New data on the diet of White Stork Ciconia ciconia in Calabria (southern Italy)
Novi podatki o prehrani bele štorklje Ciconia ciconia v Kalabriji (južna Italija)
Giulia Miraglia1, Gaetano Aloise2, Gianluca Godino1, Roberto Santopaolo1 & Marco Gustin3
1	LIPU Sezione di Rende, Via Bertoni s.n.c., Arcavacata, I-87036 Rende (CS), Italy, e-mail: info@lipurende.it
2	Università della Calabria, Dipartimento di Ecologia, via P. Bucci s.n.c., I-87036 Rende (CS), Italy, e-mail: aloise@unical.it
3	LIPU, Dipartimento Conservazione, Via Trento 49, I—43100 Parma, Italy, e-mail: marco.gustin@lipu.it
The diet of a nesting pair of White Storks Ciconia ciconia in a rural area of Calabria (southern Italy) has been studied. The nest was located on top of a high-tension pylon. The authors identified 1421 prey items in 37 pellets, the main prey being insects, which accounted for 97.7% of prey items. Vertebrates constituted only 2.3%. Orthoptera accounted for 64% of all insects and 62.5% of total prey items, and were present in 81% of the pellets. Other insects (35.1% of prey items) were present in 75.6% of the pellets and included Dermaptera, Hymenoptera, Heteroptera and Coleoptera.
Key words: White Stork, Ciconia ciconia, diet, Calabria, southern Italy Klju~ne besede: bela štorklja, Ciconia ciconia, prehrana, Kalabrija, južna Italija
1. Introduction
The White Stork Ciconia ciconia is a widespread Palearctic species that underwent a significant population decline in the 1970's, particularly in western Europe (Snow & Perrins 1998). It has experienced a recent, slight increase throughout its range (BirdLife International 2004), including the re-colonisation of countries from which it disappeared as a breeder during the last century. This increase is due in part to numerous reintroduction projects, rather than to natural range expansions (Canziani & Palumbo 2004).
The number of breeding pairs is also increasing in Italy, particularly in certain parts of northern Italy and in Sicily (Canziani & Palumbo 2004, Güstin 2004, Belardi et al. 2005), and breeding started in Calabria also in the 1990's (Capalbo 1993 & 1995, Gustin et al. 1995, Sottile 2003), where there are currently only three known breeding pairs (Santopaolo et al. 2006).
Among the causes likely to have led to the species earlier becoming rarer throughout its range, a key role has probably been played by the intensification of agriculture, along with widespread urbanization and the loss of extensive foraging areas (Dallinga
& Schoenmakers 1987, Goriup & Schulz 1991, Tsachalidis & Papageorgiou 1996, Johst et al. 2001). Climate change on the wintering grounds has also contributed as a negative factor on trophic resources (Tucker & Heath 1994, Schulz 1999).
The species is an opportunist (Snow & Perrins 1998, Etienne & Caurrette 2002) and its diet was described in detail for many European regions (Cramp & Simmons 1977, Schulz 1998).
In Italy, information on diet is generally scarce, and mostly concerns northern areas (Boano 1981 & 1992), rather than the south (Miraglia et al. 2003).
In this work, we present the results of a study on the diet of a single nesting pair of White Storks in a rural area of Calabria (southern Italy).
2. Study area
The nesting site of the pair whose diet was studied is located along the Crati river (municipality of Luzzi, Cosenza — 39°28'N, 16°14'E).
Crati is the principal Calabrian river and flows in a typical fluvial plain, whose landscape is characterized by a mosaic of cultivated land with arboreal crops (olive groves, citrus groves, peach orchards and poplar woods), uncultivated land, strips of Quercus virgiliana
Table 1: Diet of a single pair of White Storks Ciconia ciconia in Calabria (Southern Italy); 37 whole pellets were analysed (number of prey, % of prey, number of pellets with each taxon and % of pellets containing each taxon). The pellets were collected near the nest and dry dissected.
Tabela 1: Prehrana gnezdečega para belih štorkelj Ciconia ciconia v Kalabriji (južna Italija), ugotovljena z analizo 37 izbljuvkov (število enot plena, % enot plena, število izbljuvkov s posameznim taksonom, procent izbljuvkov s posameznim taksonom). Izbljuvki so bili nabrani v bližini gnezda in analizirani s suhim postopkom.
Taxa / Takson	Number of prey items / [tevilo enot plena	% of prey items/ % enot plena	No. of pellets with each taxon/ [t. izbljuvkov s posameznim taksonom	% of pellets with each taxon/ % izbljuvkov s posameznim taksonom
Gastropoda	1	0.07	1	2.70
Insecta unknown / neznano	38	2.67	7	18.92
Ortoptera indet.	888	62.49	30	81.08
Dermaptera indet.	4	0.28	2	5.41
Forficula sp.	9	0.63	7	18.92
Hymenoptera				
Apoidea indet.	2	0.14	2	5.41
Formicidae indet.	90	6.33	20	54.05
Coleoptera indet.	125	8.80	26	70.27
Tenebrionidae indet.	31	2.18	19	51.35
Carabidae indet.	42	2.96	21	56.76
Amara sp.	1	0.07	1	2.70
Chlaenius cfr. spoliatus	5	0.35	5	13.51
Chlaenius sp.	6	0.42	6	16.22
Campalita maderae	1	0.07	1	2.70
Omophrom limbatum	4	0.28	3	8.11
Scarabeidae indet.	33	2.32	23	62.16
Fillomorpha sp.	1	0.07	1	2.70
Orictes nasicornis	2	0.14	2	5.41
Coccinellidae indet.	5	0.35	4	10.81
Chrisomelidae indet.	43	3.03	22	59.46
Curculionidae indet.	8	0.56	7	18.92
Cucujidae indet.	3	0.21	3	8.11
Clinidium sp.	1	0.07	1	2.70
Heteroptera indet.	16	1.12	10	27.03
Pentatomidae indet.	27	1.90	16	43.24
Nezara viridula	1	0.07	1	2.70
Elia rostrata	1	0.07	1	2.70
Total insects / Skupno žuželke	1388	97.68	28	75.68
Fish / Ribe	10	0.73	10	27.03
Reptiles / Plazilci	3	0.21	2	5.41
Birds / Ptice	1	0.07	1	2.70
Mammals / Sesalci	6	0.44	5	13.51
Vertebrates / vreten~arji indet.	13	0.92	13	35.13
Total vertebrates / Skupno vreten~arji	33	2.32	26	70.27
Plant / Rastline			25	67.57
Inorganic garbage / Neorganski odpadki			10	27.03
Total / Skupaj	1421	100%		
woods and arboreal riparian vegetation (Alnus glutinosa, Populus sp., Salix sp.). The nest was located on the top of a high-tension pylon, a structure often used by White Storks for nest-building (Tsachalidis & Papageorgiou 1996), also in Italy (Belardi et al. 2005). The pair reached the study area in April. Three eggs were laid in the first ten days of May and chicks hatched in the first days of June; three fledglings fledged in the second half of August.
3.	Methods
Between July and August 2004, we collected 37 whole pellets near the nest (the data are therefore restricted to this period although the total breeding period was May — August). Pellets were dry dissected and the prey remnants were identified on the basis of reported diagnostic characters (Barbraud & Barbraud 1998) or by comparison with reference material from other Calabrian sites, preserved in the collections of the Museo di Storia Naturale ed Orto Botanico, University of Calabria.
Orthoptera were identified, thanks to the characteristic of mandibles and other insect remains of the exoskeleton (head, legs, elytrons, wings, mandibles). Vertebrates were identified through the presence of scales, feathers and hair. Recovery of bones is generally rather unusual and limited to splinters. These are barely recognizable after being altered by White Storks' digestive systems, which are particularly acid and often completely dissolve bone fragments (Schulz 1998).
Items were identified assuming the minimum number of specimens of each taxon, which for insects is equal to the highest number of single exoskeleton parts that are most representative of the taxon in question.
For vertebrates, since the number of individuals is not quantifiable on the basis of tegumental remains, we only considered one individual for each pellet in which the taxon was present.
We express the composition of diet in terms of: i) number of prey items and percentage for each taxon; ii) percentage of pellets in which each taxon was present.
4.	Results
We identified 1421 prey items (Table 1). The main prey of White Stork were insects, which accounted for 97.6% of prey items.
Orthoptera accounted for 64% of all insects and 62.5% of total prey items, and were present in 81%
of the pellets. In July and August when the weather was very hot and dry (temperature max. 40°C in July and more than 40°C in August), grasshoppers may have been one of the few food resources available in large numbers. Other insects (35.1% of prey items) were present in 75.6% of the pellets and they included Dermaptera, Hymenoptera, Heteroptera and Coleoptera.
Fish (30.3%) and mammals (18.2%) accounted for an important fraction of vertebrates in the White Storks' diet, whereas only one unfledged bird and three snakes (Colubridae, Reptiles) of small to medium size were found. The presence of plant material (present in 67.6% of pellets) is also significant.
5. Discussion
The diet of White Stork can change significantly with the abundance of different prey items, season and geographical area, so the percentage ofmammals, insects, aquatic animals or worms can change between sites, across the breeding season and with weather conditions (Sackl 1987, Pinowska & Pinowski 1989, Pinowski et al. 1991, Mužinic & Rasajski 1992, Schulz 1998, Johst et al. 2001, Tsachalidis & Goutner 2002).
In our study area the proportions of Gastropoda and vertebrates were low (0.07% and 2.3% respectively), but the use of pellets to characterise the diet of White Storks may be misleading, because some prey items do not leave identifiable remains, since they are readily digestible (Mužinic & Rasajski 1992, Etienne & Carruette 2002). For example, amphibian remnants in pellets were not found, but the remnants of aquatic (fish) and riparian animals (Chlaenius spp., Campalita maderae, Omophrom limbatum) were found. In the previous year in our study area the same pair, which used the same nest, was observed to capture amphibians (Miraglia et al. 2003).
It is likely that some small, unrecognizable bone fragments belonged to individuals of this taxonomic group. Observations on pellets and fresh material from the same nests can lead to very different results (De Barros & Moura 1989); however, in this study it was impossible to collect other information (prey remains, direct observations) without causing disturbance and jeopardising the nesting.
In 27% of cases, plastic, paper and cloth remnants were found. Recent studies have highlighted the ingestion of plastic or rubbish by White Storks, probably due to rubbish tips being used as foraging grounds (Martinez Rodriguez 1995, Tortosa et al. 2002, Peris 2003) as well as nearby urban areas (Martinez Rodriguez 1995).
Although White Storks are carnivorous, they may ingest plant matter accidentally (Baudoin 1973, Etienne & Carruette 2002), unless the plants are important for the production of pellets (probably the case in our study area) (Etienne & Carruette 2002). In this study an exceptionally high percentage (67.6%) of pellets contained plant remains, and 24% of them were made up exclusively of such remains.
The predominance of insects, especially Orthoptera, in the White Stork's diet of our study area confirms results obtained in other Mediterranean areas characterised by dry, cultivated environments (Melendro et al. 1977, Cramp & Simmons 1977, Dallinga & Schoenmakers 1987, De Barros & Moura 1989, Pinowska & Pinowski 1989, Mužinic & Rasajski 1992, Boukhamza et al. 1995, Barbraud & Barbraud 1998, Tsachalidis & Goutner 2002). It confirms the considerable adaptability of this species to prey abundance and availability. Acknowledgements: Special thanks are due to T. Bonacci for insect identification and to Ottavio Janni and Alberto Sorace for revising the manuscript.
6.	Povzetek
Predstavljeni so rezultati {tudije o prehranjevanju gnezde~ega para belih {torkelj Ciconia ciconia v podeželskem delu Kalabrije (južna Italija). Gnezdo je bilo zgrajeno vrh droga visokonapetostne elektri~ne napeljave. Avtorji ~lanka so identificirali 1421 enot plena v 37 izbljuvkih. Glavni plen belih {torkelj so bile žuželke s kar 97.7% enot plena, medtem ko so vreten~arji sestavljali le 2.4% njihovega plena. Ravnokrilci Orthoptera, ki so sestavljali 64% vseh žuželk in 62.5% vseh enot plena, so bili najdeni v 81% izbljuvkov. Druge žuželke (35.1% enot plena), ki so jih sestavljali kožekrilci Dermaptera, strigalice Hymenoptera, stenice Heteroptera in hro{~i Coleoptera, so bile ugotovljene v 75.6% izbljuvkov.
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Arrived / Prispelo: 14.6.2008 Accepted / Sprejeto: 19.2.2010