Inês Catry

Do different habitat preference survey methods produce the same conservation recommendations for lesser kestrels

The analysis of habitat selection underlies many conservation recommendations. Different researchers use different methods, therefore there is a need to examine whether the results are consistent. This study examined habitat selection by lesser kestrels, Falco naumanni, a globally threatened species, using two methods: visual sighting data from a 35-km transect and radio-telemetry of 33 birds. Habitat use and spatial ecology were studied across all of the breeding season in a pseudo-steppe area, where traditional agro-grazing systems are still present but some areas have been transformed into pine plantations. Telemetry data indicate that, in good quality habitat, lesser kestrels prefer to forage close to the colony. Furthermore, the home ranges obtained were smaller than those for lesser kestrels using intensively managed habitats or more forested areas. Habitat availability was determined within a 4-km radius of the colony and habitat preferences were determined using compositional analysis. Both methods were found to produce similar results, but telemetry provided a larger number of significant differences between habitats. Before the chicks hatched, lesser kestrels preferred grazed fallows, ploughed fields and cereal, while after hatching cereal stubble was the preferred habitat. In steppe habitats the protection of such foraging habitats within a 3-km radius from the colonies could be a very effective conservation measure.

Foraging habitat quality constrains effectiveness of artificial nest-site provisioning in reversing population declines in a colonial cavity nester.

Among birds, breeding numbers are mainly limited by two resources of major importance: food supply and nest-site availability. Here, we investigated how differences in land-use and nest-site availability affected the foraging behaviour, breeding success and population trends of the colonial cavity-dependent lesser kestrel Falco naumanni inhabiting two protected areas. Both areas were provided with artificial nests to increase nest-site availability. The first area is a pseudo-steppe characterized by traditional extensive cereal cultivation, whereas the second area is a previous agricultural zone now abandoned or replaced by forested areas. In both areas, lesser kestrels selected extensive agricultural habitats, such as fallows and cereal fields, and avoided scrubland and forests. In the second area, tracked birds from one colony travelled significantly farther distances (6.2 km ±1.7 vs. 1.8 km ±0.4 and 1.9 km ±0.6) and had significant larger foraging-ranges (144 km2 vs. 18.8 and 14.8 km2) when compared to the birds of two colonies in the extensive agricultural area. Longer foraging trips were reflected in lower chick feeding rates, lower fledging success and reduced chick fitness. Availability and occupation of artificial nests was high in both areas but population followed opposite trends, with a positive increment recorded exclusively in the first area with a large proportion of agricultural areas. Progressive habitat loss around the studied colony in the second area (suitable habitat decreased from 32% in 1990 to only 7% in 2002) is likely the main driver of the recorded population decline and suggests that the effectiveness of bird species conservation based on nest-site provisioning is highly constrained by habitat quality in the surrounding areas. Therefore, the conservation of cavity-dependent species may be enhanced firstly by finding the best areas of remaining habitat and secondly by increasing the carrying capacity of high-quality habitat areas through safe nest-site provisioning.

Unravelling migration routes and wintering grounds of European rollers using light-level geolocators

We used light-level geolocators to track the migratory journey of a globally near-threatened trans-Saharan migrant, the European roller Coracias garrulus, from its breeding grounds in Iberia to its wintering grounds in southern Africa. During autumn migration, birds followed the western African coast with lengthy stopovers within sub-Saharan countries before crossing the equatorial rainforests towards the wintering areas, mainly in Angola. Although based in only two tracked birds, comparison of our results with other studies suggests that western European rollers use distinct migration routes and stopover sites towards shared wintering grounds. Time spent in widely separated and ecologically disparate countries highlights the vulnerability of the species facing the cumulative risks of each area used along their journey.ZusammenfassungAufklärung der Zugwege und Überwinterungsgebiete von Blauracken mittels Hell-Dunkel-Geolokatoren Mithilfe von Hell-Dunkel-Geolokatoren verfolgten wir die Zugroute eines weltweit potentiell gefährdeten Transsaharaziehers, der Blauracke Coracias garrulus, von ihren Brutgebieten auf der Iberischen Halbinsel zu ihren Winterquartieren im südlichen Afrika. Auf dem Herbstzug folgten die Vögel der westafrikanischen Küste, wobei sie längere Rastpausen in subsaharischen Ländern einlegten, um dann die äquatorialen Regenwälder zu überqueren und in die vor allem in Angola gelegenen Überwinterungsgebiete zu fliegen. Obwohl nur zwei Vögel verfolgt wurden, legen Vergleiche mit anderen Studien nahe, dass westeuropäische Blauracken auf dem Weg in die gemeinsamen Winterquartiere klar abgegrenzte Zugrouten und Rastgebiete nutzen. Es unterstreicht die Anfälligkeit dieser Vogelart, dass sie dabei Zeit in weit auseinander liegenden und ökologisch ganz verschiedenartigen Ländern verbringt und somit den geballten Risiken aller Gegenden ausgesetzt ist, die sie auf ihrer Reise aufsucht.

Mapping beta diversity from space: sparse Generalised Dissimilarity Modelling (SGDM) for analysing high-dimensional data

Summary 1. Spatial patterns of community composition turnover (beta diversity) may be mapped through generalised dissimilarity modelling (GDM). While remote sensing data are adequate to describe these patterns, the often high-dimensional nature of these data poses some analytical challenges, potentially resulting in loss of generality. This may hinder the use of such data for mapping and monitoring beta-diversity patterns. 2. This study presents Sparse Generalised Dissimilarity Modelling (SGDM), a methodological framework designed to improve the use of high-dimensional data to predict community turnover with GDM. SGDM consists of a two-stage approach, by first transforming the environmental data with a sparse canonical correlation analysis (SCCA), aimed at dealing with high-dimensional data sets, and secondly fitting the transformed data with GDM. The SCCA penalisation parameters are chosen according to a grid search procedure in order to optimise the predictive performance of a GDM fit on the resulting components. The proposed method was illustrated on a case study with a clear environmental gradient of shrub encroachment following cropland abandonment, and subsequent turnover in the bird communities. Bird community data, collected on 115 plots located along the described gradient, were used to fit composition dissimilarity as a function of several remote sensing data sets, including a time series of Landsat data as well as simulated EnMAP hyperspectral data. 3. The proposed approach always outperformed GDM models when fit on high-dimensional data sets. Its usage on low-dimensional data was not consistently advantageous. Models using high-dimensional data, on the other hand, always outperformed those using low-dimensional data, such as single-date multispectral imagery. 4. This approach improved the direct use of high-dimensional remote sensing data, such as time-series or hyperspectral imagery, for community dissimilarity modelling, resulting in better performing models. The good performance of models using high-dimensional data sets further highlights the relevance of dense time series and data coming from new and forthcoming satellite sensors for ecological applications such as mapping species beta diversity.

Easy but ephemeral food: exploring the trade-offs of agricultural practices in the foraging decisions of Lesser Kestrels on farmland

Capsule Cereal harvesting creates high-quality but ephemeral foraging habitats for invertebrate predators. Aims To investigate how cereal harvesting affects foraging decisions and hunting success of Lesser Kestrels. Methods Habitat selection in response to changing availability of cereal fields (as patches being harvested are turned into stubble) was assessed by transects around colonies to count foraging birds. Focal observations of foraging kestrels were performed to assess hunting success and intake rate before and after harvesting. We performed transects to count Orthoptera to evaluate the impact of cereal cutting on prey abundance. Results Harvesting impacted prey accessibility due to a temporary flush of prey, which resulted in a significant reduction in foraging time and an increase in the intake rate of kestrels. Accordingly, patches being harvested became the most preferred habitat. Nonetheless, harvesting likely caused high orthopteran mortality and dispersal leading to a gradual decline in prey abundance in stubbles. Lower prey abundance increased foraging time and reduced intake rate, and stubbles became avoided by foraging individuals. Conclusion Although harvesting significantly increases foraging opportunities for Lesser Kestrels through intake rate maximization, patches being harvested represent an ephemeral high-quality habitat and its benefits are relatively short-lived as cereals are converted into low-quality stubbles.

Bird on the wire: Landscape planning considering costs and benefits for bird populations coexisting with power lines

Power-line grids are increasingly expanding worldwide, as well as their negative impacts on avifauna, namely the direct mortality through collision and electrocution, the reduction of breeding performance, and the barrier effect. On the other hand, some bird species can apparently benefit from the presence of power lines, for example perching for hunting purposes or nesting on electricity towers. In this perspective essay, we reviewed the scientific literature on both costs and benefits for avifauna coexisting with power lines. Overall, we detected a generalized lack of studies focusing on these costs or benefits at a population level. We suggest that a switch in research approach to a larger spatio-temporal scale would greatly improve our knowledge about the actual effects of power lines on bird populations. This research approach would facilitate suitable landscape planning encompassing both mitigation of costs and promotion of benefits for bird populations coexisting with power lines. For example, the strategic route planning of electricity infrastructures would limit collision risk or barrier effects for threatened bird populations. Concurrently, this strategic route planning would promote the range expansion of threatened populations of other bird species, by providing nesting structures in treeless but potentially suitable landscapes. We suggest establishing a collaborative dialogue among the scientific community, governments, and electricity companies, with the aim to produce a win–win scenario in which both biodiversity conservation and infrastructure development are integrated in a common strategy.

Mechanisms and fitness consequences of laying decisions in a migratory raptor

Seasonal decline in breeding performance is a commonly observed pattern in birds, but disentangling the contributions of environmental conditions (“timing” hypothesis) and individual quality (“quality” hypothesis) to such a pattern is challenging. Moreover, despite the strong selection for early breeding, the individual optimization model predicts that each individual has an optimal breeding window. We investigated the causes and consequences of laying decisions in the lesser kestrel (Falco naumanni) by combining a long-term dataset on reproductive traits with information on food availability. A marked seasonal decline was found in breeding success, mostly mediated by a decline in clutch size. The “timing” hypothesis, supported by the decline in consumption of mole crickets, key prey for prelaying females, seems to explain the seasonal trend in clutch size, as this pattern was recorded in both higher (adults) and lower (yearlings) quality individuals. Contrarily, the higher proportion of yearlings breeding late in the season, rather than a decay in food availability during chick rearing, seems to drive the decline in fledging success, giving support to the “quality” hypothesis. Advanced breeding and increased clutch size, as proxies of reproductive effort, were not offset by lower survival. Low repeatability in both these traits suggests that individual quality is a dynamic attribute and reproduction costs are minimized by individual optimization. Understanding the mechanisms driving individual breeding decisions is critical to anticipate species’ ability to cope with environmental changes. Here, we show that lesser kestrels failing the prelaying food window opportunity compromise reproductive performance, mostly regardless of their individual quality.

Estimation of mercury background values in sediment and biota of the Bijagós archipelago, Guinea-Bissau.

This work evaluates the mercury (Hg) contamination status (sediments and biota) of the Bijagós archipelago, off the coast of Guinea-Bissau. Sediments exhibited very low concentrations (<1-12ngg(-1)), pointing to negligible sources of anthropogenic Hg in the region. Nevertheless, Hg is well correlated to the fine fraction, aluminium, and loss on ignition, indicating the effect of grain size and organic matter content on the presence of Hg in sediments. Mercury in the bivalves Tagelus adansoni and Senilia senilis did not vary considerably among sites, ranging within narrow intervals (0.09-0.12 and 0.12-0.14μgg(-1) (dry weight), respectively). Divergent substrate preferences/feeding tactics may justify slight differences between species. The value 11ngg(-1) is proposed as the sediment background concentration for this West-African coastal region, and concentrations within the interval 8-10ngg(-1) (wet weight) may be considered as reference range for S. senilis and T. adansoni in future monitoring studies.

Major, minor, trace and rare earth elements in sediments of the Bijagós archipelago, Guinea-Bissau

Sixty sediment samples from four sites in the Bijagós archipelago were characterized for fine fraction, loss on ignition, major, minor and trace elemental composition (Al, Fe, Ca, Mg, Ti, P, Zr, Mn, Cr, Sr, Ba, B, V, Li, Zn, Ni, Pb, As, Co, U, Cu, Cs and Cd), and the elements of the La-Lu series. Element concentrations were largely explained by the Al content and the proportion of fine fraction content, with the exception of Ca and Sr. Sediments showed enhanced Ti, U, Cr, As and Cd concentrations with respect to estimated upper crust values, most likely mirroring a regional signature. Rare earth elements were in deficit relatively to the North American Shale Composite (NASC), mainly in coarser material. No pronounced Ce-anomaly was observed, while Eu-anomalies were positive in most analyzed sediments.

Freezing heat: thermally imposed constraints on the daily activity patterns of a free‐ranging grassland bird

Heat stress is a risk for birds exposed to high ambient temperatures, especially for those that live in open environments with limited protection from direct sun radiation. This makes them particularly vulnerable to climate warming. We studied how ambient temperature affects the daily activity of a threatened grassland bird, the little bustard Tetrax tetrax. The activity of 20 birds tracked by GPS satellite telemetry between 2009 and 2012 was monitored throughout the yearly cycle in the Iberian Peninsula. We found that temperatures over ~25°C strongly inhibited the activity of birds during the breeding and post-breeding seasons. High temperatures were mostly frequent during mid-day, which often forced birds to reduce activity during this period, especially during summer. We show that the expected future rise in temperatures may result in a substantial reduction in the duration of the period of the day thermally adequate for maintaining activity. With climate change inactivity levels during breeding and po...