The objective of this action is to analyse feeding habitat use in the lesser kestrel in the areas covered by the project. It aims to determine the foraging zones, in order to obtain data about the size of the forging area, degrees of use of different zones and the preference shown by the species for different types of habitat (verges, cereal crops, fallow land) as opposed to others (forested areas, irrigated land), measure the effort of different breeding individuals feeding young in relation to the distance of the foraging area from the colony and the density and size of prey, and identify the effect of herbicide use on its feeding.
The measures to undertake this are as follows:
A. Capture and marking of individuals of different ages and sex from different urban SPAs as categorised by the surrounding habitat type:
1.- Zones with predominantly traditional land use such as extensive cereal fields.
2.- Traditional habitats with high level of grazing.
3.- Forest habitats, less suitable for the species.
Thus, the data obtained will both detect and analyse the full spectrum of problems that could be affecting the species, based on the characteristics of the zone.
The capture and marking of individuals will take place at the start of the breeding season once clutches have been laid. Birds will be individually marked with an official metal ring and a PVC ring.
Individual birds will be tracked using satellite transmitters that will automatically send data to a server on the internet or GPS loggers that will be recovered when birds are recaptured in order to download the data.
During periods of migration or wintering, data will be received regularly from the satellite transmitters whilst the GPS loggers will store data that will be recovered the following breeding season. A high recovery rate is expected given the strong site faithfulness of young birds and adults to their natal colonies.
B. Characterisation of feeding habitats and prey species.
Different habitats surrounding the colonies where there are marked birds will be characterised using the latest versions of land use mapping Corine and the Information System on Land Use in Spain (SIOSE). The results will be verified through field visits and samples will be undertaken in areas used by kestrels from the data of marked individuals.
In each of the habitats suitable for the species, parcels of land will be selected at random in order to carry out regular sampling of insects to look at prey availability in time and space. Transects using insect sweep nets and samples from pitfall traps for non-flying prey. These samples will give us an idea of prey density per unit area in each of the habitats.
At the same time, pellets will be recovered from close to the nests. From the remains of ingested prey, the identification of species taken by the kestrels for food will be possible. There will also be an analysis of images obtained from cameras installed in the nests (Action D1) to identify prey carried to the nests.
C. Analysis of chemical contaminants.
The use of pesticides in arable and grazing land has been described as one of the principal causes for the decline of lesser kestrels: increasing the mortality rate of birds through direct poisoning and the reduction of prey numbers will result in a fall in breeding success.
For these analyses, arthropods collected during the sampling in the habitats will be frozen for later laboratory testing, where they will be analysed for the common pesticides used in Extremadura for control of the Moroccan locust and egg shells and infertile eggs will be taken from the nests to undertaken similar testing.
When kestrels are captured for marking, blood samples will be taken to measure the bird’s exposure to insecticides.
D. Data analysis.
A Geographical Information System (GIS) will be used to analyse the results of the samples and the movements of birds in relation to different variables, incorporating data from satellite tele detection to calculate the Normalised Difference Vegetation Index (NDVI), that will provide information on the quantity, quality and the growth of vegetation.
Owing to the string relationship between vegetation and insect abundance, the NDVI is of great importance to measure vegetation presence. Through this index, it will be possible to detect the patterns of harvest and other variables that could influence significantly the feeding areas of the lesser kestrel. All the information obtained will be stored in the GIS and available for use in the Actions C (Conservation).
In summary, through obtaining georeferenced maps showing the data from the transmitters on habitat use by the lesser kestrel together with the data on the prey species, from the analysis of pesticides and sightings logged by project staff, we will acquire better knowledge of the feeding habitat of the species, foraging preferences with respect to land use, prey availability and the relevance of chemical contaminants, with the aim to develop management measures for the habitat which will favour the species (Action C4) and to define the management guidelines (Actions A3, A4, A5) that will address the challenges of feeding habitat change and loss, one of the main threats for the lesser kestrel in Extremadura, considered to be of high impact in the “Species Action Plan for the Lesser Kestrel Falco naumanni in the European Union”.
Responsible for implementation: General Directorate of the Environment and Terra Naturalis.
