Aldina M. A. Franco

Prioritizing multiple-use landscapes for conservation: methods for large multi-species planning problems.

Across large parts of the world, wildlife has to coexist with human activity in highly modified and fragmented landscapes. Combining concepts from population viability analysis and spatial reserve design, this study develops efficient quantitative methods for identifying conservation core areas at large, even national or continental scales. The proposed methods emphasize long-term population persistence, are applicable to both fragmented and natural landscape structures, and produce a hierarchical zonation of regional conservation priority. The methods are applied to both observational data for threatened butterflies at the scale of Britain and modelled probability of occurrence surfaces for indicator species in part of Australia. In both cases, priority landscapes important for conservation management are identified.

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.

Inter- and intra-specific differences in butterfly behaviour at boundaries

To plan effective conservation measures and to predict which species will be able to change distribution in response to climate change, there is an increasing need for understanding species dispersal abilities and how species move in complex landscapes. Responses to habitat boundaries affect emigration rates from habitat and are therefore important determinants of species dispersal. There are, however, few studies linking dispersal parameters to likelihood of crossing barriers across several species. In this study, dispersal and likelihood of crossing boundaries, which are presented here as tall and dense tree plantation, were investigated for seven butterfly species. Effects of adult age and sex on the dispersal and behaviour at boundaries were also analysed. Our results demonstrate differences in movements and response to habitat boundaries between species belonging to different butterfly families. Pieridae species were the most likely to cross boundaries and most mobile, whilst with the Lycaenidae species only a small fraction of individuals crossed the tall dense boundary. Individuals and species that moved with longer move bouts (i.e. steps) were more likely to cross boundaries. Therefore, we propose using step length, which is relatively easy to measure, as a proxy for butterfly dispersal at the landscape level. Female butterflies moved less than males within habitat but crossed boundaries more often than males, indicating that dispersal data needs to be collected for the two sexes separately to provide more accurate estimates of species ability to colonise new areas.

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.

An Anthropogenic Habitat Facilitates the Establishment of Non-Native Birds by Providing Underexploited Resources

Anthropogenic modification of habitats may reduce the resources available for native species, leading to population declines and extinction. These same habitats often have the highest richness of non-native species. This pattern may be explained if recently human-modified habitats provide novel resources that are more accessible to non-native species than native species. Using non-native birds in the Iberian Peninsula as a case study, we conduct a large-scale study to investigate whether non-native species are positively associated with human modified habitats, and to investigate whether this positive association may be driven by the presence of resources that are not fully exploited by native species. We do this by comparing the functional diversity and resource use of native and non-native bird communities in a recently human-modified habitat (rice fields) and in more traditional habitats in the Iberian Peninsula. The functional diversity of native bird communities was lower in rice fields, but non-native birds were positively associated with rice fields and plugged this gap. Differences in resource use between native and non-native species allowed non-native species to exploit resources that were plentiful in rice fields, supporting the role of underexploited resources in driving the positive association of non-native birds with rice fields. Our results provide a potential mechanism explaining the positive association of non-native species with anthropogenic habitats, and further work is needed to test if this applies more generally.

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.

Experience modulates both aromatase activity and the sensitivity of agonistic behaviour to testosterone in black-headed gulls

In young black-headed gulls (Larus ridibundus), exposure to testosterone increases the sensitivity of agonistic behaviour to a subsequent exposure to this hormone. The aim of this paper is twofold: to analyze whether social experience, gained during testosterone exposure, mediates this increase in hormonal sensitivity (priming), and whether this in turn is mediated by an increase in central aromatase activity. To this end, we performed three experiments. In the first juvenile gulls were exposed to two consecutive treatments with testosterone (T1 and T2), with more than a week interval in between. During T1, half of the birds were housed in social isolation (Iso) and the other half in groups (Soc). All birds were re-housed in a new social situation during the second treatment. The increase in social behaviour during T2 was significantly more rapid in Soc than Iso birds. In experiment 2 we show that 17beta-estradiol treatment facilitates the behaviour measured in experiment 1. In experiment 3 we used a set-up comparable with that of experiment 1, but birds were sacrificed early in the T2 period. Aromatase activity in the preoptic area and the hypothalamus was measured using the tritiated water releasing method. In some parts of the preoptic area and hypothalamus aromatase activity was higher in Soc birds relative to Iso birds. The results indicate that social experience can modulate the increase of social behaviour to testosterone via modulation of aromatase activity and independently of actual hormone levels.

Role of the Mediterranean Sea in differentiating European and North African woodland bird assemblages

The Mediterranean Sea has separated the sclerophyllous forests of southern Europe and northern Africa for millions of years, but its role structuring forest bird assemblages remains unclear. To address this issue we sampled bird assemblages in cork oak woodlands located north and south of the Strait of Gibraltar and compared abundance, diversity, and species and guild assemblage structure between regions. Abundance and diversity patterns were remarkably similar, but dissimilarity analyses of species and guild composition revealed differences in bird assemblage structure between regions. Differences are partly attributable to the effect of the Mediterranean as barrier to the dispersal of forest birds; a few species were unable to colonize North Africa, and many that colonized it remained in sufficient isolation to evolve into distinct taxa. In addition to this divergence of biogeographic genesis, assemblages also differ because in North African cork oak woodlands forest and insectivorous specialist species are less abundant. This dissimilarity could be due to the effect of different exploitation levels present in each region. Managed cork oak woodlands are widespread in the Western Mediterranean, and are valuable because they conciliate economic exploitation with high biodiversity. In North Africa these woodlands are of greater conservation concern because they harbour endemic bird species that give its assemblage a distinct character, cover a smaller area, and are currently under greater pressure from overexploitation. These results highlight the importance to implement management practices that increase resilience and maintain biodiversity value throughout the range of cork oak woodlands.

Changes in habitat associations during range expansion: disentangling the effects of climate and residence time

The distributions of many species are not at equilibrium with their environment. This includes spreading non-native species and species undergoing range shifts in response to climate change. The habitat associations of these species may change during range expansion as less favourable climatic conditions at expanding range margins constrain species to use only the most favourable habitats, violating the species distribution model assumption of stationarity. Alternatively, changes in habitat associations could result from density-dependent habitat selection; at range margins, population densities are initially low so species can exhibit density-independent selection of the most favourable habitats, while in the range core, where population densities are higher, species spread into less favourable habitat. We investigate if the habitat preferences of the non-native common waxbill Estrilda astrild changed as they spread in three directions (north, east and south-east) in the Iberian Peninsula. There are different degrees of climatic suitability and colonization speed across range expansion axes, allowing us to separate the effects of climate from residence time. In contrast to previous studies we find a stronger effect of residence time than climate in influencing the prevalence of common waxbills. As well as a strong additive effect of residence time, there were some changes in habitat associations, which were consistent with density-dependent habitat selection. The combination of broader habitat associations and higher prevalence in areas that have been colonised for longer means that species distribution models constructed early in the invasion process are likely to underestimate species’ potential distribution.