Allocating active conservation measures using species distribution models: a case study of red-footed falcon breeding site management in the Carpathian Basin

Trend in an isolated population of the red-footed falcon (Falco vespertinus) at the edge of its breeding range (south-western Slovakia)

The population of the red-footed falcon in Slovakia inhabits the north-western edge of the species' breeding range. This breeding population is relatively small and came near to extinction during the population decline of this species in central Europe in recent decades. Thanks to increasing numbers of breeding pairs in Hungary, the Slovak population began to grow again. Moreover, some differences in breeding biology associated with breeding in nest boxes were found. Here we describe the dependence of the small isolated breeding population in Slovakia on the core population in the more eastern parts of the Carpathian Basin, and the impact of supporting activities (nest boxes) on this raptor species in Slovakia.

Agricultural utilisation and potential suitability of the Sysľovské polia Special Protection Area (south-western Slovakia) landscape in relation to the habitat requirements of the red-footed falcon (Falco vespertinus)

Intensification of land use in an agricultural landscape significantly affects biodiversity also in protected areas. This can be observed in the Sysľovské polia Special Protection Area in relation to the occurrence of the red-footed falcon (Falco vespertinus). The objective of this study was to evaluate the landscape structure and suitability of agrotechnical procedures for the habitat demands of this species in the course of the period from 2004 until 2017. The utilisation was assessed on the basis of four landscape elements representation in 1949 and 2017. The next step was analysis of landscape patches. The aim was to quantify the diversity and the spatial structure of the landscape mosaic using Shannon’s Diversity Index and Evenness Index as well as Simpson’s Diversity Index and Evenness Index and spatial pattern analysis in the Fragstats software programme. Assessment of crop suitability was carried out according to the following criteria: representation of positive/negative agricultural crops, diversity of crops in crop rotation, and (non-)observance of crop rotation. It was found that the agricultural landscape use did not change significantly. The study area has been used as an intensively-farmed agricultural landscape for a long time. The landscape elements have remained almost identical, with dominance of arable land. Differences emerged in the analysis of the micropatches, which are represented by natural hedgerows consisting of various species of trees, shrubs and grasses. The results show a decrease in the diversity of patches and changes in the structure of the landscape patches, which may be important in terms of the preservation of the habitat of fauna which form an important part of the F vespertinus diet. On the basis of the evaluation of the suitability of agricultural crop growing, we found that there were some areas showing negative values in all the criteria, and thus they require changes in the crop rotation focusing on increasing positive crop diversity and the share of grassland.

West Nile virus host-vector-pathogen interactions in a colonial raptor

Background

Avian host species have different roles in the amplification and maintenance of West Nile virus (WNV), therefore identifying key taxa is vital in understanding WNV epidemics. Here, we present a comprehensive case study conducted on red-footed falcons, where host-vector, vector-virus and host-virus interactions were simultaneously studied to evaluate host species contribution to WNV circulation qualitatively.

Results

Mosquitoes were trapped inside red-footed falcon nest-boxes by a method originally developed for the capture of blackflies and midges. We showed that this approach is also efficient for trapping mosquitoes and that the number of trapped vectors is a function of host attraction. Brood size and nestling age had a positive effect on the number of attracted Culex pipiens individuals while the blood-feeding success rate of both dominant Culex species (Culex pipiens and Culex modestus) markedly decreased after the nestlings reached 14 days of age. Using RT-PCR, we showed that WNV was present in these mosquitoes with 4.2% (CI: 0.9–7.5%) prevalence. We did not detect WNV in any of the nestling blood samples. However, a relatively high seroprevalence (25.4% CI: 18.8–33.2%) was detected with an enzyme-linked immunoabsorbent assay (ELISA). Using the ELISA OD ratios as a proxy to antibody titers, we showed that older seropositive nestlings have lower antibody levels than their younger conspecifics and that hatching order negatively influences antibody levels in broods with seropositive nestlings.

Conclusions

Red-footed falcons in the studied system are exposed to a local sylvatic WNV circulation, and the risk of infection is higher for younger nestlings. However, the lack of individuals with viremia and the high WNV seroprevalence, indicate that either host has a very short viremic period or that a large percentage of nestlings in the population receive maternal antibodies. This latter assumption is supported by the age and hatching order dependence of antibody levels found for seropositive nestlings. Considering the temporal pattern in mosquito feeding success, maternal immunity may be effective in protecting progeny against WNV infection despite the short antibody half-life measured in various other species. We conclude that red-footed falcons seem to have low WNV host competence and are unlikely to be effective virus reservoirs in the studied region.

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.