American whooping cranes in danger


This December 2013 video from the USA says about itself:

This week’s moment in nature takes us among the whooping cranes of the Aransas National Wildlife Refuge in Texas.

From ScienceDaily:

Whooping cranes form larger flocks as wetlands are lost — and it may put them at risk

April 2, 2020

Over the past few decades, the critically endangered whooping crane (Grus Americana) has experienced considerable recovery. However, in a report appearing April 2 in the journal Heliyon, researchers found that habitat loss and within-species attraction have led whooping cranes to gather in unusually large groups during migration. While larger groups are a positive sign of species recovery, the authors say that these large groups mean that a disease outbreak or extreme weather event could inadvertently impact a substantial portion of this still fragile population.

Whooping crane conservation is one of North America’s great success stories,” says Andrew Caven, Director of Conservation Research at Crane Trust, a non-profit organization dedicated to the protection of critical habitat for whooping cranes and other migratory birds. During the 1940s the whooping crane population fell to 16 birds, largely due to overhunting. However, after concerted conservation efforts, their numbers have increased 30-fold. “We had this species at the brink of extinction, and now there are over 500 birds. As conservation biologists, we’ve been extremely inspired by that.”

Even with this boom in whooping crane numbers, researchers are observing larger migratory flocks than they would expect from population growth alone. Historically, groups of migrating whooping cranes seldom exceeded a family unit. “Twenty years ago, a group of nine was notable; something you’d write in your natural history notes about. But now it’s becoming something quite regular. In the recent years we’ve seen bird groups over seventy multiple times.”

With a total population of only around 500 birds, groups of this size could potentially put the whole species at risk. “The largest group detected was about 150 birds near Marcelin, Saskatchewan, which represents over one-fourth of the population. In a group that size, extreme weather like hailstorms or an outbreak of avian cholera could be catastrophic for the species,” says Caven.

So Caven and his research team set out to understand why traveling groups of whooping cranes had grown so large. They collected sightings data from state, federal, and private conservation organizations as well as the public along the whooping cranes migratory path from their Texas wintering grounds to their breeding grounds in Alberta, Canada.

Results indicated that the larger flocks of whooping crane roosted most frequently in the Southern Great Plains, where wetland habitats are sparse, but a few, high-quality conserved wetlands still stand.

“Many wetland habitats in the Great Plains have disappeared due to sedimentation or have been drained for farming” says Caven. “The rate of wetland loss has actually been quite high, particularly in these basins south of the Platte River.” With limited access to quality habitat in the southward part of their migration, it appears whooping crane have adjusted by gathering in proportionally larger assemblages.

As a sort of snowball effect, the authors say these gatherings can also be promoted by conspecific attraction or attraction to like individuals. The presence of birds in a location can make it more desirable for other cranes. “Conspecific attraction helps birds indicate optimal forging resources in these patchy environments and provide vigilance in situations that could be risky. These benefits could be a major reason we are seeing the emergence of these new behaviors as the cranes recover from near extinction,” he says.

Based on these findings, Caven suggests the best way to disperse these groups is to provide more wetland habitat throughout their migration path. “Supporting conservation groups that are restoring habitats south of the Platte River, particularly wetlands, can have a serious impact. Increasing the scale of wetland restoration within the migration corridor could break up these aggregations and provide foraging space for a ton of birds, not just whooping crane.”

The Crane Trust research team also plans to evaluate how habitat quality affects the length of time whooping cranes stay at stopover locations before continuing on in their migration. This will help determine those sites that are most essential in providing necessary resources for the birds to complete their 3,000-mile journey.

Niagara Falls, a barrier for fish


This video from North America says about itself:

Niagara River 2019

Niagara River below the surface

From the American Museum of Natural History in the USA:

Is Niagara Falls a barrier against fish movement?

March 24, 2020

New research shows that fishes on either side of Niagara Falls — one of the most powerful waterfalls in the world — are unlikely to breed with one another. Knowing how well the falls serves as a barrier to fish movement is essential to conservation efforts to stop the spread of invasive aquatic species causing ecological destruction in the Great Lakes. The study is published today in the journal Molecular Ecology.

“In the past 50 years or so, aquatic invasive species have expanded in the Great Lakes as a tremendous conservation concern, causing billions of dollars’ worth of damage,” said Nathan Lujan, lead author of the study and a Gerstner Scholar at the American Museum of Natural History. “Both Canadian and American authorities are concerned about the potential impact of these species on the Great Lakes and are very interested in installing barrier technologies in the Niagara River that would slow or stop their spread.”

For more than 11,000 years since glaciers retreated from North America, most water flowing through the Great Lakes has crossed the Niagara Falls, which has a flow rate of more than 750,000 gallons per second. There’s one other way water can get through this constriction point: through the Welland navigation canal, which was built about 200 years ago and features a series of locks that bring vessels from one side of the falls to the other. The canal is relatively small compared to the Niagara River, but questions remain about how significant it and the falls are in allowing fishes to move upstream to downstream, and vice versa. The leading idea is to install a combination of barrier technologies in the Welland Canal, including electricity, sound, light, and possible physical barriers to inhibit fish movement.

“If you’re going to spend potentially hundreds of millions of dollars on installing barrier technologies and fishes can go right over the falls, then that’s obviously not a good use of resources,” Lujan said. “If people can survive it in a barrel, you’d think a fish could.”

To investigate these questions, Lujan and colleagues examined the DNA of seven native fish species to determine whether populations above and below Niagara Falls interbreed or are reproductively isolated. By gathering data from throughout the fishes’ genomes, they found that populations of all species are genetically distinct on opposite sides of the falls.

Then they modeled how DNA from different populations mix, and determined that in four species there has been no significant migration past Niagara Falls since the falls were first formed 11,000 years ago. Two other species showed some indication of migration past the falls, yet the models indicated that no species had migrated past the falls via the Welland Canal.

“These results should reassure policymakers that infrastructure being considered to prevent the movement of invasive aquatic species will not impact native species, and that the falls themselves are an effective barrier to both upstream and downstream movement of aquatic species,” Lujan said. “Additional measures to prevent fish movement can safely be restricted to the Welland Canal.”

North American birds biodiversity, new research


This 2017 video says about itself:

The National Geographic Guide to Birding in North America | The Great Courses

Look into six categories of bird behavior, as they provide vital information for identification. See how individual species are distinguished by typical or unique behavioral traits. Study the distinctive feeding habits of many species, and how we can recognize species from flight and flocking behavior. End by exploring the extraordinary mating and nesting customs of North American birds.

From Washington University in St. Louis in the USA:

Birds of a feather better not together

‘Homogenization’ threatens ecosystems at larger geographic scales

March 4, 2020

Diversity plays a key role in maintaining the stability of plant and animal life in an area. But it’s difficult to scale up smaller experiments to understand how changes will impact larger ecosystems.

A new study of North American birds from Washington University in St. Louis finds that the regional stability of ecosystems over time depends on both the total number of species present in a locality and on the variation in species identities among localities.

The results have implications for maintaining a diverse portfolio of local species in the face of major environmental threats — like climate change, biological invasions, intensifying land use and other human and natural disturbances. “Homogenization” may threaten ecosystems at larger geographic scales, the research suggests. The study is published March 4 in the Proceedings of the Royal Society B.

“Species diversity is changing in more complicated ways than just going up or down, or the total number of species,” said lead author Christopher P. Catano, a recent PhD graduate of Washington University and current postdoctoral research associate at Michigan State University. “One of the most critical and conspicuous ways that diversity is changing is by changing the distribution of species across space.”

Recent high-profile studies have tried to show how and why biodiversity is changing at regional to global scales. Scientists have sounded alarms about net losses of insect, fish, bird and plant species. Many fear that such losses may alter the functioning of ecosystems and upend their ability to provide critical goods and services that humans rely on.

“The study provides some of the first evidence to suggest that local biodiversity loss and biotic homogenization will impact the functioning and stability of ecosystems at macroscales,” said Jonathan Myers, associate professor of biology in Arts & Sciences.

A diverse portfolio — of birds

The greater the number of species in an ecosystem, the more that ecosystem tends to be stable. The general reason why this happens is something called an insurance effect.

In concept, it’s similar to why investors might want to have a diverse set of stocks in their portfolio. If one stock performs poorly, there’s a chance that it will be buffered by others that perform better than expected.

“Over time, these different stocks — or these different species, in the context of an ecosystem — can compensate for one another,” Catano said. “The fact that species may respond differently to the same environmental change is what gives that insurance effect.”

This idea is widely accepted by biologists. The basic mechanism has been confirmed by lots of studies over time, and it underlies many arguments to promote or conserve biodiversity.

But it’s not without its limitations. For example, much of the supporting research was conducted at a relatively small scale. One notable experiment was completed on plots of land that measured only about half as long as a bowling alley, each neatly planted with varying numbers and species of seeds.

Real life is not so clean. The ground is not perfectly flat, rivers cut through breeding areas, and animals and seeds travel across large areas. Ecosystem management often occurs within and across large tracts of land.

“At larger scales, it’s not just the number of species that’s potentially varying, it’s also the identity or the composition of those species across space,” Catano said.

“So there are two components to regional stability,” Catano said. “One is how stable your average local community is. And the second is how differently those local communities respond through time — relative to each other.”

Observations at a larger geographic scale

Catano and Myers decided to try to test the relative importance of these two factors — the number of species, and the amount of site-to-site variation in species composition — in determining the stability of ecosystems at a larger scale.

The researchers used 20 years of observational data from the North American Breeding Bird Survey, a joint effort of the U.S. Geological Survey and Environment Canada. They focused on 342 species of songbirds in 1,675 breeding bird “communities” — the census-block-like geographic units routinely sampled in the Breeding Bird Survey — distributed across 35 large bird-conservation regions.

The researchers used the production of total bird biomass over time as their measure of ecosystem stability.

They found that species count does matter for stability — but site-to-site variation in species composition matters three times as much at the larger geographic scale of bird conservation regions.

And what happens at a larger scale with birds is likely to affect humans, too. “Birds are major consumers of insect pests that limit production of plants and therefore ecosystems. Also, a lot of plants are dependent on seed dispersal by birds,” Catano said. “There’s a lot of critical services that are mediated by birds.”

A landscape that supports variation

The results have implications for conservation, the researchers said.

Land use managers have a key role to play in promoting variation across an area, the researchers said, by taking advantage of management techniques that introduce or maintain environmental heterogeneity.

“An example might be through grazing,” Catano said. “Animals graze somewhat patchily, and those patches create meaningful variation in the composition of other species. Fire management, or controlled burns, is another measure that, when done appropriately, can increase the resource heterogeneity in an ecosystem.

“These are things that land managers and conservation practitioners are already doing,” he added. “This just cues them into this other dimension of biodiversity that’s often overlooked when they assess the success of their restoration or management effort.

“Changes that lead to something like biotic homogenization could be destabilizing for ecosystems, even if it doesn’t lead to the loss of species.”

North American dark-eyed junco evolution


This is a dark-eyed junco video from Canada.

Snowbirds Skip Migration, Setting Off a Cascade of Changes: By and large, Dark-eyed Juncos live up north and visit the rest of the continent in winter—they’re “snowbirds.” But around 1980, a few pairs in San Diego decided to skip the trip north. This is the story of what happened next: the birds quickly adapted their plumage, song, and nesting behavior, forcing scientists to rethink ideas about the speed of evolution: here.

Black-throated blue warbler migration, new research


This 2017 video says about itself:

Black-throated blue Warbler

Although fairly common in northeastern North America (Appalachians) in deciduous and mixed undergrowth it was a challenge to film. The male as shown here singing is clean cut with blue, black, and white. Its black throat, cheeks and sides contrast with the white underparts. It has a blue-gray back and a bold white patch on its dark wings.

The female and Immature is more drab. They have brownish-olive upperparts with buffy underparts. There is a white eyebrow stripe and a small whitish wing patch.

From the American Ornithological Society Publications Office:

Fifty years of data show new changes in bird migration

February 20, 2020

A growing body of research shows that birds’ spring migration has been getting earlier and earlier in recent decades. New research from The Auk: Ornithological Advances on Black-throated Blue Warblers, a common songbird that migrates from Canada and the eastern U.S. to Central America and back every year, uses fifty years of bird-banding data to add another piece to the puzzle, showing that little-studied fall migration patterns have been shifting over time as well.

Loyola Marymount University’s Kristen Covino and her colleagues used data housed at the USGS Bird Banding Laboratory on migrating Black-throated Blue Warblers between 1965 and 2015. Across the United States, researchers working with this program safely capture migrating birds, collect data on them, and fit them with metal leg bands with unique codes that allow them to be identified if they’re captured again. Analyzing almost 150,000 individual records, Covino and her colleagues found that the timing of the birds’ spring migration has advanced over the last fifty years, with early migrants passing through banding sites approximately one day earlier each decade. Crucially, their data also covered fall migration, which has been less well-studied, and found that while the timing of the peak of fall migration hasn’t changed, fall migration takes longer today than it did fifty years ago.

The North American Bird Banding Program is one of the most expansive historical datasets on migratory birds, including records for over 38 million songbirds banded since 1960. “My coauthor Sara Morris and I were already working together on another paper on Blackpoll Warblers using data we’d requested from banding stations across North America. We wanted to take a similar large-scale approach for this study, but we wanted to demonstrate that we could do this approach with data that is completely available from the Bird Banding Lab,” says Covino. “We selected Black-throated Blue Warblers because it’s relatively straightforward to determine their age and sex, which means that the data this species generates are both accurate and powerful.”

Although the researchers emphasize that their findings can’t be explicitly linked to climate change without incorporating climate or environmental data, they believe similar methods could be useful for tracking the effects of climate change on birds. “The protraction of fall migration means that the season is getting longer overall, but it could also mean that the breeding season may be shifting, ending earlier for some individuals but later for others. To determine what this means in the context of breeding season shifts in timing, additional studies that incorporate both arrival on the breeding grounds and, importantly, departure from them are needed,” says Covino. “More studies of these patterns of fall migration timing and, even more so, both spring and fall migration timing across years are needed to gain the complete picture of how species are changing migration timing.”