Most threatened birds have small ranges

Taita Thrush, © Toon Spanhove

Most threatened species have small ranges, rendering them more susceptible to threats. Thirty six percent qualify as threatened because their ranges are less than 20,000 km2, severely fragmented, restricted to very few locations, declining, or undergoing extreme fluctuations. Three percent (42 species) of threatened species occupy less than 10 km2 globally.


Range sizes of globally threatened birds for which there is a known population
Analysis of data held in BirdLife’s World Bird Database (2016).

The majority of threatened birds have small or very small ranges. Forty-two threatened species (2.9%) have an occupied range of less than 10 km2, the majority on small islands. For example, Floreana Mockingbird Mimus trifasciatus is restricted to two tiny islets totaling just 0.9 km2 in the Galapagos Islands, Ecuador. Caerulean Paradise-flycatcher Eutrichomyias rowleyi has a total range size of 6 km2 on the island of Sangihe, Indonesia. Altogether 532 threatened birds (36.4%) qualify as threatened because they have ranges that are less than 20,000 km2, declining, fragmented, restricted to a few locations, or undergoing extreme fluctuations. In total, 625 threatened species (42.8%) are known from ten or fewer locations, with 438 (30.0%) found at five or fewer, and 167 (11.4%) restricted to a single site. For example, Honduran Emerald Amazilia luciae is currently known from just three arid interior valleys of Honduras, while the Taita Thrush Turdus helleri, pictured above, is confined to four tiny forest fragments in the Taita Hills, Kenya. The few threatened birds that have very large ranges (237 species or 16.2% have range sizes over one million km2) are considered threatened either because they have undergone steep population declines, or because they occur at very low densities and have small declining populations. For example, the Lappet-faced Vulture Torgos tracheliotus has a range of 8.1million km2 across much of Africa and the Middle East, but it is estimated that only 5,700 individuals remain and this number is declining.


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References

BirdLife International (2016) IUCN Red List for birds.

Compiled: 2004    Last updated: 2017   

Recommended Citation:
BirdLife International (2017) Most threatened birds have small ranges. Downloaded from http://www.birdlife.org on 24/06/2018