mammals recently documented in the reserve include 147 species, 130 with specimen vouchers. Twelve species were new to science, and most of these have been recently described; four others might be new and are currently being evaluated. Twenty-nine mammal species are newly added to Manu's list. The cumulative tally comprises 20 species of opossums, 1 shrew opossum, 2 armadillos, 5 sloths and anteaters, 92 bats, 14 primates, 21 carnivores, 1 tapir, 7 even-toed ungulates, 58 rodents, and 1 rabbit. Avian records include 682 species with specimen vouchers and another 108 documented by recognizable photographs or voice recordings. The avifauna is largely resident, including 911 species that are year-round residents, 42 migrants from the north, 24 migrants from the south or other tropical areas, and 28 vagrants (represented by fewer than three records).
Article
Full-text available
In studies of forest fragmentation, birds of scrubby, early-successional habitats are considered edge specialists. Because these birds are assumed to thrive in fragmented, edge-dominated areas, their landscape ecology has received little attention from ecologists. With populations of shrubland birds declining throughout the eastern United States, the question of whether or not these birds really prefer edge habitats has important conservation implications. We used a meta-analysis to test how edges affect the abundance of shrubland birds in early-successional habitats. We analyzed data for 17 species from seven studies that compared the abundances of birds in the interiors and edges of regenerating clearcuts surrounded by mature forest. The meta-analysis clearly showed that shrubland birds avoid edges. All 17 species tested had higher abundances in patch centers than along edges, and edge effects were significant for 8 of 17 species. The key implication of this result is that small or irregular patches, dominated by edge, are unlikely to provide suitable habitat for shrubland birds. Thus, management for these declining species should involve providing large patches and minimizing edges. These findings demonstrate the importance of testing widely accepted ecological classifications and the need to view landscape ecology from the perspective of non-forest wildlife.
Article
Full-text available
Both the magnitude and the urgency of the task of assessing global biodiversity require that we make the most of what we know through the use of estimation and extrapolation. Likewise, future biodiversity inventories need to be designed around the use of effective sampling and estimation procedures, especially for 'hyperdiverse' groups of terrestrial organisms, such as arthropods, nematodes, fungi, and microorganisms. The challenge of estimating patterns of species richness from samples can be separated into (i) the problem of estimating local species richness, and (ii) the problem of estimating the distinctness, or complementarity, of species assemblages. These concepts apply on a wide range of spatial, temporal, and functional scales. Local richness can be estimated by extrapolating species accumulation curves, fitting parametric distributions of relative abundance, or using non-parametric techniques based on the distribution of individuals among species or of species among samples. We present several of these methods and examine their effectiveness for an example data set. We present a simple measure of complementarity, with some biogeographic examples, and outline the difficult problem of estimating complementarity from samples. Finally, we discuss the importance of using 'reference' sites (or sub-sites) to assess the true richness and composition of species assemblages, to measure ecologically significant ratios between unrelated taxa, to measure taxon/sub-taxon (hierarchical) ratios, and to 'calibrate' standardized sampling methods. This information can then be applied to the rapid, approximate assessment of species richness and faunal or floral composition at 'comparative' sites.
Article
Changes in fire regime have been identified as the cause of the loss of nearly 50% of wet sclerophyll forest in north Queensland in the last 50 years. In the absence of fire, rainforest invades and eventually eliminates the specialized wet sclerophyll forest biota. Bird populations and foraging behaviour were monitored in areas selected to encompass both recent and advanced rainforest invasion. Foraging guilds are discussed in relation to increasing rainforest biomass. Some species, such as the Pale Yellow Robin Tregallasia capito nana were advantaged by the expansion of rainforest. Other species, such as the Golden Whistler Pachycephala pectoralis showed no significant response, whereas the endemic subspecies of the Eastern Yellow Robin Eopsaltria australis magnirostris was clearly disadvantaged. The latter species is of particular concern because in north-east Queensland it is dependent upon wet areas adjacent to rainforest and requires open ground in which to forage. Over the longer term the White-naped Melithreptus lunatus and White-cheeked Phylidonyris nigra Honeyeaters are also threatened by habitat loss. These honeyeaters favour the wetter areas adjacent to the rainforest which are gradually being lost to the invasive process. To maximize biological diversity in the wet tropics of north Queensland, it is necessary to maintain the full spectrum of natural habitats. Fire management is therefore required to maintain the wet sclerophyll forest and its dependent fauna.
Article
Intraspecific variation in plumage was used to test the null hypotheses that geographic variation in 280 species of elevationally restricted Andean forest birds is independent of elevation and is not a function of patchy geographic distribution. Both null hypotheses were rejected. At most taxonomic levels, geographic variation in plumage was correlated positively with both the mean of its elevational distribution and the size of its geographic range. Vertical amplitude of elevational distribution was not a significant predictor of geographic variation in plumage in most taxa. Independent of these elevational correlates, patchily distributed species showed significantly more geographic variation than continuously distributed species. These results show that geographic variation and presumably ongoing speciation phenomena are greater at higher elevations. The decreased species richness at high elevations may be attributable to a higher rate of extinction from catastrophic disturbance as well as to ecological factors that limit sympatry in newly formed species.
Article
Geographic ranges of widespread Andean forest bird species are linear, averaging over 300 times longer than they are wide. Among congeneric species, geographic variation in plumage was negatively correlated to the width (W) of their elevational distributions, presumably because narrower distributions are more easily fragmented by barriers to gene flow. The amplitude of a species' elevational distribution may be limited by zonation of resources and by genetic factors that prevent populations from adapting to local environments. Minimum amplitudes may be dictated by demographic consequences.
Article
Natural history characteristics of a dominant understory bamboo (Chusquea sp.) were examined in relation to a tropical montane rain forest's structure, composition, and regeneration at timberline in north-central Peru. Because of its small size and sun intolerance, this scandent bamboo does not aggressively preempt space aboveground by occupying canopy openings or understory clearings or belowground through rhizome growth. Furthermore, two years of census data on >1100 tagged trees and shrubs suggest that its presence in the understory does not affect the mortality, composition, or regeneration of the arboreal species.
Article
In a site in northern Peru, montane rain forest forms an upper timberline on steep slopes and another timberline lower down on valley bottoms. Both timberline forests had 7-m-tall canopies, but other features were very dissimilar. The upper timberline forest had few stems, relatively low basal area, and little regeneration, while the lower timberline forest was markedly different in species composition and had abundant populations of seedlings and saplings, and large basal area. Data from intervening plots along an elevational transect clarified that these contrasts originated in the differential presence and abundance of the tree and shrub species, some of which were limited to edge habitats on either or both of the timberlines, and others that regenerated in interior forest but only within narrow elevational ranges. These patterns may be typical of tropical timberlines in areas of glacially modified topography.
Article
We sampled understory insectivorous birds in Amazonian forest fragments from before isolation through 9 yr after isolation. We accumulated 3658 mist net captures of 84 insectivorous species in five 1-ha fragments and four 10-ha fragments. Abundance and species richness declined dramatically after isolation, even though fragments were separated from continuous forest by only 70-650 m. Three species of obligate army ant followers disappeared within the first 2 yr after isolation. Mixed-species flocks containing 13 commonly netted species disintegrated within 2-3 yr after isolation, although three species that dropped out of flocks persisted in fragments. Among insectivores not associated with flocks or army ants, only two species of edge specialists were unaffected by fragmentation. Overall, loss of forest insectivores was not compensated for by an increase in nonforest or previously uncommon species. Secondary vegetation surrounding fragments strongly affected use of fragments after isolation. Fragments surrounded by Vismia, the dominant regrowth where felled forest was burned and temporarily used as cattle pasture, remained depauperate. In contrast, many species returned to fragments by moving through regenerating forest dominated by Cecropia, which occurred in areas where the felled forest was not burned. Both 1- and 10-ha fragments surrounded by Cecropia were used by ant followers by 5 yr after isolation. Mixed-species flocks reassembled in 10-ha fragments surrounded by Cecropia by 7-9 yr after isolation, and augmented their group territories by foraging in secondary forest outside fragments. Solitary species were more variable in their responses, although several species returned to 10-ha fragments surrounded by Cecropia. Terrestrial insectivores, such as Sclerurus leafscrapers and various antbirds, did not return to any fragments, and appear to be the group most vulnerable to fragmentation. Ordination of the insectivore community showed that 1-ha fragments diverged from their pre-isolation communities more than did 10-ha fragments. Communities in 10-ha fragments surrounded by Cecropia were more closely associated with pre-isolation communities than those in fragments surrounded by Vismia. Over time, communities in 10-ha fragments surrounded by Cecropia became more like pre-isolation communities, although communities in other fragments generally continued to diverge.
Article
Community studies of birds often rely on abundance estimates that are obtained from counts of bird vocalizations, yet vocalizations are not equally detectable in all habitats. I broadcast vocalizations for nine bird species to evaluate biases in detection of bird vocalizations among four forested habitats (young, mature, and old aspendominated forests, and white spruce dominated forests), and in relation to height of the broadcast, whether the broadcast occurred before or after leaf formation, and the frequency of the broadcast vocalization. Virtually all of the broadcast vocalizations were detected at 50 m from the speaker. However, at 100 m from the speaker, 27% of the broadcast vocalizations were not detected and detection was highest in white spruce forest, lowest in young aspen forest, and intermediate in mature and old aspen forests. Detection of broadcasts was negatively related to the minimum frequency of the vocalization, higher for broadcasts from the canopy than for broadcasts from the shrub layer, and higher for broadcasts before than after leaf formation. I reanalyzed abundance data that were obtained from a study involving point counts of wild birds in young and old aspendominated forest. Biases among habitats in the detection of vocalizations had moderate influence on the resulting measures of habitat preferences for birds. I suggest that if a detection distance of more than 50 m is used for bird censuses within forested habitats, then comparisons among forest types should be interpreted cautiously unless the researchers demonstrate that biased detection of vocalizations does not affect their conclusions.
Article
For a set of 47 bird species whose limits (16 upper, 31 lower) coincided with the montane rain forest-cloud forest ecotone on the Cordillera Vilcabamba control transect, it was determined whether, as predicted, the species expanded or contracted their distributions in localities in which the homologous ecotones were displaced upward or downward relative to the control elevation. Where the ecotone was displaced away from species' centers of distribution, 36 of 41 species (88%) were found to have expanded their distributions. This result upholds the provisional assessment of the ecotone as a distributional barrier to these species in the control locality. Where the ecotone was shifted toward species' centers of distribution, 43 out of 44 species (98%) had failed to contract fully in distribution; they were found on the other side of the ecotone, in what had been predicted to be alien habitat. This result, not anticipated, is illustrative of a tendency of species to occupy a greater range of habitats near to vs. far from their centers of distribution. Widespread Andean bird species had expanded distributions, in both upward and downward directions, in the biogeographically isolated Cordillera de la Costa of Venezuela. Reduced avian species diversity in this range relative to the main Andean chain appears to have led to a general relaxation of distributional restraints. Competitive exclusion emerges as the factor of overriding importance in the exceedingly diverse Andean fauna. -from Author
Article
Ecotones between biomes are sensitive areas of change that could be effectively modelled and monitored for future change. Ecotones are also important in influencing local and regional biodiversity patterns and ecological flows. The ecological processes that could affect change at ecotones and within biomes include internal ecosystem processes, such as competition, and external abiotic processes, most notably drought and related disturbances. Drought followed by infestations and fire appears to be the most likely process that could mediate ecological change under a rapidly changing climate. Predictions about the dynamics of ecotones can be made qualitatively, based on a theory of patch scaling and diversity in relation to abiotic stressors. Directional climatic change should promote a coalescence of patches on one side of the ecotone and increased fragmentation on the other side. -from Author
Article
A total of 54 bird species was recorded in the subtropical heathlands of Cooloola National Park, Queensland.. The composition of the bird community and the numbers of birds present in any given heathland appeared to be dependent on the years since the last fire. Thirty-nine species were inconsistent users of the habitat. Some of these species were migrants while others were either irregular visitors occurring throughout the year or predictable visitors that take advantage of specific short-lived abundances of food (e.g. carrion after fires or the annual production of nectar or seeds). The longer a heathland was unburnt the smaller the number of inconsistent species recorded visiting that heathland. Of the 15 bird species consistently using the heathlands, 12 were breeding residents, including the Ground Parrot and Southern Emu-wren. The variable patterns of post-fire recolonisation exhibited by the consistent species was attributed to the changing structure of the preferred microhabitats and the availabilitv of food. A minimum seven to eight year fire-free interval is suggested if viable populations of most resident species are to be maintained.
Article
The structure and composition of forest edges were examined in the timberline zone of Rio Abiseo National Park in north-central Peru. Tree, shrub, and scandent plant species were inventoried in six 25 by 40 m forest plots, positioned with the long axes perpendicular to the forest-grassland boundary, and located at different elevations. Number of tree and shrub species on the 0.1 ha plots decreased from 30 to 12 (lower to higher elevation) over the 250 m elevational gradient studied; at lower elevations (3300-3350 m), there were more habitat specialists, i.e., species apparently restricted to either forest edge or forest interior. In all plots, scandent plant species were diverse (12-20 species/0.1 ha) and abundant (at total densities of 6000-10,000 stems/ha). Many were scandent by virtue of the angles formed by leaves and/or branches; none could be classified as forest-edge or -interior specialists. Forest margins were variably affected by occasional stand-destroying fires originating in the grasslands. The specifics of forest composition and structure in the timberline zone were influenced by elevation, distance from the edge, and the nature and intensity of past disturbances.
Book
"Measuring Biological Diversity assumes no specialist mathematical knowledge and includes worked examples and links to web-based software. It will be essential reading for all students, researchers, and managers who need to measure biological diversity."--BOOK JACKET.
Article
Describes a group of large flightless, flesh-eating birds known as phorusrhacoids, which lived from 62 million years to about 2.5 million years ago, and which became the dominant carnivores of South America. The history of their discovery and taxonomic classification, the reconstruction of their appearance from fossil remains, their mode of life, and their nearest living relatives, are described. The creatures ranged in height from one to three metres, and were able to kill and eat animals the size of small horses. By about five million years ago phorusrhacoids had completely replaced their nearest competitors, the doglike borhyaenoids, on the savannas of South America. However, their decline came soon after, following the emergence of the Panamanian land bridge, and the dispersion into South America of new competitors in the form of placental dogs and cats. -G.E.Hodgson
Article
In a Neotropical montane forest in southwestern Colombia, we investigated how the distribution of understory birds changed from forest edge to forest interior (0-10 m, 30-40 m, 60-70 m, and 190-200 m from the edge) and how these changes were influenced by edge age (three old [>40 yr] and three young [<12 yr] edges) and month sampled. Capture rates of frugivores were highest both at the forest edge (0-10 m) and forest interior (190-200 m); for insectivores, capture rates were highest at the forest interior; for nectarivores, they were highest at the forest edge. Distance, edge age, and month interacted in various ways. Frugivores were more abundant at the forest interior than at the edge during the dry months. Insectivores were more abundant at new edges than at old edges during the wet months. Seventeen out of 25 abundant species (≤21 captures), including the Tangara spp. assemblage, exhibited a non-uniform distribution, showing either an increase or decrease from forest edge to forest interior, or bimodal distributions. Extremely sparse species (one capture) were found more often than expected near the forest edge (0-10 m). Edges resulting from large-scale, anthropogenic disturbances influenced the distribution of understory birds in complex ways. Significant interactions between distance, month, and edge age suggest that 'edge effects' change over various temporal scales. Instead of emphasizing 'depth' of 'edge effects,' future studies should emphasize edge dynamics, i.e., how processes taking place at edges change over time, and how organisms can modify any 'edge effect.' In particular, changes in the distribution of frugivores suggest that seed dispersal may be influenced by the presence of edges, leading to changes in the structure and location of edges through time. This might be particularly true in our study area, where transient corn fields, pastures, and second-growth areas of various ages are embedded in a forest matrix.
Article
Two procedures, the jackknife and the bootstrap, are discussed as methods for estimating the number of species by the sampling of quadrats. Explicit formulas for both procedures are presented and evaluated under a model with a random distribution of individuals. The jackknife and bootstrap are shown to reduce the bias although they underestimate the actual number of species if there is a large number of rare species and the number of quadrats sampled is small. When a small number of quadrats is sampled, the jackknife is shown to give better estimates. When the number of quadrats is large, the jackknife tends to overestimate the number of species and the bootstrap performs better.
Article
Ecotones have been considered as unique environments, and the concepts of edge effect and ecotonal species have been widely used, especially in avian community ecology. We studied the patterns of bird densities across heath-wood edges at replicated sites in three locations in southeastern Australia. Multivariate analysis showed that the bird community in the ecotone was intermediate between the heath and wood communities, indicating that the ecotone contained a mixing of species rather than a unique bird community. ANOVA showed a modest increase in bird density at the wood side of the ecotone, which may be partly due to sampling biases rather than to some inherent habitat value in the ecotone. The outstanding pattern was that bird density and species richness in the wood habitat were twice as high as in the heath habitat. Of a total of 86 species, 31 occurred in sufficient numbers to categorize according to their habitat association (generalist, or heath or wood specialist) and their density at the ecotone (ecotone neutral, ecotone shy, or ecotone conspicuous). Three of these were habitat-generalist-ecotone-neutral. Fourteen species were ecotone neutral but were habitat specialists on either the wood (13 spp.) or the heath (1 sp.). Three species were ecotone shy. Although 11 species were ecotone conspicuous, they also occurred in either heath or wood or both. Thus, no species could be categorized as entirely ecotonal. We conclude that there is little evidence from this or other studies of avian communities to support an edge effect of increased density and species richness, and no evidence of entirely ecotonal species.
Article
Significant changes in the climates of Central America are expected over the next century. Lowland rainforests harbor high alpha diversity on local scales (<1 km 2), yet montane landscapes often support higher beta diversity on 10-100 km 2 scales. Climate change will likely disrupt the altitudinal zonation of montane communities that produces such landscape diversity. Projections of biotic response to climate change have often used broad-scale modelling of geographical ranges, but understanding likely impacts on population viability is also necessary for anticipating local and global extinctions. We model species' abundances and estimate range shifts for birds in the Tilarán Mountains of Costa Rica, asking whether projected changes in temperature and rainfall could be sufficient to imperil high-elevation endemics and whether these variables will likely impact communities similarly. We find that nearly half of 77 forest bird species can be expected to decline in the next century. Almost half of species projected to decline are endemic to Central America, and seven of eight species projected to become locally extinct are endemic to the highlands of Costa Rica and Panamá. Logistic-regression modelling of distributions and similarity in projections produced by temperature and rainfall models suggest that changes in both variables will be important. Although these projections are probably conservative because they do not explicitly incorporate biological or climate variable interactions, they provide a starting point for incorporating more realistic biological complexity into community-change models. Prudent conservation planning for tropical mountains should focus on regions with room for altitudinal reorganization of communities comprised of ecological specialists.
Article
Summary Growth, reproductive success and non-structural carbon pools in Polylepis tarapacana Philippi trees were examined across a transect between 4360 and 4810 m altitude on Nevado Sajama, Bolivia. The mean −10-cm soil temperature of 5·4 °C under trees at the treeline during the 265-day growing season matched the threshold temperature found at other subtropical and tropical treelines. Beyond 4400 m Polylepis is restricted to the warmer and drier equator-facing slopes, suggesting a direct thermal limitation of tree growth. Maximum tree height, annual shoot increment and mean tree-ring width decreased with altitude. Trees near the upper range limit reached a maximum tree height of 3·3 m and a maximum stem diameter of 34 cm. The smallest tree-height classes dominated populations at all altitudes, and the uppermost site revealed the highest proportion of seedlings. Tree-size demography indicates a critical phase for tree establishment during the sapling stage, when trees emerge from sheltered niches near the ground. No evidence of a depletion of mobile C stores (sugars, starch and lipids) was found in any tissue type with increasing elevation, suggesting a limitation of C investment (growth) rather than C acquisition (photosynthesis) at treeline. Functional Ecology (2005) doi: 10.1111/j.1365-2435.2005.01040.x
Article
In this field study we analysed the regional and local scale effects of disturbance and climate on altitudinal treelines dominated by Nothofagus pumilio in northern Patagonia. We compared two regions west and east of the Andes at 40° S, slopes with warm vs cool aspects and undisturbed vs locally disturbed treelines. This spatial framework allowed us to test (1) for differences among treelines affected by different types of local disturbance and (2) the traditional hypothesis that low temperature limits treeline. Contingency tables and ANOVA showed that local disturbance occurred more frequently than expected on slopes with cool aspects, steep slope angles and concave slope configuration. Disturbed treelines were locally lowered with longer ecotones and lower krummholz growth rates and vegetation cover than undisturbed treelines. Three-way ANOVA showed the significant influences of study area (regional climate) and aspect (local climate) on treeline elevation, krummholz growth rates and density, tree density and vegetation cover, while accounting for local disturbance. Treeline elevations were higher east of the Andes reflecting the more continental climate in Argentina than in Chile, plus regional impacts of volcanic eruptions. Tree density and vegetation cover were greater west of the Andes reflecting greater precipitation in Chile. Within study areas, local climate had different influences on treeline elevations and krummholz growth rates west and east of the Andes. We predict that increased tree growth and upslope advance of treeline in response to global warming is more likely in Chile than in Argentina near 40° S, unless precipitation increases east of the Andes. To test these predictions, we recommend research be stratified to account for the influences of local disturbance, which may confound climatic impacts. In northern Patagonia, suitable control (undisturbed) study sites will most likely be found at upper slope positions with low slope angles, simple microtopography and straight topographic configuration.
Article
In a montane tropical forest in southwestern Colombia, we investigated how anthropogenic edges may alter bird-mediated seed dispersal from edge to forest interior as a function of edge age and presence of treefall gaps. We estimated fruit abundance and mist-netted birds at four distances from edge to forest interior (0-10, 30-40, 60-70, and 190-200 m) in three young (40 yr) edges. Fruit-sampling plots (50-m2 plots) at each of the four distances were classified into gap and intact forest. Fruit abundance and frugivore capture rates varied from edge to forest interior, but such changes depended on edge age. At new edges, the total number of fruits was higher at the forest edge than at the forest interior, whereas bird captures showed the opposite trend. At old edges, the total number of fruits and bird capture rates did not vary among the four distances. In a first group of 12 plant and four bird species, the distribution of individuals in fruit (7 species) and captures (3 species) from edge to forest interior differed between old and new edges. In a second group of 18 plant and five bird species, which included those that were not amenable for a comparison between old and new edges and those that were not influenced by edge age, the distribution of individuals in fruit (12 species) and captures (3 species) was not uniform from forest edge to forest interior. Lastly, 124 plant and 19 bird species with
Article
Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts.Location We present the results of a data-logging campaign at 46 treeline sites between 68° N and 42° S.Methods We measured root-zone temperatures with an hourly resolution over 1–3 years per site between 1996 and 2003.Results Disregarding taxon-, landuse- or fire-driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7–8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5–6 °C) and in the subarctic and boreal zone (6–7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6–7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean (Fagus spp.) and temperate South Hemisphere treelines (Nothofagus spp.) and the native treeline in Hawaii (Metrosideros) are located at substantially higher isotherms and represent genus-specific boundaries rather than boundaries of the life-form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical.Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.
Article
In recent years, studies of bird-habitat relationships undertaken in the context of habitat fragmentation have led to the widespread use of species categorisation according to their response to edge alongside mature forest patches (edge species, interior species, interior-edge generalist species). In other research contexts, especially in less fragmented landscapes dominated by a forested land base in various age classes, bird-habitat relationships are often described in relation to their use of various successional stages (early-successional species, mature forest species, generalist species). A simple comparison of these two commonly-used classifications schemes in a close geographical range for 60 species in eastern North America as well as for 36 species in north-western Europe clearly reveals that in these two particular biomes the two classifications are not independent. We believe that this association is not only a semantic issue and has important ecological consequences. For example, almost all edge species are associated with early-successional habitats when a wide range of forest age-classes are found in a given area. Accordingly, we suggest that most species considered to prefer edge habitats in agricultural landscapes are in fact only early-successional species that could not find shrubland conditions apart from the exposed edges of mature forest fragments. To be considered a true edge species, a given species should require the simultaneous availability of more than one habitat type and consequently should be classified as a habitat generalist in its use of successional stages. However, 28 out of 30 recognised edge species were considered habitat specialists in terms of successional status. Based on these results, we conclude that “real edge species” are probably quite rare and that we should make a difference between true edge species and species which in some landscapes, happen to find their habitat requirements on edges.
Article
1 Nothofagus pumilio forms an abrupt alpine timberline (AT) at 690 m a.s.l on Balseiro mountain, 54 °S, Tierra del Fuego, Chile. Fruit and seed rain (quantity and quality), emergence, density and survival of seedlings were studied across an altitudinal gradient (450–740 m) from within the forest to above the AT. 2 Fruit rain generally declined with altitude but increased between 630 and 690 m before falling sharply beyond the AT. The proportion of seed-bearing fruits, seed viability and seed mass also declined with increasing altitude, but showed no recovery in the vicinity of the AT. 3 Fruit rain decreased exponentially with distance into the alpine zone, so that effective dispersal rarely exceeded 20 m beyond the AT and few of these fruits contained seeds. 4 Seedling emergence and density decreased with altitude both within the forest and into the alpine zone so that seedlings were found no more than 10–20 m above the AT. Even in 1996, when fruit production was high, successful seedling recruitment was limited to lower altitudes. 5 There was little correlation between altitude and the percentage survival of naturally occurring seedlings within the forest. However, transplanted seedlings survived better at the AT itself than immediately inside the forest, and showed high mortality in the alpine zone. 6 The most severe bottlenecks for tree recruitment within the forest appeared to be seedling emergence and seed production. Above the AT, seed viability and emergence were the principal bottlenecks. 7 Although not all demographic variables declined altitudinally, the overall probability of adult establishment decreased with increasing altitude and became very low once the protection by the tree canopy became unavailable. A demographic model explaining the origin and abrupt character of the AT studied is presented. Paper can be downloaded from: https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1046/j.1365-2745.2000.00497.x
Article
As natural predators of pest insects, woodland birds provide biological pest suppression in crop fields adjacent to woody edges. Although many birds using these habitats forage widely, earlier studies have found that most foraging activity occurs within 50 m of the woody edge. The goals of this study were to determine the primary area of use, or functional edge, for birds foraging in crop fields adjacent to woody edges, and to evaluate their foraging distance patterns. During the summers of 2005 and 2006, avian foraging behavior was observed at 12 research sites in east central Nebraska that contained either a shelterbelt or woody riparian edge. At each site, perches were provided at 10 m intervals out from the edge and insect larvae were placed in feeders at random locations to simulate a pest insect food resource. Birds were recorded foraging in five distance categories out from the edge (0–10, 10–20, 20–30, 30–40, and 40–50 m). Seven species foraged primarily within 20 m of the edge (72% all observations; 79% without perch or feeder observations). Ten species foraged throughout the plots but six of these generally foraged more often (45% and 49%) and four less often (30% and 30%) within 20 m of the edge. The 13 species that tended to forage more often within 20 m of the edge, with 56% of their foraging overall in this area, also tended to forage farther when perch and feeder observations were included, indicating willingness to forage farther when food resources were available. Based on a repeated measures analysis of variance, foraging distances appeared to be greater at sites with soybean as the planted crop, although this apparent trend was significant for only some species. There was no clear difference in foraging distances outward from shelterbelt versus riparian sites. These results indicate that conservation efforts within the 20 m functional edge offer potential to enhance the sustainability of both birds and crops in agricultural landscapes.
Book
NOTE: This is not a book, contrary to what ResearchGate claims. This is a software application and User's Guide. The current version is Version 9. The citations here are incomplete, since each version has its own citations. EstimateS currently has more than 4000 citations in the peer-reviewed literature. For the full list, go to GoogleScholar: http://bit.ly/11YdUlg .
Article
Both the magnitude and the urgency of the task of assessing global biodiversity require that we make the most of what we know through the use of estimation and extrapolation. Likewise, future biodiversity inventories need to be designed around the use of effective sampling and estimation procedures, especially for `hyperdiverse' groups of terrestrial organisms, such as arthropods, nematodes, fungi, and microorganisms. The challenge of estimating patterns of species richness from samples can be separated into (i) the problem of estimating local species richness, and (ii) the problem of estimating the distinctness, or complementarity, of species assemblages. These concepts apply on a wide range of spatial, temporal, and functional scales. Local richness can be estimated by extrapolating species accumulation curves, fitting parametric distributions of relative abundance, or using non-parametric techniques based on the distribution of individuals among species or of species among samples. We present several of these methods and examine their effectiveness for an example data set. We present a simple measure of complementarity, with some biogeographic examples, and outline the difficult problem of estimating complementarity from samples. Finally, we discuss the importance of using `reference' sites (or sub-sites) to assess the true richness and composition of species assemblages, to measure ecologically significant ratios between unrelated taxa, to measure taxon/sub-taxon (hier-archical) ratios, and to `calibrate' standardized sampling methods. This information can then be applied to the rapid, approximate assessment of species richness and faunal or floral composition at `comparative' sites.
Article
Four of the world's leading ornithologists and ardent conservationists have produced this unique synthesis of the ecological information on all 4,037 species of birds found from Mexico south to Tierra del Fuego. In tables that cover more than 300 pages and include much of their own unpublished data, the authors summarize details on 40 key ecological parameters for each bird species. Additional data and further analyses are provided for migratory species. Because bird communities are good indicators of habitat type and condition, and because extensive bird surveys can be done quickly, bird communities are critical to rapid evaluations of an ecosystem's biological value and integrity. The authors analyze the bird species of major habitats from a conservation perspective, and develop specific guidelines to illustrate how governments, conservation organizations, and wildlife managers can use this ecological information to anchor conservation strategies on sound biological reality. "Students of ecology and wildlife management, as well as conservationists, will benefit from this book . . . . Governmental and conservation agencies should use this book when making critical decisions about where to focus their efforts as they work to preserve the environment in fragile regions of the world." —Edward I. Saiff, Science Books & Films
Article
Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.