Over-ocean raptor migration in a monsoon regime: Spring and autumn 2007 on Sangihe, North Sulawesi, Indonesia

Francesco Germi, George Spencer Young, Agus Salim, Wesley Pangimangen, Mark Schellekens

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16 Scopus citations

Abstract

During spring and autumn 2007 we carried out full-season raptor migration counts on Sangihe Island, Indonesia. In autumn, 23 0,214 migratory raptors were recorded. Chinese Sparrowhawk Accipiter soloensis comprised approximately 98 % of the flight. The count results indicate that the largest movements of this species towards the wintering grounds of eastern Indonesia occur along the East Asian Oceanic Flyway, and not the Continental Flyway as previously thought. Both spring and autumn migrations occurred in the face of monsoon headwinds. The relationship between migrant counts and day-to-day variation in wind direction in Sangihe differed between the two seasons. More migrants were counted during crosswind conditions in spring when their route takes them along closely spaced islands than during similar conditions in autumn, when they run the risk of being blown off course during longer over-water legs. Displacement over the sea by crosswinds coupled with records from other islands point to the existence of an additional and heretofore unknown eastern route, involving longer water crossings, between Mindanao and the northern Moluccas via the Talaud Islands. We gathered evidence that Chinese Sparrowhawk behave nomadically during the non-breeding season, following local food abundances of seasonal insect outbreaks induced by rains. Predictable landfall time on Sangihe suggests that traditional roosts of thousands of migrants occur on small islands along this oceanic route. Unmonitored land use conversion on these remote islands could result in the loss of vital roosting habitats.

Original languageEnglish (US)
Pages (from-to)104-116
Number of pages13
JournalForktail
Issue number25
StatePublished - Aug 1 2009

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All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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