3 Billion Birds

[The Shrike]

Not seeing another thread on this yet so I'll start one.

With great fanfare, a new paper was published yesterday in Science estimating that overall abundance of North American birds is 3 billion fewer than in 1970. Here's a synopsis. NPR's reporting on the story here. Here's a companion website to the paper, with suggestions for things folks can do to help native birds.

This seems to be getting peoples' attention because the number is so jarring, but to ecologists and birders it is not surprising at all. It's still depressing as heck, but it's not surprising.

I'm not an author on this paper, but I'm happy to discuss it, review the science behind it, etc.

 

[Darat]

All those windmills!

 

[crescent]

The study doesn’t address why birds are disappearing,

Habitat loss? Cats? Windmills? Reflective windows on skyscrapers? Polarized reflections off glass and chrome?

There have also been studies showing significant losses on insects, at least in Germany. Many bird species consume insect - loss of food sources.

Among insects, the decline of pollinator/nectar-consuming species is becoming apparent. Some bird species also consume nectar and could be impacted by some of the same issues that are driving the decline of insect pollinators.

 

[Venom]

Habitat loss? Cats? Windmills? Reflective windows on skyscrapers? Polarized reflections off glass and chrome?

There have also been studies showing significant losses on insects, at least in Germany. Many bird species consume insect - loss of food sources.

Among insects, the decline of pollinator/nectar-consuming species is becoming apparent. Some bird species also consume nectar and could be impacted by some of the same issues that are driving the decline of insect pollinators.

This was my first suspicion.

 

[The Shrike]

The overarching reason for the declines is habitat loss and degradation. Everything flows from there.

It's notable that the one group of birds that has increased in abundance relative to a 1970 benchmark is wetland birds. This is a direct result of the passage of the Clean Water Act which meant that we first stopped being so cavalier about draining and filling wetlands and second started creating/restoring wetlands all over the country. Most of those gains have come from urban Canada Geese – itself a problem – but other birds benefit, too. Those overall gains are also a function of the US ban on DDT, which (DDT) disproportionately affected fish-eating birds, many of which spend a lot of time around wetlands.

Some raptors are also doing better these days. That's a fairly simple one in that it became a lot less common for folks to simply shoot any hawk they saw at anytime because there was only one species of hawk: "chicken hawk". Simply ending the bounties being paid for shooting hawks helped a lot.

The other groups, especially grassland birds, are in serious trouble and there's a simple reason. Grasslands are a lot less common on our landscapes than they were in 1970.

Other stuff:
1. Windmills are indeed a problem. Birds (and bats) collide with them. This disproportionately affect big, soaring birds and that's a problem because they are slower to reproduce than little songbirds and it takes longer for them to recover from population hits. But there's a habitat angle too: Where are most of our wind farms being built? On our last, best, biggest tracts of grassland. This adds to fragmentation of those grasslands and certain vulnerable species (e.g., prairie grouse) avoid them.

2. Windows. Not just on skyscrapers, but everywhere in our built environment, glass kills birds. We lose perhaps a billion individuals (of hundreds of species) to window collision every year.

3. Cats. Yes, outdoor cats are a huge problem. It could be as many as 4 billion individual birds killed by cats in the US every year.

Unless birds are producing enough babies each year to right off the top compensate for 5 billion individuals lost to windows and cats, then overall populations will decline. Our best estimates in the 1970s were that there were about 20 billion individual birds in North America at their annual peak each autumn. What this new paper is demonstrating is that the peak today is down to about 17 billion.

Other stuff. We're a lot more careful about approval for and best practices for use of pesticides today than we were in 1970. But there are still issues. There was last week an important paper published that drew the first link between widespread use of neonicitinoid pesticides and sublethal problems for wild birds. Evidently, consuming grain treated with neonics acts like an appetite suppressant for migrating birds. This keeps them from eating as much as they need to in preparation for migration when they need to lay down up to half their body weight in fat. We already know that migration periods are when most birds die during the annual cycle. This is one more thing that might be making migration a bit more deadly.

 

[sphenisc]

...

Other stuff. We're a lot more careful about approval for and best practices for use of pesticides today than we were in 1970. But there are still issues. There was last week an important paper published that drew the first link between widespread use of neonicitinoid pesticides and sublethal problems for wild birds. Evidently, consuming grain treated with neonics acts like an appetite suppressant for migrating birds. This keeps them from eating as much as they need to in preparation for migration when they need to lay down up to half their body weight in fat. We already know that migration periods are when most birds die during the annual cycle. This is one more thing that might be making migration a bit more deadly.

Got a link?

 

[Cheetah]

A neonicotinoid insecticide reduces fueling and delays migration in songbirds

Ingestion of field-realistic levels of neonicotinoid insecticides reduced feeding and accumulation of body mass and fat stores, which led to delayed departure from stopover sites. Such delays can lead to reduced migration survival and decreased reproductive success and therefore have the potential to impose population-level impacts.

 

[William Parcher]

In a New Study on Bird Loss, Some Scientists Say Subtlety Is Lost, Too

A recent paper in the journal Science documented declines in some bird populations, but did the packaging and coverage paint a skewed picture?

When a major new study on North American bird populations appeared in the journal Science last week, it included all the trappings of a typical scientific paper, along with one, less conventional addition: The study also came with its own hashtag, #BringBirdsBack.

Certainly, the central finding of the research team, led by Ken Rosenberg, a conservation scientist at the Cornell Lab of Ornithology, seemed likely to trigger strong public reaction, on and off social media. Since 1970, the researchers estimated, the North American bird population had declined by roughly 2.9 billion birds, a 29 percent drop. It was, the researchers wrote, “an overlooked biodiversity crisis.”...

...The declines were certainly notable, but some ecologists have begun to question whether the calculus undertaken in the paper truly warranted this sort of language, and the ominous future it seemed to suggest. And those concerns have raised further questions among some scientists — and even some reflection among authors of the paper themselves — about how high-stakes research, the constraints of high-profile journal publishing, and sophisticated publicity can sometimes combine to drive a story into the news cycle while eclipsing important uncertainties, and perhaps even delivering an incomplete message to the public...

...As public attention to the study has intensified, though, not all ecologists are convinced that the numbers in the news actually present such a clear-cut picture. In a post on the academic blog Dynamic Ecology, Brian McGill, a macroecologist at the University of Maine, praised the study, even as he questioned whether the data actually pointed to an impending bird apocalypse.

In the post, McGill observes that, of the 2.9 billion birds lost, many belong to species that are not native to North America. Just two of those species — the European Starling and the House Sparrow — account for close to 15 percent of the net population loss recorded by the researchers. “The irony is that land managers and conservation agencies have actually spent a lot of money to try to drive down or eliminate invasive species,” McGill said in an interview with Undark.

McGill also argues that, for many other species — especially those that thrive on farmland — population numbers may have actually been inflated in 1970, a result of generations of forest clearance and prairie destruction. By that reckoning, some of the decline may not be a catastrophic drop, but simply a return to an earlier baseline population that precedes the arrival of Europeans...

https://undark.org/article/in-a-new-study-on-bird-loss-some-scientists-say-subtlety-is-lost-too

 

[TragicMonkey]

I was reading about vultures earlier today. Their reduced numbers have serious impact as it leaves animal corpses all over the place that would have otherwise been safely disposed of. Vulture stomach acid is exceptionally potent so they can safely remove all sorts of dangerous bacteria from circulating. Lesser scavengers don't have the might and speed of vultures in fulfilling this vital function.

 

[William Parcher]

My understanding is that the plummeting vulture numbers are not happening in North America but instead elsewhere. The problem seems to mostly be in Eurasia, South Asia and Africa.

 

[Doghouse Reilly]

In a New Study on Bird Loss, Some Scientists Say Subtlety Is Lost, Too



https://undark.org/article/in-a-new-study-on-bird-loss-some-scientists-say-subtlety-is-lost-too

That definitely puts the study in a new light.

 

[The Shrike]

My understanding is that the plummeting vulture numbers are not happening in North America but instead elsewhere. The problem seems to mostly be in Eurasia, South Asia and Africa.

Correct. A huge driver in India at least was use of the drug diclofenac in cattle. Vultures and other birds of prey in Eurasia lack an enzyme that breaks down the drug, leading to death (presumably) via renal failure. With so many cattle carcasses in India, vulture numbers had been quite high. But over a span of just 20 years or so, ~99% of those birds died.

Loss of vultures --> rotten carcasses fouling waterways and stinking up the place --> higher survivorship of feral dogs that scavenged the carcasses --> significant rabies outbreaks in humans from being bitten by the rabid dogs --> the phenomenon of urban-adapted leopards and associated human conflicts, as leopards moved into cities to prey on the extra dogs --> loss of the centuries-old practice of sky burial among the Parsi, i.e., the souls of their dearly departed can no longer travel to heaven because there aren't enough vultures to escort them there.

This is a now classic and devastating illustration of the loss of vital ecosystem services from once common species becoming rare. Despite India, Nepal, and I think Pakistan banning diclofenac, it was approved in the EU in 2014.

In Africa, it's a bit more complicated. There is some diclofenac use and electrocutions from poorly-designed powerlines are common. In West Africa, vultures are frequently killed for use in spiritual medicines. There is robust trade in vulture parts. In East Africa and elsewhere, poachers have taken to intentionally poisoning elephant carcasses. Each laced carcass could kill hundreds of vultures. Poachers don't like vultures because their circling carcasses tells anti-poaching squads where an animal has gone down.

 

[The Shrike]

That definitely puts the study in a new light.

Well it kinda does and it doesn't.

True, all manner of common species are driving the numbers that indicate the overall decline. [This is really the point, i.e., that we've not lost so many species but we have lost abundance of individuals within certain species.]

True, a handful of those common species are actually invasive species that we're better off without. But false, there is no coordinated attempt to eradicate species like House Sparrow and European Starling in the US and Canada. There is some local control in places where starlings mass in unwanted numbers, but we're nowhere near trying to eradicate them on any meaningful scale.

Yes, numbers of birds at the 1970 baseline represented a century or so of inflated numbers of grassland and farmland species from human conversion of about 60–70% of our terrestrial landscapes to pastures, hayfields, and crops. The decline of these species might mean that populations are approaching something like what we might have had in North America prior to European colonization.

Buuut that pre-Columbian ideal is actually not what conservationists are working to restore. First, it's unattainable given extinctions and settlement by aforementioned invasives. More important, what people think about that ideal is highly biased toward their understanding of Native American influences on landscapes. We're learning more and more that their world was quite a bit more open and cultivated than we used to appreciate. In other words, whatever we think that pre-Columbian ideal was, we're almost certainly wrong about it.