News Release 4-Dec-2019
Migratory birds shrinking as climate warms, new analysis of four-decade record shows
University of Michigan
ANN ARBOR–North American migratory birds have been getting smaller over the past four decades, and their wings have gotten a bit longer. Both changes appear to be responses to a warming climate.
Those are the main findings from a new University of Michigan-led analysis of a dataset of some 70,000 North American migratory birds from 52 species that died when they collided with buildings in Chicago.
Since 1978, Field Museum personnel and volunteers have retrieved dead birds that collided with Chicago buildings during spring and fall migrations. For each specimen, multiple body measurements are made.
The research team analyzed this remarkably detailed dataset to look for trends in body size and shape. The biologists found that, from 1978 through 2016, body size decreased in all 52 species, with statistically significant declines in 49 species.
Over the same period, wing length increased significantly in 40 species. The findings are scheduled for publication Dec. 4 in the journal Ecology Letters.
“We had good reason to expect that increasing temperatures would lead to reductions in body size, based on previous studies. The thing that was shocking was how consistent it was. I was incredibly surprised that all of these species are responding in such similar ways,” said study lead author Brian Weeks, an assistant professor at the U-M School for Environment and Sustainability.
The senior author is Benjamin Winger of the U-M Department of Ecology and Evolutionary Biology and the Museum of Zoology. Weeks worked on the project as a postdoctoral researcher in Winger’s lab. Co-authors include David E. Willard, the Field Museum ornithologist and collections manager emeritus who measured all 70,716 birds analyzed in the study.
The new study is the largest specimen-based analysis of body-size responses to recent warming, and it shows the most consistent large-scale responses for a diverse group of birds, Weeks said.
Several lines of evidence suggest a causal relationship between warming temperatures and the observed declines in avian body size, according to the researchers. The strongest evidence is that–embedded within the long-term trends of declining body size and increasing temperature–there are numerous short-term fluctuations in body size and temperature that appear to be synchronized.
“Periods of rapid warming are followed really closely by periods of decline in body size, and vice versa,” Weeks said. “Being able to show that kind of detail in a morphological study is unique to our paper, as far as I know, and it’s entirely due to the quality of the dataset that David Willard generated.”
“It’s really been a herculean effort on the part of Dave and others at the Field Museum, including co-author Mary Hennen, to get such valuable data from birds that might otherwise have been discarded after they died from building collisions,” Winger said.
Within animal species, individuals tend to be smaller in warmer parts of their range, a pattern known as Bergmann’s rule. And while the possibility of body size reduction in response to present-day global warming has been suggested for decades, evidence supporting the idea remains mixed.
The uncertainty is likely due, in part, to the scarcity of datasets like the Field Museum trove.
For each bird, Willard measured the length of a lower leg bone called the tarsus, bill length, wing length, and body mass. In birds, tarsus length is considered the most precise single measure of within-species variation in body size.
The data analysis revealed that:
- Three measures of body size–tarsus length, body mass and PC1, a common measure of overall body size that combines several key body-part measurements–showed statistically significant declines. Tarsus length declined 2.4% across species.
- Wing length showed a mean increase of 1.3%. Species with the fastest declines in tarsus length also showed the most rapid gains in wing length.
- Mean summer temperature was significantly negatively associated with bird body size–meaning that body size decreased significantly as temperatures warmed. Temperatures at the birds’ summer breeding grounds north of Chicago increased roughly 1 degree Celsius (1.8 degrees Fahrenheit) over the course of the study.
Studies of plant and animal response to climate change often focus on shifts in the geographical range of a species or the timing of events such as springtime flowering and migration. The consistency of the body-size declines reported in the new study suggests that such changes should be added to the list of challenges facing wildlife in a rapidly warming world, Weeks said.
“It’s clear that there’s a third component–changes in body size and shape–that’s probably going to interact with changes in range and changes in timing to determine how effectively a species can respond to climate change,” he said.
Long-distance bird migration is one of the most impressive feats in the animal kingdom. The extreme energetic demands of flying thousands of miles have shaped the morphology of migrating birds–their form and structure–for efficient flight.
The authors of the Ecology Letters paper suggest that the body-size reductions are a response to climate warming and that increased wing length may help offset the body-mass losses.
The researchers plan to test that idea in a follow-up project, which will again make use of the Field Museum dataset. They’ll also look further into the mechanism behind the body size and shape changes and whether they are the result of a process called developmental plasticity, the ability of an individual to modify its development in response to changing environmental conditions.
The birds analyzed in the study are small-bodied songbirds that breed north of Chicago in the summer and migrate through the region in high numbers. Several species of sparrow, warbler and thrush make up the majority of the dataset, with thousands of individuals of each species documented as lethal collisions.
The observed changes in avian body size and shape are subtle–at most a couple grams’ difference in body mass and a few millimeters in wing length–and are not detectable with the naked eye. The Field Museum bird collision dataset highlights the value of natural history museum specimen collections, which help scientists understand how nature changes through time, the authors note.
“When we began collecting the data analyzed in this study, we were addressing a few simple questions about year-to-year and season-to-season variations in birds,” said the Field Museum’s Willard. “The phrase ‘climate change’ as a modern phenomenon was barely on the horizon. The results from this study highlight how essential long-term data sets are for identifying and analyzing trends caused by changes in our environment.”
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The authors of the Ecology Letters paper, in addition to Weeks, Winger, Willard and Hennen, are Marketa Zimova of the Institute for Global Change Biology at the U-M School for Environment and Sustainability, former U-M undergraduate Aspen A. Ellis, and Max L. Witynski of the Field Museum.
Funding for the study was provided by the Field Museum and the University of Michigan’s Department of Ecology and Evolutionary, Museum of Zoology, and Institute for Global Change Biology.
More information: April 2019 Michigan News release about nocturnal flight calls and building collisions.
Image link: https://drive.google.com/drive/folders/1u6DxrzXGE7bk48Vi_DefaX_W2eBkwxvs
cientists have long been speculating about the potential reasons for the declining number of insects and the birds that depend on these critters for their survival, with new research potentially shedding some light on this problem.
An insect apocalypse with a massive decline in the number of arthropods is underway due to the prevalence of artificial light at night, also known as light pollution, a new study published in the journal Biological Conservation claims.
Scientists from Tufts University in Massachusetts reviewed the results of more than 200 independent studies to conclude that it is artificial light at night (ALAN) that could be a significant factor driving the so-called insect apocalypse due to its influence on reproductive success, hiding from predators, and the search for food by various insect species, potentially contributing to the loss of about 40% of all species in the next few decades.
“Artificial light at night impacts nocturnal and diurnal insects through effects on development, movement, foraging, reproduction, and predation risk”, the paper claims.
“We also emphasise that artificial light at night is not merely a subcategory of urbanisation. The ecological consequences of light pollution are not limited to urban and suburban centres, but widespread along roadways and around protected areas”, researchers added.
In an Oct. 7, 2015, photo, a bucket of crickets are seen in the Detroit Zoo’s cricket breeding area in Royal Oak, Mich.
© AP PHOTO / CARLOS OSORIO
Insects Are Dying Off in Europe in Apocalyptic Wildlife Omen, New Study Suggests
The declining number of insects, in turn, leads to disruptions in the food chain and global ecosystem by causing a significant reduction in the number of birds. So, researchers believe that the loss of around 3 billion birds in the US and Canada in the last 50 years is likely to be directly related to the declining number of insects.
The study concludes by saying that this problem is still relatively easy to address in comparison to other anthropogenic problems, by, for example, reducing our reliance on artificial light or shielding outdoor illumination.
Very far afield for me, but bird wings have flexible joints and the feathers ‘feather out’. I wonder how the measuring protocol can be standardized to less than mm?
Were all measurements made at the time of collection across all the years, or were they made prior to writing the paper? What are the effects of laying around in drawers for extended time periods.
Existence of evidence of potential is not existence of evidence of outcome. Or Causality.
This has to be as silly as david Attenborough lying about walruses jumping of cliffs because of “climate change” or polar bears hunting whales, due to “climate change” 😐 Or how about a small part of victoria falls which dries up every year and has done so for many years, suddenly its “climate change” 😐 I’ve learnt from this site alone the mass lying the greens are doing, especially the Imaq ice melt….. The “We need 28 Billion Dollars Asap” U.N. is pure cancer, It seems they didn’t like traveling in non first class seats, and the 5pm Diplomats Bar closing time is interfering with them saving the planet (again) 😐
It’s 9 degrees here in Massachusetts at 9am on Sunday. But of course it’s warming everywhere else but where we are.
Has nothing to do with “warming”.
When you want a given technology of slow aircraft to fly farther on less fuel at a higher altitude you narrow the body and lengthen the wing.
The U-2 is a great example.
Basically the birds have had to fly progressively longer stretches between feedings on their migration path because of monoculture farming and urbanization. It has ZERO to do with a degree of warming.
If those that measured the birds knew the year each specimen died then the study is not valid due the potential for bias in measurements. How many measurers were there and were they calibrated with each other?
Take this study at face value. It’s data starts in 1978(New ice Age in the 70’s) to now( the hottest decade ever).
What does this have to do with CO2?
OK WAIT…
Had my coffee now.
So their “sample” was specifically birds that did not have the aerodynamic/neurological properties necessary to avoid or survive striking a building. This sounds more like a mechanical engineering and/or toxicity study than anything to do with temperature.
Any 12 year old or Janitor would have refused to publish the paper.
100% of their sample is ANECDOTAL in nature and literally taken out-of-context.
I could make the same claim around the teeth in large cats. None have had teeth as large as the sabertooth cat, therefore, I’m a warming world their teeth will continue to shrink.
Shorter, lighter body, longer wings = improved flight adaptation; but instead of celebrating this as a demonstration that natural selection can continue to improve the adaptability of species, we are told this is a climate catastrophe. Another example of how the politicization of university research has destroy science.
A couple of observations:
1. Lower body mass and larger wing area are an adaptation to lower air density from warmer air. Simple evolution, not necessarily a bad thing, or
2. Since we don’t have a representative sampling of birds that didn’t fly into buildings and die, we can’t assume
that it’s just a demonstration that dumber birds are flying into buildings. Dumber and smaller birds.
Let’s do some math. 70,000 birds/52 species is 1346 samples/species over 38 years equals 35 data points per year per species on average. (I realize this is a couple of crude assumption. This is a thought experiment.) Now according to Wikipedia the common starling “The common starling is 19–23 cm (7.5–9.1 in) long, with a wingspan of 31–44 cm (12–17 in).” So we have a 4 cm variation for length and 13cm variation in wingspan. They are claiming 1-2% change. That’s a difference millimetres.
Was there anything like an error bar? I have to wonder how is a 1.3% change can be statistically significant over that range? How much error range in their method of measurement do they get? Did they blind the researcher to make sure the researcher didn’t know what side of the data the birds were on? Did they have the same researcher measure all the birds over all 38 years? Did they control for desiccation over the years if they did?
There is one good thing about this study. This is a superb paper for ensuring more funding while eager volunteers feel they are actually doing something. I’ll give them that.
Bayesian thinking hypothesizes migratory birds showing increasing wing length and decreasing body mass die by hitting buildings in Chicago and that this must be due to a warming environment.
Karl Popper would have a field day with this one.
Strewth. As if that’s a properly representative sample of the whole population. Perhaps there’s just more smaller birds in Chicago because humans have created an environment where smaller specimens get to live longer.
Or perhaps the birds have got more stupid by chattering to climate scientists obsessed with global warming. So stupid that they’re less competent at avoiding large obstacles in their flight path.
So, when temperatures were much warmer millions of years ago- most birds must have been tiny, right?
Probably weren’t many birds millions of years ago.
They would have been, if there were skyscrapers to slam into.
Amazing-
Cities can be up to 20 degrees hotter than the surrounding country side and in this hotter micro-climate
How Wild Animals Are Hacking Life in the City
Search domain http://www.nationalgeographic.com/news/2016/04/160418-animals-urban-cities-wildlife-science-coyotes/https://www.nationalgeographic.com/news/2016/04/160418-animals-urban-cities-wildlife-science-coyotes/
Apr 18, 2016″The bird seems to be adapting to urban spaces, and it indicates we can do conservation in cities.”
wow- species adapt!
As has been pointed out this is a very superficial study at best, and even if the findings are correct- so what? To jump to “climate change ” is sheer stupidity from a science viewpoint- so it’s clearly a study designed to grab funding for the cause of the day
“Since 1978, Field Museum personnel and volunteers have retrieved dead birds that collided with Chicago buildings during spring and fall migrations. For each specimen, multiple body measurements are made.”
Could it be that the buildings simply acted to filter out the smaller / weaker / young individuals within the populations. With the larger/stronger/older individuals avoiding collisions and thereby not being represented in the measured population?
The changes may be statistically significant, but they aren’t very significant. Less than 2 percent change over 40 years and 1 degree temp change indicates , even if the temps increase 1 1/2 degrees by 2021, the changes in the birds sizes will still be insignificant. No mention of the typical variation in sizes for individuals Meaningless articl, overall
Decline in size would imply a lack of food for growth, which is not shown in warming climates. A greening/warming climate would show an increase in size. Maybe just the dumb birds run in to buildings. Why are we depending on birds that run into buildings and die to be the reflective sample to make a scientific claim?
Oh, here we go. The meat of the story:
“We had good reason to expect that increasing temperatures would lead to reductions in body size, based on previous studies. The thing that was shocking was how consistent it was. I was incredibly surprised that all of these species are responding in such similar ways,” said study lead author Brian Weeks, an assistant professor at the U-M School for Environment and Sustainability.
>I was completely surprised our study reflected exactly what we wanted to claim.<
Lots of very negative comments here. Mostly not justified IMHO.
The study presents new data, and generating and publishing new data is the most important thing that natural sciences can do (and, of course as we know well, the conspicuous absence of new data is what characterises most publications in climate science world, where model output substitutes for data. And where data itself becomes malleable so it can be used in support of pet hypotheses).
They have a hypothesis based on a correlation of changes in body dimensions with changes in temperature – that warmer climate leads to smaller bodies and longer wings. Natural selection in action. Or could it be epigenetics? I used to make snide comments about epigenetics as just being a 21st century revival of lysenkoism, but it turns out to be a real field of study about how variations in environmental conditions lead to variations in gene expression, which lead to physical variations in the phenotype. Or (as they say) it could be “developmental plasticity” which is a new one on me.
They also quote “Bergmann’s rule” that birds tend to be smaller in the warmer parts of their habitat. So perhaps their hypothesis should be that “a warmer climate may have caused their entire migratory ranges to move north by an as yet undetermined amount, so birds collected in later years come from warmer parts of those migratory ranges”. Chicago being fixed in space but not necessarily fixed in relation to avian habitat ranges. That alternative hypothesis could be tested by gathering field data (perhaps it has been tested and rejected)
Most of the negative comments have to do with the actual failings of studies like this, which are becoming more and more common in science. Mere presentation of the data would have been a great service. Trying to tie it to climate change with no actual causal link and no direct analysis of confounding factors is a *disservice* to science.
Even Bergmann’s Rule is misapplied. Bergmann’s Rule applies to populations *living* in different temperatures. This simply doesn’t apply to migratory species. You don’t have cold weather geese vs warm weather geese. You don’t have cold weather ducks vs warm weather ducks. And so on.
The entire paper is going to be published and all of the details are not available but there was no mention of what should be a standard of any study claiming to be statistically significant such mean, standard deviation, confidence level. That teeny tiny result reported in percentage on what obviously has a large range just screams out for further justification. I once had the audacity to ask on a proclimate change website about where are the error bars on that graph and I got called foul names, accused of being in the pay of big oil and summarily banned from the website. I am thus a little sensitive about small stuff like this.
“Since 1978, Field Museum personnel and volunteers have retrieved dead birds that collided with Chicago buildings during spring and fall migrations. For each specimen, multiple body measurements are made…”
Well if this is science, it should be equally valid to draw conclusions about all Tesla drivers based on a sample obtained exclusively from those that collided with stationary objects.
The study could just as easily been about the changes in human beings who fell off ladders and concluded that because the size of humans were larger by a barely measurable amount that barely measure able increase in size was due to global warming. I am not a scientist in any way but I suspect that all species if studied closely enough to measure changes so subtle as to not be observable to the naked eye would involve a whole range of reasons why such changes may exist. Perhaps evolution, perhaps random chance, perhaps changes to the gene pool. I am sure that humans are larger than previous generations by a measurable amount yet I can’t imagine that anyone in their right mind would conclude that climate change was the cause ( or even a dominant cause).
I would need more info to be convinced that such a link may exists.
According to NOAA, since 1901, the average surface temperature across the contiguous 48 states has risen at an average rate of 0.14°F per decade, which equates to 0.014°F per year.
Songbirds don’t have very long lifespans. The average lifespan of a Red-winged blackbird is 2 years. The average lifespan of an American Robin is 2 years. Some songbirds live slightly longer lives, but if we use 2 years as a reasonable average, then in the course of the bird’s life it experiences an increase in the average temperature of 3 one-hundredths of a degree Fahrenheit. (0.03°F)
We are being asked to believe that 3 one-hundredths of a degree Fahrenheit average over a 2 year period creates enough biological stress to drive evolutionary processes. Or, that the stress is perhaps not driving evolutionary processes, but instead limiting and diminishing the ability of the birds to grow to full potential.
No evidence is offered to support why this extremely small change in body size is harmful. If might be harmful or beneficial or completely unimportant. All we get is a linkage to “a warming world” – and we already “know” that all claimed anthropogenic climate change can only lead to negative consequences. Actually, all consequences are not just negative, but catastrophic. Not one – even by lucky chance – is claimed to be beneficial for any lifeform, large or small.
Furthermore, these songbirds didn’t just appear recently. They have existed for at least several glacial-interglacial cycles. The species have dealt with 100kyr long glacial cycles that were at least 12°F colder in their current range. During the last glacial period, there were at least 25 Dansgaard-Oeschger events where the temperatures increased by more than 10°F in a decade or two. These songbirds also experienced and survived interglacials of 10k-20kyrs that were more than 5°F warmer than today in their current ranges. Climate reconstructions also show that these songbirds experienced warmer periods than today over the past 2k years.
The conclusion: we have measurements of 70k dead birds, no causal link to anything, no claims as to whether the changes are beneficial or detrimental, and that all too familiar bitter aftertaste from tax-payer funded studies that allow misanthropes to link human activity to a diminished world.
The conclusion reached by the authors of this paper is ridiculous. All they have come up with is a very unscientific, leap-of-faith hypothesis. The slight decrease in body weight and increase in wing length, if its real, screams of natural selection alone. Migratory birds with lighter bodies and longer wings will travel much more efficiently for the energy expended, and are thus the best adapted among the whole species population to survive. This is all the authors are seeing in the data.