New list of American bird species


This is a video about a turquoise-browed motmot in Costa Rica.

From the American Ornithological Society Publications Office:

Goodbye northwestern crow, hello Mexican duck

Updates to the official list of North and Central American bird species

June 30, 2020

The latest supplement to the American Ornithological Society’s Checklist of North and Middle American Birds, published in The Auk: Ornithological Advances, includes several major updates to the organization of the continent’s bird species, including the addition of the Mexican Duck and the removal of the Northwestern Crow. The official authority on the names and classification of the region’s birds, the checklist is consulted by birdwatchers and professional scientists alike and has been published since 1886.

The Northwestern Crow has long been considered a close cousin of the more familiar and widespread American Crow, with a range limited to the Pacific Northwest. However, a recent study on the genetics of the two species prompted AOS’s North American Classification Committee to conclude that the two species are actually one and the same. “People have speculated that the Northwestern Crow and the American Crow should be lumped for a long time, so this won’t be a surprise to a lot of people,” says the U.S. Geological Survey’s Terry Chesser, chair of the committee. “Northwestern Crows were originally described based on size, being smaller than the American Crow, and behavior, but over the years the people who’ve looked at specimens or observed birds in the field have mostly come to the conclusion that the differences are inconsistent. Now the genomic data have indicated that this is really variation within a species, rather than two distinct species.”

However, birdwatchers disappointed to lose the Northwestern Crow from their life lists can take solace in the addition of a new species to the official checklist: the Mexican Duck. “The checklist recognized Mexican Duck until 1973, when it was lumped with Mallard,” says Chesser. “But the Mexican Duck is part of a whole complex of Mallard-like species, including Mottled Duck, American Black Duck, and Hawaiian Duck, and all of those are considered distinct species except for, until recently, the Mexican Duck. Now genomic data have been published on the complex and on the Mexican Duck and Mallard in particular, and they show that gene flow between them is limited, which was enough to convince the committee to vote for the split.”

Additional changes introduced in this year’s checklist supplement include a massive reorganization of a group of Central American hummingbirds known as the emeralds — adding nine genera, deleting six others, and transferring seven additional species between already-recognized genera — as well as an update to the criteria for adding introduced, non-native species to the list that raises the bar for introduced species to officially be considered established.

North American migratory birds, video


This 10 June 2020 video from the USA says about itself:

More than half of the migratory bird species in North America are declining. In order to conserve these migrating birds, conservation scientist and National Geographic explorer Kristen Ruegg is tracking bird DNA with the Bird Genoscape Project.

American robin migration and climate change


This 2019 video from the USA is called 5 Lovable Things About American Robins.

From the Earth Institute at Columbia University in the USA:

American robins now migrate 12 days earlier than in 1994

New GPS data show birds adjust to shifting snow conditions as climate warms

April 1, 2020

Summary: A new study concludes that robin migration is kicking off earlier by about five days each decade. The study is also the first to reveal the environmental conditions along the migration route that help the birds keep up with the changing seasons.

Every spring, American robins migrate north from all over the U.S. and Mexico, flying up to 250 miles a day to reach their breeding grounds in Canada and Alaska. There, they spend the short summer in a mad rush to find a mate, build a nest, raise a family, and fatten up before the long haul back south.

Now climate change is making seasonal rhythms less predictable, and springtime is arriving earlier in many parts of the Arctic. Are robins changing the timing of their migration to keep pace, and if so, how do they know when to migrate? Although many animals are adjusting the timing of their migration, the factors driving these changes in migratory behavior have remained poorly understood.

A new study, published in Environmental Research Letters, concludes that robin migration is kicking off earlier by about five days each decade. The study is also the first to reveal the environmental conditions along the migration route that help the birds keep up with the changing seasons. Lead author Ruth Oliver completed the work while earning her doctorate at Columbia University’s Lamont-Doherty Earth Observatory.

At Canada’s Slave Lake, a pit stop for migrating birds, researchers have been recording spring migration timing for a quarter-century. Their visual surveys and netting censuses revealed that robins have been migrating about five days earlier per decade since 1994.

In order to understand what factors are driving the earlier migration, Oliver and Lamont associate research professor Natalie Boelman, a coauthor on the paper, knew they needed to take a look at the flight paths of individual robins.

Their solution was to attach tiny GPS “backpacks” to the birds, after netting them at Slave Lake in mid-migration. “We made these little harnesses out of nylon string,” Oliver explained. “It basically goes around their neck, down their chest and through their legs, then back around to the backpack.” The unit weighs less than a nickel — light enough for the robins to fly unhindered. The researchers expect that the thin nylon string eventually degrades, allowing the backpacks to fall off.

The researchers slipped these backpacks onto a total of 55 robins, tracking their movements for the months of April through June. With the precise location from the GPS, the team was able to link the birds’ movements with weather data on air temperature, snow depth, wind speed, precipitation, and other conditions that might help or hinder migration.

The results showed that the robins start heading north earlier when winters are warm and dry, and suggest that local environmental conditions along the way help to fine-tune their flight schedules.

“The one factor that seemed the most consistent was snow conditions and when things melt. That’s very new,” said Oliver. “We’ve generally felt like birds must be responding to when food is available — when snow melts and there are insects to get at — but we’ve never had data like this before.”

Boelman added that “with this sort of quantitative understanding of what matters to the birds as they are migrating, we can develop predictive models” that forecast the birds’ responses as the climate continues to warm. “Because the timing of migration can indirectly influence the reproductive success of an individual, understanding controls over the timing of migratory events is important.”

For now, it seems as though the environmental cues are helping the robins to keep pace with the shifting seasons. “The missing piece is, to what extent are they already pushing their behavioral flexibility, or how much more do they have to go?” said Oliver.

Because the study caught the birds in mid-migration, the tracking data doesn’t reflect the birds’ full migration path. To overcome this limitation, the researchers plan to analyze tissue from the robins’ feathers and claws, which they collected while attaching the GPS harnesses, to estimate where each bird spent the previous winter and summer.

Over the long term, Oliver says, she hopes to use the GPS trackers to sort out other mysteries as well, such as how much of the change in migration timing is due to the behavioral responses found in the study versus natural selection to changing environments, or other factors.

“This type of work will be really cool once we can track individuals throughout the course of their life, and that’s on the near-term horizon, in terms of technological capabilities,” she said. “I think that will really help us unpack some of the intricacies of these questions.”

The new study is part of a broader NASA-funded research and outreach project, called the Arctic-Boreal Vulnerability Experiment, that is tracking how the rapid warming of the far north affects wildlife. Read more about the project on the researchers’ blog: https://earthobservatory.nasa.gov/blogs/fromthefield/2016/04/12/a-migration-mystery/

Oliver is now a postdoctoral associate at Yale University. Other authors on the study include Peter Mahoney from the University of Washington, Eliezer Gurarie from the University of Washington and the University of Maryland, Nicole Krikun from the Lesser Slave Lake Bird Observatory, Brian Weeks from the University of Michigan, Mark Hebblewhite from the University of Montana, and Glen Liston from Colorado State University.

With the western United States and northern Mexico suffering an ever-lengthening string of dry years starting in 2000, scientists have been warning for some time that climate change may be pushing the region toward an extreme long-term drought worse than any in recorded history. A new study says the time has arrived: a megadrought as bad or worse than anything even from known prehistory is very likely in progress, and warming climate is playing a key role. The study, based on modern weather observations, 1,200 years of tree-ring data and dozens of climate models, appears this week in the leading journal Science: here.

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.”