3,000 islands create Korea's largest seabird breeding ground. Colony size fluctuates with Yellow Sea fish stocks, making bird counts a biological indicator of marine ecosystem health.
justinjfj, CC BY 2.0, via Wikimedia Commons
An archipelago of avian life
Dadohaehaesang National Park, established in 1981, is the largest national park in South Korea, covering 2,321.5 square kilometers. The vast majority of this area is marine territory, encompassing over 1,700 islands and rocky outcrops scattered across the Yellow Sea. This "sea of many islands" provides nesting grounds for at least 147 bird species, making it one of East Asia's most significant avian breeding areas.
Two islands in particular, Gugul-do and Chilbal-do, are designated as Natural Monuments due to their immense biological value. These remote, rocky islands host enormous breeding colonies of several important seabird species. The most numerous resident is the black-tailed gull (Larus crassirostris), a medium-sized gull with a distinctive, cat-like call. Tens of thousands of these gulls arrive each spring, with breeding initiated in early April. The park is also an important breeding site for the near-threatened Swinhoe's storm petrel (Hydrobates monorhis). An estimated 100,000 pairs nest on Gugul-do island, a figure that may represent more than 75% of the entire global population for the species. Other significant breeding species include the streaked shearwater (Calonectris leucomelas) and the ancient murrelet (Synthliboramphus antiquus).
Counting birds to measure the sea
The seabird colonies of Dadohaehaesang are a wildlife spectacle; they are a, living measure of the Yellow Sea's health. The population dynamics of species like the black-tailed gull are closely linked to the availability of their primary food sources—small fish, mollusks, and crustaceans. Overfishing of commercially important species such as the small yellow croaker and hairtail has depleted fish stocks throughout the Yellow Sea. This pressure, combined with pollution from industrial and domestic waste, directly impacts the food web that the seabirds depend on.
Researchers monitor the breeding success and population sizes of the colonies to gauge these changes. A successful breeding season, with high numbers of fledged chicks, generally indicates healthy and abundant fish stocks in the surrounding waters. Conversely, a poor season with high chick mortality can signal a decline in marine resources. For this reason, long-term monitoring of the seabird populations is an important conservation strategy. The data provides an early warning system for the broader marine ecosystem, reflecting the consequences of overfishing and environmental pollution that affect the more than 600 million people living in the Yellow Sea watershed.
💡Fun Facts
Swinhoe's storm petrels are strictly nocturnal at their breeding sites, avoiding even moonlit nights to evade predation by larger gulls.
The Korean name for the black-tailed gull is *gwaeng-yi gull*, which translates to "cat gull" because of its feline-like call.
Dadohaehaesang National Park hosts 1,541 plant species, 885 insect species, and 154 species of ocean fish.
Many of the park's most important bird-breeding islands, like Hongdo and Gugul-do, are designated Natural Monuments and are restricted to public access to protect the nesting colonies.
The park is open year-round, but access to specific islands depends on ferry schedules and weather conditions. Key breeding islands are restricted during nesting season (typically spring and summer) to protect the birds.
Admission
No general park admission fee, but visitors must pay for ferry tickets to access the islands.
Accessibility
The park consists of remote, rocky islands accessible only by boat. Terrain is rugged and not suitable for wheelchairs or those with mobility issues.
