Pleske's grasshopper-warbler (Locustella pleskei)
|Also known as:||Styan's grasshopper warbler|
|Size||Length: 13 - 14 cm (2)|
Pleske’s grasshopper-warbler is classified as Vulnerable (VU) on the IUCN Red List (1).
Pleske’s grasshopper-warbler (Locustella pleskei) is a small, drab, bird with olive-coloured upperparts and faint dark spots on the feathers between the neck and back. A white ring surrounds the eye, and there is a faint grey stripe on the head which runs from the beak, above the eye and towards the back of the head. Pleske’s grasshopper-warbler has white underparts and a pale coloured breast (2).
A member of the Sylvidae family, or Old World Warblers (2), Pleske’s grasshopper-warbler shares its genus (Locustella) with eight other species (3). Once considered to be the same species as Pallas's grasshopper-warbler and Middendorff's grasshopper-warbler (2), it has more recently been recognised as an independent species in scientific literature (3).
Pleske’s grasshopper-warbler occurs on several small islands in the Siberian sub-region of the Palaearctic, ranging from eastern Russia to southern China (2) (3). It breeds on the small islands in Peter the Great Bayto the south of far-eastern Russia, as well as the Izu islands and other islands off the larger Japanese islands of Honshu and Kyushu (2) (4).
In South Korea, several sightings of Pleske’s grasshopper-warbler have been recorded on many of the small, offshore islands, whereas in North Korea, only one record of its existence has ever been recorded in the region of North Pyongan (4). More sightings have been recorded on islands off the eastern and south-eastern coast of China (2) (4), while a few winter sightings have also been witnessed in north-eastern Vietnam (2).
Pleske’s grasshopper-warbler prefers wetland habitats with thick grasses, reeds or low bushes where it can it remain hidden and breed safely (5). In winter, it has been found to inhabit low shrubs near to mangroves and reed beds (2).
In Japan, it is particularly abundant in dense bamboo grass, small camellia trees, pine forests and laurel forests (6).
Pleske’s grasshopper-warbler exhibits a characteristic skulking behaviour. It generally keeps close to the ground among thick vegetation, often making it difficult to detect (4). The breeding season typically runs from May to July, and the male usually arrives at the breeding site roughly two weeks before the female. During courtship and breeding the male often becomes much more conspicuous, perching on reed tops and singing loudly to attract a mate (4).
Unlike the female Pleske’s grasshopper-warbler, the male always re-uses the same breeding site (3), and in the majority of cases, only ever breeds with one female throughout its life (3). However in some cases the male may breed with more than one female at a time (7).
Generally, female Pleske’s grasshopper-warblers breed at different times during the breeding season, depending on their age. Younger females increase their survival rate by mating later in the breeding season, whereas older females tend to mate earlier to increase their reproductive rate. Females prefer males whose feathers have wider growth bands, as this represents a better nourished and healthier male than one with narrower growth bands (8).
Pleske’s grasshopper-warbler builds its nest low to the ground, usually below two metres, in willow thickets and shrubbery. Within the nest, Pleske’s grasshopper-warbler lays an average of four eggs, but the clutch size can range from three to six eggs. The female incubates the egg for around 14 days. The chicks leave the nest around 13 to 15 days after hatching (4).
Pleske’s grasshopper-warbler is primarily an insectivorous species (4).
The primary threat to Pleske’s grasshopper-warbler appears to be habitat loss, as a result of residential and commercial development, agriculture and pollution (2).
Large-scale development projects on the Tumen River in Russia could result in an increase in human activity and an associated increase in pollution. On the Izu islands in Japan, the Tokyo government has submitted a proposal for a tourism development project that will involve the destruction of a large proportion of this species’ habitat. Such development will no doubt have a severe negative impact upon Pleske’s grasshopper-warbler colonies on these islands. In China, there are continuous developments along the mainland coast which reduces and degrades the wetland habitat of Pleske’s grasshopper-warbler (4).
The causes of the decline of Pleske’s grasshopper-warbler are not all due to human activities. A volcanic eruption on the Japaneseisland of Miyake-jima in 2000 caused the entire area to be covered in ash, resulting in a severe decrease in the number of leaf-dwelling insects, and causing a major food shortage for the bird species that depended on the insects as a food source. The eruption also caused a collapse of land into a 400 metre deep crater, destroying 50 percent of the Pleske’sgrasshopper-warbler’s habitat, as well as emitting gases that are toxic to the warbler, further exacerbating its decline (4).
One successful way of monitoring the Pleske’s grasshopper-warbler population is through ringing. This involves attaching a small metal or plastic tag around the bird’s leg or wing. Each tag is unique and enables information such as migration patterns and mortality to be collected from individual birds, as well as enabling population trends to be recorded. Such ringing programmes are being carried out in the Mai Po Marshes Nature Reserve inChina by WWF-Hong Kong. This has contributed a lot of information on the winter habitat requirements and abundance of the Pleske’s grasshopper-warbler (2).
The control of further commercial development in the Pleske’s grasshopper-warbler’s habitat and the strengthening of buffer zones are also important in reversing the decline in Pleske’s grasshopper-warbler numbers. Buffer zones act like nature reserves in that they separate this bird’s habitat with that of the developed human-populated land. Buffer zones for this purpose have been put in place around the Mai Po Marshes region in China and on the Izu islands in Japan. Buffer zones in Russia, particularly in the Far-Eastern Marine Reserve need to be extended in order to include the islands where this species breeds (4).
One of most effective ways to help vulnerable species is by gathering further knowledge about their habitat requirements and abundance. Several research projects have been suggested to gather more information on Pleske’s grasshopper-warbler (4). Surveys on the islands within the Pleske’s grasshopper-warbler’s breeding range will aim to locate additional populations of this bird, as well as gathering further information on its distribution and habitat requirements (2). Ecological studies at specific breeding sites will increase the knowledge of its population size and habitat requirements during the breeding season (2). Returning to where Pleske’s grasshopper-warbler has been recorded in the past to carry out population studies will determine any changes in its abundance and distribution compared to the original records (2).
Find out more about Pleske’s grasshopper-warbler and other bird species:
BirdLife International - Pleske’s grasshopper-warbler:
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- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Incubate: to keep eggs warm so that development is possible.
- Insectivore: an organism that feeds mainly on insects.
- Palaearctic region: the region that includes Europe, North Africa, most of Arabia, and the part of Asia to the north of the Himalayan-Tibetan barrier.
IUCN Red List (August, 2011)
Birdlife International (August, 2011)
- Nagata, H. (1993) The structure of a local population and dispersal pattern in Styan’s grasshopper-warbler, Locustella pleskei.Ecological Research, 8(1): 1-9.
BirdLife International (2001) Threatened Birds of Asia: The BirdLife International Red Data Book. BirdLife International, Cambridge, UK. Available at:
- Austin, J.R. and Kuroda, N. (1953) The birds of Japan, their status and distribution. Bulletin of Harvard Museum of Comparative Zoology, 109: 1-637.
- Yamaguchi, Y., Kikuchi, H. and Kameyama, T. (2003) Japanese Journal of Ornithology, 52(2): 19-121.
- Nagata, H. (1988) An example of facultative polygyny in Middendorff’s grasshopper warbler Locustella ochotensis.Ecological Research, 3(1): 57-60.
- Takaki,Y., Eguchi, K. and Nagata, H. (2001) The growth bars on tail feathers in the male Styan’s grasshopper warbler may indicate quality. Journal of Avian Biology, 32: 319-325.