original scientific paper UDK 598(497.12 Sečovlje) SECOVLJE SALINA - A N ORNITHOLOGICA L ASSESSMENT O F A SLOVENE COASTA L WETLAN D iztok ŠKORNiK Ornithologist, MEDMARAV1S, 6GOOO Koper, Krožna 10, SL O ornitolog, MEDMARAVIS, 66000 Koper, Krožna 10, SL O Tihomir MAKOVEC Ornithologist, Ornithological Association IX08RYCHUS , 66000 Koper, Gasilska 8, SLO ornitolog, Ornitoloäko društvo !XOBRYC.HUS, 66000 Koper, Gasilska 8, SL O Lovrenc LiPEj MSc, Biologist, Marine Biological Station, 66330 Piran, FornaCe 41, SL O mag. biol. znan., Morska Biološka Postaja, 66330 Piran, Fornače 41, SL O ABSTRACT To date, 248 bird species have been recorded in the Sečovlje satina and neighbouring wetland areas, of which 91 are breeding species. Several waterbird species, the Black-winged Stilt Himantopus hirnantopus, Little Tern Sterna s Ibi irons and Kentish Plover Charadrius alexandrinus are important on a national level and breed only in the salina or in some Slovene coastal wetlands at the most. Each year the numbers of the breeding species are increasing, the exception is the European Kestrel Falco tinnunculus, which is declining as a result of musteiid prédation. Despite conservation efforts in the salina and its protected status, human disturbance and threats are increasing. Key words: Sečovlje Salina, wetland, birds, N Adriatic, trends, threats Kfjučne besede: Sečoveljske soline, mokrišče, ptice, Severni Jadran, trendi, ogroženost INTRODUCTION Slovenia has a relatively short coastline of only 46.6 km long. In the past the marshes and estuaries of rivers were transformed into salt-pans, the largest and most productive were the Piran Salt-pans. Since then some coastal areas have undergone urban development, only the small salt-pans in Strunjan and the more extensive 700 years old Secovlje Salina (650 ha) now remain. The Secovlje Salina is situated at the mouth of the Dragonja river, the only in Islrian Slovenia we have managed to preserve in its natural form, which flows into the northern part of the Adriatic Sea. The Salina is among the most important locations of the Slovene natural wealth, particularly as far as the environmental protection is concerned. The Salina and the immediate surroundings are an exceptional ornithological site, where numerous birds stop during the winter and on their migration. This area is generally an important coastal resting stop for a number of migratory birds. The Salina is interesting due to its striking breeders and especially as the habitat of some rare birds of scientific interest. It would be truly difficult to find a place in Slovenia that would be as intriguing and varied in all seasons of the year as is the Sečovlje Salina. Because of its rich cultural and natural heritage, the Sečovlje Salina was declared a "Landscape park" in 1989. it is listed as an important Bird Area site (Grimmet & Jones 1989), and is the only Ramsar site in Slovenia. The number of bird surveys carried out during the last 100 years (Schiavuz2i 1878, 1883, 1888, Gregori 1976, Geister & Šere 1977, Šmuc 1980, Škornik et al. 1990) i. ŠKORNIK , T . MAKOVEC , L LIRE): SEČOVLJ E SAUN A - A N ORNITHOLOGICA L ASSESSMENT O F A SLOVEN E COASTA L WETLAND , 89-94 Fig, 1: Sečovlje Saiina. Slika 1: Sečoveijske soline. have allowed us to make certain comparisons and assess the population changes in this region. The most dramatic changes were recorded after salt production ceased in the 1960s. Cregori's (1976) checklist of 132 species, was complemented by records made by Ceister & Sere (1977) and Smuc (1980). A complete survey was then made by Škornik et a/. (1990) who recorded 207 species. This list was subsequently increased to 222 species (Beltram & Lipej, 1994). The aim of this paper is to analyse the trends of the avifauna of the Sečovlje Saiina during the last 12 years, the emphasis will be on a selected number of breeding species which reflects the general trends for ali breeding species, that have been monitored regularly from 1983 to 1995 by a team of ornithologists from the Ixobrychus Ornithological Association. STUDY AREA The area of Fontanigge is increasingly becoming an important location for waterbirds, notably the species protected nationally and internationally. The high abundance and high species diversity are a direct consequence of the habitat diversity in the area. Various habitat types, including reed-beds, halophyte meadows, bushy vegetation, salt basins and dikes, are found in the area. The bird distribution within the Saiina in winter is related mainly to the available food resources (Britton & Johnson, 1987). The study site of the Sečovlje Saiina enclosed the still active salt-pans (Lera), the abandoned area of salt-pans with saltmarsh, reedbeds (Fontanigge), a small area of intertidal mudflats at the mouth of the river Dragonja and the shrubland area near the Sečovlje Airport (Fig. 1). The abandoned salt-pans are partially covered with halophyte vegetation. METHODS AND MATERIAL Complete counts were made of all breeding pairs of the Yellow-legged Cull Larus cachinnans, Common Tern Sterna hirundo, Little Tern Sterna albifrons, Kentish Plover Charadrius alexandrinus and the European Kes­trel Falco tinnunculus during the period 1983-1995 (for Kentish Plover there are no data for 1991, because of the War in Slovenia). The Black-winged Stilt Himanlo­pus himantopus was added to the list of breeding birds in 1990, (Makovec & Škornik, 1990) and successively monitored. This data together with distribution maps for all species provides a sound basis when analysing population trends. Some breeding data has already been published for certain species (Škornik 1992, Lipej 1993, Makovec 1994) but is incomplete. To assess the orni­thological importance of the Sečovlje Saiina, ail historic and published material have been checked and compared with recent data. RESULTS in this study a total of 248 bird species have been observed, 91 are breeding in the Sečovlje Saiina and surrounding area (Fig. 2). Among the recent additions to the list of breeding species, a pair of the Avocet Recurvirostra avosetta attempted to breed in the abandoned part of the Saiina in 1994 (Škornik 1994). The selected list of important breeding species are described separately, the histograms show the trends for each species, 1. Yellow-legged Gull Larus cachinnans in 1986, a small colony of 11 pairs of the Yellow-legged Gulls was discovered breeding in the Sečovlje Saiina. Since then the species has bred annually and numbers have steadily increased to a maximum of 61 pairs in 1994 (Fig. 3). This increase is not surprising as most breeding populations along the northern Mediter­ranean coastline has shown dramatic increases (škornik 1992) and research has shown that the Yellow-legged Gull is remarkably adaptable (Beaubrun 1994). I. SKORNSK, T. MAKOVEC, L. LIPEJ: SEČOVLJE SAUNA - AN ORNITHOLOGICAL ASSESS EMENT OF A SLOVENE COASTAL WETLAND, 89-94 300 250 200 CO 111 o UJ 0. 150 w a a: CU 10 0 5 0 0 SCWHVUZII GREGORI tSEFSTER ŠMUC !his work ««(.(1590) SOPEJ (1S93) {fS76) S,ŠEHE(19f7J (Î383) ŠKORNIK 8ELTRAIW (ISM) Fig. 2: Number of bird species at Sečovlje Satina ac­cording to different ornitbofaunistlc surveys in cen­tennial period. *Updated records of Gregori (1976). ^Passerines in paper not included. Slika 2: Število vrst v Sečoveljskih solinah na osnovi raz­ličnih orni to fa vnističnih popisov v stoletnem obdobju. ^Dopolnjeni seznam Gregorija (1976). **Pevke v delu niso vključene. 2. Common Tern Stems hirundo Common Terns were discovered breeding in the Sečovlje Saiina in 1983. In the breeding colony, 9 nests were counted. Nesting by the Common Tern on the Slovene coast had not been observed before. The col­ony comprised of 9 nests with eggs. The nests were on a dike (Škornik 1983). Since then 3 colonies have become established, approximately 50 pairs on small mud artificial islands, and approximately 10 pairs on dikes. Sudden increase in numbers in 1991 onwards is due to muddy artificial islands. The same was noticed in other Mediterranean Salinas (Walmsley 1993). The Saiina population has increased and today comprises about 60 pairs (Fig. 4). 3, Little Tern Sterna alhifrons In 1985, a Little Tern start to breed in a mixed col­ony of the Kentish Plover and Common Tem (Škornik 1985). This was the third known breeding by this species in Slovenia. Due to the small number of 1-3 breeding pairs a decree has been passed to protect this small but unique breeding population in Slovenia and every effort should be made to improve the breeding habitat. In 1995 3 nest with eggs were found on dikes. 4. Kentish Plover Charadrius alexandrinus The first known possible breeding record for this species dates back to the last century (Schiavuzzi 135 3 195 4 195 5 195 6 198 7 196 8 198 9 199 0 193 1 199 2 199 3 199 4 199 S Fig. 3: Breeding population of theYellow-legged Gull at Sečovlje Saiina. Slika 3: Gnezdeča populacija rumenonogega galeba na Sečoveljskih solinah. 1883). Its breeding status was confirmed as late as in 1975 by Gregori (1976). The major part of the Kentish Plover's population nests in the abandoned salt-pans, on dikes and in dry basins. Some pairs nest within the colony of the Common Tern. Recently, some pairs began to breed also in dry basins with halophyte vegeta­tion, chiefly Limonietum venetum. Some pairs of the Kentish Plover are today known to breed in other coastal wetlands (Makovec 1994). The biggest colony of Kentish Plover in Slovenia is in the basin near the Salt Museum. After 1991 (after the war in Slovenia) we noticed the first population peak, which could be a consequence of low human disturbance in period of the war. The fluctuations in numbers of breeding pairs over the years, are related also to weather conditions, and to the number of field observations. However, since the future of these wetlands is still uncertain, the Sečovlje Saiina remains the bird's most important breeding site in Slovenia (Fig. 5). 5. Black-winged Stilt Himantopus himantopus By transforming the abandoned Sečovlje salt-pans into larger salt lagoons from 1960's to date, their water surface rose to such a level that the banks became interesting for waders once more. In 1990, 2 pairs of the Black-winged Stilt were discovered breeding in this recently created habitat abandoned salt-pans (Makovec & Škornik, 1990). This long awaited event, was wel­comed by Slovene ornithologists. After a slow start, further increases were recorded in 1992 (3 pairs), and again in 1994 (6 pairs), followed by an impressive increase to 32 pairs in 1995 (Fig. 6). These population inceases are directly related to the habitat changes, water levels and protection in this habitat. Nest sites are on dikes with halophyte vegetation and on small mud I. iKOKNtK, T. MAKOVEC, L. LIPEJ: SEČOVLJE SAUNA - AN ORNITHOLOGICAL ASSESSMENT OF A SLOVENE COASTAL WETLAND, 83-94 CO K i C5 Z a lu Ui cc CO 1983 1904 1905 190S 1967 1980 19BB 1990 1991 1992 1393 1994 1995 Fig. 4: Breeding population of the Common Tern at Sečovlje Salina. Slika 4: Gnezdeča populacija navadne čigre na Sečo­veljskih solinah. islands in the basins. 6. European Kestrel Falco tinnunculus The European Kestrel Falco tinnunculus is the only bird of prey breeding in the Sečovlje Salina where it has occupied a niche in the abandoned buildings since 1976. A hundred years ago, Kestrels bred invariety of habitats, in coastal towns, and along the Dragonja river valley. Outside the salina the only known breeding sites are the rocky cliffs in the so-called Karst edge near Črni Kal (Lipej 1993, Lipej & Gjerkeš, 1994). At the Sečovlje Salina it has nested in the abandoned houses since 1976, when first couples were observed. More recent population estimates show fluctuating numbers of between 5 and 8 breeding pairs during the period 1983­1992, with a peak of 12 pairs in 1985 (Lipej 1993) (fig. 7). The sudden crash to zero pairs from 1993 to 1995 is probably due to musteiid predation. DISCUSSION To date, 248 bird species have been recorded at the Sečovlje Salina and its background, and among them at least 91 species breed there (Fig. 2). Because of the passive salt production in the area of Fontanigge, the management of water levels in basins, and the special nature of saline habitats make them ideal resting and refueling site for many birds species. Ecological studies in these artificial ecosystems have shown that Mediterranean salinas are wetlands of international importance for conservation and host rare and endan­gered flora and fauna. They also have rich invertebrate and vertebrate communities (Walmsley 1993, 1994). Certain breeding species are important on the national level, since they breed only at the Saiina (Black-winged Stilt, Little Tern) or in another Slovene coastal wetland at 1933 1984 1985 1805 19B7 1980 1909 19S0 1991 1992 1993 1994 1995 Fig, 5: Breeding population of the Kentish Plover at Sečovlje Salina. Slika 5: Gnezdeča populacija beločelega deževnika na Sečoveljskih solinah. the most (Kentish Plover, Yellow-legged Gull). The breeding population of the Little Tern with three pairs remains quite stable. The Yellow-legged Gull is increas­ing rapidly and today presents a serious threat to other breeding birds (Škornik 1992). Only in the case of the Kestrel, a decrease in the numbers of its breeding pairs has been noted, which is principally the result of the musteiid predation and the increasing human activities during its breeding season. After the 1993, no Kestrel nests have been found. Threats Despite the protected status of the Sečovlje Salina and human pressures, threats, and disturbance are today present in the area and they are increasing. Due to the growing popularity of the Sečovlje Salina, the too numerous visitors, have become a serious threat for the nesting species, because walk about in the area where Kentish Plovers breed. Some nests have been trampled. The salina is becoming increasingly popular for people from Italy and central part of Slovenia who visit the salina for weekend picnics, bath, walk, fishing etc, others visit the Salt Museum established in one of the abandoned buildings, close to where a colony of the Kentish Plover breed. Disturbance by visitors walking around in this important area will endanger the breeding population if allowed to continue. Other studies in the Mediterranean not only support this, but show that human disturbance can have a direct impact on laying dates and breeding success (Pineau 1992. In spite of the efforts of the Museum to extend their activities in a broader area, the nesting colony will be further jeopard­ized. The Yellow-legged Gull is considered an invading species in the western Mediterranean and a super predator on many waterbirds (Walmsley 1993), such as I. ŠKORNIK, T. MAKOVEC, L. UPEJ: SEČOVLJE SAL SNA - AN ORNITHOLOGICAL ASSESSEMENT O f A SLOVENE COASTAL WETLAND, 8