Edwin Scholes has taken dozens of bush plane flights, helicopters and boat trips, and spent countless hours hauling gear up muddy mountains in New Guinea, for nothing more than a song and dance. Sometimes, he only manages to capture a few seconds of footage of the rainforest performances he seeks before his subjects become spooked, vanishing amongst the trees.
Between the adventurous parts and many more hours of monotonous patience waiting to peep on courting birds over the last two decades, the leader for the Cornell Lab of Ornithology’s Birds-of-Paradise Project has recorded hundreds of videos of the mating habits of the roughly 40 known birds of paradise species. Now he and his colleagues have closely examined this footage in an effort to understand how some of the most spectacular birds on the planet evolved such wildly diverse appearances, shape-shifting mating rituals, and songs, when they all hail from a common ancestor.
They believe that choosy females unsatisfied with looks, dance or song alone have largely driven the evolution of these fantastic traits, according to a study published recently in PLOS Biology. Habitat loss due to deforestation and development means that some of these unique traits and the species which exhibit them are in danger of disappearing before we understand much about them.
The bird-of-paradise family, found mostly on the island of New Guinea but with a few species in smaller surrounding islands and Australia, includes the magnificent riflebird, which attracts mates by thrusting its blue-throated head back and forth with its feathers spread out like Dracula’s cape, and the Wilson’s bird-of-paradise which uses haunting chirps and the display of its emerald throat, bald blue head, red back and spiral-shaped violet tail feathers to attract females. Male greater birds-of-paradise sport Bon Jovi-like mullets as they hop around on branches, (though their songs are much higher in key), while some species harness the power of light-trapping nanotechnology to produce some of the blackest feathers in existence.
An obsessive categorization of the specific movements, colors, plumage difference, song notes and other characteristics of all birds-of-paradise species revealed that male birds with more colors also tend to have more song notes, and that elaborate dancers also have a larger sound repertoire. The researchers also found males displaying in a group have more colors than those who don’t, possibly as the former need to stand out. Species that court on the ground are better dancers, while males displaying their mojo in the forest canopy have more complex songs.
The exhaustive examination has led them to a theory that female choice may be driving this diversification. Since females size up potential mates based on a number of different factors including looks, song and dance abilities, the males may be able to get creative in one of those categories while still maintaining a base level of attractiveness in others. In other words, they can adopt a flamboyant dance as long as their feathers and song are sexy enough, or vice versa. If the females take a liking to this experimentation, it may eventually favor evolution in this direction.
Meredith Miles, a biology PhD student at Wake Forest University who also published a study in 2018 on the evolution of these birds, came to some of the same conclusions by reading text accounts of the dance moves of birds-of-paradise and picking out the parts describing behavior.
“We both found similar effects on the mating systems and on how the habitats affect certain traits,” she said. The conclusions they share include that birds which display on the ground have more complex moves than those in the canopies. “It’s always good news as a scientist to know you’ve converged on the same answer.”
However, Miles interprets some results differently from Scholes as far as evolution is concerned. For example, she believes females likely drive these adaptations but says that she isn’t sure that birds-of-paradise have evolved wonderful dancing because they already have great colors or vice versa. She believes that the answer is more likely that within all the birds-of-paradise, some species tend to compete more intensely than others.
In any case, there is still much to be discovered about birds of paradise. Sadly, some of the most vulnerable species are those we know the least about, Scholes says. With many species declining due to habitat loss from resource extraction and development, it may become even harder to learn more about them in the future.
Miles said the larger effort of Scholes and his coauthors to look at dances, songs, and plumage or appearance is “an astounding endeavor.” Indeed, Scholes’ dedication to documenting the unobserved behaviors of these birds often meant hours or days sitting quietly in a hideout called a blind, fighting off mosquitoes in all types of weather. Some days were made even longer trekking through rugged mountains and rainforests to get to their campsites and back.
The work also nearly cost him his life early in his career. In 2002, he was an 11-hour hike up a jungle-shrouded mountain in Papua New Guinea’s southeast attempting to catch some of the only footage of the elaborate mating dance of the eastern parotia bird-of-paradise, when his work was interrupted by a rotten appendix.
Male parotia have spectacular antenna-like wires spouting back from near their bright blue eyes. They push some lower torso feathers out to look like a black Scottish kilt before executing a dainty jig. The dance, the notes they serenade females with, and their iridescent golden-green chest patch, may be just different enough from those of the Lawes parotia to possibly warrant their status as a separate species or subspecies.
After setting up his equipment behind a blind, Scholes captured only a “tantalizing” amount of footage before he began to get sick and could no longer concentrate. Luckily, this was one of the only times he had traveled with a satellite phone, which may have saved his life. The researchers phoned in for extraction and cleared the trees off a nearby rock overhang, which wasn’t enough for the helicopter to land but allowed it to hover close enough for Scholes to climb in. Five days and several more flights later, he had the appendix removed in a hospital in Australia.
But as far as the eastern parotia is concerned, its status as a subspecies or separate species entirely is still an open question.
Joshua Rapp Learn contributes features on archaeology, ecology and the adventures involved in the research.