Introduction

Due to its isolated geographical position – its relative proximity to China compared with the Korean mainland and its central location on a suspected migrant flyway (from the Chinese coast, through south-wear Korea, and then north-east up to Siberia or east towards Japan) – it was assumed that Gageo Island (and other islands in the HuksanDo chain) would be a key area for the study of migrant birds. This assumption was based on the knowledge of bird migration at other sites in the Yellow Sea (eg at Beidaihe and Happy Island in the Gulf of Bohai), and elsewhere outside of the region (eg in south-western Japan, Europe, and North America), and was further strengthened by anecdotal evidence provided by visiting bird researchers to Chilbal Island and to Gageo Island itself some 10 years previously. One anecdote from this time described islanders complaining about thousands of Barn SwallowsHirundo rustica dying and having to be swept from doorways during cold spells in March (Lee Ki-Seop per Park J.Y.)

Method

Surveying of migrant birds was therefore conducted on Gageo Island and other islands of the HukSan Island group (ie Teahuksan and Hatae Islands) in several periods in 2000 between April 27 and May 27 and again from Gageo Island from October 13 – November 10. The visits were timed to co-incide with the major suspected periods of northward (March – May) and southward (August – December) migration. Counting on Gageo was primarily by NM, with other observations made jointly with Park Jin Young (of the National Institute of Environmental Research) on Hatae and Daehuksan Islands.

Birds were actively searched for and counted individually where possible, and especially in the autumn period during a regular “survey circuit” was established on Gageo Island enabling a better understanding of bird turnover rates. Photographs were taken of several species, especially those considered to be either vagrants or unrecorded in South Korea.

Results

In total, dependent on classification, about 237 species were recorded in the island chain, with 206 of these on Gageo Island. This is probably a higher number of species than at any other known comparable area in South Korea. At least 7 new species new to Korea (both South and North) were recorded, 6 of which were adequately photographed assisting in formal documentation. A further 2 species known to have been recorded in Korea, but not listed by Lee, Koo, and Park (2000) were also recorded, along with 14species considered by the same authors to be vagrants. All such species are listed below. In addition, at least 105 species were recorded on a single date (April 30, 2000), which is the highest known daily total anywhere in South Korea, indicating the very high diversity of migrant species.

• Northern Wheatear Oenanthe oenanthe : 1 – previously unrecorded.

• Eurasian Tree Pipit Anthus trivialis : 2 – previously unrecorded.

• Manchurian Reed Warbler Acrocephalus tangorum : 1 – previously unrecorded.

• Hume's Leaf Warbler Phylloscopus humei : 2 – previously unrecorded.

• Yellowhammer Emberiza citrinella : 1 – previously unrecorded.

• Ortolan Emberiza hortulana : 3 – previously unrecorded.

• Black-headed Bunting Emberiza melanocephala : 1 – previously unrecorded

• Pomarine Skua Stercorarius pomarinus : 1 – previously unrecorded.

• Silky Starling Sturnus sericeus : c)7 – 1st recorded on Gangwha Is., April 2000.

• Black Bittern Ixobrychus flavicollis : 1 – Vagrant (apparently 3rd record for Korea).

• Japanese Night Heron Gorsachius goisagi : 1 - Vagrant.

• Little Swift Apus affinis : 8 – Vagrant.

• Greater Short-toed Lark Calandrella brachydactyla : 3 – Vagrant.

• Citrine Wagtail Motcilla citreola : 2 – Vagrant (2nd and 3rd record for Korea).

• Rosy Pipit Anthus roseus : 1 – Vagrant (1st record since @1950).

• Black Redstart Phoenicurus ochuros : 1 – Vagrant (2nd record).

• Grey Thrush Turdus cardis : 3+ - Vagrant.

• Chinese Blackbird Turdus (merula) mandarinus : 1 – Vagrant (perhaps 4th record for Korea).

• Brown Thrush Turdus chrysolaus : @5 – Vagrant (prev. recorded Gageo, Lee Ki-Seop in lit).

• Common Starling Sturnus vulgaris : 3+ - Vagrant (@3rd and 4th records for Korea).

• Black Drongo Dicrurus macrocercus : 1 – Vagrant (2nd record for Korea).

• Ashy Drongo Dicrurus leucophaeus : 1 – Vagrant (2nd record for Korea).

Beyond these species, significant numbers of of many other migrants with widely different migration strategies were recorded. Some of the peak counts are believed to be higher than recorded elsewhere in South Korea in recent years, indicating:

1. That Gageo Island is located on these species' main migration routes.

2. That Gageo Island offers exceptional potential for monitoring these species' population trends.

A selection of such potential key species are listed below, with their status in Korea and the peak count recorded:

• Streaked Shearwater Calonectris leucomelas : common summer visitor – 2200

• Chinese Pond Heron Ardeola bacchus : rare summer visitor – 9-12

• Chinese Sparrowhawk Accipiter soloensis : common summer visitor – 80

• Common Buzzard Buteo buteo : common winter visitor – 24

• Red-rumped Swallow Hirundo daurica : common summer visitor – 700

• Barn Swallow Hirundo rustica : abundant summer visitor – 500

• Asian House Martin Delichon dasypus : rare summer visitor (North Korea) – 40-100

• Olive-backed Pipit Anthus hodgsoni : common passage migrant – 1000

• Siberian Stonechat Saxicola (torquata) maura : common summer visitor – 108

• Yellow-browed Warbler Phylloscopus inornatus : common passage migrant – 100

• Tricolour Flycatcher Ficedula zanthopygia : uncommon summer visitor – 20

• Blue-and-white Flycatcher Cyanoptila cyanomelana : common summer visitor – 60

• Japanese White-eye Zosterops japonica : common resident – 300-400

• Tristram's Bunting Emberiza tristrami : common passage migrant – 150

• Yellow-browed Bunting Emberiza chrysophrys ; scarce passage migrant – 40+

• Chestnut Bunting Emberiza rutila : common passage migrant – 380

• Yellow Bunting Emberiza sulphurata : scarce passage migrant - @16

• Black-faced Bunting Emberiza spodocephala : common passage migrant

Discussion

Due to extreme differences in mid-summer and mid-winter temperatures, the majority of bird species found within East asia (inc South korea) are largely migratory. Breeding or wintering populations of non-wetland dependent species are dispersed over very wide areas, many of which are inaccessible due to either geography or present political status. This prevents accurate understanding of many such species' populations within the region.

During migration many of these species, however, are channeled by topography, concentrating at narrow sea-crossings, often “hopping” from one island to another. During such sea crossings, inclement weather (rain, wind, fog, overcast conditions) will further cause many of these migrants to seek shelter on islands or coastal headlands. At these times spectacular concentrations of birds can occur.

This concentration of migrants is valuable for several reasons:

1. it allows, over a period of years, for a significant sample of observations to be made, to reveal whether there are significant trends in a given species' population. Presently, low breeding densities of most of the migrants prevents researchers from detecting whether species are declining or increasing within the region. Without such information, rapidly declining species cannot be identified in time to allow for critical research focussed on identifying causes, and suggest conservation possibilities.

2. concentrated migrants provide excellent opportunities for training in migrant identification, important for building identification skills of researchers and birdwatchers alike.

3. areas where migrants are concentrated are also attractive to birdwatchers and bird-watching based eco-tourism. The few accessible places within East Asia where migrants are known to be concentrated have become well-known internationally. Although the likely number of tourists will be small, they can still provide some economic benefits to the local economy, and create a positive image of the place which encourages other tourists and investment.

The HukSan Island chain, most especially Gageo island, offers an excellent opportunity to develop a much greater understanding of bird migration in South Korea. Data which can be generated by regular surveying could then be compared to data now being gathered at several sites in China, to reveal migration strategies, population trends and conservation priorities throughout the region.

Gageo Island itself offers an excellent centre for research and limited bird-watching based eco-tourism. The island has been featured in an MBC documentary, and introduced internationally in Dutch Birding magazine (Lethaby, Moores &Park 2000). Furthermore data from the 2000 observations will also be presented in a paper in Forktail or the Oriental Bird Club Bulletin late in 2001. All ensure that the number of birdwatchers visiting the island (and the island chain) will increase significantly over the next few years.

Recommendations

1. Further research into bird migration needs to be made, both within periods already covered in 2000, but especially in periods not yet covered, i.e. in March, early-late April, and from August to mid-October, to determine peak periods for migration.

2. Comprehensive surveys of nesting birds are required as both Gageo and DaeHukSan at least support nesting Black Woodpigeon Columba janthina and other globally valuable species.

3. Surveys of wintering birds (in late December-January), are required, as it is likely such work will greatly improve our understanding of several species' status in South Korea

4. Comprehensive surveys of vegetation (beyond those made approximately 10 years ago) and other biota would in probability prove extremely valuable in understanding the region's wider ecological value/uniqueness.

5. An analysis needs to be made to identify the potential for developing/promoting bird-watching based eco-tourism and environmental education in the area.

References:

• Lee, W-S., Koo, T-H., & J-Y Park, 2000. A Field Guide to the Birds of Korea. Published by LG Evergreen Foundation.
• Lethaby, N., Moores, N & J-Y Park, 2000. "Birding in South Korea." Dutch Birding 22: 204-219, 2000.