The avian community structure of a Bolivian savanna on the edge of the Cerrado system

Se estudió la estructura de una comunidad de aves en una sabana boliviana al borde del Cerrado, entre Agosto y septiembre de 1994, usando transectas de línea. La avifauna de dos hábitats, llamados campo húmedo y campo denso, se describe en detalle. Se identificó un tercer hábitat, la sabana arbolada, pero sólo se describe brevemente. La diversidad de los hábitats se comparó con otros sitios tropicales. Las áreas de campo húmedo tuvieron la mayor densidad de aves, pero en una comunidad relativamente simple, formada principalmente por granívoros que forrajeban en el suelo. El campo denso, con una mayor cobertura vegetal, tuvo mas diversidad de gremios de forrajeo, incluyendo frugívoros, insectívoros y omnívoros, los que mostraron variadas conductas y sitios de alimentación. Consecuentemente este hábitat contuvo el mayor número de especies. La diversidad de aves estuvo correlacionada con la estructura de la vegetación y abundancia de nichos.The avian community structure of a Bolivian savanna on the edge of the Cerrado ecosystem was studied during August and September 1994, using line-transects. The avifauna of two habitats, wet campo and dense campo, is described in detail. A third habitat, wooded savanna, is identified, but only briefly described due to limited survey effort. The diversity of these habitats is compared to data from other tropical studies. Areas of wet campo contained the greatest density of birds, but were characterized by a relatively simple bird community, formed prirnari1y of granivorous, ground-gleaning species. Dense campo habitats, characterised by greater vegetation cover, supported a higher diversity of foraging guilds, including frugivores, insectivores and omnivores, exhibiting a variety of foraging strata and behaviours. Consequently, this habitat contained the greatest number of species. Bird species diversity was therefore re1ated to vegetation structure and niche availability

Winter wren populations show adaptation to local climate

Most studies of evolutionary responses to climate change have focused on phenological responses to warming, and provide only weak evidence for evolutionary adaptation. This could be because phenological changes are more weakly linked to fitness than more direct mechanisms of climate change impacts, such as selective mortality during extreme weather events which have immediate fitness consequences for the individuals involved. Studies examining these other mechanisms may be more likely to show evidence for evolutionary adaptation. To test this, we quantify regional population responses of a small resident passerine (winter wren Troglodytes troglodytes) to a measure of winter severity (number of frost days). Annual population growth rate was consistently negatively correlated with this measure, but the point at which different populations achieved stability (λ = 1) varied across regions and was closely correlated with the historic average number of frost days, providing strong evidence for local adaptation. Despite this, regional variation in abundance remained negatively related to the regional mean number of winter frost days, potentially as a result of a time-lag in the rate of evolutionary response to climate change. As expected from Bergmann's rule, individual wrens were heavier in colder regions, suggesting that local adaptation may be mediated through body size. However, there was no evidence for selective mortality of small individuals in cold years, with annual variation in mean body size uncorrelated with the number of winter frost days, so the extent to which local adaptation occurs through changes in body size, or another mechanism remains uncertain

Population decline is linked to migration route in the Common Cuckoo

Migratory species are in rapid decline globally. Although most mortality in long-distance migrant birds is thought to occur during migration, evidence of conditions on migration affecting breeding population sizes has been completely lacking. We addressed this by tracking 42 male Common Cuckoos from the rapidly declining UK population during 56 autumn migrations in 2011–14. Uniquely, the birds use two distinct routes to reach the same wintering grounds, allowing assessment of survival during migration independently of origin and destination. Mortality up to completion of the Sahara crossing (the major ecological barrier encountered in both routes) is higher for birds using the shorter route. The proportion of birds using this route strongly correlates with population decline across nine local breeding populations. Knowledge of variability in migratory behaviour and performance linked to robust population change data may therefore be necessary to understand population declines of migratory species and efficiently target conservation resources

Experimental Evidence for the Effect of Small Wind Turbine Proximity and Operation on Bird and Bat Activity

The development of renewable energy technologies such as wind turbines forms a vital part of strategies to reduce greenhouse gas emissions worldwide. Although large wind farms generate the majority of wind energy, the small wind turbine (SWT, units generating <50 kW) sector is growing rapidly. In spite of evidence of effects of large wind farms on birds and bats, effects of SWTs on wildlife have not been studied and are likely to be different due to their potential siting in a wider range of habitats. We present the first study to quantify the effects of SWTs on birds and bats. Using a field experiment, we show that bird activity is similar in two distance bands surrounding a sample of SWTs (between 6-18 m hub height) and is not affected by SWT operation at the fine scale studied. At shorter distances from operating turbines (0-5 m), bat activity (measured as the probability of a bat "pass" per hour) decreases from 84% (71-91%) to 28% (11-54%) as wind speed increases from 0 to 14 m/s. This effect is weaker at greater distances (20-25 m) from operating turbines (activity decreases from 80% (65-89%) to 59% (32-81%)), and absent when they are braked. We conclude that bats avoid operating SWTs but that this effect diminishes within 20 m. Such displacement effects may have important consequences especially in landscapes where suitable habitat is limiting. Planning guidance for SWTs is currently lacking. Based on our results we recommend that they are sited at least 20 m away from potentially valuable bat habitat

Hydrologically driven ecosystem processes determine the distribution and persistence of ecosystem-specialist predators under climate change

Climate change has the capacity to alter physical and biological ecosystem processes, jeopardizing the survival of associated species. This is a particular concern in cool, wet northern peatlands that could experience warmer, drier conditions. Here we show that climate, ecosystem processes and food chains combine to influence the population performance of species in British blanket bogs. Our peatland process model accurately predicts water-table depth, which predicts abundance of craneflies (keystone invertebrates), which in turn predicts observed abundances and population persistence of three ecosystem-specialist bird species that feed on craneflies during the breeding season. Climate change projections suggest that falling water tables could cause 56–81% declines in cranefly abundance and, hence, 15–51% reductions in the abundances of these birds by 2051–2080. We conclude that physical (precipitation, temperature and topography), biophysical (evapotranspiration and desiccation of invertebrates) and ecological (food chains) processes combine to determine the distributions and survival of ecosystem-specialist predators

Trade-offs between the natural environment and recreational infrastructure:A case study about peatlands under different management scenarios

The importance of peatlands for conservation and provision of public services has been well evidenced in the last years, especially in relation to their contribution to the net zero carbon emission agenda. However, little is known about the importance of recreation relative to conservation and their trade-offs. In this paper we address this knowledge gap by exploring the trade-offs between natural properties of peatlands and recreational infrastructures for different categories of recreationists (walkers, cyclists, anglers, and birdwatchers) of an open heather moors and peatlands landscape. We do so building on a series of management scenarios formulated through participatory methods and applying choice experiment related to an Area of Outstanding Natural Beauty and UNESCO Global Geopark in the UK. Results show a high degree of heterogeneity in landscape preferences across different user groups. Recreationists had a higher appreciation for semi-natural habitats compared to pristine or restored peatland (e.g., land rewetting). Walkers and cyclists were more sensitive to changes in the availability of recreational facilities than to environmental quality, while anglers’ and birdwatchers’ preferences were more aligned with values promoted by restoration policies. Overall, our results point to a potential value conflict between benefits generated by conservation and the benefits valued most by some groups of recreationists. To maximise success conflicts like the one revealed here need to be considered in strategies that provide a central role for peatlands in net zero climate mitigation strategies

The sensitivity of breeding songbirds to changes in seasonal timing is linked to population change but cannot be directly attributed to the effects of trophic asynchrony on productivity

A consequence of climate change has been an advance in the timing of seasonal events. Differences in the rate of advance between trophic levels may result in predators becoming mismatched with prey availability, reducing fitness and potentially driving population declines. Such “trophic asynchrony” is hypothesized to have contributed to recent population declines of long-distance migratory birds in particular. Using spatially extensive survey data from 1983 to 2010 to estimate variation in spring phenology from 280 plant and insect species and the egg-laying phenology of 21 British songbird species, we explored the effects of trophic asynchrony on avian population trends and potential underlying demographic mechanisms. Species which advanced their laying dates least over the last three decades, and were therefore at greatest risk of asynchrony, exhibited the most negative population trends. We expressed asynchrony as the annual variation in bird phenology relative to spring phenology, and related asynchrony to annual avian productivity. In warmer springs, birds were more asynchronous, but productivity was only marginally reduced; long-distance migrants, short-distance migrants and resident bird species all exhibited effects of similar magnitude. Long-term population, but not productivity, declines were greatest among those species whose annual productivity was most greatly reduced by asynchrony. This suggests that population change is not mechanistically driven by the negative effects of asynchrony on productivity. The apparent effects of asynchrony on population trends are therefore either more likely to be strongly expressed via other demographic pathways, or alternatively, are a surrogate for species' sensitivity to other environmental pressures which are the ultimate cause of decline

Spatial variation in spring arrival patterns of Afro‐Palaearctic bird migration across Europe

Aim: Geographical patterns of migrant species arrival have been little studied, despite their relevance to global change responses. Here, we quantify continent-wide inter-specific variation in spatio-temporal patterns of spring arrival of 30 common migrant bird species and relate these to species characteristics and environmental conditions.Location: EuropeTime period: 2010-2019Major taxa studied: Birds, 30 speciesMethods: Using citizen science data from EuroBirdPortal, we modelled arrival phenology for 30 Afro-Palearctic migrant species across Europe to extract start and duration of species arrival at a 400 km square resolution. We related inter and intra-specific variation in arrival and duration to species characteristics and temperature at the start of the growing season (green-up) .Results: Spatial variation in start of arrival times indicates it took on average 1.6 days for the leading migratory front to move northwards by 100 km (range: 0.6—2.5 days). There was a major gradient in arrival phenology, from species which arrived earlier, least synchronously, in colder temperatures and progressed slowly northwards to species which arrived later, most synchronously and in warmer temperatures, and advanced quickly through Europe. The slow progress of early arrivers suggests that temperature limits their northward advance; this group included Aerial Insectivores and species wintering north of the Sahel. For the late arrivers, which included species wintering further south, seasonal resource availability in Africa may delay their arrival into Europe.Main conclusions: We found support for the green-wave hypothesis applying widely to migratory landbirds. Species arrival phenologies are linked to ecological differences between taxa, such as diet, and wintering location. Understanding these differences informs predictions of species’ sensitivity to global change. Publishing these arrival phenologies will facilitate further research and have additional conservation benefits such as informing designation of hunting seasons. Our methods are applicable to any taxa with repeated occurrence data across large scales. Key words: phenology, European-African migrants, bird migration, spring arrival, spatial variation, intraspecific and interspecific variation, EuroBirdPortal, citizen scientists, complete lists and casual record