A warbler’s flashy yellow throat? There are genes for that

(University of British Columbia. 8 Oct 2017; Photo Alan Brelsford)

Birds get their bright red, orange and yellow plumage from carotenoid pigments—responsible for many of the same bright colours in plants. But how songbirds turn carotenoids into the spectacular variety of feathered patches found in nature has remained a mystery.

Now University of British Columbia (UBC) research might have pinpointed some of the genetic machinery responsible for the plumage colouration in Audubon’s and myrtle warblers, related but distinctly feathered North American songbirds.

“Audubon’s and myrtle warblers interbreed in a narrow band across British Columbia and Alberta,” says David Toews, co-author of a new Proceedings of the Royal Society paper exploring the birds’ colouration.

“Those hybrid warblers, while considered oddities to some birders, were key for this study because their plumage traits and genes are all jumbled and mixed, allowing us to link their differing colours to genetic markers and hopefully the genes responsible.”

Both types of warblers use colourful carotenoid pigments to make several yellow feather patches, including their yellow-rumps—the birds are colloquially referred to as ‘butter butts’.

But only Audubon’s also used carotenoids in their telltale yellow throats. Myrtles have white throats and the hybrids have a mix of white and yellow.

The study identified several genomic region s— one including a member of the scavenger receptor gene family that affects carotenoids in other animals—that might be involved in this selective distribution of yellow carotenoid colours.

“We found strong associations with several genomic regions across a handful of distinct plumage traits” explains co-author Alan Brelsford. “Now we can now dig even deeper into these regions to understand the mechanisms that make warblers so colourful and diverse.”

“This study is unusual in that it focused on variation in multiple colour patterning traits,” says co-author Darren Irwin, a professor of zoology at UBC. “Two of the plumage differences between the species, eye spot and eye line colouration, appear to be encoded by a single region in the genome.”

Dance Moves Support Evidence for New Bird-of-Paradise Species

(Cornell LoO 29 June 2017; Photo Tim Laman)

Ithaca, NY—The Superb Bird-of-Paradise—the shape-shifting black bird of central New Guinea that woos its mate with an iridescent blue “smiley-face” dance—has an equally superb cousin in the isolated mountains of Indonesia’s Bird’s Head Peninsula in the island’s far west. Scientist Ed Scholes and photographer Tim Laman, with the Cornell Lab of Ornithology’s Birds-of-Paradise Project, have now visually documented the distinct differences between the western population in the Arfak Mountains and the more common form found elsewhere on the island. Both believe the western form should be considered a new species.

“The courtship dance is different. The vocalizations are different. Even the shape of the displaying male is different,” says Scholes. “For centuries, people thought the Superb Bird-of-Paradise in the mountains of the Bird’s Head region was a little different from the other populations throughout the rest of New Guinea, but no one had ever documented its display in the 200 plus years this bird has been known to occur there.”

“Even after many trips to the region, we’d never seen the Arfak birds do their courtship display,” says Birds-of-Paradise Project co-leader Tim Laman. “When we finally located a display site and saw a male open his cape for the first time, what we saw was a complete surprise!”

When expanded for courtship display, the western male’s raised cape creates a completely different appearance—crescent-shaped with pointed tips rather than the oval shape of the widespread form of the species. The way the western male dances for the female is also is distinctive, being smooth instead of bouncy.

The raised cape of the western male (left) is crescent shaped and unlike the oval shape of the widespread Superb Bird-of-Paradise (right) found throughout most of New Guinea. Left image by Tim Laman/Macaulay Library. Image on right is from video by Ed Scholes/Macaulay Library.

Scholes and Laman have been studying and filming birds-of-paradise behavior in the Arfak Mountains for the past 13 years. They first uncovered this population’s unique courtship behaviors in June 2016 and returned again this year to gather additional documentation for a forthcoming scientific paper.

A recently published independent genetic study confirms the visual and behavioral evidence collected by Scholes and Laman. A team of researchers from Sweden and Australia used DNA samples from museum specimens to examine the evolutionary relationships among Superb Bird-of-Paradise forms throughout New Guinea. Their research, published online in the Zoological Journal of the Linnean Society, found that the western form is more genetically distinct from the widespread form than previously thought. They, too, say the western population should be recognized as a full species called Lophorina neidda inopinata. 

“The timing of this DNA-based study is perfect,” said Ed Scholes, “because it is great to have our field observations supported by solid genetic evidence. We really appreciate this in-depth study of the evolutionary relationships among the different forms of Superb Bird-of-Paradise.”

The Cornell Lab’s Birds-of-Paradise Project (birdsofparadiseproject.org) is a research and education initiative to document, interpret, and protect the birds-of-paradise, their native environments, and the other biodiversity of the New Guinea region—one of the largest remaining tropical wildernesses on the planet.

Birds’ migration genes are conditioned by geography

(Lund University 6 July 2017; Photo Max Lundberg)

The genetic make-up of a willow warbler determines where it will migrate when winter comes. Studies of willow warblers in Sweden, Finland and the Baltic States show that “migration genes” differ — depending on where the birds breed in the summer. The willow warblers that breed in southern Sweden migrate to West Africa, while those in northern Sweden, Finland and the Baltic States fly to southern or eastern Africa.

According to a new study led by biologists at Lund University, the key to the willow warblers’ differing migration patterns probably lies in their genes.

The researchers studied the entire genetic make-up of willow warblers that breed in southern and northern Sweden, Finland and the Baltic States. The comparison shows that the genomes are almost completely identical, but there are significant differences between the birds that breed in southern Sweden and those that breed in the northern parts of the country and east of the Baltic.

The differences are restricted to two regions in the genome, where the comparison shows extensive differences in over 200 genes.

“Of these 200 or so genes, there are several that can be considered to be important for migration-related physiological adaptations and others that, according to our present knowledge, have a poorly characterized or unknown function,” says Max Lundberg, researcher at Lund University.

According to him and his colleagues, the genetic differences are probably decisive in determining that willow warblers in southern Sweden migrate to West Africa, whereas the more northerly willow warblers head for the south-east of Africa.

Researchers have previously known that the migration behaviour of many birds is strongly determined by genetics. Inherited information in the genes determines the direction of migration and a schedule that contains information about when and how far the birds are to migrate. The migration over thousands of kilometres also requires inherited physiological adaptations, for example to store and use fat and energy as efficiently as possible. Up to now, however, very little has been known about the specific changes in the genetic make-up that underlie where birds, in this case willow warblers, migrate.

“Our results represent an important addition to the understanding of migration-related genetics and will guide future studies in the subject,” says Staffan Bensch, a professor at Lund University.