Loon birds and their calls, video


This 1 September 2019 video says about itself:

The eerie calls of Common Loons echo across clear lakes of the northern wilderness. Summer adults are regally patterned in black and white. Listen to the calls of the four other types of North American Loons.

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American cowbirds, polygamy and monogamy


This April 2017 video says about itself:

These Birds Trick Others Into Raising Their Gigantic Kids | Today I Learned

In this week’s Today I Learned, National Geographic explorer Luke Powell tells you about some of the worst bird parents out there – brood parasites. These birds don’t build nests, but sneak their eggs into other birds’ nests and fly.

From the University of Illinois College of Liberal Arts & Sciences in the USA:

A closer look at monogamy and polygamy in brood parasitic birds

September 30, 2019

Summary: Researchers have discovered that cowbirds conform to Bateman’s Principle, despite investing no energy into parental care. Surprisingly, 75% of the cowbirds in the system were monogamous. Future research will expand upon these findings and broaden the understanding of how cowbirds might select the nests they parasitize, what role the males could play to assist the females, and why monogamy could be such a benefit.

Researchers at the University of Illinois have shown through a multi-year study that cowbirds (Molothrus ater) conform to Bateman’s Principle, which holds that reproductive success is greater in males than in females when they have more mates. Cowbirds are distinct from 99% of other bird species in that they are brood parasites and lay their eggs in nests of birds of other species for them to raise. The researchers confirm a 70-year old theory that males in this species are more likely than females to have greater variation in the number of offspring they produce.

While Bateman’s Principle has been shown to be accurate in many species, the research team at Illinois wanted to see if this nest parasite parenting style of the cowbird would change the variation of reproductive success between males and females.

To do this, the team placed nestboxes for the host species prothonotary warbler (Protonotaria citrea) in 15 sites across the Cache River watershed in southern Illinois. Between 2007 and 2013, researchers collected DNA from over 1500 adult cowbirds and offspring from the sites and used the software COLONY to evaluate genetic relationships and determine a pedigree structure between adult and young parasites.

“The great part about using this program was that it made it possible for us to create genetic profiles of adults that we weren’t able to catch,” said study co-author Prof. Mark Hauber. “You end up getting these broods that are from the same parents or have one parent in common and you can extrapolate from the data to create genetic profiles of the other ‘virtual’ parent.”

Results from the study indicate that cowbirds do conform to Bateman’s Principle, with males exhibiting greater variance in the number of mates they had and the number of offspring they sired.

“The females clearly had preferences for certain males, which end up siring more offspring. That kind of selection just doesn’t happen in the females, which is what we would expect to see if Bateman’s Principle applies,” said Dr. Wendy Schelsky, the study’s senior-author. “This is supported by the pattern that cowbirds exhibit sexual dichromatism — the sexes look different, in other words. The males are iridescent dark and shiny and sing a complex song, whereas the females are brown and more cryptic.”

However, the data also suggested an unexpected result — approximately 75% of the cowbirds in the system were monogamous for the whole breeding season, despite not providing their offspring with food or other resources. “These birds are emancipated from the costs needing a mate to take care of the young, and yet they are engaging in monogamy. It’s the opposite of what you would predict by theory,” said Hauber.

There are a number of potential explanations for this finding, including benefits that paired males provide females that might not be immediately obvious. “There were a lot of males in the system, so females are not limited by their ability to choose males. Females were the rarer sex in this system, so the fact that they’re monogamous indicates that they receive some sort of benefit from only choosing one male,” Schelsky explained.

“This study is about the discovery of how sexual selection works in systems that are not considered ‘normal’ — in terms of parenting styles, in this case,” added Schelsky. “Our system also gave us the opportunity to be one of the most comprehensive studies providing detailed field data on the number of offspring that are produced each year by female brood parasites. The access that we were able to get with the samples — we were able to genetically profile over 1500 individual cowbirds. It gives us a really good idea of what’s going on with these birds on a larger scale.”

Future research will expand upon these findings and broaden the understanding of how cowbirds might select the nests they parasitize, what role the males could play to assist the females, and why monogamy could be such a benefit.

Purple martin migration, unexpected research results


This 29 July 2019 video from Pennsylvania in the USA says about itself:

Life in a Purple Martin nest: 2019 nestcam recap

Watch as a nest of Purple Martins at the Purple Martin Conservation Association headquarters in Erie, PA progresses from eggs to fledglings.

Purple Martins are completely reliant on humans to survive. Learn how you can help here.

2019 was a great year for our livestream nest, but not without drama. As you see in the video, we encountered a “capped egg”, subadult martins causing problems, a nestling whose airway was blocked by a large dragonfly, a near miss by a hungry Cooper’s Hawk, and a House Wren intent on pecking the nestlings. Such is life for the Purple Martin, a struggle to survive in the face of habitat loss, predators, and competition.

Incredibly, these parents (nicknamed Carl and Jolene) successfully raised and fledged seven birds…the highest number we’ve witnessed.

From the University of Illinois at Urbana-Champaign, News Bureau in the USA:

Purple martin migration behavior perplexes researchers

September 30, 2019

Purple martins will soon migrate south for their usual wintertime retreat, but this time the birds will be wearing what look like little backpacks, as scientists plan to track their roosting sites along the way.

The researchers recently discovered that purple martins are roosting in small forest patches as they migrate from North America to Brazil. The scientists published their findings in the Journal of Field Ornithology.

“This is highly unusual behavior for songbirds, which typically roost in heavily forested areas,” said Auriel Fournier, a co-author of the study with University of Manitoba biological sciences professor Kevin Fraser, who led the research. Fournier is the director of the Forbes Biological Station at the Illinois Natural History Survey.

“It’s surprising to see them roosting in these forest islands, which are small, isolated clusters of trees typically surrounded by agriculture, water or recently cut forest,” Fournier said.

The researchers want to determine whether the birds are responding to a change in the environment or whether their surprising roosting behavior is something purple martins have always done.

“We believe they must be intentionally seeking out the forest islands,” Fournier said. “Because these habitats don’t occur very frequently on the landscape, the birds’ use of them is unlikely to be by chance.”

“We are curious if birds are choosing these isolated patches of habitat because they have fewer predators than in larger patches of forest,” Fraser said.

About 13% of the world’s birds are colonial nesters, and purple martins are the only songbird species that requires a nest site surrounded by the nests of other similar birds, the researchers said.

“During migration, these birds flock in numbers up to the hundreds of thousands,” Fournier said. “It’s wild because their flocks are sometimes big enough to be detected by radar.”

The researchers had to wait for technology to catch up before they could identify precisely where the birds were stopping to rest during migration. A purple martin weighs about 1.6 ounces (45 grams) and flies an estimated 6,200 to 13,700 miles (10,000 to 22,0000 kilometers) a year. Too much additional weight — even that of a tiny tracker, for example — could interfere with the bird’s trek.

Thanks to advances in technology, the scientists are using GPS tracking devices small enough to be carried by purple martins. The devices use satellites to pinpoint the birds’ location with such accuracy that Fraser and Fournier can identify down to a single tree where a tagged purple martin is roosting at night during migration.

“No one has looked at habitats during migration,” Fraser said. “But we need to look so that we can start protecting these birds and their habitats across international boundaries.”

The researchers plan to continue tracking purple martins, monitoring whether they faithfully return to the same roosting sites in forest islands. And they are working with conservation groups across this species’ range to better preserve purple martin habitat.

Long ago, I saw purple martins wintering in a park in Quito, Ecuador.

How Venus flytraps catch insects, spiders


This 27 September 2019 video says about itself:

Venus flytraps rarely catch flies, despite their name — instead, spiders and ants make up most of their diet. When a victim walks by and brushes against a trigger hair on the inside of the trap’s modified leaves, it sets off an electrical signal. If the bug doesn’t escape within 20 to 30 seconds, the trap slams shut faster than you can blink!

Ice Age North American big mammals’ extinction


This August 2019 video says about itself:

Until the end of the last ice age, many giants called North America home. It has long puzzled scientists why these animals and other megafauna — creatures heavier than 100 lbs. (45 kilograms) — went extinct about 10,000 years ago.
Rapid warming periods called interstadials and, to a lesser degree, ice-age people who hunted animals are responsible for the disappearance of the continent’s megafauna, according to studies.

Both research and the debate surrounding the reasons for the extinction of these animals will undeniably continue. In the meantime, researchers continue to find fossils of these massive creatures.

Here’s a look at 14 such extinct giant animals from the last North American ice age, and what scientists know about their lives.

1. North American Horses
2. Glyptodon
3. American lion
4. Smilodon fatalis
6. Mastodons
7. Mammoths
8. Giant Short-faced bear
9. Dire wolf
10. American cheetah
11. Ground sloths
12. Giant beaver
13. North American Camels

From the University of Nebraska-Lincoln in the USA:

Division by subtraction: Extinction of large mammal species likely drove survivors apart

Disappearance of mammoths, other giants likely reduced interactions of smaller mammals

September 19, 2019

Summary: A new study suggests that the extinctions of mammoths, dire wolves and other large mammal species in North America drove surviving species to distance themselves from their neighbors, reducing interactions as predators and prey, territorial competitors or scavengers. The discovery could preview the ecological effects of future extinctions, the researchers say.

When a series of large mammal species began going extinct roughly 12,000 years ago, many surviving species began going their separate ways, says new research led by Macquarie University and the University of Nebraska-Lincoln.

Published Sept. 20 in the journal Science, the study analyzed distributions of mammal fossils across North America following the last ice age, after the retreat of massive glaciers that had encroached south to the modern-day United States. The aftermath saw the disappearance of many famously large mammal species: mammoths, mastodons, saber-toothed cats, dire wolves and ground sloths, among others.

Surviving mammal species often responded by distancing themselves from their neighbors, the study found, potentially reducing how often they interacted as predators and prey, territorial competitors or scavengers.

The ecological repercussions of the extinctions are likely still echoing today and could preview the effects of future extinctions, said study co-author Kate Lyons.

“For 300 million years, the (cohabitation) pattern of plants and animals looked one way — and then it changed in the last 10,000 years,” said Lyons, assistant professor of biological sciences at Nebraska. “This paper addresses how that happened in mammal communities.

“If connectedness among species makes ecosystems more stable, what this suggests is that we’ve already lost a lot of those links. What this potentially tells us is that modern ecosystems are probably more vulnerable than we think they are.”

Led by Macquarie’s Anikó Tóth, the team analyzed records of 93 mammal species at hundreds of fossil sites during three timespans: 21,000 to 11,700 years ago, when the extinctions began; 11,700 to 2,000 years ago; and 2,000 years ago to the present. The researchers then assessed whether, and to what extent, a given species lived among each of the other 92 at those sites.

That data allowed the team to calculate how often a random pair of species would be expected to cohabit a site, providing a baseline for whether each pair overlapped more or less often than predicted by chance — aggregating vs. segregating, respectively. The proportion of aggregating pairs generally declined following the extinctions, and the strength of associations often dropped even among species that continued to aggregate, the researchers found.

“The loss of the giant carnivores and herbivores changed how small mammals such as deer, coyotes and raccoons interacted,” Tóth said. “Our work suggests that these changes were triggered by the ecological upheaval of the extinctions.”

Tóth, Lyons and their 17 co-authors effectively ruled out climate change and geography as drivers of the growing division. Surprisingly, the team also concluded that surviving species began cohabiting less frequently even as they expanded into larger swaths of their respective geographic ranges.

Lyons said the specific reasons for the seeming paradox and the overall trends are unclear, though the ecological consequences of losing species such as the mammoth could explain them. Mammoths toppled trees, compacted soil and, by eating and excreting masses of vegetation, transported nutrients around ecosystems, Lyons said. Those behaviors helped sustain the so-called mammoth steppe, an ecosystem type that once covered vast areas of the Northern Hemisphere. The loss of the mammoth effectively doomed the mammoth steppe, possibly compartmentalizing the expanses of land that hosted many species.

“If you’re an open-habitat species that used to occupy the mammoth steppe, and now the mammoth steppe has gone away, you might inhabit, say, open grassland areas that are surrounded by forests,” Lyons said. “But that meadow is much smaller. Instead of supporting 10 species, it now might support five. And if those patches of open habitat are spread farther apart, you might expand your geographic range and potentially your climate range, but you would co-occur with fewer species.”

Also uncertain: why common species became more common, and some rare species became even rarer, following the extinctions. Continuing to study the dynamics underlying such trends could help sharpen perspectives on current ecosystems and their possible fates, the researchers said.

“We had a complement of large mammals in North America that was probably more diverse than what we see in Africa today,” Lyons said. “Additional extinctions could have a cascading effect and huge implications for the mammal communities that we have left.”

Tóth, Lyons and their co-authors represent 18 institutions from Australia, the United States, Chile, Portugal, Finland, Canada and Denmark. All are members of the Evolution of Terrestrial Ecosystems Program at the Smithsonian Institution, which funded the team’s research.

This video is called The Short-Faced Bear: America’s Top Predator.

From the University of Arkansas in the USA:

Anthropologist contributes to major study of large animal extinction

September 20, 2019

As part of an international research group based at the Smithsonian Museum of Natural History, anthropology assistant professor Amelia Villaseñor contributed to a large, multi-institutional study explaining how the human-influenced mass extinction of giant carnivores and herbivores of North America fundamentally changed the biodiversity and landscape of the continent.

In their study published today in Science, researchers from Australia, the United States, Canada and Finland showed that humans shaped the processes underlying how species co-existed for the last several thousand years. Smaller, surviving animals such as deer changed their ecological interactions, the researchers found, causing ecological upheaval across the continent.

The researchers’ work has implications for conservation of today’s remaining large animals, now threatened by another human-led mass extinction.

The study’s primary author is Anikó Tóth at Macquarie University in Sydney, Australia. Tóth collaborated with Villaseñor and several other researchers at the Smithsonian’s Evolution of Terrestrial Ecosystems Program, as well as researchers at other institutions.

Tóth and the co-authors focused on how large mammals were distributed across the continent in the Pleistocene and Holocene geological epochs. (The Pleistocene Epoch occurred from about 2.5 million to 11,700 years ago. Starting at the end of the Pleistocene, the Holocene is the current geological epoch.) To do this, the researchers analyzed how often pairs of species were found living in the same community or in different communities.

To rule out community changes that were the result of reduced diversity or lost associations involving extinct species, the researchers analyzed only those pairs in which both species survived. Prior to the extinction, co-occurrence was more common. After extinction, segregations were more common.

Villaseñor’s research focuses on human fossil remains as a way to understand how human ancestors interacted with mammal communities for the last 3.5 million years. Her more recent research explores how modern humans have shaped today’s ecosystems.

“Rather than thinking of humans as separate from ‘natural’ environments, our research has illuminated the major impacts that humans have had on the ecosystem for many thousands of years,” Villaseñor said. “The results of this paper and others from our group illuminate the outsized impacts that human-mediated extinction has had in North America.”

By the end of the Late Pleistocene in North America, roughly 11,000 years ago, humans contributed to the extinction of large mammals, including mammoths and sabre-toothed cats. Recent work, driven by today’s crisis in biodiversity, has looked at understanding the ecological and evolutionary legacies of this event. There was ecological transformation across the continent — the mammoth steppe disappeared, vegetation and fire regimes changed and large carnivores were lost.