Annually, the territory of Indonesia becomes a stopover site for thousands of "guests" from the northern hemisphere. Migratory birds visit Indonesia during winter in their original places and will return once the conditions are warm enough to reproduce. The migration movement to non-breeding ground (autumn migration) occurs in September-October while migration toward breeding ground (spring migration) usually occurs in March-April. There are eight main flyways of global bird migration according to BirdLife International, namely Pacific Americas, Central Americas, Atlantic Americas, East Atlantic, Black Sea – Mediterranean, East Asia – East Africa, Central Asia, and East Asia – Australasia.
The territory of Indonesia is included in the East-Asia Australasian Flyway, which contains two routes namely East Asia Continental Flyways and East Asia Oceanic Flyways. The land route means birds migrate through the mainland of Asia stretching from China, Laos, Thailand, Malaysia, and into Indonesia. Sea route means birds migrated from the northern hemisphere to Japan, China, Taiwan, Philippines, then Indonesia by crossing the ocean and rely on small islands along the way as their stopover sites. On the East Asia Oceanic Flyways, Sangihe is important in linking the Philippines with Indonesia.
Sangihe has a total land area of 736.98 km and is located in North Sulawesi Province, Indonesia. Even though it is a small island, Sangihe has a high level of endemicity and ecological function. It has been designated as an Endemic Bird Area (EBA), one of the 33 Important Bird and Biodiversity Areas (IBA) in Sulawesi, and a Key Biodiversity Area (KBA). Its located at the northern tip of Indonesia and surrounded by the Sulawesi Sea and the Pacific Ocean, makes Sangihe a bridge island for various types of birds that pass from the Philippines to the mainland of Sulawesi.
At least 87 species of birds live and thrive on Sangihe Island. One of the roosting sites for them is the Mount Sahendaruman Protected Forest. Of these, 32 species are migratory birds and seven bird species are endemic with a high level of global extinction threat. Indonesia has 262 species of migratory birds, which means 12.2% of them can be found on Sangihe Island. In 2007, Francesco Germi and his colleagues conducted a study on the phenomenon of migratory birds of prey during one season. Observations which were conducted during the autumn migration and spring migration recorded 230,214 individuals from six types of migrant raptors passed Sangihe’s sky.
The forest of Mount Sahendaruman, the last stronghold of the Sangihe’s endemic and endangered species (Photo: Burung Indonesia/Ganjar A. Cahyo)
Burung Indonesia (2020) observed the spring migration season from March to April 2020 for 11 effective observation days on two different locations from 07:00-12:00 PM. During the observation 5,981 individuals from six types of migrant raptors were seen passing the sky, namely the Chinese Sparrowhawk (Accipiter soloensis), Japanese Sparrowhawk (Accipiter gularis), Common Kestrel (Falco tinnunculus), Grey-faced Buzzard (Butastur indicus), Osprey (Pandion haliaetus), dan Oriental Honey-buzzard (Pernis ptilorynchus). Similar to the findings of Germi et al, the type of raptor that most dominates in number is the chinese albatross, followed by the gray eagle. The unequal number of observation days, different locations, observation periods and starting time of observations (presumably in the middle of migration) might be the cause of the significant difference in results. The fog that enveloped most of the Sangihe area during observations until 08.30 PM inhibited the process, thus many individuals were not observed properly.
Observing the phenomenon of migratory raptors is important. Since raptors occupy the top position in the food chain, their presence can suppress pest populations that are detrimental to humans as well as controlling ecosystem sustainability. The number of thousands or even hundreds of thousands in one migration period provides natural fertilizer for the restoration of vegetation in the habitat. In addition, by observing the phenomenon of migration, it can provide information about locations that have the potential as a stopover or migration destination, then provide information and advice for stakeholders and policy makers to determine steps and priorities for conservation, both types and natural habitats.
Unfortunately, both resident and migratory birds are now increasingly threatened by habitat change and land use change. Massive and unsustainable land clearing and management leaves only 1,821 hectares of primary forest on Sangihe Island or 2.5% of the total land area of Sangihe Island remaining. The results of the participatory mapping conducted by Burung Indonesia and its partners in 2018 stated that the remaining natural forests only exist on the peaks and cliffs that stretch across the Gunung Sahendaruman II Protected Forest.
This is an important concern and conservation efforts must be increasingly encouraged. If we ignore it, not only endemic birds will be under extinction threat, but also 32 species of the 292 migratory birds in Indonesia will be lost from Sangihe. Therefore, Burung Indonesia is currently making efforts to conserve birds and their habitats by increasing the capacity of communities, increasing alternative livelihoods, and encouraging multi-stakeholder agreements which are expected to become a reference for local governments, village governments and communities in managing and developing sustainably. (GAN)