Removing predators doesn’t guarantee bird safety

Removing predators doesn't guarantee bird safety
(University of Queensland; 11 May 2018)

Removing introduced predators might not provide greater protection of nesting birds in Australia’s temperate forests and woodlands, according to a new University of Queensland study.

UQ School of Biological Sciences researcher Graham Fulton’s review of 300 scientific papers on nest predation has found that getting rid of medium-sized predators might actually increase attacks from smaller predators.

“In Australia, the introduction of foxes and cats, along with the reduction in dingo numbers is thought to have adversely impacted a range of smaller animals,” he said.

Mr Fulton said areas where foxes were baited showed increased nesting success, but controlling fox numbers could increase the number of cats, which also target .

In turn, controlling cat numbers could empower smaller predators such as black rats or mice.

“But it’s not only predators which are to blame, humans are too,” he said.

“Birds such as currawongs, grey butcherbirds, Australian magpies and crows have increased their range and numbers as a result of the clearing of forest and woodlands.

“These same birds are known predators of nestlings and eggs.”

He said more research was needed to improve the understanding of interactions between birds, their predators, and their habitats.

The study is published in Pacific Conservation Biology

Angry birds: Size of jackdaw mobs depends on who calls warning

(Physorg; University of Exeter; 10 May; Photo: Alex Thornton)

Jackdaws recognise each other’s voices and respond in greater numbers to warnings from familiar birds than strangers, new research shows.

The birds produce a harsh “scolding call” when they spot a predator, calling fellow jackdaws to mob the intruder and drive it away.

University of Exeter researchers have discovered that each bird has a unique call, and the size of the mob depends on which bird calls the warning.

The scientists played recordings of individual calls and found that the largest mobs assembled when birds heard the cry of a member of their own colony.

“Joining a mobbing event can be dangerous, as it involves approaching a predator, so it makes sense for individuals to be selective in whom they join. Our results show that jackdaws use the ability to discriminate between each other’s voices when deciding whether to join in potentially risky collective activities,” said Dr Alex Thornton, of the Centre for Ecology and Conservation on the University of Exeter’s Penryn Campus in Cornwall.

“We also found a positive feedback loop – if birds joining a mob made alarm calls of their own, this in turn caused more birds to join in, magnifying the size of the mob.”

The researchers studied wild jackdaws, a highly social member of the crow family, as part of the Cornish Jackdaw Project, a long-term study of jackdaw behaviour and cognition in sites across Cornwall.

In playbacks at nest-box colonies during the breeding season, they broadcast the warning calls of a resident from each nest-box, another member of the same colony, a member of a different colony, and a rook (a species that often associates with jackdaws).

Jackdaws were most likely to respond to a warning from a bird from the resident nest-box owner, followed in turn by other colony members, non-colony members and rooks.

Responses were also influenced by caller sex, with jackdaws less likely to echo a warning if the caller was a female stranger from a different colony.

The paper, published in the journal Scientific Reports, is entitled: “Caller characteristics influence recruitment to collective anti-predator events in jackdaws.”

 

 

Birds wearing backpacks trace a path to conservation

Birds wearing backpacks trace a path to conservation (Samantha Knight And Ryan Norris, The Conversation; 9 May 2018; Photo: Julia Baak)

With the arrival of spring, we look forward to the return of hundreds of species of migratory songbirds from their wintering grounds.

Sparrows, swallows, warblers and thrushes, among other songbirds, will be returning from their wintering sites anywhere between the southern United States and distant South America.

Some of these birds will return with a small “backpack” that has recorded their entire migration from their North American breeding grounds to their wintering grounds and back.

Birds provide important ecosystem services, such as preying on insects, dispersing seeds, scavenging carcasses and pollinating plants. Unfortunately, there have been dramatic declines in many migratory songbirds over the past few decades, with some of these populations dropping by more than 80 per cent.

If we are to find ways to slow or reverse these declines, we must first figure out what’s causing them. Climate change, habitat loss and predation by cats are among the leading causes of bird declines.

But with the vast distances these birds move over the course of the year, it can be difficult to pinpoint the main cause for a given species —and where it’s occurring.

Migratory connections

To answer this question, we need to know where individual birds spend their time throughout the year.

We have a good idea of the range —or the total area —the birds occupy during the breeding and wintering periods. But ranges are composed of many populations, and we still have a very poor understanding of how individuals within each of these populations are connected between seasons.

Individuals from different breeding populations may remain segregated during the winter. For example, some ovenbirds winter in the Caribbean whereas others spend their winters in Mexico and Central America.

Or a bird may mix with individuals that originate from other breeding populations, such as bobolinks that mix in South America during the winter.

These patterns of migratory connectivity have critical implications for predicting how migratory songbirds will respond to environmental change.

Habitat loss —deforestation, for example —in one place can have different effects. If habitat loss occurs in a wintering area where breeding populations mix, it may have wide-ranging, yet diffuse, effects on the breeding populations. But if the habitat loss occurs in a wintering area that is occupied by a single breeding population, the effect may be more focused.

For example, habitat loss in South America will likely have range-wide effects on bobolinks, while habitat loss in the Caribbean may only influence a portion of the breeding populations of ovenbirds.

Backpacks for birds

We know that the breeding and wintering populations of most species mix to some extent, but…

Read more

Russian cuckoo invasion spells trouble for Alaskan birds, study finds

(Diana Yates, University of Illinois; 7  May 2018)

Common cuckoos and oriental cuckoos in eastern Russia appear to be expanding their breeding range into western Alaska, where songbirds are naive to the cuckoos’ wily ways, researchers report. A new study suggests the North American birds could suffer significant losses if cuckoos become established in Alaska.

Like brown-headed cowbirds, cuckoos are “brood parasites,” laying their eggs in the nests of other species, said University of Illinois animal biology professor Mark Hauber, who led the new research with Vladimir Dinets of the University of Tennessee, Knoxville. Cuckoos time their egg-laying so that their chicks will hatch first. The chicks then kick the other eggs out of the nest, “thereby eliminating the entire reproductive success of their hosts,” Hauber said.

“Brood parasitism is a rare strategy among birds. Only about 1 percent of birds engage in it,” he said. “Obligate brood parasites do it always. They never build a nest, they never incubate the eggs, they never feed their chicks. Instead, they sneak their eggs into somebody else’s nest, forcing the foster parent to take care of the young.”

Birdwatchers and ornithologists occasionally report seeing oriental cuckoos and common cuckoos in Alaska, and Alaskan natural history museums already contain a handful of cuckoo specimens collected locally, Hauber said. These birds are likely traveling from sites in Beringia, in eastern Russia.

“We don’t have evidence of them breeding in Alaska, but it’s likely already occurring,” Hauber said. “We wanted to know whether the potential Alaskan hosts are ready for this cuckoo invasion.”

In the new study, researchers tested whether more than a dozen Alaskan bird species had evolved defenses to counter the cuckoos’ parasitic ways. Such defenses are common among bird species that frequently encounter brood parasites elsewhere.

Read more

Should I stay or go? Birds migrate to save energy: study

(Mariëtte Le Roux; Nature Ecology & Evolution; 7 May 2018)

 

Why have some birds opted for a taxing life of constant migration—seeking out temperate climes to feed as winter arrives, only to return months later to breed?

Seemingly paradoxically, the behaviour is driven by a quest for energy efficiency, a study said Monday.

Migrating birds, researchers found, gain more energy from whatever is on the destination menu than they expend getting there and back, or could find without making the trek.

Why don’t they just stay in the warm place? Because there is too much competition for food with other species, said the study published in the journal Nature Ecology & Evolution.

Instead, they return to their cold, northern hemisphere home where they don’t have to fight others for the food there is.

The work “provides strong support for the hypothesis that birds distribute themselves in an optimal way in terms of energy,” study co-author Marius Somveille of the University of Oxford’s zoology department told AFP.

While it was known that birds migrate in search of food, it has remained a puzzle why they have adopted this exacting lifestyle.

The new study explains the behaviour of not only migratory birds, but also that of sedentary or “resident” ones, its authors said.

These too weighed the available food against greener pastures, and came to a different conclusion.

Most resident birds are found in the tropics, where food is easier to get by.

Fly or die

The study used a theoretical model to examine why birds migrate—about 15 percent of the total—while others do not.

It started with a model world with similar climatic differences between regions than our real one.

The researchers then added virtual birds, and the estimated amount of “energy”, or food, available in different regions.

Given these inputs, the model birds dispersed very similarly to what happened in real life.

The birds started off in the food-rich tropics, but growing competition forced some to start moving further afield.

“In our increasingly crowded virtual world, species progressively started exploiting more extreme pockets of seasonally available energy supply, often migrating longer distances,” the team wrote.

The model adds to our understanding of how Earth’s plants and animals came to be distributed as they are, the researchers added.

It could also be useful in predicting the future movements of other animals—to determine how they might migrate in response to global warming, for example.

When the Too-Early Bird Sings

(National Geography, Arnaud Da Silva, Mihai Valcu, and Bart Kempenaers, Max Planck Institute for Ornitholog; 2018)

In spring songbirds greet the rising and setting sun with a cacophony
of chirps meant to entice mates and claim territory. But artificial light
has made the night sky brighter and disrupted the seasonal rhythms
of birds that use day length as a cue to sing. Of six songbird species
that scientists studied in Germany, four started singing earlier in the year
because of night lighting. The long-term effects of light pollution on
birds’ ecosystems, and their survival, remain unclear.

Woodpeckers show signs of possible brain damage, but that might not be a bad thing

(Field Museum, ScienceDaily 2 February 2018; Photo:Arlene Koziol)

With woodpeckers, the answer’s in the question—true to their name, they peck wood. And when they do, they peck hard—with each peck, the bird undergoes a force of 1,200 to 1,400 g’s. By comparison, a measly force of 60-100 g’s can give a human a concussion. The fact that a woodpecker can undergo fourteen times that without getting hurt has led helmet makers to model their designs around these birds’ skulls. However, a new study in PLOS ONE complicates this story by showing that woodpecker brains contain build-ups of a protein associated with brain damage in humans.

“There have been all kinds of safety and technological advances in sports equipment based on the anatomic adaptations and biophysics of the woodpecker assuming they king. The weird thing is, nobody’s ever looked at a woodpecker brain to see if there is any damage,” says Peter Cummings of the Boston University School of Medicine, one of the new study’s authors.

To find the answer to this question, researchers used bird brains from the collections of The Field Museum and the Harvard Museum of Natural History and examined them for accumulation of a specific protein, called tau.

“The basic cells of the brain are neurons, which are the cell bodies, and axons, which are like telephone lines that communicate between the neurons. The tau protein wraps around the telephone lines—it gives them protection and stability while still letting them remain flexible,” explains lead author George Farah, who worked on the study as a graduate student at the Boston University School of Medicine.

In moderation, tau proteins can be helpful in stabilizing brain cells, but too much tau build-up can disrupt communication from one neuron to another. “When the brain is damaged, tau collects and disrupts nerve function—cognitive, emotional, and motor function can be compromised,” says Cummings.

Since excessive tau can be a sign of brain damage in humans, Farah and his team decided to examine woodpecker brains for tau build-up. The Field Museum and Harvard loaned the researchers bird specimens pickled in alcohol—Downy Woodpeckers for the experimental data and non-head-injury-prone Red-winged Blackbirds as a control. The researchers then removed the birds’ brains—“The brains themselves were well-preserved, they had a texture almost like modeling clay,” says Farah—and took incredibly thin slices, less than a fifth the thickness of a sheet of paper. The slices of brain tissue were then stained with silver ions to highlight the tau proteins present.

The verdict: the woodpeckers’ brains had far more tau protein accumulation than the blackbirds’ brains. However, while excessive tau buildup can be a sign of brain damage in humans, the researchers note that this might not be the case for woodpeckers. “We can’t say that these woodpeckers definitely sustained brain injuries, but there is extra tau present in the woodpecker brains, which previous research has discovered is indicative of brain injury,” says Farah.

“The earliest woodpeckers date back 25 million years—these birds have been around for a long time,” says Cummings. “If pecking was going to cause brain injury, why would you still see this behavior? Why would evolutionary adaptations stop at the brain? There’s possibility that the tau in woodpeckers is a protective adaptation and maybe not pathological at all.”

So, woodpeckers show signs of what looks like brain damage in humans, but it might not be a bad thing. Either way, the researchers believe that the study’s results could help us humans. For example, the knowledge about woodpecker brains that could help make football equipment safer for kds, says Cummings. On the other hand, he notes, “If the tau accumulation is a protective adaptation, is there something we can pick out to help humans with neurodegenerative diseases? The door’s wide open to find out what’s going on and how we can apply this to humans.”

Farah notes that the study relied heavily upon the museum collections that the bird brains came from. “Museums are gateways to the past and a source of new innovation,” he says. “The role of museums in this project was immense—we couldn’t have done our study with just one woodpecker.”

Ben Marks, The Field Museum’s Collections Manager of Birds, said of the researchers’ request to use the Museum’s bird brains, “With one of the world’s best bird collections, we’re always trying to let people know what we have, why we have it, and what it can be used for. We get over a hundred requests for specimen loans every year—this one stood out because it was a novel approach that had real world applications. Some of the specimens used in this study were collected in the 1960s. Our staff cared for them for over 50 years before until they were requested for this study and used in a way the original collector couldn’t even envision.”