Change of Feeding Strategy Prior to Migration: A Comparative Diet Analysis in the Lesser Kestrel (Falco Naumanni)

Abstract

Assessing the variation in diet composition of a species, over different years and between periods, offers insights to comprehend its ecological niche as well as to define different feeding strategies. We studied the diet of the Lesser Kestrel ( Falco naumanni) by analysing 1040 regurgitated pellets collected in the city of Ioannina (northwestern Greece). We compared diet composition between the breeding period (data from years 2010–2015) and the pre-migration period (data from 2013–2015) at the study site. A total of 8920 prey items were identified and classified into 13 different prey families. The Lesser Kestrel shows a consistent pattern of diet composition throughout years, displaying significant differences between breeding and pre-migration periods. The diet is rather diverse during the breeding season (Levins' diet breadth, B = 4.12) and is composed mainly of Orthoptera and Coleoptera, while during pre-migration, the species shows a more narrow diet breadth ( B = 1.98) and feeds more often and on larger amounts of Orthoptera. These results indicate a specialised feeding strategy during pre-migration. In addition, the examination of the Orthoptera consumption during this period indicates a peak in the abundance of grasshoppers (Acrididae) in the second half of August. We suggest that at this time birds exploit high elevation open grasslands around the roosting site where grasshopper abundance is high. Thus, such areas are of high conservation importance as Lesser Kestrels depend on this localised abundance of Orthoptera in order to fuel up before their trans-Saharan migration.

Different trends of neighboring populations of Lesser Kestrel: Effects of climate and other environmental conditions

“…Movements of breeding adults are limited mainly to within 3 km from their colony during nest attendance (Bondì & Sarà, ; Cecere et al, ; Gustin, Giglio, Pellegrino, Frassanito, & Ferrarini, ; Tella, Forero, Hiraldo, & Donázar, ; Vlachos et al, ). Chicks are therefore mainly fed with prey collected in the immediate area surrounding the colony (Bounas & Sotiropoulus, ; Morganti, Franzoi, Bontempo, & Sarà, ). After breeding, they move to premigratory areas in Sicily, where they stay from late June to mid‐October fattening before migration (Bounas & Sotiropoulus, ; Sarà et al, ).…”

“…Chicks are therefore mainly fed with prey collected in the immediate area surrounding the colony (Bounas & Sotiropoulus, ; Morganti, Franzoi, Bontempo, & Sarà, ). After breeding, they move to premigratory areas in Sicily, where they stay from late June to mid‐October fattening before migration (Bounas & Sotiropoulus, ; Sarà et al, ). Migration of this species is quite fast, and the journey from pre‐migratory areas to winter quarters takes only a few days.…”

Using genetic markers to unravel the origin of birds converging towards pre-migratory sites

“…There they exploit the temporal abundance of food resources, mainly insects, so as to build up the appropriate fat reserves and replace – at least partially - their flight feathers (i.e. moult) 37 – 39 . It has also been suggested that such gatherings may facilitate the selection of future breeding habitats and aid spring navigation 40 .…”

The Orthoptera of Castro Verde Special Protection Area (Southern Portugal): new data and conservation value

“…For example, O. tarda , T. tetrax and F. naumanni consume orthopterans during the breeding and pre-migration periods ( Rocha et al 2005 , Jiguet 2002 , Catry et al 2014 , Bounas and Sotiropoulosa 2017 ). Despite its importance, to date no comprehensive inventory on Orthoptera fauna has been performed in Castro Verde SPA .…”