“The closer one gets to the tropics, the greater the variety of structures, graceful forms and color combinations.” Such were the words of German naturalist, geographer and explorer Alexander von Humboldt (1769-1859), one of the founders of the school of biogeography.
During his extensive travels in the Americas in the early 19th century, Humboldt noticed — concurrently with other household names from the field, including Alfred Russel Wallace and Charles Darwin — that both plants and animals were more colorful in regions near the equator.
Today, more than a century and a half later, a study analyzing high-resolution digital imagery of 4,500 passerine, or perching, birds from around the globe confirms what Humboldt suspected all those years ago: that birds really do come in a much broader range of colors in the tropics. The study also goes on to identify likely reasons for this clear relationship between colorfulness and latitude.
On average, the study found that birds inhabiting forests in countries like Brazil, New Zealand, Indonesia, Australia, Ecuador and Chile, among others, are 30% more colorful — as measured by reflectance of their plumage — than those found in the Northern Hemisphere.
According to the study, the most colorful birds live mostly in dense and humid forests in the Amazon, West Africa and Southeast Asia.
Lead Image: A painted bunting (Passerina ciris), a bird native to the forests of Central America. Image by Andrew C via Wikimedia Commons (CC BY 2.0).
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