Is island life easier?

Lemon-bellied White-eye (Zosterops chloris)

For over 10 years we have been making regular visits to islands in the Sulawesi region of Indonesia. We trap birds on these islands, collecting morphometric data. Each bird we trap is measured, marked with a plastic ring and released. As our dataset grows we gain more insight into the lives of the birds on these islands.

In 2007 and 2010 we visited the island of Kaledupa in the Wakatobi archipelago. In 2010 we made a point of revisiting all of the sites we had trapped at in 2007. This gave us an opportunity to look for the birds we had originally caught in 2007.

The Wakatobi islands

In 2010 we caught four of the birds we had marked in 2007. These birds were all lemon-bellied white-eyes (Zosterops chloris). Using an equation for survival (the Lincoln–Petersen method), we calculated the average lifespan of the lemon-bellied white-eyes on Kaledupa. Our birds had a similar lifespan to white-eyes from an Australian island, but lived much longer than white-eyes from the African mainland.

While the number of studies is still small, there is a suggestion that island populations of white-eyes have longer lifespans. Smaller islands generally have lower biodiversity. This can lead to reduced competition and predation, so “prey” species are likely to experience reduced environmental stress. Recent work on the fossils of island cattle species supports this idea (Jordana et al. 2012).

References

1. Kelly, DJ and Marples NM (2012) Annual survival rate and mean life-span of Lemon-bellied White-eyes Zosterops chloris flavissimus on Kaledupa island, Wakatobi, south-east Sulawesi, Indonesia. Forktail 28, 148-149.

2. Jordana, X Marin-Moratalla, N DeMiguel, D Kaiser, TM, Kohler, M (2012). Evidence of correlated evolution of hypsodonty and exceptional longevity in endemic insular mammals. Proceedings of the Royal Society B: Biological Sciences; DOI: 10.1098/rspb.2012.0689

Authors

David Kelly djkelly[at]tcd.ie

Nicola Marples nmarples[at]tcd.ie

Photo Credit

David Kelly

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