It turned out that various spots on the plumage of these birds developed in time independently of each other. A study published in BMC Evolutionary Biology helps explain why a dazzling variety of colors can be seen on the beak and chest of birds - from bright ultraviolet blue visible only to other birds to dark red and black - while their wings and the back is usually the same color: green.
Predator protection or attractiveness for partners?
"All birds must balance, being attractive to potential mates, while at the same time having a kind of camouflage against predators, " said Brian Smith, junior curator of the ornithology department of the American Museum of Natural History and one of the co-authors of a new study. "So how do lorikeets, which have a very bright appearance, become so colorful without being attacked by lizards or hawks?"
Museum Specimen Research
To help answer this question, Smith and John Mervyn, a museum researcher who started the project while still a student at Columbia University, photographed in visible and ultraviolet light 98 historical exhibits at the Australian Lorikeet Museum - those living in New Guinea, Australia and around archipelagos and represent almost all the diversity in the group. Many birds can see in the ultraviolet spectrum, to which most people are blind, so the researchers used a special program that translates color into "bird's vision." They collected data on 35 plumage areas of birds near the beak, on the head, back, wings, chest and lower abdomen. This color data was modeled on the lorikeet tree of life to check if different plumage plots of birds are more likely to develop under certain scenarios.
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They found that the plumage spots, which are likely to be involved in protection from predators, largely persist for a long evolutionary period. While spots that are likely to be involved in partner recognition or courtship processes developed quite rapidly. The likely explanation is that when looking for a partner, this can help each species have different colors in front so that they can find their own look. But when they are hunted from above, it is beneficial for birds to merge with trees, so their backs can be adapted for disguise, and their colorful plumage of the front of the body for easy recognition by partners.
Mosaic evolution
In general, the researchers identified three groups of plumage that evolved over time: plumage at the beak and head, back and wings, as well as the chest area and lower abdomen. This so-called mosaic evolution - when subsets of characters develop independently of others - underlies the extraordinary diversification of the plumage color observed today in lorikeets.
"The range of colors demonstrated by lorikeets is one third of the colors that birds can theoretically recognize, " Mervyn said. "We were able to capture variations in this study that are not even visible to the human eye. The idea that you can take color data from museum samples, draw conclusions and gain a deeper understanding of how these birds evolved is truly amazing."
