Global Patterns of Geographic Range Sizes in Birds
Author Information
Author(s): Orme C. David L, Davies Richard G, Olson Valerie A, Thomas Gavin H, Ding Tzung-Su, Rasmussen Pamela C, Ridgely Robert S, Stattersfield Ali J, Bennett Peter M, Owens Ian P. F, Blackburn Tim M, Gaston Kevin J
Primary Institution: Imperial College London
Hypothesis
How do geographic range sizes of bird species vary globally?
Conclusion
The study reveals that bird range areas do not follow a simple latitudinal pattern, with smaller ranges found on islands and in mountainous areas.
Supporting Evidence
- The mean range area of the 9,505 extant species is markedly larger than the median.
- More than a quarter of bird species have geographic range areas smaller than 225,000 km².
- The distribution of species range areas is strongly right-skewed.
- Spatial models reveal a weak tendency for areas with high species richness to house species with significantly smaller median range area.
- Geographic range area does not decline towards the tropics as previously suggested.
Takeaway
Birds have different sizes of living areas around the world, and these sizes don't just get smaller as you go closer to the equator.
Methodology
The study used a global database of avian distributions mapped on an equal area projection to derive estimates of range sizes.
Potential Biases
The analysis may be influenced by spatial autocorrelation due to shared species composition in neighboring areas.
Limitations
The study primarily focused on birds and excluded marine species, which may limit the generalizability of the findings.
Statistical Information
P-Value
p ≪ 0.001
Statistical Significance
p ≪ 0.001
Digital Object Identifier (DOI)
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