Acrocephalus 110 - lll.qxd 19.12.2002 11:02 Page^rl Acrocephalus 23 (110-111): 21 – 2.6, 2002 Diet of the Red-backed Shrike Lantus collurio in Bulgaria Prehrana rjavega srakoperja Lantus collurio v Bolgariji Boris P. Nikolov Bulgarian Ornithological Centre, Institute of Zoology, Bulgarian Academy of Sciences "Tsar Osvoboditel" Blvd., 1000 Sofia, Bulgaria, e-mail: bnikolov@sf.icn.bg The diet of the Red-backed Shrike Lanius collurio was studied from pellets and food remains collected beneath perches, as well as from food samples obtained from nestlings, using neck collars, during the breeding season (May - July), in 1995 – 1997. The following parameters of 23 pellets were established (mm): 17.4 x 7.7 (12.0 – 27.7 x 6.5 – 9.0). A total of 377 prey items belonging to 59 taxa were found. Invertebrates were represented mainly by insects Insecta (94.72 %). Spiders Aranea were also identified (3.4 %), harvestmen Opiliones (0.80 %), worms Lumbricomorpha, snails Gastropoda and millipedes Juliformia, 0.27 % each. Vertebrates (Common Vole Microtus arvalis) comprised 0.27 % of total prey. The most varied elements of the prey were beetles Coleoptera (41.11 % of all prey items): at least 11 families were established. Almost half the beetles (48 %) were Scarabaeidae and Carabidae species. In comparison with adult birds, soft and non-sclerotized prey predominated in the nestlings’ diet: Aranea (6.8 versus 3.6 %), Lepidoptera caterpillars (5.8 vs. 1.8 %), Opiliones (1.9 vs. 0 %), and Lumbricomorpha (1.0 vs. 0 %). The results for the adults diet could be underestimated, while it is difficult to identify the above-mentioned organisms in the remains in pellets. Some taxa were found only in the nestlings’ food: Opiliones, Juliformia, Lumbricomorpha and, surprisingly, rodents Rodentia. Remains of Gastropoda were found only in adults’ diet. Key words: Red-backed Shrike, Lanius collurio, food spectrum, Bulgaria Klju~ne besede: rjavi srakoper, Lanius collurio, prehrana, Bolgarija 1. Introduction population is declining in Europe (Tucker et al. 1994). Using only the method of stomach analysis also makes The diet of the Red-backed Shrike Lanius collurio is it difficult to identify soft and poorly chitinized comparatively well studied throughout most parts of invertebrates. Pellet analysis is the best method, in spite its breeding range (see compilation in Cramp & of the considerable effort required to identify prey, but Perrins 1993). As an opportunistic feeder this species the use of other methods (identification of stored prey preys mainly on insects and other invertebrates. and prey remains collected under perches, as well as However, small vertebrates can sometimes play an collar-sample analysis) provides complementary important role in its food spectrum (Cramp & information (Hernández 1999). This complex study Perrins 1993). of Red-backed Shrike diet was undertaken with the In Bulgaria there are very few data on the food of purpose of trying to clarify the food spectrum of this Red-backed Shrike. The information is based mostly species in Bulgaria. on analysis of stomach contents (Talev 1962, Prostov 1964, Simeonov & Bogdanov 1967, Daraktchiev & 2. Material and methods Germanov 1974, Daraktchiev 1981). Today, collecting birds just to study their food is not A total of 377 prey items (mainly invertebrates) were acceptable, especially as the Red-backed Shrike established in the food of Red-backed Shrike by 21 Acrocephalus 110 - lll.qxd 19.12.2002 11:02 Page^rS .P. NiKOLOv: Diet of the Red-backed Shrike Lantus collurio in Bulgaria analysis of pellets (93.4 %), food remains collected beneath perches (1.3 %) and collar-samples (5.3 %). Caching food takes place rarely among this species in Bulgaria (only fragmentary data exist), at least in the lower parts of the country (Nikolov unpubl.) and, for that reason, stored prey analysis has been excluded from this work. The data for the present study was collected during May to July for 3 years (i995 — ^997). Field work was carried out for 117 days. Two localities in the Sofia region, W. Bulgaria, were investigated – Pasarel (a village on the Iskar river, about 30 km SE of Sofia) and the Kambanite area (close to the SE outskirts of Sofia, just outside the ring-road). Additional data were collected from Yablanitsa (Lovech region, N Bulgaria). These three study areas are characterized by moderate continental climate and low mountain (900 m a.s.l.), kettle-like (590 m a.s.l.) and hilly relief (450 m a.s.l.) respectively. The adult Red-backed Shrike pellets and food remains were collected beneath perches. Pellets of nestlings were collected during regular nest examinations. The collar-samples were obtained using neck rings and methods after Malchevskiy & Kadochnikov (1953) and Ko uli gin (1981). All pellets, food samples and prey remains were preserved in 75 % ethanol and subsequently analysed. The minimum number of individuals of prey per taxon was estimated for every pellet. 3. Results and discussion 3.1. Pellets Out of 34 intact pellets collected, the average measurements of 23 were 17.4 x 7.7 mm (12.0 – 27.7 x 6.5 - 9.0). They were oblong in shape and generally straight, with one of the ends sharply pointed. Usually the adult shrike pellets were glossy black and smooth, while most of the nestling ones were brown. Size difference between the pellets of adults and nestlings was not established. These dimensions are similar to those given by Hernandez (1995) for 505 pellets from Spain: 19.6 x 8.44 mm. Mielewczyk (1967) in Poland also obtained similar results (N = 12): 25 x 8.5 mm. 3.2. Food spectrum A total of 377 prey items belonging to 59 taxa were identified in the composition of Red-backed Shrike diet, among them 1 class, 10 orders, 4 suborders, 2 superfamilies, 15 families, 1 subfamily, 20 genera and 6 species (Table 1). Table 1: Diet of the Red-backed Shrike Lanius collurio during the breeding season in Bulgaria Tabela 1: Prehrana rjavega srakoperja Lanius collurio v gnezditvenem obdobju v Bolgariji Prey items/ Sofia Yabla- Total/ Enote plena region nitsa Skupaj N N N % Lumbricomorpha Lumbricus terrestris 1 1 0.26 Gastropoda g. sp. 1 1 0.26 Opiliones g. sp. 1 1 2 0.53 Zachelus crista 1 1 0.26 Aranea g. sp. 8 8 2.12 Araneidae g. sp. 1 1 0.26 Araneus sp. 1 1 0.26 Lycosidae g. sp. 3 3 0.79 Diplopoda Juliformia g. sp. 1 1 0.26 Orthoptera g. sp. 24 3 27 7.16 Gryllus sp. 3 3 0.79 Gryllus campestris 2 1 2 1 0.53 0.26 r Acridoidea g. sp. v Tettigonoidea g. sp. 1 1 0.26 Dermaptera g. sp. 1 1 0.26 Homoptera Cicadinea g. sp. 1 1 0.26 Heteroptera g. sp. 8 1 9 2.39 Aelia sp. 1 1 2 0.53 Palomena sp. 3 3 0.79 Rhinocoris sp. 1 1 0.26 Coleoptera g. sp. 3 3 0.79 Cantharidae Cantharis sp. 5 5 1.33 Carabidae g. sp. 23 6 29 7.69 Cerambycidae g. sp. 8 8 2.12 Clytus sp. 1 1 0.26 Dorcadion sp. 18 1 19 5.04 Chrysomelidae g. sp. 1 1 0.26 Cicindelidae Cicindela sp. 1 1 0.26 Curculionidae g. sp. 19 19 5.04 Otiorrhynchus sp. 5 5 1.33 Elateridae g. sp. 6 1 7 1.86 Histeridae g. sp. 3 3 0.79 Atholius sp. 1 1 0.26 Hister sp. 2 2 0.53 Scarabaeidae g. sp. 3 1 4 1.06 22 Acrocephalus 110 - lll.qxd 19.12.2002 11:02 Page^r^ ACROCEPHALUS 23 (iIO-IIl): 21 — 2ć>, 2002 nadaljevanje tabele 11 continuation of Table 1 Prey items/ Sofia Yabla- Total/ Enote plena region nitsa Skupaj N N N % Amphimallon sp. 4 4 1.06 Anisoplia sp. 1 1 0.26 Aphodius sp. 2 2 4 1.06 Caccobius sp. 1 1 0.26 Onthophagus sp. n 1 12 3.18 Rhizotroginae g. sp. 17 1 18 4.77 Silphidae g. sp. 2 2 0.53 Staphylinidae g. sp. 1 1 0.26 Psendocypus sp. 1 1 0.26 Staphylinus sp. 1 1 0.26 Staphylinus caesarus 2 2 0.53 Hymenoptera g. sp. 9 6 15 3.98 Formicidae g. sp. 52 37 89 23.61 Formica polyctena 1 1 0.26 Apoidea g. sp. 13 3 16 4.24 Bombus sp. 4 3 7 1.86 Vespoidea g. sp. 1 1 0.26 Vespidae g. sp. 2 2 0.53 Lepidoptera g. sp. 4 4 1.06 r "\ Geometridae g. sp. I NonGeometridae g. sp. 4 1 4 0.26 \. j 1.06 Diptera g. sp. 1 1 0.26 Nematocera g. sp. 10 10 2.65 Rodentia Microtus arvalis 1 1 0.26 Total / Skupaj 303 74 377 -100 0.7%0.7% 15.8« The proportion, by numbers, of invertebrates and vertebrates in food was 99.73 : 0.27 % (Figure 1). The most frequent prey were various species of beetles (mostly Scarabaeidae, Carabidae, Cerambycidae and Curculionidae), hymenopterans (Formicidae mainly) and Orthoptera species (crickets and grasshoppers), forming together almost 85 % of all prey items. The share of the remaining orders in the diet of Red-backed Shrike ranged between 0.27 and 3.98 %. Figure 2 shows the number of families in every main taxon represented in the diet of this species. Except for Coleoptera, all other groups were represented by 1 to 3 families. Beetles were the most diverse group - at least 11 families were established, comprising 41.11 % of all prey items. Almost half (48 %) were Scarabaeidae and Carabidae species (Figure 3); long-horned Cerambycidae and snout beetles Curculionidae played a considerable role as well. The participation of 7 other beetle families was minor (1.3 – 4.6 %). 18.4% 3.9« 19.1« 3.3% 3.3% 1.3% ¦ Scarabaedae D Silphidae ¦ Cantharidae ¦ Carabidae ^ Chrysomelidae ¦ Cicindelidae ¦ Elateridae D Histeridae 28.9% ¦ Staphylinidae ¦ Cerambycidae ¦ Curculionidae Figure 3: Proportion of the beetle Coleoptera families (N = 153 prey items) in the diet of the Red-backed Shrike Lanius collurio in Bulgaria Slika 3: Dele` dru`in hro{~ev Coleoptera (N = 153 enot plena) v prehrani rjavega srakoperja Lanius collurio v Bolgariji The food of adults and nestlings was compared on the basis of the material collected in the Sofia region -303 prey items (Figure 4). In both cases Coleoptera represented about half of the prey. In the adults’ diet, hymenopterans were ranked as second. Their large number was due mainly to the ants, which are rather unprofitable for feeding the nestlings, from a nutritional and bioenergetical point of view. In the food of the youngsters in the nests the hymenopterans were fewer than orthopterans and they were represented mainly by bees Apoidea (mostly Bombus sp.) and wasps Vespoidea. Soft and non-sclerotized invertebrates (Aranea, Lepidoptera caterpillars, Opiliones, and Lumbricomorpha) predominated 2 to 3 fold in nestling versus adult bird diet. Due to the difficulty of identifying the above mentioned organisms from remains in pellets, it is possible that the results for the adults have been, to some extent, underestimated. Opiliones, Juliformia, Lumbricomorpha and, surprisingly, Rodentia were established among the food of nestlings alone. Remains (teeth) of Common Vole Microtus arvalis were found in a pellet close to the village of Pasarel. That confirms the data for Red-backed Shrike diet in Lozen mountain (Simeonov & Bogdanov 1967). Remains of Gastropoda shell were identified only in adult diet; single cases have been 23 Acrocephalus 110 - lll.qxd 19.12.2002 11:02 Page^Hj .P. Nikolov: Diet of the Red-backed Shrike Lantus collurio in Bulgaria ! i 4° 4a 4° 4° jr 4° 4° J? $r jr & 4° 4" j • Figure 1: Prey proportion in the diet of the Redbacked Shrike Lanius collurio in Bulgaria (N = 377 prey items) Slika 1: Dele`i plena v prehrani rjavega srakoperja Lanius collurio v Bolgariji (N = 377 enot plena) 12 Figure 2: Number of families per main taxon, taking part in the food composition of the Red-backed Shrike Lanius collurio in Bulgaria (N = 377 prey items) Slika 2: [tevilo dru`in v posameznih vi{jih taksonih, najdenih v prehrani rjavega srakoperja Lanius collurio v Bolgariji (N = 377 enot plena) 24 Acrocephalus 110 - lll.qxd 19.12.2002 11:02 Page^HB tj- Acrocephalus 23 (110-111): 21 – 26, 2002 Rodentia Gastropoda Lumbricomorpha Juliformia Opiliones Lepidoptera Diptera Aranea Heteroptera Orthoptera Hymenoptera Coleoptera 60 50 40 30 20 10 0 proportion / delež (%) 0 10 20 30 40 50 60 proportion / delež (%) Figure 4: Comparison between the food of nestlings (N = 134 prey items, left side) and adults (N = 169 prey items, right side) of the Red-backed Shrike Lanius collurio in Sofia region, W Bulgaria Slika 4: Primerjava med prehrano mladi~ev (N = 134 enot plena, leva stran) in odraslih ptic (N = 169 enot plena, desna stran) rjavega srakoperja Lanius collurio v sofijski regiji, Z Bolgarija described of specialized individuals eating these mollusks (Lachner 1958). Acknowledgements: Grateful thanks are expressed to all my colleagues (most of them from the Faculty of Biology, Sofia University) who helped me with the identification of prey items: Ognyan Iliev – Insecta, Aranea; Dr. Plamen Mitov – Opiliones; Angel Vasilev – Lumbricomorpha; Albena Lapeva – Formicidae; Teodora Minkova (Institute of Zoology, Bulgarian Academy of Sciences) – Rodentia. I am much indebted to the anonymous referees who commented on the earlier draft, and Katerina Rakovska as well for polishing my English. 4. Povzetek Avtor je v letih 1995–1997 preu~eval prehrano rjavega srakoperja Lantus collurio iz izbljuvkov in ostankov hrane, najdene pod srakoperjevimi po~ivali{~i, in primerkov hrane, dobljenih od srakoperjevih gnezdomcev z uporabo ovratnikov med gnezditvenim obdobjem (maj-julij). Pri 23 izbljuvkih so bili ugotovljeni naslednji parametri (mm): 17,4 x 7,7 (12,0 – 27,7 x 6,5 – 9,0). Na{tetih je bilo 377 enot plena, pripadajo~ih 59 taksonom. Med nevreten~arji je bilo najve~ `u`elk Insecta – 94,72 %. Identificirani so bili tudi pajki Aranea – 3,4 %, suhe ju`ine Opiliones – 0,80 %, malo{~etinci Lumbricomorpha, pol`i Gastropoda in stonoge Juliformia – s po 0,27 %. Vreten~arji – poljska voluharica Microtus arvalis – so sestavljali 0,27 % celotnega plena. Najbolj raznolik del plena so sestavljali hro{~i Coleoptera – 41,11 % vseh enot plena: ugotovljenih je bilo kar 11 dru`in. Skoraj polovico hro{~ev (48 %) sta zastopali vrsti iz dru`in Scarabaeidae in Carabidae. V primerjavi z odraslimi srakoperji je prehrana gnezdomcev vsebovala predvsem mehek, neotrdel plen: Aranea (6,8 proti 3,6 %), Lepidoptera caterpillars (5,8 in 1,8 %), Opiliones (1,9 in 0,0 %) in Lumbricomorpha 25 Acrocephalus 110 - lll.qxd 19.12.2002 11:02 Page^r^ .P. Nikolov: Diet of the Red-backed Shrike Lantus collurio in Bulgaria (1,0 in 0,0 %). Kar zadeva prehrano odraslih srakoperjev, so rezultati lahko podcenjeni; v ostankih iz izbljuvkov je te`ko identificirati omenjene organizme. Nekateri taksoni – Opiliones, Juliformia, Lumbricomorpha in presenetljivo glodalci Rodentia – so bili najdeni le v prehrani mladi~ev, medtem ko so bili ostanki pol`ev ugotovljeni samo v prehrani odraslih srakoperjev. 5. References Cramp, S. & C. Perrins (eds.) (1993): The Birds of the Western Palearctic. Vol. VII. Oxford Univ. Press, Oxford, New York. Daraktchiev, A. & A. Germanov (1977): Über die Nahrung des Neuntöters in dem Rhodopi-Gebirge. Nature, Univ. Plovdiv 7 (1): 107 – 110. Daraktchiev, A. (1981): Sur la nourriture des oiseaux de la region Tchernatitza des Rhodopes. Trav. scient., Univ. Plovdiv 19 (4): 173 – 207. (in Bulgarian) Hernández, A. (1995): Descripcion de las egagropilas de tres species de alcaudones (real Lantus excuhitor L., dorsirrojo Lantus collurio L. y comun Lantus senator L.). Ecología 9: 435 – 440. Hernández, A. (1999): Tres métodos para el estudio de la dieta de los alcaudones (Lantus spp.): ventajas e inconvientes. Chioglossa 1: 87 – 93. Kouligin, S. (1981): [A new method of using neck collars on nestlings of insectivorous birds for studying their food]. Ornithologiya 16: 174 – 175. (in Russian) Lachner, R. (1958): Rotrückenwürger (Lantus collurio) jagt Schnecken. Ornithol. Mitt. 10 (10): 195 – 196. Malchevskiy, A. & N. Kadochnikov (1953): [Methodology for studying the food of insectivorous bird nestlings]. Zool. J. 32 (2): 277 – 282. (in Russian) Mielewczyk, S. (1967): O pozywieniu gąsiorka, Lanius collurio L., w okolicy Gniezna (woj. poznanskie). Acta ornithol. 10 (6): 157 – 175. Prostov, A. (1964): [Study on the ornithofauna of Bourgas region]. Bull. L’inst. zool. mus 15: 5 – 68. (in Bulgarian) Simeonov, S. & Z. Bogdanov (1967): [The Birds of Lozen mountain]. Annual of Sofia Univ. 59 (1): 43 – 67. (in Bulgarian) Talev, V. (1962): [On the taxonomy, ecology and biology of the Red-backed Shrike (Lanius collurio L.) in Sofia region]. Diploma thesis, Sofia Univ., Faculty of Biology. (in Bulgarian) Tucker, G. M., M. F. Heath, L. Tomialojc & R. F. A. Grimmett (1994): Birds in Europe: Their Conservation Status. BirdLife International, Cambridge. Prispelo / Arrived: 18.3.2002 Sprejeto / Accepted: 23.9.2002 26