Category Archives: Climate change

May 15, 2022 · 10:07 pm

Crow curiosities: do crows migrate?

That birds travel seasonally is perhaps one of the most familiar facts about the natural world. Whether it’s the arrival of technicolor spring migrants, or the din of waterfowl above our heads in the fall, it takes no formal training to recognize that something novel and beautiful has suddenly erupted into our lives. Their ephemeral presence offers an opportunity to ground ourselves in time and place and reflect on the shape of our lives since our last meeting. Or, if you don’t want to get that deep with it, there’s always Looney Tunes or any number of other children’s cartoons to remind us that some birds come and go with the seasons.

At the same time, for most of us living in the continental United States, that crows will be nearby to accompany us throughout our year is something we take for granted. Their predictability on our telephone poles and near our garbage cans is one of those quiet details not everyones thinks of often, but whose consistency surely calms us as so many other things feel unsteady. But at the intersection of these truths is an interesting question: if migration seems such an essential part of bird life, why don’t crows do it? Or do they?

Of the world’s ~ten thousand birds species, only 18% actually undertake annual long distance migrations.1 But there are other types of migration including short distance migration, altitudinal migration (short migrations from shorter to higher altitudes) and partial migration. Partial migration is when only certain individuals within a population migrate, while others are sedentary, and it’s this one that applies to crows. Because while crows in temperate Seattle may be quite comfortable year round, those that call higher latitudes “home”, say central Canada, would have a tougher time making it through the winter unscathed. So much like a wealthy aging relative, they snowbird it to more welcoming climates for the winter.

Until the last decade or so that’s really all we knew about about crow migration. Some did it, some didn’t, and that was that. But given the value of better understanding this behavior, as well as the technological advances that make it possible, western science has finally turned its eye to inspecting these patterns more closely. Because there are so many questions one could ask about this phenomenon. Why do some crows migrate and others do not? Do the same crows migrate each year or can they opt out? Do they return to the same place? How far do they fly? How do they survive the journey? How do they sleep?

In some cases the answers to these questions are surprisingly nuanced. For instance, birds living in the Central and Southern Canadian provinces will nearly always migrate hundreds of miles south into the US, which makes sense because Canadian winters can be especially harsh. But studies have shown that other crows make even shorter migrations, only about 350 miles between contiguous US states with similar climates.2 What motivates these shorter-distance trips remains to be seen. Likewise, whether migrating is a discretional activity is still in question. From a climate change perspective, that individual birds might be able to choose whether or not to migrate each year would have important implications in their ability to adjust to changing conditions. But in the studies conducted so far there’s been no evidence that crows pick and choose each year, rather it seems that you’re either a migratory individual or not, albeit this is based on low sample sizes.3 As a result, migrating crows show extremely high site fidelity; returning to the same breeding and winter sites each year.

As far as distances go, there’s huge variability there as well. In a study that looked at crows from both sides of the country, the average distance traveled by east coast crows was 287 miles, while west coast crows traveled an average of 366 miles.3 The longest migration on record is 1740 miles.4 One thing that’s for certain is that migration is a daytime affair. While most birds migrate at night, crows are among the minority that stick to business hours for their travels. The most compelling explanation for strategy is the “fly-and-forage” hypothesis. Look, even for the arguably most efficient fliers in the animal kingdom, flying is hard work and crows need a lot of calories to sustain flight speeds up to 37mph covering as much as 186 miles in a single day.2 To accomplish this, crows will make up to several pit stops during a marathon flight session, allowing them to refuel and prepare for the next leg. Importantly, although crows migrate both in groups and alone, when stopped they almost always make sure to dine with others. Traveling in the daytime probably helps facilitate finding other crows, and by extension, the local feeding grounds.

When it comes to sleeping, crows leave the fancy mid-flight naps to the swifts and the frigatebirds, opting instead to sleep at night in communal groups. In fact crows will sometimes abruptly change direction just to follow local birds to the nearest roosting grounds. In other cases though, crows have been know to travel routes that allow for stops at the same roosts year after year, underscoring why roost locations should be considered key pieces of habitat.2

So as it stands, crow migration can be summarized the same way as most other parts of their lives: we know some stuff, not everything, we’re probably wrong about a few things, and our best bet is to accept our role as eager pupil and celebrate the gifts of knowledge as they are granted to us.

Literature cites
1. Sekercioglu C.H. 2010. Partial migration in tropical birds: The frontier of movement ecology. Journal of Animal Ecology: https://doi.org/10.1111/j.1365-2656.2010.01739.x

2. Ward M.P. and Raim A. 2011. The fly-and-social foraging hypothesis for diurnal migration: Why American crows migrate during the day. Behavioral Ecology and Sociobiology 65: 1411-1418

3. Townsend A.K., Frett B., McGarvey A. and Taff C.C. 2018. Where do winer crows go? Characterizing partial migration of American crows with satellite telemetry, stable isotopes, and molecular markers. The Auk 135: 964-974

4. Brewer D., Diamond A.W, Woodsworth E.J, Collins B.T.,, and Dunn E.H. 2000. Canadian Atlas of Bird Banding, vol 1: Doves, Cuckoos, and Hummingbirds through Passerines, 1921-1995. Canadian Wildlife Service, Ottawa, ON, Canada

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Filed under Climate change, Crow behavior, Crow life history, Movement

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October 20, 2021 · 9:54 pm

How smoke affects wildlife

It’s September 8th, 2020 when I step out my front door in Eastern Washington into a landscape that looks like the aftermath of a Martian dust storm. The video I am recording captures my bizarre, sepia-colored surroundings as I try to put words to the experience of having your world an entirely different color than it was the day before. Like any inconsequential casualty in a disaster movie, my usual sense of self-preservation has been abandoned in favor of standing in harm’s way, mouth agape with my phone outstretched to the sky. After a minute, I realize my error and head back inside where I, and millions of other people on the West Coast spent the next several weeks hiding from air that can kill you.

That year, wildfires would go on to burn a total of 10.2 million acres on the west coast, cause $19.8 billion dollars in damage and directly kill at least 37 people. Over the last 30 years, fire severity and duration have increased and it’s impossible not to notice. Decades of wrongheaded fire management coupled with increasingly hotter, drier summers have meant that the 2-3% of wildfire starts we fail to suppress burn under the very worst conditions, pumping the air full of the kind of fine particulates that are irritating at best and deadly at worst. Unsurprisingly, the public health community has been swift to respond, with hundreds of studies examining the outcomes of smoke inhalation on humans. But while I and many other people were able to escape indoors during the worst of it, crows were unanimously stuck in a sepia haze…breathing. One has to ask; how do they cope? How does any wild animal cope?

Among those wondering was Olivia Sanderfoot, an imminent PhD graduate from the University of Washington. While there, she spent the majority of her time asking different questions about how smoke impacts wildlife, especially birds. In pursing her own research, Dr. Sanderfoot made a striking realization: despite the fact that nearly every birder, biologist and person were all wondering about how animals deals with smoke, there were only a few research studies. So with the help of her graduate lab, including myself, she resolved to collect and synthesize what papers were available into a comprehensive review. Published just this week, I am eager to share what we found.

As of the time our article was accepted, there have been only 41 English language studies examining the impacts of smoke on wildlife. Of those, less than half (44%) examined in situ (free ranging) animals dealing with real smoke events. Most were controlled studies where animals were intentionally exposed to smoke to learn about its impacts on their health or behavior. We found that from insects to sugar gliders a variety of different animals had been studied, but only 7 papers focused on birds (and sadly none on crows). Birds are of particular interest not only because, crows, but also because birds have a more efficient respiratory system than any other vertebrate. While this usually offers many advantages, it also quite literally makes them the canary in the coal mine—their high sensitivity to air quality acting as an important bioindicator in addition to the obvious consequences to welfare and conservation.

Although we had hoped to find clear answers to exactly how wildfire smoke impacts animal health, we only found 10 papers that addressed health outcomes specifically, and only 4 that ultimately looked at survival. Still, there are many more papers examining this question either in domestic animals, or animals models that are used as proxies for humans. When taken together with those findings, it’s clear that smoke isn’t good for animals, resulting in anything from carbon monoxide poisoning, to respiratory tissue damage, higher blood acid levels, stunted growth, compromised immune systems, and even death. Beyond direct health effects, exposure to smoke can may also reduce reproductive success. For example, researchers monitored the red-knobbed hornbill, a sort of toucan-like bird native to Indonesia, suggested that smoke might have contributed to a decline in the bird’s nesting success.

Smoke can induce behavioral responses among animals as well. Animals may become confused, agitated, vocal, lethargic, or quiet. For example, Bornean orangutans rest more during and after smoke events, Bornean white-bearded gibbons sing less, and sugar gliders extend the duration of torpor. Meanwhile pinecone lizards flick their tongues more, Psammodromus lizards start running, and many species of bats rouse from their torpor. Some birds are harder to detect like bald eagles, bushtits, killdeer, osprey and marsh wrens, while cedar waxwings, western tanagers, red breasted nuthatches, and yellow warblers actually become easier to detect as particulate matter (smoke) increases.

When taken together, it’s clear that wild animals are sensitive to smoke, and that smoke can have dramatic impacts on their health and behavior. But perhaps the most important finding of our review is that the predictability of these consequences for any future wildfire event remains almost completely out of reach. Because the thing about smoke is that it’s not all created equal. Smoke can have vastly different consequences to health depending on what’s burning (just think of the carcinogenic difference between cannabis and cigarette smoke), not to mention the impact that concentration and duration of exposure can have. And unfortunately, most existing studies haven’t undertaken the kinds of robust studies of air quality that are needed for this kind of future predictive power. Still, knowing this, and having a framework of existing knowledge and methodology, means that future studies are poised to finally start building the foundation we need for sophisticated, predictive modeling.

Until then, we can expect that smoke events like the kind we experienced in 2020 will continue to haunt our changing planet, and while some humans can safely nest alongside their air purifiers, many more, and all our wildlife, are at the mercy of an airscape they cannot retreat from. For now, this is our reality but it need not get inhospitably worse. Just has humans are capable of bullheaded, catastrophic damage, we are also capable of a profound capacity to change, improve and heal. It’s time to take bold, industry/system level steps towards changing our climate future, if only we can find the will to do so.

Read the whole paper here: https://iopscience.iop.org/article/10.1088/1748-9326/ac30f6/pdf

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Filed under Birding, Climate change, Conservation, Corvid health, New Research, Wildlife

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October 27, 2018 · 10:32 pm

Denali Diaries Part II: The Wildlife

While Denali is worth visiting on the basis of its scenery alone, it’s the wildlife that will truly shape your experience.  In the summer, Denali is host to some eight species of medium to large sized mammals, including foxes, lynx, wolves, grizzly bears, black bears, caribou, Dall sheep and moose.  Among those, the moose, grizzly bear, caribou, wolf, and Dall sheep make up what’s known as the “Denali Big 5.”

Seeing wildlife in Denali is mostly about luck and timing, but the longer you’re in the park the more chances you have to view wildlife.  As I described in my earlier post, I scheduled and bus hopped my trips in such a way that I stayed in the park most of the day.  This is particularly important for moose, which are generally crepuscular, meaning they are more active in the morning and evening . Everything else is really just a gamble. Sometimes the odds are in your favor and sometimes they’re not. For what it’s worth, though, out of my four all-day trips into the park I got The Big 5 twice, both during the times I stayed primarily on the bus.

While I always left the park having experienced something new, there were definitely trips that were more memorable than others, and the range of experiences really made me appreciate the luxury of being able to go multiple times.  Whatever wildlife you do have the privilege of encountering is sure to fan the flames of your love affair with this park, but I imagine for many people that affair starts first and foremost with the most visible and charismatic of Denali’s wildlife: The grizzly bears.

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I took this photo in late August, just as the colors started to change.

By late July, bears across Alaska are gearing up for hibernation by entering a phase called hyperphagia, where they basically eat constantly and gain somewhere on the order of 400 pounds.  In the park, their diet consists mostly of blueberries, soapberries, and roots, but they will gladly eat whatever mammals they can catch, including small rodents, caribou, moose and even other bears.

A big highlight when bear watching is seeing sows out with spring cubs. Unlike mom, the young are generally a lot darker in color, prompting people to sometimes mistake them as black bears.  Observing cubs playing, foraging, and trying to keep up with mom is definitely the kind of experience that will make you wonder if you were somehow transported, Truman style, to some kind of nature documentary, but in the best kind of way.

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While I won’t pretend for a second that seeing bears ever gets old, they honestly weren’t the animal that I was most looking forward to encountering when I arrived in Denali.  Maybe it’s because I’d never seen one before, or because of some deep affection instilled by decades of Christmas marketing, but something about caribou utterly charms me.

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Unlike many of Alaska’s other herds, the Denali caribou do not undertake an immense seasonal migration, opting instead to remain almost exclusively within the bounds of the park year round. Unless you can travel into the interior of the park, however, you’ll have little luck seeing them in the winter.

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Denali used to play host to a herd that ranged in the tens of thousands, but after decades of over hunting followed by a mysterious period of low calf survival and harsh winters, Denali’s herd has dwindled to around 2,000 individuals.  Fortunately, things seem to have stabilized for the time being. I wish I had seen more before the end of the season, but I’ll never forget what it was like watching this small herd move through this painted hillside.

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The ungulates that seemed to most delight my fellow visitors, however, were the moose.  For all of Denali’s hooved animals fall is the rut, which means males have grown out their antlers or horns and are putting them to use in sparring (practice) matches, as they ready themselves for the violent matches to come.  I only saw such behavior between moose once.  They locked antlers for a few seconds and went back to grazing shortly thereafter.  Unfortunately it was too far away to bother with any photos.  I’ll admit, seeing a bull moose, particularly on foot, is a gripping experience.  However big you imagine them to be, they’re bigger in person.  The rack alone can be 40lbs.

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In Denali, the stakes of these fights are high, as the moose here operate in a polygynous system, where the victor will mate with and defend an entire heard of females.  In other places, moose form monogamous pairs for the breeding season.

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It was early morning still when we watched this cow move her two calves across the valley. They seemed pretty wary of our bus, though her biggest real threat is the park’s main carnivorous predator: The gray wolf.

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Even in Yellowstone I don’t get my hopes up about seeing wolves despite there being far more individuals there. Across the Denali’s 6 million acres, there are only 30 known packs comprising about 75 adults. You can imagine my delight then, when, as we were making our way out of the park at dusk on our first trip, we rounded a corner to see this rump trotting up ahead of us. As it happens, I had been walking the road on foot only minutes before. I probably wouldn’t have caught up with it had I not gotten on the bus, but it’s still pretty incredible to imagine that I more or less went hiking with a wolf. We must have followed this adult for about a mile. It stopped a few times, evening giving it’s signature mournful howl a before it disappeared off the side of the road. Honestly, that would have been enough for me, but our second to last trip had something really special in store.

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I had heard whispering about wolf pups back at our housing campus but I never thought much of it. I figured that was deep interior kind of stuff, the kind of trek our field schedule just wouldn’t permit. So while I figured it was something exciting when we arrived at a jam packed road, I just wasn’t picturing this…

Cue total F-ing meltdown on my part.

This pup was born sometime mid-may to the single male and female that comprise the Riley Creek West pack.  By around four months the pups start venturing away from their den site.  Lucky for us, for a few day stretch the area they were exploring was right near the road by Toklat.  After a few days, they moved away from the road, which was no doubt for the best.

The last animal I have the great pleasure to highlight is the most iconic of Denali’s wildlife.  In fact, it was this animal for whom the park was dedicated.  The endemic Dall sheep.

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In 1906, hunter and conservationist Charles Sheldon noticed a worrying decline in the Dall sheep favored by hunters.  He feared that without protection, they would be hunted to extinction. Now this is an all too familiar concept, but coming off the heels of the “era of abundance” this was actually a revolutionary way of thinking in western culture.  Until 1900, colonists/settlers in the United Stated hunted without regulation and, seemingly, without much thought or worry as to the integrity of ecosystems. As a frame of reference, the field of wildlife management wouldn’t come onto the scene for another two decades.

Sheldon, however, had the foresight to recognize that something must be done and set out to establish Denali as a national park.  It took 11 years, but in 1917 Woodrow Wilson signed the bill into law. Since that time Dall sheep populations rebounded and are currently considered healthy.

Despite their robust numbers, however, most of my experiences of seeing Dall sheep in the park were “technical”.  As in, “technically those white specks on the mountain side are Dall sheep”. So on our last day as we traveled out of the park, I couldn’t believe my eyes when a ewe and her lamb were jogging down a hillside close enough that you could judge their forms as Dall sheep even with your naked eye. For the minute or so that we were able to watch them, I felt myself overcome with equal parts joy and despair.  I was profoundly grateful for the gift of such beauty and yet so sad that once again its integrity is under such threat.

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Driving home one night, my fellow passengers and I shared our backgrounds and motivations for visiting the park.  Some came to experience mammals the size of which dwarfs anything in their native country, some were fulfilling missions to visit all the National Parks, while others had arrived with a spirit of adventure and little else.  Together, we marveled at the unforgettable things we had seen and shared our anxieties that future generations may not be so lucky.  We discussed our anger and disappointment (or among some of the foreign tourists utter bafflement) at the US government’s unwillingness to act more effectively on climate change.

One hundred years ago someone looked at this land, recognized that change must be implemented, and fought for over a decade to convince congress that in fact wild spaces and wildlife mattered enough to act.  As a result, my fellow passengers and I got to see and experience things that will bring us joy the rest of our lives.  The question now is whether we will wage our own fight for the future, or if we will watch from the sidelines as it turns to ash in our warming world.

***

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For information about climate change in the arctic please visit the following resources

NASA’s Arctic-Boreal Vulnerability Experiment

The National Snow and Ice Data Center

Chasing Ice

And remember…
~PLEASE VOTE ON NOV 6TH~

 

 

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Filed under Climate change, Conservation, Denali Diaries, Ecosystem, Photography, Wildlife

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