Relatively little is known about the longevity of free-living landbirds, especially in the tropic... more Relatively little is known about the longevity of free-living landbirds, especially in the tropics. We used mark-recapture data for birds originally banded in 2005 and 2006, and later recaptured between 2011 and 2016 to estimate minimum longevity for 20 species from southeastern Peru. The oldest recorded longevity was 10 yr, 6 months for a Black-billed Treehunter (Thripadectes melanorhynchus). Another notable record was for a Russet-crowned Warbler (Myiothlypis coronata; 9 yr, 2 months). Our estimated minimum longevity records generally reflect the findings of other researchers, indicating that tropical birds are often markedly site faithful and long-lived.
This study establishes an altiudinal gradient, spanning from the highland Andes (2400 m) to lowla... more This study establishes an altiudinal gradient, spanning from the highland Andes (2400 m) to lowland Amazon, as a productive region for the study of bird pollination in Southeastern Peru. The 'Manú Gradient' has a rich history of ornithological research, the published data and resources from which lay the groundwork for analyses of plant-bird interactions. In this preliminary expedition we documented 44 plants exhibting aspects of the bird pollination syndrome, and made field observations of hummingbird visits at three sites spanning the Manú Gradient: 2800 m (Wayqecha), 1400 m (San Pedro), and 400 m (Pantiacolla). Some of the documented plant taxa are underrepresented in the bird pollination literature and could be promising avenues for future analyses of their pollination biology. The Manú Gradient is currently the focus of a concerted, international effort to describe and study the birds in the region; we propose that this region of Southeastern Peru is a productive and perhaps underestimated system to gain insight into the ecology and evolution of bird pollination.
Knowledge of molt patterns and their resulting plumages is useful for aging and sexing birds and,... more Knowledge of molt patterns and their resulting plumages is useful for aging and sexing birds and, in mono-chromatic species, morphometric measurements can help to discern males from females. However, these data are largely undescribed for the majority of the world's bird species, especially in the tropics. We sought to classify the molt strategy for 10 species of Neotropical passerines during their breeding seasons and considered whether a combination of wing chord, tail length and mass could be used to determine their sex. We used banding data from three years of mark-recapture study at Wayqecha Biological Station (2900 m a.s.l.) along the east slope of the Andes in southeastern Peru to characterize molt and estimate morphological measurements. Each of the species exhibited a complete definitive prebasic molt and either a partial (nine species) or partial-incomplete (one species) preformative molt, which we interpreted to be consistent with a complex basic molt strategy. For five of the 10 species, we found that wing, tail, and body mass measurements were useful in distinguishing between males and females. This study contributes to our understanding of tropical bird molt by providing previously undescribed aging and sexing criteria for some tropical landbirds common to high elevations of southern Peru. Resumen · Patrones de muda y criterios para categorizar sexo y edad en diez especies de aves altoandinas en el sur-este de Perú Los patrones de muda en la mayoría de las aves Neotropicales son poco conocidos y en especial se desconoce si las medidas corporales pueden ser usadas para determinar el sexo en especies sin dimorfismo sexual. En este trabajo clasificamos la estrategia de muda para 10 especies de paserinos Neotropicales y también exploramos si una combi-nación de medidas de longitud del ala, longitud de la cola y masa corporal pueden ser usadas para la determinación del sexo. Usamos datos de anillamiento de tres años de un estudio de recaptura en la Estación Biológica Wayqecha (2900 m s.n.m.) en el flanco oriental de los Andes al sureste de Perú. Cada especie exhibió una estrategia básica compleja de muda con una muda prebásica definitiva compleja, y una muda preformativa parcial (nueve especies) o parcial-incompleta (uno especie). Para cinco de cada 10 especies, la combinación de medidas de la longitud del ala, la cola, y la masa corporal sirvieron para distinguir entre machos y hembras. Este estudio contribuye a la creciente lite-ratura sobre los patrones de muda en aves tropicales y provee herramientas para clasificar la edad y el sexo de aves con plumaje sexualmente monocromático.
Few studies have examined the patterns of co-occurrence between diurnal birds such as woodpeckers... more Few studies have examined the patterns of co-occurrence between diurnal birds such as woodpeckers and nocturnal birds such as owls, which they may facilitate. Flammulated Owls (Psiloscops flammeolus) and Northern Saw-whet Owls (Aegolius acadicus) are nocturnal, secondary cavity-nesting birds that inhabit forests. For nesting and roosting, both species require natural cavities or, more commonly, those that woodpeckers create. Using day and nighttime broadcast surveys (n = 150 locations) in the Rocky Mountain biogeographic region of Idaho, USA, we surveyed for owls and woodpeckers to assess patterns of co-occurrence and evaluated the hypothesis that forest owls and woodpeckers co-occurred more frequently than expected by chance because of the facilitative nature of their biological interaction. We also examined co-occurrence patterns between owl species to understand their possible competitive interactions. Finally, to assess whether co-occurrence patterns arose because of species interactions or selection of similar habitat types, we used canonical correspondence analysis (CCA) to examine habitat associations within this cavity-nesting bird community. We found that Flammulated Owls co-occurred more with Hairy Woodpeckers (Picoides villosus), Northern Saw-whet Owls co-occurred with Northern Flickers (Colaptes auratus) and Red-naped Sapsuckers (Sphyrapicus nuchalis) and, when primary excavators were considered as a group, each species of owl was positively associated with the presence of woodpeckers. The owl species were distributed independently of one another suggesting a lack of competitive interactions. The CCA had relatively low explanatory power but suggested that habitat associations alone did not explain the patterns of positive co-occurrence we observed: Flammulated Owls and Hairy Woodpeckers associated with different habitats and Northern Saw-whet Owls, Northern Flickers, and Red-naped Sapsuckers appeared as habitat generalists. We interpret these patterns of co-occurrence and habitat use as evidence that woodpeckers facilitate presence of these species of owl and suggest management for forest owls could also include focus on the diurnal species with which they appear to associate. Profils de cooccurrence des pics et des strigidés nocturnes nichant dans des cavités dans une forêt de l'Idaho RÉSUMÉ. Peu d'études ont examiné la cooccurrence des oiseaux diurnes, comme les pics, et les oiseaux nocturnes, comme les strigidés. Les Petits-ducs nains (Psiloscops flammeolus) et les Petites Nyctales (Aegolius acadicus) sont des utilisateurs secondaires de cavités nocturnes nichant en forêt. Pour nicher et se reposer, ces deux espèces ont besoin de cavités naturelles ou, plus couramment, celles excavées par des pics. Au moyen de relevés diurnes et nocturnes accompagnés d'enregistrements sonores (n = 150 sites) réalisés dans la région biogéographique des Montagnes Rocheuses en Idaho, aux États-Unis, nous avons inventorié les strigidés et les pics afin d'évaluer leur tendance à cooccurrer et de valider l'hypothèse selon laquelle les pics et les strigidés forestiers cooccurrent plus souvent que le voudrait le hasard en raison de la nature facilitante de leur interaction biologique. Nous avons aussi examiné les profils de cooccurrence entre les espèces de strigidés afin d'essayer de comprendre leurs interactions compétitives possibles. Finalement, pour évaluer si les profils de cooccurrence découlaient d'interactions spécifiques ou de la sélection d'habitats similaires, nous avons réalisé une analyse de correspondance canonique afin d'examiner les associations avec l'habitat de cette communauté d'oiseaux nichant dans des cavités. Nous avons trouvé que les Petits-ducs nains cooccurraient plus souvent avec les Pics chevelus (Picoides villosus), tandis que les Petites Nyctales cooccurraient davantage avec les Pics flamboyants (Colaptes auratus) et les Pics à nuque rouge (Sphyrapicus nuchalis). Lorsque les excavateurs primaires étaient considérés en tant que groupe, chaque espèce de strigidés était associée positivement avec la présence de pics. Les espèces de strigidés étaient réparties indépendamment les unes des autres, laissant supposer l'absence d'interactions compétitives. L'analyse de correspondance canonique n'a pas vraiment montré de capacité explicative, mais indiquait que les associations avec l'habitat seules n'expliquaient pas les profils de cooccurrence positive que nous avons observés : les Petits-ducs nains et les Pics chevelus associés avec des habitats différents, et les Petites Nyctales, les Pics flamboyants et les Pics à nuque rouge s'avérant des espèces plus généralistes en termes d'habitat. Ces profils de cooccurrence et d'utilisation d'habitat sont sans doute des indications que les pics facilitent la présence de ces espèces de strigidés. Enfin, nous pensons que l'aménagement destiné aux strigidés forestiers devrait aussi inclure une attention particulière aux espèces diurnes avec lesquelles les strigidés semblent s'associer.
Proceedings of the National Academy of Sciences, 2018
Montane species worldwide are shifting upslope in response to recent temperature increases. These... more Montane species worldwide are shifting upslope in response to recent temperature increases. These upslope shifts are predicted to lead to mountaintop extinctions of species that live only near mountain summits, but empirical examples of populations that have disappeared are sparse. We show that recent warming constitutes an "escalator to extinction" for birds on a remote Peru-vian mountain-high-elevation species have declined in both range size and abundance, and several previously common moun-taintop residents have disappeared from the local community. Our findings support projections that warming will likely drive widespread extirpations and extinctions of high-elevation taxa in the tropical Andes. Such climate change-driven mountaintop extirpa-tions may be more likely in the tropics, where temperature seems to exert a stronger control on species' range limits than in the temperate zone. In contrast, we show that lowland bird species at our study site are expanding in range size as they shift their upper limits upslope and may thus benefit from climate change. biotic attrition | global warming | mountaintop extinction | range shift | tropical mountain C limate change is causing many montane species to shift their distributions upslope to track their optimal climate (1-3). Summit-dwelling species lack higher-elevation habitats to receive them and are widely predicted to decline or disappear altogether as upslope shifts drive an "escalator to extinction" (4-6). Indeed, mountaintop extinctions are a primary mechanism underlying the broader projection that climate change alone will lead to extinctions on the order of ∼10% of all eukaryotic species on Earth by 2100 (7, 8). Mountaintop extinctions may be more likely in the tropics, where the nearly flat latitudinal gradient in temperature means that tropical montane taxa are unlikely to persist by shifting to higher latitudes, an option that is more available to taxa in the temperate zone where the latitudinal temperature gradient is much steeper (9). In light of these predictions, conservation biologists and global change researchers have substantial interest in documenting the impact of recent warming on the distributions of high-elevation species. If projections of widespread mountaintop extinctions are valid, we expect to uncover empirical examples of mountaintop populations that have been extirpated associated with recent climate change. However, despite a large literature reporting the geographic responses of species to recent climate change, there are surprisingly few examples of recent mountaintop extirpations plausibly driven by climate change (10). Models that predict mountaintop extinctions to be pervasive assume that temperature is the primary factor that controls range limits of montane species. The observation that species are generally shifting toward historically cooler environments associated with recent temperature increases is strong evidence that temperature is indeed a generally important factor limiting species' distributions, although biotic interactions can also influence range limits (11). Crucially, however, observed range shifts for temperate zone species typically lag far behind those predicted by recent warming (1). In contrast, observed shifts among tropical species roughly match those predicted by climate shifts (12). These observations suggest the hypothesis that current mean temperatures (or perhaps factors tightly correlated with temperature) are a dominant driver of most tropical species' elevational range limits, while additional factors set range limits of temperate zone species. If so, recent temperature increases may be more likely to cause mountaintop extirpations in tropical populations than in temperate zone ones. While populations of high-elevation tropical species are already threatened due to introduced diseases (13-15) and habitat destruction (16), extir-pations of tropical mountaintop populations driven primarily by climate change have yet to be documented. We tested the prediction that populations of high-elevation tropical species are threatened by climate change by examining how birds on a remote Peruvian mountain have shifted their elevational distributions in response to recent temperature increases. We compared the results of a modern survey conducted in 2017 with data from a historic survey conducted in 1985 by J.W.F. and colleagues from the Field Museum. This historic survey was specifically designed to document elevational limits of bird species along a ∼8-km river-to-ridgetop transect in the Cerro de Pantiacolla (470 m at the Palatoa River to 1,415 m at the ridge summit) (Fig. 1). This dataset provided the opportunity to test the idea of mountaintop extirpations, because the historic survey documented 16 species of birds that were restricted to the ridgetop (i.e., found only above 1,300 m). Our resurvey, conducted in 2017, covered the same ground at the same time of year and matched the methods of the historic survey (Methods and SI Appendix, Table S1). The Pantiacolla Transect remains uninhabited by humans and consists of primary evergreen forest. While no anthropogenic land use changes have occurred between Significance Global warming is predicted to constitute an "escalator to ex-tinction" for species that live on mountains. This is because species are generally moving to higher elevations as temperatures warm, and species that live only near mountaintops may run out of room. However, there is little evidence that high-elevation populations are disappearing as predicted. Here, we show that recent warming does indeed act as an escalator to extinction for birds that live on a remote Peruvian mountain. High-elevation species have shrunk in range size and declined in abundance, and several previously common species have disappeared. We suggest that high-elevation species in the tropics are particularly vulnerable to climate change.
—I report on the unusual behavior of an adult House Wren (Troglodytes aedon) leading recently fle... more —I report on the unusual behavior of an adult House Wren (Troglodytes aedon) leading recently fledged young back to the nest for two consecutive nights. The ambient temperature reached below 0uC during both nights. Despite disadvantages associated with remaining in the nest, this observation suggests that adult birds may assess trade-offs between perceived risks versus the benefits of engaging in other activities, in this case roosting communally for thermoregulation.
Spatially explicit models depicting species occupancy offer a useful conservation tool for land
... more Spatially explicit models depicting species occupancy offer a useful conservation tool for land
managers. Using occurrence data collected in 2009 and 2010 from the Boise National Forest, Idaho, we
developed distribution models for Flammulated Owls (Psiloscops flammeolus) and Northern Saw-whet Owls
(Aegolius acadicus) to explore associations between habitat factors and owl occupancy. We then spatially
applied these models in a Geographic Information System. We considered land cover and topographic
variables at three spatial scales: 0.4-km, 1-km, or 3-km-radius plots centered on point-count locations (n 5
150) with resolution of land covers at 30 m. Flammulated Owls occupied 27 (18%) point-count locations
and occurred in areas with a higher proportion of Douglas-fir (Pseudotsuga menziesii) at the 0.4-km scale, less
diverse land cover composition at the 1-km scale, and in south-facing aspects at the 3-km scale. Northern
Saw-whet Owls occupied 45 (30%) point-count locations and were associated with relatively flat terrain at
the 0.4-km scale that had larger proportions of non-forest land cover. At the 1-km and 3-km scales,
Northern Saw-whet Owls occurred in areas with south-facing aspects having a higher proportion of ponderosa
pine (Pinus ponderosa), respectively. Biologists and land managers interested in the conservation of
Flammulated Owls and Northern Saw-whet Owls can use our approach to delineate habitats important for
these owls or to help identify locations suitable for restoration.
Relatively little is known about the longevity of free-living landbirds, especially in the tropic... more Relatively little is known about the longevity of free-living landbirds, especially in the tropics. We used mark-recapture data for birds originally banded in 2005 and 2006, and later recaptured between 2011 and 2016 to estimate minimum longevity for 20 species from southeastern Peru. The oldest recorded longevity was 10 yr, 6 months for a Black-billed Treehunter (Thripadectes melanorhynchus). Another notable record was for a Russet-crowned Warbler (Myiothlypis coronata; 9 yr, 2 months). Our estimated minimum longevity records generally reflect the findings of other researchers, indicating that tropical birds are often markedly site faithful and long-lived.
This study establishes an altiudinal gradient, spanning from the highland Andes (2400 m) to lowla... more This study establishes an altiudinal gradient, spanning from the highland Andes (2400 m) to lowland Amazon, as a productive region for the study of bird pollination in Southeastern Peru. The 'Manú Gradient' has a rich history of ornithological research, the published data and resources from which lay the groundwork for analyses of plant-bird interactions. In this preliminary expedition we documented 44 plants exhibting aspects of the bird pollination syndrome, and made field observations of hummingbird visits at three sites spanning the Manú Gradient: 2800 m (Wayqecha), 1400 m (San Pedro), and 400 m (Pantiacolla). Some of the documented plant taxa are underrepresented in the bird pollination literature and could be promising avenues for future analyses of their pollination biology. The Manú Gradient is currently the focus of a concerted, international effort to describe and study the birds in the region; we propose that this region of Southeastern Peru is a productive and perhaps underestimated system to gain insight into the ecology and evolution of bird pollination.
Knowledge of molt patterns and their resulting plumages is useful for aging and sexing birds and,... more Knowledge of molt patterns and their resulting plumages is useful for aging and sexing birds and, in mono-chromatic species, morphometric measurements can help to discern males from females. However, these data are largely undescribed for the majority of the world's bird species, especially in the tropics. We sought to classify the molt strategy for 10 species of Neotropical passerines during their breeding seasons and considered whether a combination of wing chord, tail length and mass could be used to determine their sex. We used banding data from three years of mark-recapture study at Wayqecha Biological Station (2900 m a.s.l.) along the east slope of the Andes in southeastern Peru to characterize molt and estimate morphological measurements. Each of the species exhibited a complete definitive prebasic molt and either a partial (nine species) or partial-incomplete (one species) preformative molt, which we interpreted to be consistent with a complex basic molt strategy. For five of the 10 species, we found that wing, tail, and body mass measurements were useful in distinguishing between males and females. This study contributes to our understanding of tropical bird molt by providing previously undescribed aging and sexing criteria for some tropical landbirds common to high elevations of southern Peru. Resumen · Patrones de muda y criterios para categorizar sexo y edad en diez especies de aves altoandinas en el sur-este de Perú Los patrones de muda en la mayoría de las aves Neotropicales son poco conocidos y en especial se desconoce si las medidas corporales pueden ser usadas para determinar el sexo en especies sin dimorfismo sexual. En este trabajo clasificamos la estrategia de muda para 10 especies de paserinos Neotropicales y también exploramos si una combi-nación de medidas de longitud del ala, longitud de la cola y masa corporal pueden ser usadas para la determinación del sexo. Usamos datos de anillamiento de tres años de un estudio de recaptura en la Estación Biológica Wayqecha (2900 m s.n.m.) en el flanco oriental de los Andes al sureste de Perú. Cada especie exhibió una estrategia básica compleja de muda con una muda prebásica definitiva compleja, y una muda preformativa parcial (nueve especies) o parcial-incompleta (uno especie). Para cinco de cada 10 especies, la combinación de medidas de la longitud del ala, la cola, y la masa corporal sirvieron para distinguir entre machos y hembras. Este estudio contribuye a la creciente lite-ratura sobre los patrones de muda en aves tropicales y provee herramientas para clasificar la edad y el sexo de aves con plumaje sexualmente monocromático.
Few studies have examined the patterns of co-occurrence between diurnal birds such as woodpeckers... more Few studies have examined the patterns of co-occurrence between diurnal birds such as woodpeckers and nocturnal birds such as owls, which they may facilitate. Flammulated Owls (Psiloscops flammeolus) and Northern Saw-whet Owls (Aegolius acadicus) are nocturnal, secondary cavity-nesting birds that inhabit forests. For nesting and roosting, both species require natural cavities or, more commonly, those that woodpeckers create. Using day and nighttime broadcast surveys (n = 150 locations) in the Rocky Mountain biogeographic region of Idaho, USA, we surveyed for owls and woodpeckers to assess patterns of co-occurrence and evaluated the hypothesis that forest owls and woodpeckers co-occurred more frequently than expected by chance because of the facilitative nature of their biological interaction. We also examined co-occurrence patterns between owl species to understand their possible competitive interactions. Finally, to assess whether co-occurrence patterns arose because of species interactions or selection of similar habitat types, we used canonical correspondence analysis (CCA) to examine habitat associations within this cavity-nesting bird community. We found that Flammulated Owls co-occurred more with Hairy Woodpeckers (Picoides villosus), Northern Saw-whet Owls co-occurred with Northern Flickers (Colaptes auratus) and Red-naped Sapsuckers (Sphyrapicus nuchalis) and, when primary excavators were considered as a group, each species of owl was positively associated with the presence of woodpeckers. The owl species were distributed independently of one another suggesting a lack of competitive interactions. The CCA had relatively low explanatory power but suggested that habitat associations alone did not explain the patterns of positive co-occurrence we observed: Flammulated Owls and Hairy Woodpeckers associated with different habitats and Northern Saw-whet Owls, Northern Flickers, and Red-naped Sapsuckers appeared as habitat generalists. We interpret these patterns of co-occurrence and habitat use as evidence that woodpeckers facilitate presence of these species of owl and suggest management for forest owls could also include focus on the diurnal species with which they appear to associate. Profils de cooccurrence des pics et des strigidés nocturnes nichant dans des cavités dans une forêt de l'Idaho RÉSUMÉ. Peu d'études ont examiné la cooccurrence des oiseaux diurnes, comme les pics, et les oiseaux nocturnes, comme les strigidés. Les Petits-ducs nains (Psiloscops flammeolus) et les Petites Nyctales (Aegolius acadicus) sont des utilisateurs secondaires de cavités nocturnes nichant en forêt. Pour nicher et se reposer, ces deux espèces ont besoin de cavités naturelles ou, plus couramment, celles excavées par des pics. Au moyen de relevés diurnes et nocturnes accompagnés d'enregistrements sonores (n = 150 sites) réalisés dans la région biogéographique des Montagnes Rocheuses en Idaho, aux États-Unis, nous avons inventorié les strigidés et les pics afin d'évaluer leur tendance à cooccurrer et de valider l'hypothèse selon laquelle les pics et les strigidés forestiers cooccurrent plus souvent que le voudrait le hasard en raison de la nature facilitante de leur interaction biologique. Nous avons aussi examiné les profils de cooccurrence entre les espèces de strigidés afin d'essayer de comprendre leurs interactions compétitives possibles. Finalement, pour évaluer si les profils de cooccurrence découlaient d'interactions spécifiques ou de la sélection d'habitats similaires, nous avons réalisé une analyse de correspondance canonique afin d'examiner les associations avec l'habitat de cette communauté d'oiseaux nichant dans des cavités. Nous avons trouvé que les Petits-ducs nains cooccurraient plus souvent avec les Pics chevelus (Picoides villosus), tandis que les Petites Nyctales cooccurraient davantage avec les Pics flamboyants (Colaptes auratus) et les Pics à nuque rouge (Sphyrapicus nuchalis). Lorsque les excavateurs primaires étaient considérés en tant que groupe, chaque espèce de strigidés était associée positivement avec la présence de pics. Les espèces de strigidés étaient réparties indépendamment les unes des autres, laissant supposer l'absence d'interactions compétitives. L'analyse de correspondance canonique n'a pas vraiment montré de capacité explicative, mais indiquait que les associations avec l'habitat seules n'expliquaient pas les profils de cooccurrence positive que nous avons observés : les Petits-ducs nains et les Pics chevelus associés avec des habitats différents, et les Petites Nyctales, les Pics flamboyants et les Pics à nuque rouge s'avérant des espèces plus généralistes en termes d'habitat. Ces profils de cooccurrence et d'utilisation d'habitat sont sans doute des indications que les pics facilitent la présence de ces espèces de strigidés. Enfin, nous pensons que l'aménagement destiné aux strigidés forestiers devrait aussi inclure une attention particulière aux espèces diurnes avec lesquelles les strigidés semblent s'associer.
Proceedings of the National Academy of Sciences, 2018
Montane species worldwide are shifting upslope in response to recent temperature increases. These... more Montane species worldwide are shifting upslope in response to recent temperature increases. These upslope shifts are predicted to lead to mountaintop extinctions of species that live only near mountain summits, but empirical examples of populations that have disappeared are sparse. We show that recent warming constitutes an "escalator to extinction" for birds on a remote Peru-vian mountain-high-elevation species have declined in both range size and abundance, and several previously common moun-taintop residents have disappeared from the local community. Our findings support projections that warming will likely drive widespread extirpations and extinctions of high-elevation taxa in the tropical Andes. Such climate change-driven mountaintop extirpa-tions may be more likely in the tropics, where temperature seems to exert a stronger control on species' range limits than in the temperate zone. In contrast, we show that lowland bird species at our study site are expanding in range size as they shift their upper limits upslope and may thus benefit from climate change. biotic attrition | global warming | mountaintop extinction | range shift | tropical mountain C limate change is causing many montane species to shift their distributions upslope to track their optimal climate (1-3). Summit-dwelling species lack higher-elevation habitats to receive them and are widely predicted to decline or disappear altogether as upslope shifts drive an "escalator to extinction" (4-6). Indeed, mountaintop extinctions are a primary mechanism underlying the broader projection that climate change alone will lead to extinctions on the order of ∼10% of all eukaryotic species on Earth by 2100 (7, 8). Mountaintop extinctions may be more likely in the tropics, where the nearly flat latitudinal gradient in temperature means that tropical montane taxa are unlikely to persist by shifting to higher latitudes, an option that is more available to taxa in the temperate zone where the latitudinal temperature gradient is much steeper (9). In light of these predictions, conservation biologists and global change researchers have substantial interest in documenting the impact of recent warming on the distributions of high-elevation species. If projections of widespread mountaintop extinctions are valid, we expect to uncover empirical examples of mountaintop populations that have been extirpated associated with recent climate change. However, despite a large literature reporting the geographic responses of species to recent climate change, there are surprisingly few examples of recent mountaintop extirpations plausibly driven by climate change (10). Models that predict mountaintop extinctions to be pervasive assume that temperature is the primary factor that controls range limits of montane species. The observation that species are generally shifting toward historically cooler environments associated with recent temperature increases is strong evidence that temperature is indeed a generally important factor limiting species' distributions, although biotic interactions can also influence range limits (11). Crucially, however, observed range shifts for temperate zone species typically lag far behind those predicted by recent warming (1). In contrast, observed shifts among tropical species roughly match those predicted by climate shifts (12). These observations suggest the hypothesis that current mean temperatures (or perhaps factors tightly correlated with temperature) are a dominant driver of most tropical species' elevational range limits, while additional factors set range limits of temperate zone species. If so, recent temperature increases may be more likely to cause mountaintop extirpations in tropical populations than in temperate zone ones. While populations of high-elevation tropical species are already threatened due to introduced diseases (13-15) and habitat destruction (16), extir-pations of tropical mountaintop populations driven primarily by climate change have yet to be documented. We tested the prediction that populations of high-elevation tropical species are threatened by climate change by examining how birds on a remote Peruvian mountain have shifted their elevational distributions in response to recent temperature increases. We compared the results of a modern survey conducted in 2017 with data from a historic survey conducted in 1985 by J.W.F. and colleagues from the Field Museum. This historic survey was specifically designed to document elevational limits of bird species along a ∼8-km river-to-ridgetop transect in the Cerro de Pantiacolla (470 m at the Palatoa River to 1,415 m at the ridge summit) (Fig. 1). This dataset provided the opportunity to test the idea of mountaintop extirpations, because the historic survey documented 16 species of birds that were restricted to the ridgetop (i.e., found only above 1,300 m). Our resurvey, conducted in 2017, covered the same ground at the same time of year and matched the methods of the historic survey (Methods and SI Appendix, Table S1). The Pantiacolla Transect remains uninhabited by humans and consists of primary evergreen forest. While no anthropogenic land use changes have occurred between Significance Global warming is predicted to constitute an "escalator to ex-tinction" for species that live on mountains. This is because species are generally moving to higher elevations as temperatures warm, and species that live only near mountaintops may run out of room. However, there is little evidence that high-elevation populations are disappearing as predicted. Here, we show that recent warming does indeed act as an escalator to extinction for birds that live on a remote Peruvian mountain. High-elevation species have shrunk in range size and declined in abundance, and several previously common species have disappeared. We suggest that high-elevation species in the tropics are particularly vulnerable to climate change.
—I report on the unusual behavior of an adult House Wren (Troglodytes aedon) leading recently fle... more —I report on the unusual behavior of an adult House Wren (Troglodytes aedon) leading recently fledged young back to the nest for two consecutive nights. The ambient temperature reached below 0uC during both nights. Despite disadvantages associated with remaining in the nest, this observation suggests that adult birds may assess trade-offs between perceived risks versus the benefits of engaging in other activities, in this case roosting communally for thermoregulation.
Spatially explicit models depicting species occupancy offer a useful conservation tool for land
... more Spatially explicit models depicting species occupancy offer a useful conservation tool for land
managers. Using occurrence data collected in 2009 and 2010 from the Boise National Forest, Idaho, we
developed distribution models for Flammulated Owls (Psiloscops flammeolus) and Northern Saw-whet Owls
(Aegolius acadicus) to explore associations between habitat factors and owl occupancy. We then spatially
applied these models in a Geographic Information System. We considered land cover and topographic
variables at three spatial scales: 0.4-km, 1-km, or 3-km-radius plots centered on point-count locations (n 5
150) with resolution of land covers at 30 m. Flammulated Owls occupied 27 (18%) point-count locations
and occurred in areas with a higher proportion of Douglas-fir (Pseudotsuga menziesii) at the 0.4-km scale, less
diverse land cover composition at the 1-km scale, and in south-facing aspects at the 3-km scale. Northern
Saw-whet Owls occupied 45 (30%) point-count locations and were associated with relatively flat terrain at
the 0.4-km scale that had larger proportions of non-forest land cover. At the 1-km and 3-km scales,
Northern Saw-whet Owls occurred in areas with south-facing aspects having a higher proportion of ponderosa
pine (Pinus ponderosa), respectively. Biologists and land managers interested in the conservation of
Flammulated Owls and Northern Saw-whet Owls can use our approach to delineate habitats important for
these owls or to help identify locations suitable for restoration.
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Papers by Micah Scholer
preliminary expedition we documented 44 plants exhibting aspects of the bird pollination syndrome, and made field observations of hummingbird visits at three sites spanning the Manú Gradient: 2800 m (Wayqecha), 1400 m (San Pedro), and 400 m (Pantiacolla). Some of the documented plant taxa are underrepresented in the bird pollination literature and could be promising avenues for future analyses of their pollination biology. The Manú Gradient is currently the focus of a concerted, international effort to describe and study the birds in the region; we propose that this region of Southeastern Peru is a productive and perhaps underestimated system to gain insight into the ecology and evolution of bird pollination.
managers. Using occurrence data collected in 2009 and 2010 from the Boise National Forest, Idaho, we
developed distribution models for Flammulated Owls (Psiloscops flammeolus) and Northern Saw-whet Owls
(Aegolius acadicus) to explore associations between habitat factors and owl occupancy. We then spatially
applied these models in a Geographic Information System. We considered land cover and topographic
variables at three spatial scales: 0.4-km, 1-km, or 3-km-radius plots centered on point-count locations (n 5
150) with resolution of land covers at 30 m. Flammulated Owls occupied 27 (18%) point-count locations
and occurred in areas with a higher proportion of Douglas-fir (Pseudotsuga menziesii) at the 0.4-km scale, less
diverse land cover composition at the 1-km scale, and in south-facing aspects at the 3-km scale. Northern
Saw-whet Owls occupied 45 (30%) point-count locations and were associated with relatively flat terrain at
the 0.4-km scale that had larger proportions of non-forest land cover. At the 1-km and 3-km scales,
Northern Saw-whet Owls occurred in areas with south-facing aspects having a higher proportion of ponderosa
pine (Pinus ponderosa), respectively. Biologists and land managers interested in the conservation of
Flammulated Owls and Northern Saw-whet Owls can use our approach to delineate habitats important for
these owls or to help identify locations suitable for restoration.
preliminary expedition we documented 44 plants exhibting aspects of the bird pollination syndrome, and made field observations of hummingbird visits at three sites spanning the Manú Gradient: 2800 m (Wayqecha), 1400 m (San Pedro), and 400 m (Pantiacolla). Some of the documented plant taxa are underrepresented in the bird pollination literature and could be promising avenues for future analyses of their pollination biology. The Manú Gradient is currently the focus of a concerted, international effort to describe and study the birds in the region; we propose that this region of Southeastern Peru is a productive and perhaps underestimated system to gain insight into the ecology and evolution of bird pollination.
managers. Using occurrence data collected in 2009 and 2010 from the Boise National Forest, Idaho, we
developed distribution models for Flammulated Owls (Psiloscops flammeolus) and Northern Saw-whet Owls
(Aegolius acadicus) to explore associations between habitat factors and owl occupancy. We then spatially
applied these models in a Geographic Information System. We considered land cover and topographic
variables at three spatial scales: 0.4-km, 1-km, or 3-km-radius plots centered on point-count locations (n 5
150) with resolution of land covers at 30 m. Flammulated Owls occupied 27 (18%) point-count locations
and occurred in areas with a higher proportion of Douglas-fir (Pseudotsuga menziesii) at the 0.4-km scale, less
diverse land cover composition at the 1-km scale, and in south-facing aspects at the 3-km scale. Northern
Saw-whet Owls occupied 45 (30%) point-count locations and were associated with relatively flat terrain at
the 0.4-km scale that had larger proportions of non-forest land cover. At the 1-km and 3-km scales,
Northern Saw-whet Owls occurred in areas with south-facing aspects having a higher proportion of ponderosa
pine (Pinus ponderosa), respectively. Biologists and land managers interested in the conservation of
Flammulated Owls and Northern Saw-whet Owls can use our approach to delineate habitats important for
these owls or to help identify locations suitable for restoration.