All About Inversions

Last week I mentioned in passing that I’d get around sometime to doing a post about inversions as soon as we got a bad one. Someone must have heard me. We’re in the midst of a really gross inversion, and so I guess I’m out of excuses not to blog about them.

Saturday I had mountain bike fever, and everything’s snowed under around here, so I left the house before dawn and did 2 different rides out in the West Desert. The rides had me in and out of the inversion a couple of times. Today I’m going to do a brief post explaining what an inversion is, why they occur around here so often in Winter, and why they… well, suck. Tomorrow I’m going to explain the impact of inversions on trees in the Great Basin, and how they (inversions) make the Great Basin look the way it does not just when they occur, but all the time. Then- if I don’t get distracted, bored or simply flake out- I’ll do 2 more posts that zero in on one of the 2 trees most strongly impacted by inversions. Here we go-

The Basics

Most of the time, in most places around the world, temperature and altitude work like this: for every 1,000 feet you go up, the temperature decreases by 3.6F. That’s why going up the canyons is such a pleasant escape from Salt Lake in the summer. But sometimes this temperature/altitude relationship gets inverted, with colder air down low close to the ground and warmer air up above, and this inverted state is called a (wait for it…) thermal inversion.

Thermal inversions happen all over the world. Los Angeles, Shanghai, Mexico City, London all get terrible inversions. In fact the polar regions in winter are under inversion most of the time. There are a few different types of inversions with different causes. For this post, I’m focusing just on the causes of inversions in the Great Basin.

Normally during the day, the ground gets heated up by the sun (which you already know if you’ve ever burned a bare foot on sand or pavement.) The hot ground warms up the air immediately above it, and that warmed air rises. But in winter, with snow on the ground and a low sun-angle, the ground is often colder than the air, and acts to cool the air immediately above.

The cool air is dense and so it doesn’t rise; it sinks, hugging the floor of the valley. When the weather is “nice”, with clear skies and high pressure, warmer air in the sky above, the warmer air sits on top of the cold air, which can’t rise, holding it in place in the valley below. During an inversion, freezing water vapor from a water source- such as snow- is produced by evaporation (technically sublimation if directly from snow.) The water vapor can’t rise up to dissipate or form clouds or whatever, and instead and fills the cold-air layer with a chilly mist. The damp air serves to amplify the chill, especially for us Westerners, who are accustomed to a ”dry cold.”

Side note: Utah Lake provides a ready source for such moisture, which is why Utah County, which basically encircles Utah Lake, so often goes on “Red Air Alert” before Salt Lake County, which lies at a bit more of a distance from Great Salt Lake, despite having far more cars driving around.

In a valley ringed by mountains, like Salt Lake, or Cache or Utah or Tooele valleys, the effect is worsened because there’s no “open wall” for the cold air to escape through without rising.

Inversions are completely natural. They happen throughout the Great Basin, and have been doing so since long before people showed up. What’s not natural is a million people driving cars back and forth for a week in a single valley during an inversion, and that’s where inversions become unhealthy.

The Gross Part

Automobile exhaust fills the air with nitrous oxide (NO), carbon monoxide (CO), and various hydrocarbon compounds. Under normal conditions, the warmer air near ground-level continually rises, carrying these pollutants upwards with them to a higher altitude where they can be dissipated by winds. But in an inversion they don’t go anywhere; they just sit and stew. And by stew, I mean that sunlight acts on them to produce various chemical reactions that produce ozone, and a whole slew of nasty compounds, such as peroxyacetyl nitrate (PAN, chemical diagram right). These compounds are known as secondary pollutants, as they’re not the stuff that comes directly out of your tailpipe, but rather the result of the sunlight-fueled reactions between the tailpipe emissions and other stuff in the atmosphere.

Strong oxidants, such as ozone (O3), irritate mucous membranes, including eyes and lungs. Irritated lungs can stress hearts. Some of the other nasty hydrocarbon-derived molecules produced are worse, even carcinogenic. This is why the weather-guy tells you not to run or bike outside during a bad inversion.

Tangent: I do so anyway. Outdoor exercise is extremely important to my mental health. I figure I’d rather live 50 happy years than 80 morose ones. But do what I say, not what I do.

There are other sources of pollutants that contribute to bad air conditions during inversions, but cars account for the lion’s share by far. The air quality effects are exacerbated by thin air, which is a by-product of altitude, which is why 8,000-foot high Mexico City suffers so terribly from inversion-produced smog. At ~4,300 feet, the altitude is also a factor in Salt Lake’s inversions.

Tangent: In Salt Lake City, you have about 90% of the air you would at sea level. In Denver, (5,280 feet) you have 82%. At 8,000 feet you’re at about ¾ of the air you have at sea level, and at 10,000 feet, it’s around 2/3. Atop 14,000-foot high Mt. Evans, you’re down to 54%. I know all this because when I lived in the Denver area I had a watch with a barometer.

For about a decade I went through a succession of watches with built-in barometers, altimeters, compasses and altitude logging computers. Then at around age 40 I realized I really didn’t need to know every time I changed 100 feet in elevation- and it wasn’t like the watch could actually do anything about the altitude- like change it or anything. Now I just wear a watch.

So now we know what causes inversions and why they suck, and why we really shouldn’t be driving during them. But before I wrap it up and link inversions to trees, here’s a cool bit of inversion trivia.

Bonus Inversion Trivia

The cold air/warm air boundary in an inversion acts as a refractive/reflective transition barrier on waves, such as electromagnetic waves. I talked about refraction and reflection when I explained how a rainbow works back in August. I won’t repeat the explanation here, but check out that post if you want to understand how refraction works.

FM radio transmissions sometimes are reflected off the boundary, then sometimes off the ground, then off the boundary again, and so on, allowing your FM radio to pick up transmission from a station dozens, even hundreds, of miles away. This effect doesn’t manifest itself much in a fairly small valley like Salt Lake, but occurs pretty often in a huge valley, like California’s Central Valley (which has awful inversions.)

A similar effect can happen with light, leading to a type of image known as a Fata Morgana, which sounds like a character out of Lord of The Rings, but is actually just a fancy-sounding word for a mirage. Fata morganas are most often seen under conditions combining inversions and far horizons, such as the ocean. Ships, icebergs and islands all can be the subject of them, and the fata morgana can actually make one of these objects visible even when it would otherwise be hidden by the curvature of the Earth.

The same effect can occur not only with electromagnetic waves, but with shock waves. And in fact just such a shock wave reflection happened in what is today Kazakhstan in 1955, when the Soviet Union conducted its first successful test of a hydrogen bomb. The shock wave from the blast was reflected back from the inversion-boundary, killing 3 observers on the ground.

Next Up: So what do inversions have to do with trees?

Line Of Sight

I have a “real” post today, and it’s a cool one. But I can’t start into it without first observing the passing of Ricardo Montalban.

Tangent: I loved Ricardo Montalban, and here’s why: He had the Best Accent Ever. Charming, elegant and melodious, his accent was simply captivating.

I’ve always wished that I could sound like Ricardo Montalban when I spoke a foreign language, so that native-speakers would be immediately taken with my presence, sophistication and je ne sais quoi. But the only other language I speak (poorly) is Spanish, and I’ve had enough frank conversations with native Spanish speakers to know that an American accent is not pleasing to the Spanish ear.

Now in English, different accents sound more pleasing than others. Most of us native English-speakers would agree that we find a French accent, for example, more appealing than a Russian, Indian or Chinese accent. So my question is this: In what foreign language does speaking with an American accent make me sound like Ricardo Montalban to the native-speakers? Because wherever that country is, if I ever find out, I am dropping everything, moving my ass there, learning the language and spending the rest of my days exuding silky charm, elegance and sophistication.

Adiós, Don Ricardo. Que le vaya bien.

The Real Post

I post a lot of photos in this blog. Usually they’re intended to be helpful, to give the reader a feel of the place or thing I’m blogging about, and sometimes they’re just to show off me or my kids, or poke fun of my friends. In any case, they’re usually not essential to the story; I just like stories with pictures, and I assume other people do as well.

This photo’s different. Though it’s one of the least impressive photos to appear in this blog, you need to look at it to get the post.

I took this photo on a morning following a storm last week from the Olympus Cove shopping center parking lot, right off of I-215. The ridge in the foreground in Stansbury Island in the Great Salt Lake. The high peak rising behind it is Pilot Peak, just across the state line in Nevada, about 15 miles North/Northwest of Wendover. I shot the photo with 12X magnification (hence the lousy quality.) The distance from the Oly Cove parking lot to Pilot Peak is 119 miles.

History-Tangent: Pilot Peak (pic left = Pilot Peak seen from Desert Peak, high point of Newfoundland Range) is so named because it’s the landmark that westward-bound pioneers aimed for when crossing the 80-mile waterless stretch of salt/mud flats on the route known as the Hastings Cutoff. The springs at the base of Pilot Peak provided the first water at the end of that stretch, and the path across the salt flats leading toward the Peak were littered with dead livestock, stuck/broken wagons, and abandoned gear. The Hastings Cutoff was the path followed by the Donner Party. Though they had a difficult time across the salt flats, the delay that caused their eventual misery in the Sierra happened a week or so earlier, when they spent several days hacking a road down Emigration Canyon.

Pilot Peak is the furthest thing you can see from the Salt Lake Valley. It’s only visible on clear days, which is why I always make a point of looking for it the morning after a storm.

Tangent: Everyone who lives along the Wasatch Front knows that storms clear out inversions and pollution. Much of this clarity comes of course from the disruption of the thermal layers that constitute an inversion.

Nested Tangent: I plan to do a post on inversions, where I explain what’s going on with them and why they’re so darn interesting, even if they are gross and cold. There just hasn’t been a bad one yet this year to blog about. But I’ll get to it.

But the other reason for the clarity is that precipitation actually removes particulate matter from the atmosphere, and the reason for this is that both snowflakes and raindrops typically form around a bit of dust at their center, and so as billions of snowflakes/raindrops are formed and fall to the ground, billions of little particles are “pulled down” along with them. I explained the mechanism of snowflake formation around a dust particle back in October, so I won’t repeat it here, but you can check out that post if you’re interested.

When you grow up in the East and then relocate to the West, you never stop being amazed by How Far You Can See. 119 miles. That’s as if from the house I grew up in, in the suburbs of Boston, I could see clear to Albany, New York. That is astounding. I never cease to be amazed by it, and I am equally amazed that the million or so people in this valley with me hardly seem to notice.

Tangent: What really amazes me about my valley-mates (and is probably more properly the topic of another post, but when did that ever stop me from going off…) is how they can live for decades under the shadow of these fantastic peaks- Lone Peak, Timpanogos, Pfeifferhorn, Twin Peaks, Olympus, Ben Lomond, Nebo- and never climb them. How can they bear it? To never see how grand and majestic and utterly magnificent our valley is from these peaks- Isn’t it torture?

Nested Tangent: Yes, I’ve climbed (nearly) all of them, a topic I’ll return to later in the post, probably in yet another tangent…

To see things 50 or 100 miles away- and know what you’re seeing- gives you a sense of scale and feel for the landscape that you don’t get if you live your life in places where you can’t see faraway things. And if you’ve actually stood atop the point you’re looking out at, then that sense and feel is an order of magnitude clearer.

In October, 2002 I climbed Pilot Peak. It’s a trail-less scramble, typical of so many West Desert climbs, only higher, at nearly 11,000 feet. (For a more detailed description of the methodology and experience of such climbs, see this post.) From the summit I could see West to the crest of the Ruby Mountains, where I’ve also stood. (pic right = Liberty Lake, in the Ruby range.) From the Ruby summits you can look down into the Humboldt valley and Elko, NV. That’s a continuous line of site- with just 3 segments- from the Oly Cove shopping center to Elko, NV, a distance of ~200 miles.

I’m just getting started.

From the summit of Pilot, if you turn South you’ll see Ibapah Peak in the Deep Creeks (pic left), which I climbed back August, 2004. From Ibapah you can see 13,000 ft Wheeler Peak, further South, in Great Basin National Park, which I climbed in October, 2005. From Wheeler Peak you have a clean line-of-sight to Notch Peak (climbed May, 1998 and October, 2005) in the House Range, back East across the UT state line.

Tangent: Notch Peak is unbelievably dramatic; its West side is a sheer, 3,000 foot cliff, far and away the biggest, scariest, most awesome cliff East of Yosemite. (pic right = looking down 3,000 ft cliff en route to peak.) The climb is a piece of cake (<2 hours hiking) and offers an easy side hike to an outstanding ancient Bristlecone Pine forest. There’s never anyone there, and I know hardly anyone else who’s been there. Utah readers: Go do it- you will be blown away.

From the crest of the House range you can look back East to the crest of the Tushars behind Fillmore and Beaver.

Tangent: If you’re a Utah mtn biker, add the Skyline Trail East of Beaver to your must-ride list (pic right). Rugged, challenging singletrack though pristine spruce/fir forest with plenty of great views.

From the Tushar crest you can see clear to the Aquarius Plateau, which sort of merges into Boulder Mountain on its Eastern side. I’ve been all over the Aquarius and Boulder Mountain on several trips over the years. From Boulder Mountain you can easily see the Henry Mountains (last range in the lower 48 to be mapped) to the East. I climbed the high point of the Henrys, 11,000 ft Ellen Peak, in September 1995. From there you can look East to the La Sals (high point = Mt. Peale, climbed June, 2006) or Southeast to the lower Abajo Mountains, just West of Monticello. (pic left = Abajo range, seen from Mt. Peale)

Tangent: Ellen Peak is so easy a climb, you could practically do it in your flip-flops. You start at Bull Creek Pass, and it’s maybe a mile and a half of super-mellow climbing, great views the entire way.

On a clear day in September, 1993, from a minor summit in the Abajos, I spied Shiprock, the sandstone monolith outside the namesake town, in Northwestern New Mexico.

That’s a continuous (if circuitous) line of sight from my home to Shiprock, NM, a crow-fly distance of ~340 miles. I’ve done similar lines of sight East to Grand Mesa, CO, North to the Sawtooths in ID, all over Southwest UT and Southern NV to Las Vegas, and a cool one from Organ Pipe Nat’l Monument to the Sea of Cortez.

And this brings me to the point of this post, and my dream line-of-sight project: a continuous line of sight from my home in Salt Lake to the Pacific Ocean.

I’ve got a good start, with a solid line out to the Rubies. I’ve also been on the Toiyabe Crest (pic right), and could probably make a Toiyabe – Ruby connection with just 2 climbs. From the Toyaibe Crest I could probably make the Sierras in 2 climbs, the first one maybe being the Desatoya range, which I noted on our Cross-basin road trip back in August.

For the Sierras I’d need a bit more research. They’re a wide range, so I’d probably need to do at least 2 summits, and the other problem is summiting at a point where I could see across the Central Valley to one of the Coast ranges. This part would be easier if I summited further North, where the Central Valley narrows a bit, but the coast ranges up North get “fatter” and merge with full-on inland ranges, like the Trinity Alps.

So the California part isn’t yet clear, but the Salt Lake to Sierra Crest connection is within my grasp.

Tangent: This is as good a time as any to mention another, almost-completed, project: the Every Peak I See Project. Sometime in 1997 I was out in the middle of the Salt Lake Valley, running an errand or something, and I took a moment to look around. I decided then that I wanted to climb every major peak visible from the valley floor. I’ve done all but 3. Red dots on the map below indicate valley-floor-visible peaks I’ve climbed, yellow dots indicate the remaining 3.

2 of the remaining 3 are on Kennecott property, and will require getting permission. (I hear this is a tedious and difficult process.) The 3^rd, Grandview Peak (not to be confused with Grandeur Peak) is just a really long, tedious access, for an (allegedly) unspectacular peak. I’ll get around to it…

I like to keep multi-year projects like this in the back of my head. They give me something to dream about. Me, my truck, my boots, a daypack, and one week. Just one week, and I can make the Sierra connection.

Berry-Go-Round Reminder

Just a quick reminder that the next edition of Berry-Go-Round will be hosted here on Watching the World Wake Up around the end of the month. Submissions are due January 26^th; email them to me at adventurebotanist@yahoo.com, or use the BGR submission form. All plant-related submissions are welcome, and I included some ideas in this post last month.

Dr. A over at The Phytophactor said this to me earlier this week:

If everyone were a botanist, or liked plants like a botanist, the world would be a better place. Actually I think everyone wants to be a botanist, but it takes some people longer to figure that out than others.

I say right on, Dr. A. Plant-lovers make the world a better place, and I’ll follow up his wise words with this:

There are 2 kinds of people in the world- people who know plants are way cool, and people who haven’t yet realized how cool they are. If you’re one of the 1^st kind, help the 2^nd kind out and make the world a better place; submit a post for the next BGR.

(Plus, I will say great things about your blog, and if you haven’t already figured it out by now, I am an awesome pitch-man.)

It’s Called “Limber” For A Reason

Saturday I had a full day of backcountry skiing with Organic Chemistry Rick (guy who never reads my blog) and Clean Colin.

Tangent: Actually it was only skiing for OC Rick and me; Clean Colin is a snow-boarder, and he takes a split-board into the backcountry. A split-board is a diabolically clever contraption that looks like a normal snowboard, except that it comes apart, or “splits” longitudinally into two separate boards. The bindings disconnect from the standard snowboard position and reconnect into a ski-binding-like position on either piece of the board. The boarder applies mohair skins to the two pieces and ascends the slope like a backcountry skier. At the top, he/she removes the 2 pieces, reassembles the board, and reinstalls the bindings. At the bottom of the run, the process is repeated and reversed.

The downside of the whole split-board methodology is that it is huge equipment dick-dance, requiring a speedy, non-trivial, MacGyver-like disassembly/reassembly process, with various cables and clamps, not once, but two times for every run. Clean Colin does the routine as smoothly as any boarder I’ve seen; nonetheless, it makes me tired just watching.

Nested Tangent: One of my big regrets from the 80’s is that I didn’t watch more MacGyver. I think I caught a total of about 5 episodes. My favorite (and least plausible?) was the one where he was being held captive in this big storage tent in the jungle camp of a South American drug lord, and escapes by building an airplane out of spare parts he finds in the tent. I can still remember him looking around, looking real thoughtful, like, “OK, let’s see… I’ve got a lawn-mower, some plywood, a coil of rope, and a Betamax VCR… hmm… What could I do with this stuff?...” Loved that show.

We skied/boarded in an area known as Meadow Chutes, a series of parallel Northeast-facing runs in a side drainage on the South side of Big Cottonwood Canyon. For the most part the trees in this area are standard Wasatch fare: Tall Englemann Spruce in the bottom of the drainage, and stands of Douglas Fir mixed with large swathes of Aspen on the sunnier slopes. All of the runs in Meadow Chutes are accessed from a common ridgeline, and this ridgeline is treed with a mix of Douglas Fir, and our old friend, Limber Pine, Pinus flexilis.

Tangent: The Douglas Firs on this ridge have the largest cones, up to 3.5” long, of any I’ve come across in the Wasatch (pic right).

I’ve blogged about Limber Pine before, focusing mainly on its fascinating co-evolutionary history with Corvids, and its range and presence in the Wasatch. But I haven’t talked about one of its interesting and unique characteristics- the flexibility, or “limber-ness” for which it is named.

As I’ve mentioned previously, Limber Pine in the Wasatch tends to occur up on high, exposed ridgelines, and these are places that see plenty of snow and vicious winds throughout the winter. Oftentimes Limber Pine grows where other trees can’t grow, or if they do grow in such places, the grow up all gnarled and misshapen. But Limber Pine seems to do fine in such spots, and the reason is its namesake flexibility. Limber Pine is the most flexible real tree in Utah. You can take any branch of 2 fingers or less diameter and bend it 90+ degrees without breaking, as I did in this video. You can bend any branch/twig of 1 finger or less diameter and bend it clear back on itself (net 180 degrees) as I did in this video.

Tangent: OC Rick has zero patience for my screwing out with tree videos/experiments on powder days. (Actually, OC Rick has zero patience for anything other than climbing and skiing on a powder day. He doesn’t stop to eat, drink, pee or anything. The guy is a backcountry machine. Every ski day with OC Rick is a Powder Jihad. If we don’t finish the day with at least 6,000 vertical feet, he returns to the car mildly grumpy and sour.) To get these videos, I had to kick it into high gear on one of our yo-yo climbs, and outpace him returning up our skin-track, which gave me the necessary 3-4 minute window to make these videos.

Try this trick with any other tree in the Wasatch, and you’ll just snap it off. In fact, you can sometimes even tie a Limber Pine twig in a knot, as I almost did in this home video later that evening (videography courtesy of Bird Whisperer.)

This flexibility means that Limber Pine limbs can bend and sway in high winds, then rebound to their normal position without breaking. It also enables these limbs to bend under the weight of heavy snow, rather than stiffly fighting the weight till they snap. And this bending not only eases strain; by drooping the limbs actually shed excess snow. In fact, though you’ll often see snow-loaded spruces, firs and Douglas Firs following a storm in the Wasatch, you’ll almost never find a Limber Pine with more than a dusting of snow on its boughs.

How It Works

The 2 most common substances in plants are cellulose and lignin. Cellulose is present in all plants, as well as green algae, and is the most common organic substance in the world. Cotton is about 90% cellulose; most wood is more like ½ cellulose.

Lignin is present in all woody plants, and is the substance that strengthens plant tissue. Without lignin, plants can only “stand up” via water pressure in their tissues. If an Arrowleaf Balsamroot, or a Glacier Lily or a Tulip gets dried up, it wilts. If an Oak or Maple or Spruce dies of thirst (technically a xylem-embolism) it remains standing, a dead snag.

Geeky Chemistry Deep-End

Tangent: There are no animal enzymes capable of breaking down either cellulose or lignin. Specifically, cellulose consists of a long chain of glucose “units” connected to one another by a type of linkage called a beta acetal.

An acetal is any molecule with 2 oxygen atoms attached to the same carbon atom. A beta acetal is an acetal where the 2 oxygen atoms are attached to the same side of the carbon atom. There is no animal enzyme known that can break down the beta acetal bond between glucose units in cellulose.

Nested tangent: Interestingly though, there are animal enzymes capable of breaking down beta acetal bonds in other organic molecules, the best example being lactase, which breaks the beta acetal bonds in lactose. Animals (including people) that produce lactase can digest lactose, and therefore milk.

Animals that “digest” cellulose or lignin, such as sheep, horses and termites, do so with the assistance of bacteria living in their guts. These bacteria produce enzymes capable of breaking the beta acetal bonds in question.

We’ve already talked about the Standard Wood Architecture and some of the basic plant tissue types, such as xylem (moves water) and phloem (moves sugars.) There are a few other types we haven’t looked at yet, and one of these is collenchyma. The primary function of collenchyma cells is to provide structural support for the plant. These cells have thick, tough, lignin-rich walls that are extra thick at their corners, so that many of them fit together firmly, like bricks in a wall. Obviously collenchyma cells are present in wood, but their also present in non-woody tissues that need a little stiffening, like leaf-stalks.

But the wood of Limber Pine is different. Its collenchyma cells occur in long, thin bands, and are elongated, thin-walled, and lignin-poor. The cells occur in strands throughout the wood rather than as a solid cylinder in the middle of the stem, as is typical in woody plants. This allows them provide support, while leaving the wood flexible.

Limber Pines area small minority of PLTs in the Wasatch, but they’re easy to recognize. They typically occur on exposed ridgelines or by rocky outcrops. From a distance they’re distinctly bushy-looking compared to the surrounding spires of spruce and fir, and close-up they’re the only conifer in the Wasatch with needles in bunches of 5. They’re accessible in all of Big/Little Cottonwood ski areas. Next time you come across one, try tying a twig in a knot.

Bird Feeder Week Part 4: Diet and Brood Parasitism

So to cap off Bird Feeder Week I’m blogging about what I think is the most interesting thing about the House Finch, and that’s its relationship with another bird, the Brown-Headed Cowbird.

Note to Birders: Of course, you already know all about the Brown-Headed Cowbird and its creepy, parasitic lifestyle. But unless you’re really on top of recent research, this post has a surprise ending, so stick with it.

The Brown-Headed Cowbird (BHC), Molothrus ater, (pic left, male) isn’t at my feeder, or anywhere around the Wasatch, right now. But it was here last summer (Bird Whisperer saw some down at Sugarhouse Park) and it’ll be back again in around 90 days or so. (The BHC isn’t a super-long-distance migrator. This time of year you can still find them down in AZ and NM.) What makes the BHC so darn interesting and horrifying at the same time is that it is a brood parasite.

A brood parasite is a bird that, instead of raising its own chicks, surreptitiously lays its eggs in the nest of another bird species, who then ideally (at least from the brood parasite’s perspective) rears the chick, which then matures, flies off, mates and repeats the cycle anew. Brood parasitic behavior has evolved independently multiple times, and there are about 80 known species of brood parasite birds in the world. The best known brood parasite is the Cuckoo, Cuculus canorus, (pic right) native to Eurasia and Africa. Here in the US, the BHC is by far the most common bird of this type.

Tangent: Guess what other critter has evolved brood parasitism? Bees. Such bees are called “Cuckoo Bees”, and they lay their eggs in the brood cells of other bee species. When they hatch, the larvae often kill and eat the host larvae cohabiting the brood cell. Brood parasitism in bees has apparently evolved separately dozens of times, and there are species that target solitary bees as well as others that target social bees. There are also brood parasitic wasps, who pull off the same trick with other wasp species. Which strikes me as kind of rich because of course the whole wasp reproductive “schtick” is parasitic, with different species parasitizing everything from acorns to caterpillars to figs to tarantulas. (To be accurate, the wasp “parasitism” of figs is more correctly mutualistic, in that Fig Wasps fertilize fig trees.) Oo- I feel a wasp post coming on next Spring… danger… danger… tangent getting too long… must return to topic at hand…

Molothrus includes 5 species of Cowbird, all native to the Western hemisphere, and 3 of which, the BHC, the Bronzed Cowbird, M. aeneus, and the Shiny Cowbird, M. bonariensis, are native to the US. Of these, the BHC is far and away the most widespread. Pre-Euro-contact it was a bird of the Plains, following buffalo herds. But with European settlement came cleared pasture/fields and domestic cattle, and its range has spread dramatically. This increase in range has had a disastrous effect on the populations of many species that traditionally had no contact with the BHC. The Kirtland Warbler, Dendroica kirtlandii, (pic below, right) in particular, which is native to Upper Michigan and Southern Ontario, faces possible extinction in the next couple of decades due in large part to the depredations of the BHC.

Different brood parasites have evolved different techniques for ensuring their eggs are accepted by the host species and that their young receive the lion’s share of food. Many brood parasites hatch more quickly than their host species. Others lay eggs that match the coloration and spotting pattern of targeted host species. Some brood parasites use a beak or hooked claw to destroy neighboring eggs as soon as they hatch. The Cuckoo hatches first, then pushes other eggs out of the nest.

The BHC has 2 key adaptations that help make it successful. First, it lays eggs fast. A typical bird preyed upon by the BHC takes anywhere from 20 minutes to over an hour to lay a single egg. A female BHC lays an egg in under a minute. BHCs are prolific breeders; females lay up to 40 eggs per year, and both males and females typically mate with several different birds in a single season.

Tangent: When I wrote that last section, I had to refrain from making a snarky comment about the BHC. We tend to think of birds in positive, family-centric terms: monogamous, building nests together, caring for their young. But the BHC brushes aside all these stereotypes: It’s deceitful, abandons its young to a foster-nest, and is promiscuous to boot. From a human perspective, it’s hard to warm up to this bird. But when I blog about critters like Weevils or Black Widows and Rattlesnakes, I have to remind myself that they’re not us, and if I try to judge them as “little people” I’ll be continually disappointed.

Second, the BHC (pic left, female) is versatile; it parasitizes the nest of a whopping 240 different bird species, far and away the most of any brood parasite. By comparison, the Cuckoo parasitizes 130 species, and some brood parasites parasitize just a single species.

Side Note: To make things a bit more complicated, most individual BHC females focus on just one target species, although many females are much more indiscriminate and target lots of species.

But what’s interesting about this versatility is that the BHC does not successfully parasitize 240 species. Out of those 240, a known 96, including the Blue Jay and the American Robin, reject the eggs outright, destroying them and/or chucking them overboard as soon as they return to the nest. The remaining 144 species are apparently fooled, accept the BHC eggs, incubate them and rear the chicks after hatching.

Tangent: Or maybe not… there’s another, controversial hypothesis about the BHC, called the “Mafia Hypothesis.” (Don’t you just love that?) Under this hypothesis, the host species is aware that the egg is an impostor, but takes no action against it because of the perceived threat of the BHC exacting revenge by returning to the nest and destroying the host’s own eggs. Possible evidence for this idea includes BHCs revisiting parasitized nests and occasionally destroying eggs within them following a rejection of its own egg.

And now back to our friend the House Finch. In the chart above, I’ve grouped the BHC-target species in 2 groups. Category 1 accepts the eggs, Category 2 rejects them. The House Finch is firmly in Category 1; it routinely accepts and incubates BHC eggs, and feeds BHC hatchlings. But here’s where things get interesting: over a 5-year study of 99 BHC-parasitized House Finch nests, not one BHC hatchling survived. Although a majority of BHC eggs were successfully incubated and hatched, the average life span of the hatchlings was just 3 days. All but one were dead after a week. The dead hatchlings were developmentally retarded, weighing 22% less than normal at death, and feather growth appeared to be delayed. After 14 days, the one survivor fledged (left the nest), but was found dead the next day.

So, BHCs regularly parasitize House Finch nests. House Finches are (apparently) duped. They obligingly play the part cast for them of sucker/foster parent. But (virtually) none of the BHC chicks survive. What’s going on?

What’s going is diet. This past week, the House Finches have been cleaning out my feeder daily. And that feeder is filled with seeds. House Finches are vegetarians, and feed their young regurgitated seeds and other plant matter. But BHCs are insectivores; that’s why they follow cattle around. And a chick from a species that’s evolved to thrive on the protein-rich diet of bugs fares miserably when raised on a vegetarian diet.

And so the real group of BHC target-hosts looks more like this:

With House Finches in a Category 1B- birds that accept the impostor egg, but from whose nests (virtually) no adult BHCs are ever raised. Last laugh is on the Cowbird.

So why would the BHC waste its time, effort and eggs parasitizing House Finch nests? The likeliest answer is that their historic ranges had minimal overlap. Both birds have seen dramatic, human-caused range expansions over the past century, which have brought them into broad contact. Perhaps after more time together, BHCs parasitism of House Finch nests will decrease. (And in fact there may already be indications that this is the case in the Eastern US.)

As its range has expanded, the BHC has come into contact with dozens of new bird species. Its versatility in targeting new species is sometimes a home run, as in the case of the Kirtland Warbler, and sometimes, as with the House Finch, a dead end.

Tangent: Similar studies have been conducted with BHC eggs in the nests of American Goldfinches and European Sparrows- both seed-eaters- with similarly dismal results for the BHC.

That wraps up Bird Feeder Week. I hope you enjoyed reading about it as much as I did blogging it. There’s been lots more going on at the feeder this past week, and some new arrivals, including a pair of Spotted Towhees, Pipilo maculates. But it’s time to take a break from birds and get back to plants.

Bird Feeder Week Part 3: The House Finch’s Saga

I’ve blogged previously about how clueless I was about trees until a couple of years ago, and the sad truth was that I was even more clueless about birds until even more recently- like the past year or so. But over the past year I’ve gradually learned to recognize the birds at our feeder.

Tangent: And I should give credit where credit’s due- to the Bird Whisperer. Over the past year, while I’ve been in the kitchen or family room and spotted a bird I didn’t recognize at the feeder, I must have yelled, “Hey [HIS NAME], get over here, I need a bird ID!” at least 80 times, and every time the little guy has dropped whatever he was doing, reading or watching- Yugi-Oh!, dinosaurs, sharks, Bigfoot-related web sites- and run over to help me out. He is a wonderful kid, and I could not be a happier or prouder father.

And probably the first I learned to recognize, and by far the most common, is the House Finch, Carpodacus mexicanus. (pic left) The House Finch isn’t a particularly large, glamorous, or (at all) unusual bird; if you live in the US and have a feeder in your yard, you probably see them all the time. And so quickly I became pretty blasé about seeing House Finches; out of the corner of my eye, I’d see movement of the feeder, turn and look, think, “Oh, House Finch…” and turn away.

But then about a month or so ago, I spent a few hours learning what I could about them, and now I don’t turn away so quickly. Today’s post and the next post are all about this guy, the star of my feeder, and if you hang with me, maybe you won’t turn away so quickly the next time you see him either.

The genus Carpodacus is commonly called the Rose Finches and includes 2 dozen species across the Northern hemisphere, but only 3 here in North America: The House Finch, the Purple Finch, C. purpereus- which is native mainly to the Northeastern US and Southeastern Canada (but also strangely has a distinct subspecies population out in California) - and Cassin’s Finch, C. Cassinii (pic right)- which is native to the Western US and Canada, is also resident year-round in Utah, and looks a lot like a House Finch, but bigger.

Male House Finches have a red breast and head. (pic left, male on right, female left) (I’ve read that they can also have yellow head and breast, but I’ve seen only red in our yard.) The red pigment isn’t produced by the bird, but rather obtained from food eaten while in molt. (We looked at another bird- the Western Tanager- that also obtains red feather-pigments via diet, last Spring.) Females are attracted to the males with the reddest head/breast feathers, and so the red coloring may act as a “fitness” indicator, signaling that the male is an effective forager. House Finches are seed-eaters, eating only the occasional aphid along with seeds. (Remember this- we’ll come back to it in the next post.) They love Dandelion seeds and are suckers for Sunflower seeds in feeders.

House Finches are found all over the US, but are actually only native to the Western US. Around 1940, they were apparently released in Long Island, and quickly became naturalized and spread throughout the Eastern US. I’ve found a few different variants of the story of this introduction, and have chosen the most dramatic to tell here: Supposedly in 1940, an unscrupulous bird dealer in Long Island was selling House Finches illegally, as “Hollywood Finches”. Tipped off that police were on the way to bust him, he released his entire stock of House Finches, which founded the Eastern population.

Tangent: As wonderfully exciting as this story sounds, I think it reeks of urban legend, with a plotline that seems a strange amalgam of Midnight Express and the Aeneid. I think it’s likelier they just weren’t selling (they’re not terribly spectacular birds…) and one or more pet shop owners released them, and/or successive pet owner released them over a number of years…

However they were introduced, they spread quickly, and as they’ve done so they’ve had a big negative impact on the native Purple Finches. (pic left, male on left, female right) The 2 species seek similar foods and nesting sites, and so compete for territory. The House Finch is the more aggressive species, and so when the 2 scrap, the Purple Finch almost always is the one to withdraw/back down.

Tangent: The Purple Finch has, unfortunately, suffered somewhat of a double-whammy as a result of human introductions. Almost a century before the House Finch appeared on the East Coast, the introduction of the European House Sparrow, Passer domesticus, caused a similar, earlier disruption in Purple Finch range and population.

Revenge of the Purple Finch

But after half a century in its expanded range, the House Finch met its own challenge. In the mid 1990’s East Coast House Finch populations started to decline dramatically, as a result of a virulent strain of eye conjunctivitis. There are several causes of eye conjunctivitis (think Pink-Eye) in birds, including bacteria, fungi and viruses. The causative agent in this case is a bacterium, Mycoplasma gallisepticum (MG). MG has long been a scourge of domestic chickens and turkeys, and it’s thought that a new strain evolved in the 90’s that was able to infect the House Finch. Infected birds display scabby, runny or cloudy eyes. The disease can blind the Finches, causing them to starve.

Side Note: Mycoplasma is a genus of about 100 known species of bacteria. One of the other species, M. pneumonia, is a cause of “walking pneumonia” in humans. Mycoplasma is an interesting genus in that it lacks a cell wall, and instead utilizes a type of organic molecule called sterols that it obtains from its host to stabilize its outer membrane. In humans the most commonly used sterol is cholesterol (diagram right).

Now most antibiotics, including penicillin, fight bacteria by latching onto the cell wall of the bacterium in question, and then preventing that wall from growing new cells. As the bacterium continues to grow, the wall can’t keep up with it, and it weakens and ruptures, killing the bacterium. But because Mycoplasma lacks a cell wall, none of these “standard” (specifically beta-lactam) antibiotics work against it. For this reason, there was for many years confusion about the cause of M. pneumoniae-induced walking pneumonia, with many researchers believing it was caused by a virus.

A possible aggravating factor may be the limited genetic variability of Eastern House Finches (pic left = sick female). Since they’re descended from a small founding population (whether from pet shop or no) all Eastern House Finches are pretty closely related. As a rule of thumb, populations of animals (or plants) with greater genetic diversity tend to do better when faced with disease, because there’s a higher likelihood that some individuals will have a bit more resistance to a specific disease, and those individuals will be a little likelier to survive and reproduce, thereby passing that resistance on to the next generation.

So far MG hasn’t appeared in the West, though its range is spreading and it’s now been found as far West as Michigan. MG isn’t expected to wipe out Eastern House Finches, but it’s reduced their numbers by somewhere around half, and may be giving the Purple Finch- which is also susceptible to MG, but not nearly as affected by the disease- bit of breathing room.

Tangent: In tests, the other bird that is both very susceptible to and highly affected by MG is the American Goldfinch, Carduelis tristis. But oddly, American Goldfinches in the East, which routinely visit the same feeders as House Finches (as they do in my yard) seem largely un-impacted by MG. Why this should be, and whether there’s some behavioral difference between the 2 species that facilitates transmission between House Finches more so than Goldfinches, is as yet unknown.

So the plain old House Finch isn’t so boring after all. But I’ve saved the most interesting thing about the House Finch for last.

Next Up: House Finches, Brood Parasites and Diet.