Olive-tree Warbler
Hippolais olivetorum Strickland, 1837
Hypolais olivetorum (Strickl.): Reiser, 1894: 51.
Order Passeriformes
Family Sylviidae
Conservation status: in Bulgaria: Vulnerable VU [A3c, B2b(iii),c(ii),(iv)], BDA-II, III; International: ETS (R); BD-I, BeC-II, BoC-II.
General distribution. An Eastern Mediterranean species breeding in the western and southern seaside regions of Turkey, Greece (including many islands), Bulgaria, Macedonia, Albania, Croatia and Montenegro [1, 2]. It mainly winters in Eastern and Southern Africa.
Distribution and abundance in Bulgaria. The first reports about the species were for the region of the town of Sliven (1875) and much later for the village of Gyulovtsa, Burgas region [3]. In the last 40 years the species was found breeding in all the regions with significant Mediterranean biotic impact: the valley of the river Struma (from the Kresna gorge to the south) and the Sandanski-Petrich field; the valley of the river Mesta (from the town of Momina Klisura to the south); and the Rhodopi range (the valleys of the rivers Arda, to the east of the town of Kardzhali, Krumovitsa and Byala Reka); the Sakar mountain, the Tundzha hills, the Derventski hills, Strandzha and the Black Sea coast [4, 5, 6, 7, 8]. The territory of distribution is about 6000 km2. The population is fragmented and many habitats have several pairs each. Abundance 950 – 1 100 breeding pairs on 1 200 – 1 400 km2 habitats possible for the species at an average density of 0,8 pairs/1 km2. The average maximum density for the country is 1,6 pairs/1 km2 (1). There are estimates close to the maximum but with much lower minimal (100 – 500 pairs) abundance [2, 9, 10]. Other estimates give much higher values – up to 3 500 pairs [9, 11].
Biology. Passage migrant. The nest is usually built in shrubs and junipers. The incubation of the eggs (3-4) in Southwestern Bulgaria starts at the beginning of May [4, 5, 6]. Sometimes the pair has 2 clutches (P. Simeonov, unpublished information).
Habitats. Dry stony slopes, valleys and gorges with bush vegetation and light low forests of the Mediterranean type in the hilly and the pre-mountain belt and along the sea shore.
Negative factors. Destruction and change of habitats (construction on the sea shore and disturbance by tourism, clearing terrains for agriculture, fires, felling); the restricted area and the low abundance of the world population (a minimum of 11 000 pairs) presuppose significant fluctuations in the numbers of the species.
Conservation measures taken. The species is protected and many of its habitats fall within Protected Territories and sites of the Natura 2000 network.
Conservation measures needed. Carrying out investigations on the biology and the ecology of the species and monitoring of its state. Declaration of Protected Zones and Territories.
References. 1. Hagemeijer, Blair (Eds), 1997; 2. BirdLife International, 2004; 3. Patev, 1950; 4. Simeonov, 1971; 5. Vatev, Simeonov, 1978; 6. Spiridonov, Simeonov, 1988; 7. Nankinov, 1993; 8. Iankov, in press; 9. Kostadinova, 1997; 10. Snow, Perrins, 1998; 11. Nankinov et al, 2004.
Authors: IIliya Vatev, Geko Spiridonov, Pavel Simeonov
