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.