Joana Santana

Seasonal patterns of spatial variation in understory bird assemblages across a mosaic of flooded and unflooded Amazonian forests.

We examined seasonal patterns of spatial variation in understory bird assemblages across a mosaic of upland and floodplain forests in central Amazonia, where variation in flooding patterns and floodwater nutrient load shapes a marked spatial heterogeneity in forest structure and composition. Despite great differences in productivity due to flooding by either nutrient-rich “white waters” (várzea) or nutrient-poor “black waters” (igapó), bird assemblages in the two floodplain forest types were relatively similar, showing lower abundances than adjacent upland forests (terra firme) and sharing a set of species that were absent or scarce elsewhere. Species that breed in pensile nests overhanging water were abundant in floodplain forests, whereas species that feed on the ground were generally scarce. Flooding affected assemblage dynamics in floodplain forests, with some influx of ground-dwelling species such as ant-following birds from adjacent upland during the low-water season, and the occupation by riverine and aquatic species such as kingfishers during floods. Spatial configuration influenced the seasonal pattern of assemblage structuring, with movements from terra firme occurring primarily to adjacent igapó forests. No such influx was detected in várzea forests that were farther from terra firme and isolated by wide river channels. Results support the view that habitat heterogeneity created by flooding strongly contributes to maintain diverse vertebrate assemblages in Amazonia forest landscapes, even in the case of largely sedentary species such as understory forest birds. Including both upland and floodplain forests in Amazonia reserves may thus be essential to preserve bird diversity at the landscape scale.

Structuring of Amazonian bat assemblages: the roles of flooding patterns and floodwater nutrient load

1. River system dynamics results in ecological heterogeneities that play a central role in maintaining biodiversity in riverine regions. In central Amazonia, large expanses of forest are seasonally flooded by nutrient-rich water (várzea forests) or by nutrient-poor water (igapó forests). Inundation patterns and the nutrient load of floodwaters are perhaps the most important abiotic factors determining spatial ecological variations in lowland Amazonia, and so they are expected to strongly influence the structuring of animal communities. 2. We examined how inundation patterns and water-nutrient load influence the structure of neotropical assemblages of bats, one of the most diverse vertebrate groups in tropical forests. Bat assemblages were sampled with mist nets in central Brazilian Amazonia, across a mosaic of várzea, igapó, and non-flooding nutrient-poor terra firme forests in the low- and high-water seasons. 3. An ordination analysis clearly separated the assemblages of the three forest types, demonstrating the structural relevance of both flooding and floodwater-nutrient load. Flooded forests had lower species richness because of the absence or rarity of species that make roosts out of leaves of understorey plants, and of those that feed on fruits of shrubs. Gleaning insectivores, also partly dependent on the understorey, were less abundant in flooded forests, but aerial insectivores more abundant, presumably because they benefited from a less cluttered foraging environment. These differences suggest that flooding affects bat assemblages mostly because it reduces the availability of niches associated with understorey vegetation, which tends to be sparser in flooded forests. 4. Nutrient-rich várzea forests had a bat biomass twice that of nutrient-poor igapó and unflooded forests. This difference was not only mostly due to a greater overall abundance of bats, but also attributable to a disproportionate higher abundance of large-bodied bat species. 5. We concluded that both flooding and floodwater-nutrient load are very important in the structuring of lowland Amazonian bat assemblages, with inundation mostly constraining the species composition of the assemblages, and water-nutrient load mostly influencing the abundance of species. The distinctiveness of bat assemblages associated with flooding emphasizes the need to preserve inundated forests, which are under particular pressure in Amazonia.

Optimizing sampling design to deal with mist-net avoidance in Amazonian birds and bats.

Mist netting is a widely used technique to sample bird and bat assemblages. However, captures often decline with time because animals learn and avoid the locations of nets. This avoidance or net shyness can substantially decrease sampling efficiency. We quantified the day-to-day decline in captures of Amazonian birds and bats with mist nets set at the same location for four consecutive days. We also evaluated how net avoidance influences the efficiency of surveys under different logistic scenarios using re-sampling techniques. Net avoidance caused substantial declines in bird and bat captures, although more accentuated in the latter. Most of the decline occurred between the first and second days of netting: 28% in birds and 47% in bats. Captures of commoner species were more affected. The numbers of species detected also declined. Moving nets daily to minimize the avoidance effect increased captures by 30% in birds and 70% in bats. However, moving the location of nets may cause a reduction in netting time and captures. When moving the nets caused the loss of one netting day it was no longer advantageous to move the nets frequently. In bird surveys that could even decrease the number of individuals captured and species detected. Net avoidance can greatly affect sampling efficiency but adjustments in survey design can minimize this. Whenever nets can be moved without losing netting time and the objective is to capture many individuals, they should be moved daily. If the main objective is to survey species present then nets should still be moved for bats, but not for birds. However, if relocating nets causes a significant loss of netting time, moving them to reduce effects of shyness will not improve sampling efficiency in either group. Overall, our findings can improve the design of mist netting sampling strategies in other tropical areas.

Combined effects of landscape composition and heterogeneity on farmland avian diversity

Abstract Conserving biodiversity on farmland is an essential element of worldwide efforts for reversing the global biodiversity decline. Common approaches involve improving the natural component of the landscape by increasing the amount of natural and seminatural habitats (e.g., hedgerows, woodlots, and ponds) or improving the production component of the landscape by increasing the amount of biodiversity‐friendly crops. Because these approaches may negatively impact on economic output, it was suggested that an alternative might be to enhance the diversity (compositional heterogeneity) or the spatial complexity (configurational heterogeneity) of land cover types, without necessarily changing composition. Here, we develop a case study to evaluate these ideas, examining whether managing landscape composition or heterogeneity, or both, would be required to achieve conservation benefits on avian diversity in open Mediterranean farmland. We surveyed birds in farmland landscapes of southern Portugal, before (1995–1997) and after (2010–2012) the European Unions Common Agricultural Policy (CAP) reform of 2003, and related spatial and temporal variation in bird species richness to variables describing the composition, and the compositional and configurational heterogeneity, of the natural and production components of the landscape. We found that the composition of the production component had the strongest effects on avian diversity, with a particularly marked effect on the richness of farmland and steppe bird species. Composition of the natural component was also influential, mainly affecting the richness of woodland/shrubland species. Although there were some effects of compositional and configurational heterogeneity, these were much weaker and inconsistent than those of landscape composition. Overall, we suggest that conservation efforts in our area should focus primarily on the composition of the production component, by striving to maximize the prevalence of biodiversity‐friendly crops. This recommendation probably applies to other areas such as ours, where a range of species of conservation concern is strongly associated with crop habitats.

Landscape makers and landscape takers: links between farming systems and landscape patterns along an intensification gradient

ContextAgricultural intensification is a leading cause of landscape homogenization, with negative consequences for biodiversity and ecosystem services. Conserving or promoting heterogeneity requires a detailed understanding of how farm management affects, and is affected by, landscape characteristics.ObjectivesWe assessed relationships between farming systems and landscape characteristics, hypothesising that less-intensive systems act as landscape takers, by adapting management to landscape constraints, whereas more intensive systems act as landscape makers, by changing the landscape to suit farming needs.MethodsWe mapped dominant farming systems in a region of southern Portugal: traditional cereal-grazed fallow rotations; specialization on annual crops; and specialization on either cattle or sheep. We estimated landscape metrics in 241 1-km2 buffers representing the farming systems, and analysed variation among and within systems using multivariate statistics and beta diversity metrics.ResultsLandscape composition varied among systems, with dominance by either annual crops (Crop system) or pastures (Sheep), or a mixture between the two (Traditional and Cattle). There was a marked regional gradient of local landscape heterogeneity, but this contributed little to variation among systems. Landscape beta diversity declined from the Sheep to the Crop system, and it was inversely related to agriculture intensity.ConclusionsLess intensive farming systems appeared compatible with a range of landscape characteristics (landscape takers), and may thus be particularly suited to agri-environmental management. More intensive systems appeared less flexible in terms of landscape characteristics (landscape makers), likely promoting regional homogenization. Farming systems may provide a useful standpoint to address the design of agri-environment schemes.

Using beta diversity to inform agricultural policies and conservation actions on Mediterranean farmland

Summary Spatial variation in species composition (β-diversity) is an important component of farmland biodiversity, which together with local richness (α-diversity) drives the number of species in a region (γ-diversity). However, β-diversity is seldom used to inform conservation, due to limited understanding of its responses to agricultural management, and lack of clear links between β-diversity changes and conservation outcomes. We explored the value of β-diversity to guide conservation on farmland, by quantifying the contribution of bird α- and β-diversity to γ-diversity variation in low- and high-intensity Mediterranean farmland, before (1995–1997) and after (2010–2012) the Common Agricultural Policy reform of 2003. We further related β-diversity to landscape heterogeneity, and assessed the conservation significance of β-diversity changes. In 1995–1997, bird diversity was highest in low-intensity farmland, where it further increased in 2010–2012 due to a strong positive contribution of α-diversity to γ-diversity. In high-intensity farmland, diversity converged over time to much the same values of low-intensity farmland, with strong positive contributions of both α- and β-diversity. These patterns were largely consistent for total, farmland and species of European conservation concern assemblages, and less so for steppe birds. Beta diversity increased with landscape heterogeneity, particularly related to spatial gradients from agricultural to natural habitats in low-intensity farmland, and from annual to permanent crops (olive groves) in high-intensity farmland. The first gradient was associated with the replacement of steppe birds of high conservation concern by more generalist species, while the second was associated with the replacement between species with lower or higher affinity for woodland and shrubland habitats. Synthesis and applications. In low-intensity farmland, spatial variation in species composition (β-diversity) was largely stable over time, reflecting a positive conservation outcome related to persistence of landscape heterogeneity patterns required by endangered steppe bird species. In contrast, β-diversity in high-intensity farmland was favoured by increases in landscape heterogeneity driven by olive grove expansion, contributing to enhancement of total bird diversity. Overall, our results stress the value of β-diversity to understand impacts of agricultural policies and conservation actions, but also highlight the need to evaluate β-diversity changes against specific conservation goals.

Mismatches between habitat preferences and risk avoidance for birds in intensive Mediterranean farmland

Land use intensification may create habitats that organisms perceive as suitable, but where reproduction or survival is insufficient to maintain self-sustaining populations. Such conditions may qualify as ecological traps, but their existence is often hard to prove. Here, we provide a practical framework to evaluate a potential ecological trap resulting from mismatch between habitat preferences and predation risk, focusing on ground-nesting farmland birds of conservation concern. The framework is based on species-specific associations with safe or unsafe habitat types (i.e. field and landscape types with high or low nest survival), and the occurrence of risk avoidance (i.e. negative responses to predator abundances or to nest failure rates after controlling for habitat effects). Bird densities were far more influenced by field characteristics than landscape context. Corn bunting and fan-tailed warbler were associated with tall swards (safe habitats), and did not show risk avoidance. Tawny pipit and and Galerida larks were associated with short swards (unsafe habitats), with the former avoiding fields with high nest predation rates, and the later avoiding high mongoose abundances. Short-toed lark was associated with fields with short swards and low nest trampling rates. Results suggest that short-toed lark may be the most vulnerable to ecological trapping, because it nests on unsafe habitats and did not show predation risk avoidance. Our approach provides a practical first step to infer vulnerability to a potential ecological trap, though further research is needed to confirm this effect. Management actions increasing nest survival in short sward fields will likely favour grassland bird conservation in intensive Mediterranean farmland.

The Orthoptera of Castro Verde Special Protection Area (Southern Portugal): new data and conservation value

Abstract With the increasing awareness of the need for Orthoptera conservation, greater efforts must be gathered to implement specific monitoring schemes. Despite recent surveys, little is known about Portuguese Orthoptera populations. This study was performed in 2014 and 2015 mainly in Castro Verde Special Protection Area (SPA), southern Portugal, and is the first Orthoptera inventory conducted in the area. A total of 35 Orthoptera species was recorded, with two new species reported for Portugal. We provide species’ habitat occurrences within the protected area and use information on the conservation status and the Iberian distribution of each documented species to discuss the importance of Castro Verde SPA for Orthoptera conservation. The data presented here sheds new light on Castro Verde SPA biodiversity and emphasizes the inclusion of this area in the conservation of Orthoptera diversity, particularly in the protection of threatened endemic species.

Influence of moonlight on nightjars’ vocal activity: a guideline for nightjar surveys in Europe

Abstract Strictly nocturnal or crepuscular habits on birds are restricted to a very limited number of species such as nightjars. Physiological skills of these species combined with ecological and behavioural adaptations provide them the ability to colonise a less competitive niche. Nightjars’ nocturnal ecological adaptations have been largely neglected on bird survey methods, which can bias the obtained results. Here, we studied the factors affecting vocal activity of two nightjar species, red-necked nightjar Caprimulgus ruficollis and European nightjar C. europaeus in a Mediterranean area of southern Portugal by modelling observed vocal activity of both species as a function of astronomic variables, particularly moon phase and day of the year. Red-necked nightjar vocal behaviour was positively associated with brighter moon phases and springtime, whereas European nightjar was only influenced by the season, being more active in the summer. This reveals the importance of light conditions on vocal activity of the former species. We suggest that specifically designed field surveys for these species should be preferentially conducted during brighter nights, when the lunar cycle is close to full moon. Furthermore, positive contacts with birds are maximized from late spring to early summer, at least for the red-necked nightjar.