- Welcome, everyone to Wednesday Nite @ the Lab.
I'm Tom Zinnen.
I work at the UW-Madison Biotechnology Center.
I also work for the Division of Extension, Wisconsin 4-H.
and on behalf of those folks and our other co-organizers,
PBS Wisconsin, the Wisconsin Alumni Association,
and the UW-Madison Science Alliance,
thanks again for coming to Wednesday Nite @ the Lab.
We do this every Wednesday night, 50 times a year.
Tonight, it's my pleasure to introduce
to you Benjamin Zuckerberg.
He's a professor
in the Department of Forest and Wildlife Ecology
here at UW-Madison.
He was born in Brooklyn, New York,
and went to Packer Collegiate Institute for high school,
and then he went to Connecticut College
for his undergraduate degree in zoology.
He got his master's degree
at the University of Massachusetts in Amherst,
and then did his PhD at the State University of New York's
College of Environmental Science and Forestry
in the city of Syracuse.
He then did a post-doc
at the Cornell Laboratory of Ornithology
before coming to UW-Madison.
Tonight, he's gonna speak with us
about birds as sentinels of climate change.
Would you please join me in welcoming Benjamin Zuckerberg
to Wednesday Nite @ the Lab?
- Well, thank you Tom,
for the invitation to come to speak with you today.
And the topic I'm going to discuss is birds,
and how they are important
in potentially serving as this very important indicator
and the sentinels of climate change.
And so I'm going to begin my talk kind of positing
an important hypothesis, that birds are awesome.
And they are awesome really
for a number of different reasons.
One, that they are numerous.
We have birds that occupy almost every different kind
of habitat and ecosystem throughout the world,
from the Arctic, to wetlands, to the tropical rainforest.
And at the same time, they are incredibly diverse.
You know we can walk outside and see warblers and kinglets,
and we can also of course see eagles and raptors and owls.
And another important aspect of birds is that they show
an amazing array of behaviors,
from tool use, to the use of supplemental food,
to being able to use novel types of habitats and shelters.
And importantly, because of this behavioral sort of array,
they can actually show pretty amazing adaptations
and changes in response
to environmental pressures and stressors.
Importantly, birds also clearly play
a very important role in our culture.
They've infused themselves in terms
of our song and our artistry,
and we have well over 35 million people
in this country alone
who actively go out and feed their backyard birds,
and many millions more throughout the world
that go out and look for birds through bird watching.
An important aspect of birds also
is that birds have always served
as important sentinels of environmental change.
And some of the stories and lore of coal miners
bring canaries into the mines in order to serve
as that important environmental and health indicator
that something is wrong in the mine.
In fact, if a canary, let's say,
started showing signs of distress,
then that was a good sign and indicator
for the miners to evacuate that coal mine.
Unfortunately, over the last 100 years,
many of our sentinels are not doing particularly well.
We've seen rising threats in the form of habitat loss
and fragmentation, environmental pollution,
and the use of insecticides and pesticides
in the environments,
over hunting and overuse of many bird populations,
as well as the proliferation of domestic pets,
as well as domestic pests that have infiltrated
many bird populations with significant damage.
So much so that over the last 30 to 40 years,
we've seen roughly the loss of 2.9 billion birds
throughout the United States alone.
Compounded all these different stressors
and overlaying many of these environmental changes
is of course modern climate change.
And what we're seeing here is an animation
of global temperatures comparison to pre-industrial era
of the 1850s to 1900 showing pretty remarkable change
in the global climate system.
In fact, what you'll see here,
starting roughly in the 1970s and early 1980s,
is a pretty rapid and dramatic change
in the Earth's system,
and a rapid warming throughout much of the Earth.
There's a couple aspects of this that I wanna really focus on,
especially as it relates to birds.
One is that the ubiquitous and uniformity of warming
is widespread throughout the globe.
There are very few regions of the world
where we've seen a bucking of the trend, so to speak,
where we've seen cooler regions, or regions that are not warming.
This warming is so uniform and widespread
that we've seen roughly about one degree warming
compared to pre-industrial era of the late 19th century.
Another important aspect of this
is that those northerly latitudes,
those northerly ecosystems of the northern hemisphere
are warming at a rate that is anywhere
from two to three times faster
than what we've seen throughout the rest of the world.
It's an important aspect of this when we look
and can reconstruct temperature data throughout the world,
dating back the last 2,000 years,
and it's very clear that what we've seen in terms of changes
in the late 19th century and in the early 2000s here
is relatively unprecedented.
In fact, if we reconstruct data going back
the last 10,000 or 100,000 years,
what we can say is that this is one of the warmest periods
that the Earth has experienced.
What we're seeing at a global level,
we are also seeing here in the United States.
So like the Earth,
much of the United States is getting warmer.
In fact, every decade has generally been warmer
than the decade before it, going back to the 1980s.
Some other areas that are getting warmer the fastest
are absolutely in Alaska, the Northeast,
and here in the upper Midwest.
And like the globe, we are seeing very few areas
that are showing a reversal or difference
in that trend of warming.
In fact, that warming hole that we can see
there in the Southeast really only
is one of the few areas that hasn't warmed as fast,
but what we are beginning to see
is that warming hole is in fact closing,
and now much of the warming in the Southeast
is beginning to catch up.
Another area or signal of climate change
has been what we've seen in sort of changes
in precipitation and rainfall.
And part of what we've been able to document
is that some areas of the United States are getting wetter,
and some areas are getting drier.
Places like the Northeast, in fact,
are showing pretty strong changes and increases
in rainfall and precipitation,
and a higher likelihood of these extreme events,
like flooding.
Parts of the upper Midwest, kind of a mixed bag.
Some areas are seeing drought-like conditions,
and some areas are seeing increases in rainfall,
like here in southern Wisconsin.
Parts of the west of the United States
are showing what we know to be mega-drought events,
where we're seeing drought-like conditions
that stretch for years, and in some cases, decades.
At the same time, with all these changes in terms
of temperature and precipitation,
it is clear we are seeing unprecedented changes
in carbon dioxide in the atmosphere.
When climate scientists have been able
to reconstruct carbon dioxide levels,
going back 20 million years,
we can see that the levels that we're experiencing today
are in novel and in uncharted waters.
800,000 years ago, and looking at the CO2 reconstructions,
suggests we rarely got above 400 parts per million.
And now the current level is about 413 parts per million.
When we look at the changes
in carbon dioxide in the atmosphere
under different scenarios,
as you can see here with these different lines,
even the best case scenario, that orange line,
suggests we won't go below that 400 parts per million line
over the next 100 years.
And under the worst case scenario,
in terms of that purple line,
we're seeing that carbon dioxide levels
are likely to double due to human emissions.
An interesting experiment is what's referred to
as a pulse experiment,
and the idea here is that if we were able
to basically burn all the fossil fuels
that we've already taken up out of the Earth
and are now existing in our car tanks,
what we would see is that the CO2 levels would rise
to roughly 2,000 parts per million.
It would take roughly about 1,000 years
for those levels to start going down.
So at the same time we're seeing these changes
in rainfall, temperature throughout the world
at an unprecedented rate,
we've seen these concurring changes in carbon dioxide
due to human fossil fuel emissions.
Taken together, all these lines of evidence
tend to point in the same direction.
We are seeing CO2 concentration levels
at the highest they've been
in at least the last two million years.
We've seen sea level rise at the fastest rate
in the last 3,000 years.
And we've seen changes in Arctic sea ice
that is at its lowest level in at the last 1,000 years.
And we've seen a glacier retreat
that's relatively unprecedented over the last 2,000 years.
All together, the signals come together and suggest
that it is unequivocal that human influence
has warmed the atmosphere, ocean, and land.
Widespread and rapid changes in the atmosphere,
ocean, cryosphere, and biosphere have occurred.
So the question I'd like to talk about today with you
is this overarching set of questions of how birds might
actually respond to these changes in temperature,
rainfall, and other factors.
Ultimately, birds have three different choices.
They can one, move, and we can certainly see that.
Birds are highly mobile, they're vagile,
they can move great distances,
and clearly one aspect or pathway for them to respond
to these new changes is by movement; moving to new areas
and tracking their climate space over time.
Or birds can sit where they are and stay where they are,
and ultimately adapt.
Perhaps they can change, use new food resources,
perhaps they can adapt to a new climate,
and essentially stay where they are.
But if a bird and a species cannot move and/or adapt,
then ultimately, they face extinction.
So for today, I'm gonna walk you through
a few case studies and stories.
I'll talk about how birds might be responding
to climate change and serving as these important sentinels.
I'm going to talk about bird behavior
and changes in behavior.
I'm gonna talk about range changes
and how they may be shifting their distributions over time.
Phenological changes, and the timing
of reoccurring events like migration.
The conservation concern of population declines,
a response to climate change.
And ultimately, one of the main concerns is the emergence
of infectious disease that can influence multiple species
and impact populations across multiple regions.
So first, the question of behavior.
One of the areas and times of the season
that I'm particularly fascinated about
in terms of how birds respond behaviorally
to climate change is winter.
And winter is changing rapidly
throughout much of the northern hemisphere.
In fact, if we look at snow cover extent,
going back to the 1970s,
we can see that there has been a pretty marked decline
in snow cover and seasonal snow cover
throughout the northern hemisphere.
Really, going back to 1980 and continuing from there on.
These changes, especially during the transition
from winter to spring, have resulted in the loss
of roughly four million square kilometers
of seasonal snow cover.
To put that in perspective, that's basically losing an area
the size of Texas per decade.
If we conceive of snow as habitat,
just like we might think about tropical rainforest,
well, we can clearly see this as a form of habitat loss
that rivals anything that we see throughout the world.
And what we're seeing globally and at the hemispheric level,
we're also seeing here in the state of Wisconsin.
We've seen changes in snow pack
of upwards about 20 to 15 days fewer since 1970,
in terms of persistent snow pack in the state.
So much so that the peak of winter has now shifted
from February to January.
So this leads to a question of how might birds respond
to this changing winter landscape and environment?
Ruffed grouse are a perfect example of a species
that is emblematic of the northern forests of Wisconsin
and the upper Midwest and has a distribution
that's into boreal Canada,
and meets its somewhat southern range boundaries
and distributional limits here in the upper Midwest
and down the Appalachians.
This is a bird that is clearly adapted
to the winter environment.
It is not a migratory species
like we see with spring migrants,
and they have to really be able
to take advantage of that winter environment
and display a number of unique behaviors
to allow 'em to get to that very strong
sort of winter and snow-covered landscape.
One of those behaviors is seen here.
- Man: Can we move forward? - Woman: Yeah, you can try to.
[wings flapping]
- So what you just saw was a really unique behavior
that ruffed grouse show; it's called snow roosting.
So like a lot of different birds,
especially during the winter,
grouse will use this roosting behavior
almost about 80% of the time to conserve their energetics.
And they can do this roosting behavior on the ground.
Like other birds, they can roost up into trees,
but unlike other birds, they'll actually roost into snow,
and they'll do this in a couple different ways.
They either create these snow bowls,
which they'll kind of burrow down into the snow
and kind of encapsulate themselves
in this little bowl in the snow,
or in some cases, they'll fly up into the air and dive bomb
underneath the snow and create a snow cave.
So these snow roosts have a couple of advantages
if you're a grouse trying to survive the winter.
One, you can avoid predators.
If you're a grouse and you're hiding underneath the snow,
there's probably less likely a chance that you're gonna get
picked off by some kind of owl or a raptor.
The other real advantage, however, is temperature.
And if we look at temperatures that a grouse
is experiencing in the snow roost compared to the ground,
well, they're almost seven degrees warmer
if they burrow underneath the snow.
In this case, you can imagine that the snow is basically
serving like a snow blanket,
and keeping a very sort of stable thermal environment
that the grouse is taking advantage of.
One of our questions has been, what is the real advantage
of these snow roosts for grouse in order for them
to get through the winter?
So we were able to track and measure multiple grouse
and individuals over time and show that
their stress hormone levels,
as measured here by corticosterone.
And this is a naturally occurring stress hormone
that we have.
And in fact, many grouse and other species have.
And generally speaking, when we are stressed,
our corticosterone levels go up.
Well, we showed that over multiple winters
when there were cold snaps,
that many of these grouse showed increases
in their stress hormone levels.
Meaning that those cold temperatures induced
this stress response in these free-living grouse.
But interesting component of this was that they were able
to use this behavior, snow roosting,
to basically buffer themselves
from that temperature-induced stress response.
So if we look at the corticosterone levels
of the individual grouse that are able to roost in the snow,
we can see here that that relationship disappears.
They are no longer affected by those cold snaps,
and their stress levels remained relatively stable.
If we look at the population as a whole,
what we can see is that once there's about 20 centimeters
or about seven to eight inches of snow on the ground,
that the population generally of grouse
experience reduced stress levels.
When you don't have 20 centimeters on the ground,
those stress levels go up pretty significantly.
An interesting aspect of this is that 20 centimeters of snow
on the ground is roughly the average amount of snow
that Wisconsin experiences throughout the winter,
but almost all projections agree that that level
is gonna be decreased by half.
So about 10 centimeters of snow will now be the average.
And you can imagine what that'll do
for many of these grouse.
So here was a nice example
of snow serving as this very important refugia for grouse,
but I would also point out that it's not just grouse
that take advantage of this snow refugia.
We have many small mammals and plant populations
and species, as well as even in fact,
amphibians and frogs that go through
a whole body freezing event and have to survive
underneath the snow.
All these species use that blanket of snow
to protect themselves what is
an increasingly variable winter climate.
Unfortunately, almost all projections are in agreement
that what we've seen in terms of the reduction in snow cover
and the shortening of our winter season
is only going to increase over time.
So that was an example of behavior,
and how a very important behavior
in terms of snow roosting
for a bird has allowed them to deal and cope
with what is an increasingly variable winter environment.
The next question is about range changes.
How might birds be changing in terms of their distributions
over time and over space in relationship to climate change?
So back in the 1990s, when scientists first started
becoming concerned about the effect of climate change
on wildlife and birds, one of the initial predictions
was that if we are experiencing northern
or warmings throughout the northern hemisphere,
that species are going to move northward
in response to that.
So how this would work would be that if, for example,
we've got two species here throughout
the northern hemisphere in the United States,
and we've got that sort of orange, warm-adapted species
that has its southerly distribution.
And maybe we have a cold-adapted species up there
in the blue, in the north.
And if we're looking at their range boundaries,
what we'd expect to see for that warm,
southerly-adapted species is that if warming continues,
we'd see expansion, a northward movement
of that range boundary as they colonize new areas.
If you're a cold-adapted species, however,
what you expect to see is a retraction
in that southerly range boundary,
and a movement northward.
Taken together then, what we would expect to see
from many species is what's referred to as
a poleward shift in their ranges over time.
But how can we go about measuring that
from multiple species, multiple regions of the world?
Well, one of the tools that we have at our disposal
are breeding bird atlases.
Breeding bird atlases are a citizen science effort
where volunteers go out and they record the presence
or absence of multiple birds is in what's referred to
as these atlas blocks.
So what you can imagine, it's almost like an ice cube tray
that's spread out across a state,
or in some cases an entire country,
and volunteers are going out and recording what birds
that they're seeing in different types of habitats
within each of those different blocks.
Here in Wisconsin, we have well over 5,000 atlas blocks
and over 1,000 different volunteers
go out there and they record what bird
that they have seen over roughly about a five-year period.
There's 400 or so atlases, if not more,
that are conducted throughout the world.
And this paints a very important picture in terms
of where species are found
throughout a given region or state.
The most powerful aspect of atlases
is that you can repeat them.
So here in Wisconsin,
we had our first Wisconsin breeding bird atlas
between 1995 and 2000, over five years of collecting data.
And we just wrapped up our second atlas.
So what can you do with two atlases to answer this question
about range shifts?
So for example, here we've got a beautiful bird,
the evening grosbeak.
It's a northerly distributed,
you could call it a cold-adapted species.
And here are its distribution
in the first Wisconsin breeding bird atlas.
There you can see those purple and pink atlas blocks
in which volunteers recorded the presence
of the evening grosbeaks.
And perhaps we could kind of delineate
their range boundary there,
in terms of their most southerly distributed location
in the state.
So what happened when they went back out there
for the second atlas?
Now, that's the map in the second atlas.
And we can see that the number and the presence
of evening grosbeaks declined significantly over time.
So much so that we might imagine that their range boundary
has shifted northward.
What about a warm or southerly-adapted species?
So here's the orchard oriole.
Again, another beautiful bird that's generally primarily
associated with more southerly areas of this country.
And all those dots you can see there
are where they recorded them
in the first Wisconsin breeding bird atlas.
And maybe again, we can delineate where
that range boundary is.
What happened 20 years later?
A massive increase in their distribution and range,
and a strong push in that range boundary over time.
This type of phenomenon, a poleward shift,
has now been documented in multiple states and regions
throughout the world.
It's not just been documented for birds,
but also for mammals, as well as insects and plants.
So much so that we've estimated that many of these birds
have shown a systematic poleward shift
of roughly about 10.5 miles per decade.
So over 30 to 40 years, we're talking about bird ranges
that are shifting 30 to 40 miles.
The question then is that if all these individual species
are moving, what are we seeing in terms
of entire communities of birds?
So to answer this question,
I'd say it's always fun to think about how backyard birds
are changing over time.
Again, to explore this, we need to turn to citizen science.
And one of the programs
that I've been particularly interested in
has been data from Project FeederWatch.
Project FeederWatch is a citizen science program
that's run by the Cornell Lab of Ornithology
and Bird Studies Canada.
It enlists well over 20,000 people every year to go out
and watch the birds in their backyards.
And so, with this map,
you can see that each one of those little blue dots
actually represents a Project FeederWatch participant.
So when people outside and looking through
their kitchen window at their backyard bird feeders,
they're recording the number of birds that they see
showing up and the species,
every two days across a five-day period
throughout the course of the winter season.
When you have this kind of data,
you can start analyzing the composition
and community of birds in your backyard.
So Project FeederWatch has been conducted since 1990.
And we were really interested in whether or not
the composition and the community of birds
are changing in relationship to climate change.
So if you can imagine that you're
a Project FeederWatch participant,
and you're looking at your backyard bird feeder,
you might see an assemblage of birds
that look a little bit like this:
with Northern cardinals and tufted titmouse,
and goldfinches and blue jays.
When you live in the Mid-Atlantic states,
maybe you have seen many of these same species
and the usual suspects,
but maybe you start seeing some other species as well.
Maybe juncos, as well as house finches
and black-capped chickadees.
And as you move more north,
let's say here in the Great Lakes,
well, now we have another assemblage
and community of wintering birds.
Maybe you see American tree sparrows
and white-breasted nuthatch.
So if all these different species are potentially moving
and changing their ranges in relationship
to a shifting climate,
then are we actually beginning to see an entire change
in the community of birds?
And that's exactly what we've seen since 1990.
So over the last 20 to 30 years,
we've seen that many of these northerly bird communities
are becoming increasingly dominated by these southerly
and warm-adapted species.
So much so that we think of this as the reshuffling
of the winter bird communities here in North America,
where warm-adapted birds are increasing
in their distribution and their numbers.
Many of these are smaller-bodied species
that are more sensitive to climate
and can take advantage of these potentially warming winters
and changing conditions,
and have generally been southerly species
that are increasing over time.
So this has led us to believe that more than half
of observed animal range boundaries have already shown
a documented response to modern climate change
by moving and shifting their ranges polewards over time.
In terms of phenology now,
range changes generally speaks about
changes at geographic levels,
but phenology is looking at changes over time.
To borrow a quote from Aldo Leopold, who described phenology
as "Many of the events of the annual cycle reoccur
"year after year in a regular order.
"A year-to-year record of this order is a record
"of the rates at which solar energy flows to
"and through living things.
"They are the arteries of the land.
"By tracing their response to the sun,
"phenology may eventually shed some light
on the ultimate enigma, the land's inner workings."
I think what Leopold is poetically capturing here
is that the variation and changes in the Earth's system
happen in a very predictable fashion,
as the reoccurring shift from winter to spring
across the northern hemisphere.
And so, if we are seeing warming,
the question is how are these patterns changing over time?
In particular, one clear behavior that we can focus on
for birds is migration and spring migration.
So again, we can turn to Project FeederWatch data
to look at this.
Here, we are seeing Project FeederWatch data
for American robins.
Those red areas are areas with a high number of robins,
those sort of yellow areas have maybe a few robins,
and those gray areas have no robins.
And what this captures is that overwintering range
and distribution of American robins,
where they're generally overwintering in large numbers
in the Southeast and the Northeast and along the coast,
and are few and far between in the upper Midwest.
What about February?
Looks a lot like January.
Generally overwintering in these areas for the most part
in the early 1990s and 2000s.
But in March, we see the arrival of spring
and the migration phenomenon begins.
A large number of these individuals of robins
and other species shift northward
and move northward to start looking
for their breeding grounds.
And what we've been able to document
using citizen science data like Project FeederWatch
is that the spring arrival for many of these
short-distance migrants are moving earlier and earlier,
so that their first arrival in the 1990s
may have been somewhere maybe in mid-March,
and now is happening in the 2000s much more
like late February or early March.
And the species that are really taking advantage of this
are species like brown-headed cowbirds and robins
and red-winged blackbirds.
And these are all species that tend to overwinter
in the southern part of the United States.
And these are the ones that
are showing some of the fastest rates of changes
in their spring arrival and migration.
But then the question is,
are we seeing changes in their breeding as well?
Are they beginning nest building and egg laying
earlier and earlier?
And that's exactly what we've been able to document as well.
One program that has been fascinating to explore
has been data from the nest record programs.
And again, these are citizen science data,
volunteers going out, finding nests,
and writing down and recording what species are nesting
and how many eggs they're finding
and whether or not that nest was successful.
Some of these nest record programs go back to the 1960s.
And what we've been able to document is not only
are birds arriving earlier at their breeding grounds,
but they're also beginning to nest earlier.
And this is definitely true during very warm springs.
However, we are entering a new era of citizen science
and data for birds throughout the world.
And one program that we're particularly
excited about is eBird.
eBird is another program that's run through
the Cornell Lab of Ornithology,
which people record what birds that they are seeing
in real time throughout the world,
and continuously contribute that data to an online database.
That biological database
is one of the fastest-growing databases in the world.
When you have data now,
and observations that people are collecting in real time,
we can begin to explore how species are shifting
in terms of their migration and their distributions.
Here, we have a statistical model that shows
where tree swallows are likely to occur at different parts
of their annual life cycle.
So here we can see their migration in November, December,
where they're overwintering
in central and southeastern United States,
and then moving northward and arriving in spring and summer
to their breeding grounds.
An amazing power and representation
of citizen science,
and being able to explore how those
migration patterns are changing.
One real powerful way of doing this is to combine
these observations with satellite data,
and measurements of what's referred to as the Green Wave,
which is changes in productivity
and springtime emergence of plants
in the northern hemisphere at the end of winter,
into spring, and fall senescence.
And by combining these two different data sources,
we can show how birds ride that greening up,
that changing of the ecosystem from winter to spring
to summer and fall.
What we've shown is that many of these birds are in fact
taking advantage of an earlier and earlier Green Wave.
So much so that they're arriving
about 2.5 days earlier per decade.
The birds that can really take advantage of this are birds
that tend to be a little bit slower in their migration.
They kind of come a little bit earlier in terms of
that migration period in March and April,
and they're the ones who have to travel the least amount,
because they're overwintering here in the United States.
They're not going all the way down
to Central and South America for their wintering grounds.
However, what we've been able to show is that
that change in phenology is not consistent
across different trophic levels.
Meaning that the earlier phenology in plants
has to be matched pretty closely by insect emergence
like caterpillars.
Both those groups, plants and insects,
tend to respond pretty quickly to changes
in spring temperatures.
Some of these birds can respond to those changes as well,
just like the ones I talked about,
those early arriving species.
But the species that have to travel long distances
that we refer to as Neotropical migrants.
These are species
that are considered long-distance migrants
that overwinter in Central and South America.
And their migratory cues are less about temperature
and much more about day lengths.
So when the days start shortening and changing,
their migration will shift.
When they start changing again in spring,
that's their cue head out of their overwintering grounds
and head north.
This leads to a particular problem that we refer to
as phenological mismatch.
So the idea here is that for a species like,
in this case, the pied flycatcher,
which has to migrate a very long distance;
it's a species that generally breeds in northern Europe
and overwinters in North Africa.
So in this case, their migratory cue
is less about temperature and much more about day lengths.
As we all know, day lengths is not changing over time,
but temperature is, and in particular, their resources are.
So for example, caterpillars are very responsive
to temperature change.
And this is a bird that relies heavily on those caterpillars
and really timing their migration to sync up
with the peak in that food resource.
So when that change in food availability shifts
to an earlier date, like we can see here,
but their arrival date of the birds remain unchanged,
you have a potential problem.
A good analogy would be if you're lucky enough to come home
for dinner at the same time, at 6 o'clock, let's say,
but every year, your dinner starts becoming earlier
and earlier at the dinner table,
maybe five minutes and ten minutes,
but you are coming home at the same time at 6 o'clock.
Well, you can imagine then, then you're sitting down
eventually for a cold dinner.
And that's exactly what's happening with these birds,
that their resource and their food availability
is moving earlier, but their arrival time is unchanged.
Now, for adult birds, that's actually not that bad,
not that big a deal.
They can take advantage of different resources,
but in particular, what that food availability is good for,
and that peak in food availability is that
they have enough food available to feed to their nestlings.
And so what we've found over time
is that this phenological mismatch is most acute
for these long-distance migrants that are really chasing
that peak in caterpillar abundance,
in particular so that they can feed them to their young.
Their arrival time is unchanged,
how long it takes to find a mate and set up a territory,
build a nest and start laying eggs.
That all has remained the same,
but it's no longer synchronized with that peak food supply.
In particular, those species that have to travel the longest
tend to be the most desynchronized with their food.
And in those populations, we're seeing in some cases,
a 90% decline over the past two to three decades.
So we've gone through an example of behavior, of range changes,
and changes in time, changes in phenology.
Well, what about population declines?
To explore this idea that climate change could in fact
be leading to population declines,
or at least contributing to them,
I'm gonna focus on a group of birds that we know
are in trouble, and these are grassland birds.
So I think many of us in the Midwest are familiar
that many species will occupy these prairie grassland,
in some cases agricultural lands,
species like bobolinks, eastern meadowlarks,
Henslow's sparrows, and dickcissels.
What we know is that many of these populations
of these species are declining significantly, as seen here.
All those red areas that we see throughout the maps
of North America for these three species of grassland birds
are areas where we're seeing declining populations.
What is causing these declines?
Well, we know that grassland habitat
is one of the most endangered type of habitat
and ecosystem in North America.
We've lost well over 95% of native prairies and grasslands,
primarily due to agricultural intensification
and the conversion of native grassland to agriculture,
as well as a rise and spread of suburban
and exurban developments.
So habitat loss is absolutely the primary threat
affecting populations of grassland birds,
but unfortunately, another threat is climate change.
So you can imagine these grassland systems
are highly exposed to changes in temperature
and precipitation.
So much so that when there are extreme events,
many of these grassland birds are highly exposed
to these flooding, as well as drought events
that can occur over decades.
We've estimated that well over half of grassland birds
are already facing additional pressures of climate change,
as well as habitat loss.
And that these grasslands are becoming drier
and more exposed to extreme events.
And even some of the common species that we consider
to be common are species of concern.
In particular, these climate pressures are interacting
with habitat loss.
So when we've explored how nest success,
so the ability of birds to raise nests successfully
in relationship to temperature,
what we found is that these smaller patches,
these more fragmented grasslands,
are exposed to these extreme temperatures.
And that's really where we're seeing
the decline in nest success.
So these grassland birds are being increasingly pushed
to these smaller and suboptimal grasslands.
While at the same time,
they're experiencing extreme temperature changes
both in spring and summer,
and these concurrent effects on their ability to reproduce.
What this has amounted to is that we've seen the loss
of roughly 720 million grassland birds since 1970.
In fact, if we look at all the different growths
of birds species from forest species to wetland birds,
grassland birds are showing the biggest declines.
A 53% population loss in grassland birds
since that 1970 period.
And even species that we once thought of being
relatively common like eastern meadowlarks here,
we've lost three out of four meadowlarks
during that time period.
And lastly, following behavior and range changes
and shifts in phenology, as well as population declines
attributed to climate change,
the other big and important component is disease
and the emergence of disease outbreaks.
One eye-popping and very visual phenomenon
is when we have mass mortality events in the Great Lakes.
And we can see this over time where we've been able
to document that in some years, we get a large number
of bird carcasses coming up on shores.
So here's Lake Michigan, dating back to the 1960s.
And you can see in some years,
thousands of bird carcasses wash up.
And then the other important pattern
is that you can see that the prevalence of those outbreaks
and those big mass mortality events
is becoming more common in the 2000s.
And it's just not Lake Michigan.
We've seen it in other Great Lake systems as well,
like Erie and Ontario.
So what is happening here?
These type of outbreaks are largely considered
to be botulism outbreaks.
Botulism outbreaks start with the prevalence
of an anaerobic bacterium,
a bacterium that grows in these low-oxygen environments,
that leads to these botulism type E outbreaks
in all systems, in all the Great Lakes.
The botulism type E produces the neurotoxin,
which is ingested and is magnified
in many of these bird species.
It leads to a loss of motor control, third eyelid paralysis,
and what's referred to as the limberneck syndrome,
where they lose muscular control in their neck
and slowly, their head descends below the water surface level,
they experience respiratory distress, and they drown.
This all begins in the sediment and alga outbreaks
that happen along the lake bottom
and in the shallow or surf, shallower waters.
This bacterium proliferates through the food chain,
from mollusk and crustaceans,
all the way up to bottom-feeding fish.
And then of course, the birds that are eating the fish
ingest it as well.
So this to the perfect example
of what's referred to as biomagnification.
And the creeping up of this bacterium through the food chain
and affecting multiple species of birds
that use the Great Lakes, especially during migration.
Species like common loons, long-tailed ducks,
horned grebes, and ring-billed gulls.
So how might climate change be exacerbating this problem?
Well, we've used satellite data to identify those years
when we see these big, massive outbreaks.
And one thing that is relatively common
throughout all these years is when lake temperatures rise
and are warming, which is what we've seen historically
and into the future, as well as the presence
of these algae mats that have been contributing
and getting worse due to the runoff from agricultural areas.
When you have these two components together,
warmer waters and the prevalence of algae,
that's when you get these botulism outbreaks.
And what we're beginning to see then
is that these warming conditions
will synchronize these outbreaks from multiple species
so that when the outbreaks do occur,
they affect more species
and extend across larger areas of the lakes.
So this returns us to this idea of birds
as sentinels of climate change.
And what I would say is that given these lines of evidence,
our sentinels are telling us that something is in fact wrong.
We've seen evidence of behavioral adaptations
that can only help so far,
significant range changes across the globe,
phenological changes, but also mismatches for those species
that are unable to track with a changing climate,
clear evidence of altered communities,
and populations are increasingly on the brink
due to the synergistic and interactive effects
of not just climate change, but habitat loss.
And finally, the climate-induced risk
of emerging infectious diseases
that can affect multiple species over large areas.
In terms of what we expect to see in the future,
almost all projections are in agreement
that even under our best estimates, by 2040,
we're gonna be about 1.5 degrees warmer than we were
compared to pre-industrial time.
That by 2060, it's more likely to be
about two degrees warmer.
And by the end of the century, we're pushing three degrees.
But under the worst case scenario,
that may be even worse and maybe even far-reaching
and warmer temperatures.
And we begin to look at this in terms of the geography
and the extent of that warming.
We can see that compared to the late 20th century,
we're only at the tip of the iceberg of warming.
But by the end of the 21st century,
we're likely in the realm of two, four,
and in some cases, maybe in these northerly environments,
six degrees warmer than where we were
in the pre-industrial era.
In terms of changes in precipitation,
what we're expecting is that dry areas
will only become drier,
and wet areas will only become wetter.
A lot of climate scientists are now concerned
that we are getting to the point of what's referred to
as planetary tipping point.
The idea here is over the last 10,000 years,
we've benefited from a climate system that has allowed us,
as a species, to dominate the world.
But because of human-induced changes in the land,
as well as fossil fuel emissions,
we're getting to the point where so much warming
will kick in intrinsic feedback cycles and systems
in the Earth's climate system.
So much so that we will be entering a new geological epoch
of a hothouse Earth,
which will be characterized by warmer temperatures,
mega droughts, increased extremes like flooding
and earlier springs,
as well as the persistent and chronic loss of snow cover
around much of the northern hemisphere.
But we really haven't reached that point yet.
We do have changes that can be enacted that can put us
on a different course in terms of Earth system stewardship,
and what we can do in terms of stabilizing
the Earth's climate system.
When we start thinking about the future for these species,
we are beginning to get a sense that many of these species
will be exposed
to an increasingly novel climate space.
For example, the Audubon Society has put a lot of effort
in terms of trying to predict which species
are going to be most affected by our future climate space.
Here, you have the common loon,
showing their wintering range climate,
as well as their breeding range climate
in the year 2000, 2020, 2050, and 2080.
And what we can see very clearly is that that climate space,
both in terms of where they overwinter and where they breed
is shifting strongly, strongly northward.
So much so that here in Wisconsin,
that climate space where they're breeding
will be completely gone by the middle of the century.
They've estimated that over 300 bird species
will lose more than half their climate space
by the end of the century.
So let's go back to my original idea, my hypothesis:
Birds are awesome.
But the question is,
are we pushing them to the limits of their awesomeness?
Indeed, our sentinels are telling us
that something is wrong in the mine cave,
but unfortunately, we can't really evacuate the mine.
So I'll make a couple of final points
when we think about climate change adaptation.
One is that degrees matter.
So here we see a chart looking at the proportion of birds
that are losing more than 50% of their range
by the end of the century
under different scenarios of global warming.
So 1.5, 2 degrees, 3.2, and 4.5 degrees.
What I would point out is that when warming is limited
to 1.5 degrees compared to with 3 degrees,
the number of species projected to lose
more than half their range is reduced by almost 40%.
Meaning that if we constrain our warming to 1.5 degrees,
we might be worrying about roughly about
10%, 12% of these birds.
As opposed to warming of three degrees or more,
where now we're talking about more than half
of these species are going to be increasingly at risk
'cause they're losing much of their climate space.
The other aspect of this is oftentimes noted that birds
and other species will simply adapt.
That birds, mammals, plants have all experienced
pretty amazing changes in the Earth's climate system,
from glaciation to deglaciation events.
And so, birds will simply put on that gas mask,
so to speak, and be able to kind of survive those changes
and what they're experiencing now.
There's a couple reasons
why this is likely not going to happen.
One is that the rate of warming that we are experiencing now
and are predicted to experience over the next 50 years
is unprecedented.
And because of that, the rate of adaptation
is likely not going to match that rate of warming.
Another important point here is that
we have altered the Earth's template.
We've converted more than 40% of the Earth's surface
to agriculture.
So all those corridors and pathways that used to exist
for species to be able to move in response
to a changing climate are no longer there.
Finally, I'd like us to think about this idea
of climate-smart conservation for birds.
And I think many of these ideas and strategies
are not novel or new to us.
We can think about identifying refugia.
How do we manage their habitats?
How do we think maybe about translocating species
that are particularly vulnerable?
For those species that are actively hunted and managed,
maybe we should revisit some of those harvest quotas,
think about additional monitoring of those populations.
Perhaps we need to revisit protected lands,
like sanctuaries or wildlife management areas
or national parks.
Are these areas still going to serve the same purpose
that they do now, 50 or 100 years into the future?
And finally, we need to better monitor
and manage disease outbreaks when they occur,
and to anticipate how climate may be influencing
those disease risks.
So it leads us to this question of "What can I do?"
And I would say there's a couple things.
That first, we can continue to thrive for being
more energy efficient in our own household and lifestyles,
whether it's changing to an electric vehicle
or thinking about energy efficient appliances.
I think every little difference we make does add up.
Second, environmental issues like climate change
oftentimes rank high on national polls
and suggest that people are concerned about this,
but sometimes they don't enter the political discussion.
And I would encourage us to think about climate change
not just globally, but also locally,
making it an issue for local politics as well.
What can we do at the county level,
at the city level, and at the town level?
And finally, let's continue to tell stories.
This may not necessarily be in terms of climate change,
but just continue to talk to your friends and partners
and family about some of the changes that you're seeing,
maybe in your own backyard.
Are there species that maybe you saw when you were a kid
that you no longer see?
Are there species that you don't remember seeing
that are suddenly showing up?
I think these stories are important and help to convey
a broader message about how species and birds
are responding to climate change.
And finally, become a citizen scientist.
Join iNaturalist, eBird, or Project FeederWatch.
You don't have to be an expert, you can be a beginner,
but every single data is important
in terms of what we can say in terms of how birds
are responding to climate change.
I think it's fair to say that I'd have a lot less to say
in terms of my presentation today without those data
and those efforts.
And with that, I'd like to acknowledge what is probably
one of the most inspirational component of what I do,
which is working with a whole host of graduate students
and research scientists,
as well as collaborators and funding agencies
who see the value of this work and will continue to work
and research into the future.
So thank you for joining me today.
I hope you can start seeing how birds
are these important sentinels of climate change,
and as a call to action of what we need to do
in order to mitigate and adapt to a changing climate.
Thank you.