Vagrant species of birds captured at Durankulak ringing camp,..

The area of Coastal Dobrudzha in NE Bulgaria is well known for its richness of vagrants. A long-term research project was started at a location at Durankulak Lake, on the northern Black Sea Coast, aiming to obtain data on the characteristics of autumn migration of passerine birds and on the presence of vagrants there. A total of 20 mist nets with an overall length of 200 meters were set betweenAugust and October in two different habitats – reed bed and broad-leaved forest. In 2019, a total of 9344 birds of 84 species were caught and ringed. In 2020, the number of the birds caught increased to 13786 of 93 species. Vagrants such as dusky warbler (Phylloscopus fuscatus), yellow-browed warbler (Phylloscopus inornatus) and red-flanked bluetail (Tarsiger cyanurus) were captured in 2020. Detailed information about these findings is given in the present work.


Introduction
Autumn passerine migration is not systematically studied along the northern part of the Bulgarian Black Sea Coast. The area of maritime Dobrudzha is well known for its richness of vagrants and rare birds of different orders having eastern or northern origin like Phala-ropus fulicarius, Charadrius mongolus, Lanius isabellinus, Serinus pussilus, Phylloscopus proregulus and many others (Dontschev, 1967;Mitev & Welsch, 2011;Simeonov, 2013;Ignatov et al., 2015;Simeonov, 2015). Along the North Bulgarian Black Sea Coast, records of vagrants are mostly a result of intensive field monitoring. Until 2019, ringing activities had occa- Fig. 1. Dusky warbler (Phylloscopus fuscatus), 5.10.2020, Durankulak Lake (Photo: Pavel Simeonov) sional and sporadic character. There is no functioning ringing station in the coastal part of NE Bulgaria. Until now, occasional short term ringing activities, mostly during summer and autumn, had been carried out at Durankulak Lake and Shabla Tuzla Lake (Dimitrov et al., 2018;own unpublished data).
Thus we decided to start a long-term research at a study point at Durankulak Lake, NE Bulgaria, on the Black Sea Coast. The aim was to study the characteristics of autumn migration of passerine birds, and to obtain data about the presence of vagrants on Bulgarian territory. We expected that some of those species recorded in Romania might also be captured in our ringing camp, which would be a valuable contribution to the knowledge of the avifauna of Bulgaria. In August -October of 2019 and 2020, we organised large-scale autumn ringing campaigns at Durankulak Lake ringing camp.
The ringing activities at Durankulak Lake are also valuable for the education of students and volunteers. Across both years, 45 and 80 experts and volunteers, respectively, took part in the ringing camp.

Materials and methods
The ringing camp was situated at the south-eastern part of the Durankulak Lake, Dobrich Province, NE Bulgaria, at coordinates 43°39'38.49N and 28°33'56.81E. A total of 20 mist nets with an overall length of 200 meters were set in two separate lines, covering two different habitats. Nine to ten nets (100 m) were set in a reed bed along a dyke dividing a shallow south-eastern bay of the lake from the main lake. Ten nets (100 m) were set in low mixed broad-leaved forest with bushes, close to the sea shore. The forest was dominated by Ulmus sp., Fraxinus sp., Robinia pseudoacacia and other low trees. The distance between the two lines of nets was approximately 700 m.
The period of the study in 2019 was between 24 August and 15 October. In 2020 the study expanded in time covering the period 15 August -1 November. The position and number of the nets remained the same for both years.
Recordings of bird calls and songs were used to attract birds to the nets at both habitats. For each month collections of sounds of different species were used in the forest and in the reeds. The species were chosen taking into account the prevailing migrant composition for the particular month and habitat according to the available literature sources for other locations from the Balkan Peninsula (Nankinov, 2009;Ivanov, 2011;Marton, 2020) and our own data.

Results and discussion
In 2019, a total of 9344 birds of 84 species (including recaptures) were caught and ringed at Durankulak ringing camp. In 2020, the numbers of birds caught increased to 13786 of 93 species. The following vagrant birds were captured:

Dusky warbler (Phylloscopus fuscatus)
One 1st year dusky warbler was caught on the morning of 05.10.2020 in the forest line of nets (Figs 1-3).
Description: Small warbler, generally brown in colour. Obvious dark eye stripe and whitish supercilium. Supercilium quite short, not extending to the nape. Legs dark brown and long. Toes yellowish from below. Breast and belly are greyish-white. Weak, unclear dark throat band. Fine bill, dark with yellowish base of lower mandible. Tail quite long, with great distance between central and outer tail feathers.
Wing formula: First primary very long, much longer than primary coverts. Tip of the wing formed by the fourth primary. Outer emarginations presented on 3, 4, 5, 6 primaries. The line from the tip of the 2nd primary equals the tip of the 8th primary.
Discussion: This species is new for the Bulgarian ornithofauna (Ivanov et al., 2009;Ivanov et al., 2015). Its breeding range is situated in Central and Eastern Siberia, NE Kazakhstan, Northern and Eastern China and North Korea (Cramp et al., 1992). It is a migratory species wintering normally in Southern China, Thailand, Burma, India, Nepal (Cramp et al., 1992). Rare vagrant to Europe -it is observed or captured in Great Britain, Ireland, France, Spain, Poland, Austria, Italy, Estonia, Cyprus, Greece, Albania, etc. (Cramp et al.1992;Handrinos & Akriotis, 1997; Albanian Ornithological Society, Facebook). In Romania, two specimens have been caught and ringed on 2.10.2016 and 14.10.2016 at Chituc ringing station (Marton, 2020) and one more on 29.09.2008 at Sfintu George, Danube Delta (Martin & Pochelon, 2008). Most of the records of the species in Central and Eastern Europe are between September and February (Bozo et al., 2016), and on the British Isles -between mid-October and mid-November (Harrop, 2007).

Yellow-browed warbler (Phylloscopus inornatus)
One adult yellow-browed warbler was caught on the morning of 06.10.2020 in the reed line of nets .
Description: Very small warbler, with short tail and fine bill. Strong yellow supercillium. Long, clear black eye-stripe. It has two clear white wing-bars. Crown and back olive-greenish. Underparts whitish. Legs dark brown.
Wing formula: First primary longer than primary coverts. Tip of the wing formed by the third primary. Outer emarginations presented on 3, 4, 5 primaries. The line from the tip of the 2nd primary equals the tip of the 6th primary.
Discussion: The species is a rare vagrant recorded at least five times in Bulgaria until now. According to Ivanov et al. (2021), it has been observed three times in Bulgaria until 2019. One bird was ringed on 28.09.2005 at Atanasovsko Lake, close to Burgas (Nankinov et al. 2005). Another bird was observed few days later -on 2.10.2005 at Cape Kaliakra, Dobrich District. A third bird was seen and photographed again in October -on 14.10.2013 (locality not mentioned). Another two observations were not included as confirmed by Ivanov et al. (2021). The first observation of the species in Bulgaria was made on 27.09.1987 in Plovdiv (Kyuchukov, 1997). One day earlier to our finding, on 5.10.2020, one yellow-browed warbler was observed and photographed at Gorun Village, Dobrich District (Yanko Yankov, pers.comm.). That locality is situated 18.9 km SW from Durankulak Lake ringing camp.
The species normally breeds from the NE parts of European Russia (including Ural Mts) to the Pacific Ocean Coast and in Mongolia, NE China and Japan. It overwinters in E India, SE China and the Malay Peninsula (Cramp et al., 1992, Keller et al., 2020. It is the most regular Siberian vagrant in Europe (Williamson, 1983). In some European countries (UK, Sweden, Netherlands, France), it is already considered as a "regular migrant" during autumn (Van den Berg & Bosman, 1999;Reeber et al., 2008). In NW Europe, the records of the species are numerous and show a peak in September and October but become much scarcer in SW Europe (De Juana, 2008). The later study suggests the explanation that the majority of these birds reach only as far as NW Europe, do not continue to the Iberian Peninsula and Africa and migrate back directly to Asia. Similarly, records of the yellow-browed warbler are also scarce from the Balkan Peninsula. At Chituc ringing camp, Romania, a total of ten yellowbrowed warblers were captured during autumn migration over 6 years, 2014-2019 (Marton, 2020). In NE Europe, a slight shift of breeding range of the species towards the west was recorded (Keller et al., 2020). This can explain the high number of records of the species in W and C Europe during the recent decades.
Description: Typical plumage of a female having blue tail and rump, orange flanks, white belly and breast, greenish-brown back, mantle and head. Bill and legs black, iris -dark brown.
Discussion: Before the observation presented here the species had been recorded in Bulgaria on only in two occasions (Ivanov et al., 2021) and had never been captured or ringed. The first observation was made by Petar Iankov at Cape Emine (Burgas District) on In Romanian Dobrudzha, the species has been caught and ringed at Chituc Station -three specimens, one every autumn in the period 2017-2019 (Marton, 2020). Also one individual was captured at the Agigea Station, on 22.10.2020, only two days before the finding of the species at Durankulak Lake (Agigea Ringing Station, Facebook). During the same month the species was re-corded for the first time in Serbia as well -at Bajina Basta, Tara Mt (Medenica I., Facebook). We can conclude that, although very scarce, the red-flanked bluetail passes regularly through the Balkan Peninsula, mostly in October, and especially along the Black Sea Coast.