Tag Archives: research

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

warbler2.JPG

(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.”

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Migrating birds use a magnetic map to travel long distances

Migrating birds use a magnetic map to travel long distances
(Richard Holland 18 August 20017)

Birds have an impressive ability to navigate. They can fly long distances, to places that they may never have visited before, sometimes returning home after months away.

Though there has been a lot of research in this area, scientists are still trying to understand exactly how they manage to find their intended destinations.

Much of the research has focused on homing pigeons, which are famous for their ability to return to their lofts after long distance displacements. Evidence suggests that pigeons use a combination of olfactory cues to locate their position, and then the sun as a compass to head in the right direction.

We call this “map and compass navigation”, as it mirrors human orienteering strategies: we locate our position on a map, then use a compass to head in the right direction.

But pigeons navigate over relatively short distances, in the region of tens to hundreds of kilometres. Migratory birds, on the other hand, face a much bigger challenge. Every year, billions of small songbirds travel thousands of kilometres between their breeding areas in Europe and winter refuges in Africa.

This journey is one of the most dangerous things the birds will do, and if they cannot pinpoint the right habitat, they will not survive. We know from displacement experiments that these birds can also correct their path from places they have never been to, sometimes from across continents, such as in a study on white crowned sparrows in the US.

Over these vast distances, the cues that pigeons use may not work for migrating birds, and so scientists think they may require a more global mapping mechanism.

Navigation and location

To locate our position, we humans calculate latitude and longitude, that is our positon on the north-south and east-west axes of the earth. Human navigators have been able to calculate latitude from the height of the sun at midday for millennia, but it took us much longer to work out how to calculate longitude.

Eventually it was solved by having a highly accurate clock that could be used to tell the difference between local sunrise time and Greenwich meantime. Initially, scientists thought birds might use a similar mechanism, but so far no evidence suggests that shifting a migratory bird’s body clock effects its navigation ability.

There is another possibility, however, which has been proposed for some time, but never tested – until now.

The earth’s magnetic pole and the geographical north pole (true north) are not in the same place. This means that when using a magnetic compass, there is some angular difference between magnetic and true north, which varies depending on where you are on the earth. In Europe, this difference, known as declination, is consistent on an east west axis, and so can possibly be a clue to longitude.

To find out whether declination is used by migrating birds, we tested the orientation of migratory reed warblers. Migrating birds that are kept in a cage will show increased activity, and they tend to hop in the direction they migrate. We used this technique to measure their orientation after we had changed the declination of the magnetic field by eight degrees.

First, the birds were tested at the Courish spit in Russia, but the changed declination – in combination with unchanged magnetic intensity – indicated a location near Aberdeen in Scotland. All other cues were available and still told them they were in Russia.

If the birds were simply responding to the change in declination – like a magnetic compass would – they would have only shifted eight degrees. But we saw a dramatic reorientation: instead of facing their normal south-west, they turned to face south-east.

This was not consistent with a magnetic compass response, but was consistent with the birds thinking they had been displaced to Scotland, and correcting to return to their normal path. That is to say they were hopping towards the start of their migratory path as if they were near Aberdeen, not in Russia.

This means that it seems that declination is a cue to longitudinal position in these birds.

There are still some questions that need answering, however. We still don’t know for certain how birds detect the magnetic field, for example. And while declination varies consistently in Europe and the US, if you go east, it does not give such a clear picture of where the bird is, with many values potentially indicating more than one location.

There is definitely still more to learn about how birds navigate, but our findings could open up a whole new world of research.

Stress in the nest can have lifelong effect

(The Norwegian University of Science and Technology, Science Daily 16 August 2017)

Why do some sparrows hatch six chicks while others don’t hatch any? How does upbringing affect the remainder of their lives? Physiological stress in the nest can actually affect birds’ DNA and possibly their lifespan.

On average, a mere 10 to 20 per cent of sparrow nestlings survive until the next breeding season. But the survival rate varies between different parents, according to Thomas Kvalnes and Michael Pepke Pedersen at the Norwegian University of Science and Technology’s (NTNU) Centre for Biodiversity Dynamics (CBD).

In order to learn more about this variation, they’re studying birds by banding them.

Good conditions in NTNU birdhouse

At the NTNU Gløshaugen campus in Trondheim, Kvalnes and Pedersen have been following a pair of Eurasian blue tits, which eventually laid ten eggs and were incubated for two weeks. Then the real work started for the parents. No fewer than nine chicks hatched and they all wanted to eat — at the same time.

The blue tit chicks — which are part of the sparrow family — grew enormously fast during the nesting period, growing from less than one gram at hatching to 10 to 12 grams at around 15 days old. This requires a lot of food. The parents in the NTNU birdhouse seem to have access to good nutrition, because all nine young were alive and growing normally when they were 12 days old.

Banding for research

By the age of 12 days, the young had a lot of feathers and were able to regulate their body temperature well. They were also small enough not to get scared and fly out when the lid on the birdhouse was opened. This is important to think about when banding chicks, because the bands must not adversely affect the birds.

The researchers banded all nine baby birds with metal rings, each having a unique identity number. This allows researchers to recognize the individuals later and to follow their development throughout their lives.

Banding is a widely used method by researchers at the NTNU’s Centre for Biodiversity Dynamics.

How does upbringing affect the rest of a bird’s life?

New research suggests that the first days and weeks have a big impact on how the rest of a bird’s life unfolds. In some clutches, the young get a lot of food and grow fast, whereas in others the chicks face tougher competition or the nest is more exposed to the weather. However, conditions in the nest can actually leave a genetic impression in the birds, more specifically on the ends of the chromosomes that make up the DNA.

The telomeres (from Greek, meaning “end pieces”) that protect the DNA from breaking down are found here, say Kvalnes and Pedersen.

“Each time a cell divides, the DNA must be copied, but the entire DNA sequence cannot be copied, and that impacts the telomere structures, which get shorter after each copying. At the same time, the telomeres wear down if exposed to oxidative or physiological stress, the researchers say.

Molecular thread of fate?

When the telomeres become too short, cell function may become impaired and the entire organism may be affected by age-related illnesses. Some studies have shown that birds’ telomere length can predict how long they will live — a bit like the thread of fate that is clipped by the Norns in Norse mythology and decides the length of human lives.

The most rapid shortening of the telomeres in life occurs when the young chicks grow fast. At CBD, researchers are investigating the connection between sparrow telomeres and their life stories. The researchers follow them from their time in the nest until they become parents themselves — and perhaps grandparents — until their death.

Telomeres in birds and humans

Much of our understanding of telomeres comes from studies of animals in captivity or laboratories, but there’s a lot we don’t know about how these fundamental physiological processes work in typical natural circumstances. CBD researchers hope to help answer these questions.

“The telomeres in birds are identical to those found in humans and all other vertebrates, and they speak to our common origin. In fact, telomere mechanisms exist in all organisms except simple bacteria and archaea. So it’s conceivable that we’ll be able to transfer our knowledge of telomere dynamics in birds to many other organisms,” the researchers say.

New Government Report Contradicts Trump Administration Climate Claims

Common Loon with chicks. Photo: Richard D. Pick/Audubon Photography Awards(Andy McGlashen 8 August 2017)

The report, which paints a dire picture of the planetary changes caused by warming temperatures, is awaiting official White House approval. But scientists worry its findings will be downplayed or suppressed.

The White House has found itself in yet another tough spot: Will the president and cabinet officials approve a report that contradicts their own public statements about climate change, or face backlash for suppressing the report and its inconvenient conclusions? Either way, they only have until August 18 to make a decision, and a sudden frenzy of news coverage this week has increased pressure as the deadline looms.

As originally reported by The New York Times on Monday, the draft report from scientists at 13 federal agencies shows severe warming in recent years, projects continued, significant temperature increases, and says human activity is chiefly to blame. According to the Times, scientists involved in the study are concerned that the Trump administration will hide or downplay the findings of the report, which was publicly available during its review period in December but received little press coverage until now.

Trump infamously called climate change a Chinese hoax during his campaign for the White House, has since moved to undo domestic climate policies, and has pulled the United States out of the Paris climate accord signed by nearly 200 countries in 2015. He also made Scott Pruitt the administrator of the Environmental Protection Agency. Pruitt, who is a known climate change denier, would need to approve the report before it went public. Pruitt has spent much of his time in office weakening the EPA’s climate change research, and as the Times notes, in March, he said that carbon dioxide is not a “primary contributor” to global warming.

The draft report thoroughly undermines the Trump administration’s climate change claims and policies. “Evidence for a changing climate abounds, from the top of the atmosphere to the depths of the oceans,” it says. “Many lines of evidence demonstrate that human activities, especially emissions of greenhouse (heat-trapping) gases, are primarily responsible for recent observed climate changes. There are no alternative explanations, and no natural cycles are found in the observational record that can explain the observed changes in climate.” You can read the full report here.

Our planet has warmed by 1.6 degrees Fahrenheit since 1880, and it is “extremely likely” that most of the 1.2 degrees of warming since 1951 is due to human activity, the report concludes. We could expect another half-degree of warming by the end of the century, even if humans stopped pumping greenhouses gases into the atmosphere today. And under more realistic emissions scenarios, “the temperatures of recent record-setting years will become relatively common in the near future,” the authors write.

Along with rising temperatures, the report paints an unsettling picture of other planetary changes already underway. In the northeastern U.S., for example, extreme precipitation events are 17 percent more frequent than they were in the first half of the 20th century. Global sea levels have risen 3 inches since 1990, and the oceans are becoming more acidic faster than at any period in the past 66 million years. Permafrost is thawing and sea ice is melting in the Arctic, which is warming more than twice as fast as the rest of the planet. “Residents of Alaska are on the front lines of climate change,” the report says. “Crumbling buildings, roads, bridges, and eroding shoreline are commonplace.” 

While most scientists have long been cautious about blaming climate change for specific weather events, the report notes that new tools and techniques are making it possible to detect its influence on specific extreme weather events.

In addition to being a danger to human life, especially the socioeconomically disadvantaged, the global changes documented in the report threaten birds and other wildlife. As Audubon has reported, warming oceans are changing seabird diets and possibly even causing die-offs, while rising seas threaten bird habitat. And Audubon’s 2014 Birds & Climate Change Report, published in peer-reviewed scientific journals, found that climate change is the biggest threat to 314 North American bird species. In South America, where many of these species migrate for the winter, climate change-related droughts also put birds at risk.

The draft Climate Change Special Report is part of the National Climate Assessment charged with reporting the latest climate science to Congress and the president every four years. The National Academy of Sciences has approved the draft, but it won’t be final until the White House signs off. If the administration did have plans to quietly scuttle the report or water down its urgent message, it will now have a much harder time doing so.

Penguin forensics: Tracking the winter whereabouts of penguins by analyzing tail feathers

Penguin forensics
( Louisiana State University, Physorg 8 >August 2017; Photo M. Polito)

While a postdoctoral researcher at Woods Hole Oceanographic Institution, Polito and his colleagues conducted high-resolution forensic analyses of the chemical composition of the feathers using a technique called compound-specific stable isotope analysis of amino acids.

The scientists were able to identify the unique chemical signatures of penguin’s wintering areas in the ocean based on the coordinates from the tags and the data from the feather analyses. From this understanding, they were able to deduce where the other penguins that had not been tagged went over the winter based solely on the analyses of their tail feathers.

“This novel approach could be applied to different tissues from a wide variety of marine animals that migrate over long distances including seabirds, sea turtles, seals and whales,” Polito said. “Using stable isotope forensics to increase the size and scope of animal tracking studies will help us to better understand these charismatic species and ultimately aid in their conservation.”

Knowing where and how Antarctic penguins, and other seabirds and marine predators, migrate is critical for conservation efforts. Although electronic tracking devices have helped scientists track marine animals’ migration patterns, the devices can be expensive, invasive for the animal and challenging to retrieve. Scientists have discovered a new and potentially better way to track where penguins go over the winter using forensics.

“You can say, penguins ‘are where they eat,’ because a geochemical signature of their wintering area is imprinted into their feathers,” said LSU Department of Oceanography & Coastal Sciences Assistant Professor Michael Polito, the lead author of this study that will be published Aug. 9 in Biology Letters.

Chinstrap and Adélie penguins are part of the family of “brush-tailed” penguins named after their approximately 15-inch long, stiff tail feathers. These birds shed all of their feathers after each breeding season and before they migrate to their oceanic wintering grounds. However, their long tail feathers continue to grow well into the winter when penguins are at sea.

Polito and his collaborators from NOAA Southwest Fisheries Science Center, Oxford University and the Instituto Antártico Argentino attached tags to 52 adult Chinstrap and Adélie penguins at their breeding colonies and retrieved the tags the following breeding season to determine where the birds went over the winter. When they retrieved these tags, the researchers also took a tail feather grown over the winter from each tracked penguin and from 60 other penguins that had not been tagged.

How do birds get their colors?

(Physiological and Biochemical Zoology, Physorg 5 August 2017)

A new article in Physiological and Biochemical Zoology explores the role of melanins in creating complex plumage patterns in 9,000 species.

Birds’ feathers, or plumage, are some of the most strikingly variable animal characteristics that can be observed by the naked eye. The patterns that we see in birds’ feathers are made up of intricate combinations of mottles, scales, bars, and spots. But, how are these colors and patterns made?

We already know why birds have colored feathers. For many birds, plumage coloration may make them less visible to predators by helping them to blend in to their surroundings, or more appealing to potential mates by helping them to stand out from their peers. These aspects are well known. A greater mystery has been how the patterns are created on a cellular level.

Dr. Ismael Galván and his team of expert researchers studied plumage coloration to see what types of pigments were present in birds’ complex feather patterns. Plumage coloration mainly happens courtesy of two types of pigments: melanins, which produce a range of black, grey, brown, and orange colors, and carotenoids, which are used by specialized feather structures to generate brighter color hues.

Birds cannot produce carotenoids on their own. For feathers with bright colors, birds must consume food items that contain these pigments, and the carotenoids circulate through the bloodstream and to the feather follicles. Birds’ bodies do not have direct cellular control of synthesizing and depositing carotenoids; nor do they have control of the specialized feather structures, which react to the consumed carotenoids with a mechanism that is not regulated by specialized cells.

Melanins, on the other hand (or should that be “on the other wing”), are synthesized by in the birds’ bodies in special cells called “melanocytes,” which work together with feather follicles to achieve a fine control of pigmentation. Although studies frequently focus on carotenoids in bird coloration, Dr. Galván and group are the first to test whether melanins are indeed the only pigmentary element that birds’ bodies directly control on a cellular level.

Galván says, “Knowing beforehand that different pigments and structures produce different types of colors in feathers, we examined the appearance of the plumage of all species of extant birds and determined if the color patches that they contain are produced by melanins or by other pigmentary elements. We also identified those plumage patterns that can be considered complex, defining them as those formed by combinations of two or more discernible colors that occur more than two times uninterruptedly through the plumage.” This study was very large in scope, examining about 9,000 bird species, with the goal of supporting a general conclusion for all birds, to finally answer the question of how birds develop colorful and detailed patterns.

The team found that about 32% of the species studied have complex plumage patterns, with the vast majority of these complex patterns produced by melanins rather than carotenoids. Metaphorically, if the birds were artists, they would use carotenoids as a broad brush to produce color patches, with melanins as a detail paint brush to produce more intricate designs.

A few birds are exceptions to this rule: Three bird families do have complex plumage patterns without melanins. Fruit doves, cotingas and one type of stork have unusual colors that appear to be produced by their bodies making metabolic modifications to the carotenoid pigments that they consume.

Isotope fingerprints in feathers reveal songbirds’ secret breeding grounds

Using isotope fingerprints in feathers, researchers have pinpointed the northern breeding grounds of a small, colourful songbird.

Myrtle warblers breed across much of Canada and the eastern United States, but winter in two distinct groups—one along the Atlantic and Gulf coasts, another along the US Pacific Coast. They are also one of the few breeds of eastern warbler that have been able to extend their range into the far northwest of the continent.

“The Pacific Coast warblers migrate through the Vancouver area, but it’s been a bit of a mystery exactly where they breed over the summer,” says David Toews, who began the research while a graduate student at the University of British Columbia (UBC).

So Toews, UBC undergraduate student Julian Heavyside, and UBC professor Darren Irwin used isotope signatures to pinpoint where the myrtle warblers breed.

‘We were able to match stable hydrogen isotopes in feathers collected in Vancouver to latitudinal isotope records in rainwater, to determine where the feathers were actually grown,” says Toews, who conducted the analysis as a postdoctoral researcher at Cornell University.

It turns out the warblers that summer on the Pacific Coast breed in Alaska and Yukon, suggesting this form of the eastern warbler spends its entire lifecycle—wintering, migrating and breeding—near the western edge of the continent.

The observatory was started in 2010 by WildResearch, a non-profit dedicated to conservation science and outreach. The observatory allows researchers to monitor how birds use Iona Beach Regional Park, estimate population trends, and create training and

These high latitude warblers also have longer wings and tails, likely adaptations for their longer migration. The evolution of the shorter migration route to wintering sites on the Pacific Coast may have facilitated the breeding expansion of myrtle warbles into northwestern North America.

“Migration has been shown to be genetically based in many species of songbirds such as warblers,” says Irwin. “An intriguing possibility is that the genes for the western migratory route were introduced to the myrtle warblers through interbreeding with a related western group, the Audubon’s warblers.”

The feathers were collected by Heavyside and volunteers at the Iona Island Bird Observatory in Iona Beach Regional Park, Vancouver, with permission from Metro Vancouver Regional Parks.

“UBC has fantastic research opportunities for undergraduate students, and I really enjoyed the chance to contribute to this project,” says Heavyside.

“I’ve volunteered at the IIBO station for several years and it was exciting to see a collaboration form between UBC and WildResearch. Holding a bird in the hand will never get old, and it’s amazing what we can learn from a single feather.”