Assessing the relative importance of managed crops and semi-natural grasslands as foraging habitats for breeding lesser kestrels Falco naumanni in southeastern Italy

Michelangelo Morganti,Cristina Tarantino,Silvia Quilici,Palma N. Blonda,Matteo Griggio,Jacopo G. Cecere,Roberto Ambrosini,Diego Rubolini

doi:10.2981/wlb.00800

Abstract

Farmland habitats host important populations of several threatened bird species. So far, how to reconcile farmland management with the maintenance of viable populations of these taxa is a major challenge for conservation biology. Southeastern Italy hosts ca 7000 pairs of breeding lesser kestrels Falco naumanni, representing one of the European strongholds of this small colonial raptor of conservation concern. We firstly assessed the relative importance of managed crops versus semi-natural grasslands in determining the local abundance of lesser kestrels at the landscape scale, and we successively studied the foraging habitat preferences at a smaller spatial scale. Surveys of foraging birds were associated with land-use collection at 191 homogeneous habitat sampling parcels from 14 plots of 16 km2 each, uniformly distributed over a 2400 km2 area. Each plot was visited six times during the 2017 breeding season (May–July). Land-use markedly changed along the season, unripe cereals being dominant in May, while harvested cereal crops prevailed in July. Land-use did not affect lesser kestrel distribution early in the season while foraging birds were more abundant in plots with a greater proportion of harvested cereal crops and a lower one of semi-natural grassland in the late breeding season. In accordance, the analysis of foraging habitat preferences within plots showed that in May unripe cereal crops and semi-natural grasslands were used proportionally to their availability. In June and July, harvested cereal crops were used more than expected from their availability, while semi-natural grasslands were significantly avoided. Our landscape-scale analysis thus indicates that semi-natural grasslands are much less used in comparison to harvested crops during the mid and late parts of the breeding season, suggesting that lesser kestrel may be able to take advantage of crop management practices more than other farmland birds of conservation priority.

Highlights

We investigated foraging habitat preferences of the lesser kestrel Falco naumanni, a migratory colonial raptor of conservation priority that is tightly linked to cereal steppe habitats, in the Apulo–Lucanian region
Through a landscape-scale randomized survey, we showed that lesser kestrels of the Apulo–Lucanian region, hosting 15% of the European population of this species, evenly distributed among patches at the beginning of the breeding season while later on they tended to concentrate where the proportion of harvested cereal crops prevaile over semi-natural grasslands
The preference for semi-natural grasslands versus managed crops as feeding grounds changed in the course of the breeding season: at the beginning of the season, semi-natural grasslands and unripe cereal crops were used in proportion to their availability, while later in the season the birds preferred to forage on harvested cereal crops and actively avoided semi-natural grasslands

Summary

Introduction

We investigated foraging habitat preferences of the lesser kestrel Falco naumanni, a migratory colonial raptor of conservation priority that is tightly linked to cereal (and residual natural) steppe habitats, in the Apulo–Lucanian region (southeastern Italy) This area currently hosts ca 7000 breeding pairs of the species (La Gioia et al 2018), corresponding to 15% of the current estimated European population size. We tackle the study of habitat selection in a breeding area of pivotal importance for the European conservation of the species using randomized surveys of land-use and foraging lesser kestrels at an unprecedented broad spatial scale (ca 2400 km2), accounting for major changes in agricultural habitat structure that occurred during the sampling period. Our analysis contributes to disentangling the relative importance of managed and unmanaged crops in defining a favourable landscape for breeding lesser kestrels, possibly contributing to the design of future conservation interventions

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