As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Friday, 3 July 2020

Dawn song of the male great tit attracts other males rather than females

JUNE 23, 2020

Female great tits (Parus major) stay clear of territories with better singing males while competing males are attracted to the territories with better singers. This unexpected conclusion was reached by researchers of Wageningen University & Research in collaboration with the Netherlands Instituut for Ecology (NIOO-KNAW). This conclusion is diametrically opposed to the current assumption that male birds use their song to impress females and repel males to stay away from their territory.
Previous research showed that songbirds often cheat on their partners. One would thus expect male birds to use their song to lure any close-by females. But nature tells a different story, the research team discovered.
"Our knowledge to date on the daily behavior between males and females is largely based on knowledge under lab condition because it is so difficult to follow a songbird for a long time," professor Marc Naguib explains. "We know what colors are prefered by the females, and what songs they prefer if they exhibit an immediate reaction. But how they show territorial behavior and respond to males in the open field was hitherto almost unknown."
Dawn song attracts male competition
Ph.D. researcher Nina Bircher and her co-authors expected that the most enthusiastic singers would attract the most female interest. This appeared completely false. The male great tits with the most extensive repertoire that started singing the earliest and showed the most persistence attracted fewer females. Male great tits, however, entered their singing competitor's territory, captivated by the performance, the researchers write in the scientific journal Behavioral Ecology.
The reason for this behavior remains a mystery. Naguib: "Males may enter the competitor's territory to check out why the competitor is better than they are, or why he may be more suited to produce offspring." Whatever the reasons, the discovery sheds new light on the complexity of songbirds social and communication network.
The prevailing assumption that the female great tit would more frequently enter a different territory when she is fertile is thus not supported. The premise is she would visit other territories specifically for extra-pair mating. In reality, however, this research shows that she enters territories other than her own once she has laid eggs in an effort to find food for her young.

Long-tailed tits avoid incest by recognising the calls of relatives

JUNE 23, 2020
Long-tailed tits actively avoid harmful inbreeding by discriminating between the calls of close family members and non-family members, according to new research from the University of Sheffield.
Inbred animals typically suffer from reduced survival and reproductive success, so incest is usually avoided. But, in species where young stay close to where they were born, relatives are often encountered as potential mates, increasing the risk of harmful inbreeding.
Long-tailed tits often breed close to home, allowing kin to help raise each other's chicks, but also incurring a risk of incest that reduces the reproductive success of offspring. The research, led by Dr. Amy Leedale from the University of Sheffield's Department of Animal and Plant Science, found that despite this risk, close relatives are actively avoided when pairs form each spring.
Long-tailed tits use distinctive calls to recognize close relatives so that they can help raise their offspring. The authors suggest that these calls also explain how the birds avoid inbreeding.
Dr. Amy Leedale, who led the research as a Ph.D. student at the University of Sheffield, said: "We recorded the calls of males and females in many pairs of long-tailed tits and found that the calls of breeding pairs were less similar than the calls of close relatives that they could have bred with. Call similarity within breeding pairs was, instead, similar to that observed among distant relatives or unrelated birds."
Long-tailed tit calls are learned in the nest, when parents, offspring and siblings are closely associated. Call similarity can therefore act as a reliable indicator of close relatedness in adulthood. This study reveals a potential mechanism by which long-tailed tits can avoid harmful inbreeding as well as gaining benefits from cooperating with kin.

Research suggests a better way to keep birds from hitting power lines

JUNE 24, 2020

by Steve Lundeberg, Oregon State University
Suspended, rotating devices known as "flappers" may be the key to fewer birds flying into power lines, a study by Oregon State University suggests.
The findings by researchers in OSU's College of Agricultural Sciences are important because around the globe both the number of power lines and concern over bird fatalities are on the rise.
Research has documented more than 300 species of birds dying from hitting power lines, with one study estimating that more than 170 million perish annually in the United States and another estimating the global death toll to be 1 billion per year. There's also the problem of power outages that bird strikes can cause.
Conservation managers and utilities many years ago developed flight diverters, basically regularly spaced devices that make the lines more visible, as a step toward reducing the number of birds flying into the lines.
The most common type are the PVC spirals, which are durable and easy to install, but how well they actually work isn't well understood. Though they've been in use for nearly four decades, strike rates remain high for a number of species.
OSU researchers Virginia Morandini and Ryan Baumbusch were part of an international collaboration that compared the effectiveness of three types of flight diverters: yellow PVC spiral; orange PVC spiral; and a flapper model with three orange and red polypropylene blades with reflective stickers.
The flapper hangs from a power line and its blades, 21 centimeters by 6.2 centimeters, rotate around a vertical axis.

Thursday, 2 July 2020

Cowbirds change their eggs' sex ratio based on breeding time

JUNE 24, 2020

Brown-headed cowbirds show a bias in the sex ratio of their offspring depending on the time of the breeding season, researchers report in a new study. More female than male offspring hatch early in the breeding season in May, and more male hatchlings emerge in July.
Cowbirds are brood parasites: They lay their eggs in the nests of other birds and let those birds raise their young. Prothonotary warblers are a common host of cowbirds.
"Warblers can't tell the difference between their own offspring and cowbirds," said Wendy Schelsky, a principal scientist at the Illinois Natural History Survey and co-author of the study. "They do a really good job of raising cowbirds, even though cowbird chicks are larger and need more food."
The researchers studied the interactions between cowbirds and warblers for seven years to determine whether there was a difference in the relative number of males and females among cowbird offspring. They collected DNA samples from cowbird eggs or newly hatched chicks.
"Other scientists have not seen any difference in the sex ratios of brood-parasitic birds," said study co-author Mark Hauber, a professor of evolution, ecology, and behavior at the University of Illinois at Urbana-Champaign. "This is the first time anyone has detected a seasonal bias and we believe that it is due to our large sample sizes."
More female than male cowbirds are hatched early in the nesting season, and the pattern is reversed in July, new research finds. An adult female cowbird, upper right, perches on tree stems above an adult male cowbird. Credit: Photo (c) by Michael Jeffords and Sue Post
The researchers think their results may reflect the different developmental trajectories of male and female cowbirds.

Resident parasites influence appearance, evolution of barn swallows

JUNE 24, 2020
by Kelsey Simpkins, University of Colorado at Boulder
Barn swallows live almost everywhere on the planet, recognizable by their forked tail and agility in the air. Yet while they share these characteristics, these little birds often look slightly different in each place they live—with some so distinct they're splitting off to become new species.
Researchers at CU Boulder think that local parasites are influencing why barn swallows in Europe, the Middle East and Colorado are choosing their mates differently. Their new research, published in Evolution, finds that these parasites could be playing an important role in changing the traits displayed to attract mates early in the process of the creation of new species.
"It's possible we haven't appreciated just how important parasites might be in shaping the evolution of their hosts," said lead author Amanda Hund, who conducted the research as a doctoral candidate in the Ecology and Evolutionary Biology Department.
Every organism, including humans, has co-evolved with a unique community of parasites, that by definition live at the expense of their host. While they are not beneficial to us like many other microbes are, parasites have shaped our own immune system, pheromones and even our mate selection, previous research has shown.
Hund set out to characterize as many parasite communities as she could in barn swallows, to find out if they could be influencing their mate selection, and therefore the male birds' physical traits and the creation of new species.

Antarctic penguins happier with less sea ice

JUNE 24, 2020

by Research Organization of Information and Systems
Researchers have been surprised to find that Adélie penguins in Antarctica prefer reduced sea ice conditions, not just a little bit, but a lot. As climate models project rapid reduction of the continent's sea ice over the rest of the century, this iconic polar predator could be a rare global warming winner. Their research findings are published on June 24, 2020 in Science Advances.
In recent decades, Antarctica has experienced a steady increase in the extent of its sea ice—frozen seawater—even as its polar twin, the Arctic, has suffered through a marked decrease. But this is not expected to last for much longer as the climate changes, with Antarctica also projected to see a decline in its sea ice, with all the consequences of such changes to the maritime habitat for the organisms that live there.
But such consequences aren't always negative.
Polar biologists have known for some time that Adélie penguins, the most common species of penguin in Antarctica, tend to see population increases during years of sparse sea ice and suffer massive breeding failures during those years with the greatest growth of sea ice.
But until now, researchers didn't really know why this happened. The handful of studies that made mention of the relationship between population growth and sea ice have only ever established a correlation, not a cause.

Wednesday, 1 July 2020

Warming climate is changing where birds breed

Migratory behavior and winter geography drive differential range shifts of eastern birds in response to recent climate change
Date: May 26, 2020
Source: S.J. & Jessie E. Quinney College of Natural Resources, Utah State University
Spring is in full swing. Trees are leafing out, flowers are blooming, bees are buzzing, and birds are singing. But a recent study published in Proceedings of the National Academy of Sciences found that those birds in your backyard may be changing right along with the climate.
Clark Rushing, Assistant Professor in the Department of Wildland Resources and Ecology Center, Quinney College of Natural Resources at Utah State University, and colleagues at the U.S. Geological Survey wanted to know how climate change has already affected where birds breed. They used data from the Breeding Bird Survey -- one of the oldest and longest citizen-science programs in the world -- to conduct their research. "Thousands of devoted volunteers, cooperators, and a joint U.S.-Canadian wildlife management team have contributed to the success of the surveys for the last 54 years," said Andy Royle, a USGS senior scientists and co-author of the study. "The Breeding Bird Survey is fundamental to our understanding and management of wild bird populations in North America."
The research team combined Breeding Bird Survey data with powerful computer models to discover changes in breeding range for 32 species of birds found in eastern North America. What they found is surprising:
Some birds' ranges are expanding. Birds that both breed and winter in North America are extending their ranges north to take advantage of new, warm places to breed. These birds are also maintaining their southern ranges. These results bring hope that some bird populations, such as Carolina wrens and red-bellied woodpeckers, may be resilient to future climate change.