Ravens: Big Bird Brains

I've been working a lot with Korppi (our captive raven) these past couple of weeks, as I try to develop new enrichment activities for her and formalize an enrichment schedule. I know that she is a smart bird. In a recent training session, she learned that when I said "station" I wanted her to perch on a rock in the corner of her enclosure in a matter of five minutes and then proceeded to try and trick me into giving her more treats. I can see the wheels turning in her head when we present her with a contraption that she has to open or unlock to retrieve the food inside. At the risk of anthropomorphizing her, I would classify her reaction as "curious" when I hung a pair of sparkly pants from one of her perches last week. She's a smart bird. And I know from the literature (and straight up reputation) that ravens are considered one of the smartest. But I wanted to know why.

Korppi tries to retrieve peanuts punched into an old egg-carton top that was dangling from her perch.

So, I turned once again to Bernd Heinrich, biologist, author, and raven expert. I recently finished his second book about ravens, Mind of the Raven: Investigations and Adventures with Wolf-Birds. This is his account of his observations, experiments, and experiences with a group of captive ravens he reared, as well as many wild ravens that he encountered. I highly recommend the book - one story after another of the amazing feats and incredible mind-power of these intriguing birds.

To answer the "why" of all these smarts, we have to go straight to the brain. All vertebrates have a similar brain structure, composed of a hindbrain, midbrain, and forebrain. The hind and midbrain are generally responsible for sensory information and organizing movement and attention. The forebrain, on the other hand, is where conscious activity takes place, including learning and memory. While hind and midbrains don't show much size-variability in different vertebrate species, forebrain sizes are incredibly diverse. The reason humans have such large brains is because of our large forebrains.

In general, the greater one's brain volume, the more information that species can process. Bigger animals require bigger brains simply to control their bigger bodies; so brain size predictably increases proportionally to body size. When a brain is bigger than predicted based on body size, this is called "encephalization." Thus, second only to dolphins, humans are the most encephalized animals on the planet. In the 1940's Adolphe Portman, a Swiss zoologist measured and compiled data on bird brain volumes. He discovered that on average, the corvids (the family of birds to which ravens belong, in addition to crows and jays) have the highest encephalization of all bird families. As it turns out, ravens are not only the most encephalized of the corvids, but of all the birds.

We can correlate intelligence with brain size because more brain volume means more neurons and synapses, which are directly connected to one's information processing powers (this is neuroscience at its most watered down aka the only way I will ever understand neuroscience!). When discussing intelligence, though, we have to clarify intelligence "with reference to what." Most primates, for example, have high levels of encephalization and the extra "brain space" is dedicated to visual processing, because they are highly visual creatures.

So why do ravens have such high levels of encephalization? One could argue that extra bird-brain-space is needed for flight capabilities; however, dragonflies (and other flying insects) have four wings, six legs, and no encephalization, while ravens only have two wings and two legs. Furthermore, having a large brain is a HUGE energy expenditure: humans' brains take up 1.5% of our body weight but 20% of our energy reserves. Anthropological studies have shown that human brains made a leap in size when humans switched from being strictly herbivores to omnivores. Nonetheless, hawks and ravens are equally effective predators, despite hawks' significantly smaller brains, so the ability to hunt is a weak explanation for an enlarged brain.

The latest research is actually indicating that ravens' (and our) large brains could primarily be accounted for by social complexity. In turn, the ability to not just recognize others, but SPECIFIC others increases social complexity, creating a sort of positive feedback (big brains enable social complexity which encourages bigger brains). Ravens are highly social creatures: Heinrich describes in many chapters the social hierarchies that exist within groups, their ability to recognize other individuals, the formation of pairs and coalitions of pairs, and the mutual relationships formed with dangerous predators. These and more require instant reactions and making choices that when made in the head, are much safer and quicker. In other words, they require consciousness. That ravens are such social creatures seems to explain, more than anything else, their large brain size. And that large, encephalized brain, is why Korppi has no trouble remembering where she's cached hundreds of raisins all over her enclosure, among many other remarkable feats.

Korppi investigates the strange, black box I've brought into her enclosure.

Owls Everywhere!

On Tuesday, I joined my favorite engaged naturalist couple Anne and Tom for a brief birding excursion. We'd heard that at this time of year, great gray owls are frequently seen on Forest Road 11. There had been multiple reports of great gray owls being spotted in this area in the past week, so we thought it was worth a try. We drove slowly, just before sunset, looking in all the trees for that distinctive owl shape. Sure enough, after about four miles, perched right out in the open, we found what we were looking for - an AMAZING bird. We observed and photographed this owl for probably 20 minutes, hardly able to contain our excitement.

When great grays are mentioned, anyone who has been around this area for awhile will immediately be reminded of the Great Gray Owl Irruption of 2004-2005. I've heard many stories of this irruption in the past week, especially with all the boreal owl and great gray owl sightings that have been happening. That winter, hundreds of great gray owls were spotted in Northern Minnesota by avid birders (there's one report of a birder seeing 226 in a single day!). The Minnesota Ornithological Union predicted that at least 5,225 great gray owls made their way into Minnesota that year. For comparison, the previous winter, they predicted 35 total great grays.

In Minnesota, irruptions of the northern, boreal owl species (specifically great gray owls, boreal owls, snowy owls, and Northern hawk owls) happen regularly. Snowy owl irruptions have been recorded as far back as 1833, and have been identified as happening every 3-5 years since. Irruptions are fairly unpredictable, though. Some years, only one species of owl may irrupt, while other years may see all four boreal species making their way south.

Irruptions are not related to any migratory patterns. Instead, it has to do with the owls' food source. Snowy owls in the north feed primarily on brown and collared lemmings; the others eat mostly red-backed and meadow voles. In all cases, these are small mammal species that go through regular "boom-and-bust" population cycles, meaning that, for whatever reason, sometimes there are TONS of them and other times there are NONE of them (scientists have not yet come up with a logical explanation for why these cycles happen). When there's lots of food, the owls can eat plenty and put more energy into making baby owls. The owl population increases, but sooner or later, their food source will enter the "bust" phase of its population cycle. When this happens, there isn't enough food for the entire owl population to stay north, so they have to start wandering south, sometimes in massive numbers, to find food for the winter. Luckily, most find a good food source; irruption years do not regularly find higher levels of mortality in the owl populations.

This year, we are experience a boreal owl irruption. A recent article in the Duluth New Tribune (http://www.duluthnewstribune.com/event/article/id/258144/) made me realize just how big of a deal this is. Boreal owls are rare species, one that many birders across the country long to add to their life list. Because of this, people have been flying from as far away as Virginia and California for the sole purpose of seeing a boreal owl and adding it to their life list. How lucky that I was able to see one without any effort right at my workplace!

And in this past week, four different great gray owl sightings have been reported in our area, many more than usual. Could the great gray owls be experiencing a minor irruption as well? Maybe they are relying on a food source similar to the irrupting boreal owls? All I know is that there are a lot of owls around and I'm so excited that I've been able to get out and see them.

Last night, Sara (yet another of the first year naturalists) and I went back to county road 11 to see if the great gray owl was still there. Sure enough, right where we left it the day before, it was perched right out in the open. This time, though, as we watched, we noticed it was pretty fixated on the ground. And right before our awe-struck eyes, the owl flew down from its perch and landed on a tasty treat. Through the binoculars, we saw a small mammal hanging out of its mouth and it quickly began to munch down its prize. Too cool.

Wolf Ridge's Mystery Owl

A small owl of boreal and montane forests, the Boreal Owl is found throughout Alaska and Canada, and across northern Eurasia, as well. It is found in the lower 48 states only in the mountains of the West, in extreme northern Minnesota, and as an occasional winter visitor to the northern states.

I was doing a bird banding presentation for a class yesterday morning. I started it as I always do, by asking the kids what birds they'd seen today. One girl started listing the usual cast of characters: "black-capped chickadees, red-breasted nuthatches, common redpolls, a hawk owl, downy woodpeckers..."

"Hang on just a second there," I cut her off. "Did you say hawk owl?" Their naturalist, Robyn, nodded and smiled. I thought that maybe the kids had thought they'd seen a Northern hawk owl and Robyn was letting them enjoy that rather than correcting them. But they all insisted, and when Joe (a significantly experienced naturalist evaluating the class at the time) also confirmed the sighting, I found myself stumbling for words, until I finally sputtered something like, "you saw an owl and didn't come and get me?!"

Small owl; no ear tufts; white face outlined in black; fine spots on top of head; underparts dirty white, streaked with brown; bill yellow.

After teaching her class about bird banding, I booked it back to my office to grab a camera and took off for Chickadee Landing, the location of the owl sighting. With five or six other naturalists in tow, we started scanning the trees for the little ball of fluff allegedly perched above us. We scanned the area for about fifteen minutes, and I even tried playing some hawk owl calls on my iphone, but to no avail.

Lives in boreal forests with spruce, aspen, poplar, birch, and balsam fir. In mountains of West, found in subalpine forests of fir and spruce.

At lunch, I learned from Robyn that our owl was not perched out in the open, as I had originally thought, but rather, tucked back into the branches of a spruce tree. She offered to take Tessa, Dan (more WR nats) and me back out to look for the little guy one more time. And thank goodness we returned, because as soon as we arrived, "oh sure, he's right where I left him," Robyn declared.

Diet: small mammals, birds, and insects.

Sure enough, tucked into the branches of a spruce tree sat a very passive owl. Clearly content with just hanging out, it would occasionally look our way, especially as we got closer, but otherwise, seemed entirely unperturbed by our presence. In fact, we were probably the least of its concerns, given the many black-capped chickadees noisily flitting about in its tree. We really hoped this owl might take an opportunity to make a meal out of one of them, but instead, it continued to sit. This is normal behavior for owls during the day - quietly hanging out and minding their own business.

Boreal owls usually are considered monogamous, with one male mating with one female. Several studies in Europe found that one male may mate with up to three females, and a female occasionally mates with two different males. They found that such multiple mating occurs most frequently when mice numbers are at their highest. (Finding easy prey to feed the young means that less help is needed in raising young owls.) When mice numbers are low, all the owls were monogamous.

When we first saw the owl, we instinctively found ourselves questioning its original identification as a hawk owl. I suggested that maybe it was a boreal, but we immediately brushed off that suggestion given the size; this owl looked much bigger than the boreal owls we'd seen in captivity or taxidermied. Plus, the other naturalists had already identified it as a Northern hawk owl - why question that? However, last night when I posted a picture and blog entry about the owl sighting labeled as a Northern hawk owl, I almost immediately got a phone call from my raptor banding mentor at Hawk Ridge, Frank, informing me that the image was definitely a boreal owl. And that makes sense. The tail is short and rounded, there is no horizontal barring on the front, and this is an irruption year for boreal owls, meaning that they are being spotted all over the place in northern Minnesota (I'll write more about this in a future blog entry). This particular boreal owl just so happened to be quite large. Or maybe it was just a female.

The female boreal owl is much larger than the male. The species shows the most extreme reversed sexual dimorphism (the phenomenon in the raptor world where the female is larger than the male) of any American owl.

"It makes you wonder how often we miss these kinds of things," Tessa mused, as we watched the owl peacefully perched in its tree. We would not have noticed this owl if Robyn hadn't taken us back out and pointed its exact location. How many other awesome plants and animals are we missing every single time we go outside because of their passive, reclusive nature and our inability to catch every detail?

(Field guide notes from:  http://www.allaboutbirds.org/guide/Boreal_Owl/id)

Eagles, Golden and Great

This is very important. A few weeks ago, while teaching a birds class, a student and I got into a conversation about whether or not the Great Eagles of Middle Earth featured in the latest Lord of the Rings cinematic adventure "The Hobbit: An Unexpected Journey" could be considered the same species as the golden eagles that occupy our world. Well, I had to check this out myself. So, last week, I finally got around to seeing the movie with my friend (and former WR nat) Max and began my investigation.

A Great Eagle of Middle Earth

Here's the scene with the eagles (this is the end of the movie, so you probably shouldn't watch if you haven't seen it yet): http://www.youtube.com/watch?v=0amNOI0vsxI

By looks alone, it's clear that these birds are bigger than any bird in our world. Even considering that they are carrying dwarves and hobbits, no eagle is that much larger than a human being. Golden eagles have a wingspan of 6-8 feet. By simply eye-balling the eagles in the movie, and taking into consideration the average height of a Middle Earth dwarf (4-5 feet) I'd guess the Great Eagles to have a wingspan of about 20-30 feet (3-4 times greater than our golden eagles). According to the Silmarillion, J.R.R. Tolkein's prequel to The Hobbit, Thorondor, the Lord of the Eagles, had a wingspan of 30 fathoms, which translates to 180 feet! (Okay, but this was the greatest eagle of them all).

A Great Eagle with Bilbo Baggins, a hobbit on its back

Besides the obvious size difference, we have to take vocalizations into consideration. The Great Eagles in the youtube clip sound an awful lot like our red-tailed hawks, a high-pitched, descending screeeeeeeech (it is not uncommon for Hollywood to use the sound of a red-tailed hawk as the call of any number of raptors as it is easily the most epic sounding of raptor calls). In contrast, golden eagles are relatively quiet birds; the most commonly heard sounds are the beggings of hungry chicks, or the parents, announcing their return to the nest with food (sound clip: http://www.allaboutbirds.org/guide/Golden_Eagle/sounds).

Despite their "small size" and apparent inability to save dwarves from unfortunate situations, golden eagles are pretty incredible raptors in their own right. For one, they are the largest naturally occurring bird found in Minnesota (and second only to the California condor in the US). They can dive up to 200 miles per hour, and one of their courtship displays involves 20 of these steep dives in sequence. They exhibit teamwork. Mated pairs work together to hunt prey (like rabbits) from the ground; oftentimes, one eagle will distract the animal while the other goes in for the kill.

Golden Eagle (Aquila chrysaetos)

Golden eagles are the subject of important research happening here in Minnesota thanks to a partnership between the National Eagle Center, Audubon Minnesota, and the MN DNR. The golden eagle conservation project strives to better understand breeding habits and origins of golden eagles that winter in Minnesota to develop conservation and management strategies for these birds. A major component of this study involves tracking golden eagles via GPS units attached to the birds. In November, one such golden eagle was caught by Frank, one of my bird banding mentors at Hawk Ridge in Duluth, MN. Goden eagles are rarely caught at Hawk Ridge, so it was a big deal. The GPS unit was attached to the bird (now known as Golden Eagle 53) and now, every two or three days, a digital map is updated with the location of the eagle, which at this point, appears to be wintering a little south of Springfield, MO. The website for the project is: http://mn.audubon.org/golden-eagle-conservation and the digital map can be found here: http://www.arcgis.com/home/webmap/viewer.html?webmap=05cdea90335348998641ccee6670ff81 (Golden Eagle 53 is the purple line on the map).

Golden Eagle 53, outfitted with a GPS backpack (designed to in no way interfere with this bird's natural behavior)

As it turns out, I'm fairly certain the Middle Earth Great eagles are an entirely different species from our golden eagles (although, probably in the same genus: Aquila). The mythical great eagles are pretty incredible and fun to watch on the big screen. Even so, I'd say we're pretty lucky to have an equally incredible bird here in our world.

"Nature is the standard of truth and beauty." 

-Bernd Heinrich

January Bird Count

I'm not doing a Big Year (if you don't know what I'm talking about, you should probably check out the movie "The Big Year" or, if you're really committed, read the book!). Big Years provide for great stories, but I'm kind of opposed to the idea on a philosophical level. That's a whole conversation you can engage me in if you are interested.

However, at the beginning of this year, my house-mate and fellow second year Anne mentioned that one of her resolutions was to keep track of every bird species she sees this year. I've never done that before and decided I wanted to try it too. It's not a Big Year because I'm not going out of my way to see these birds (okay, I will probably take an occasional birding field trip) but it is more just a record of what birds happen to make their way into my life this year. Plus, now Anne and I have something to be competitive about.

January Bird Count:

1/2/13: On our first day of winter training, we participated in "Superior Snowshoe" in which we basically go snowshoeing to an overlook and back. It gave me a great opportunity to check mark off a lot of the super common winter birds around here:

1. Downy Woodpecker: Wolf Ridge, between Marshall Mountain and Raven Lake trails

2. Black-capped Chickadee: Wolf Ridge, at the Kennedy Creek campsite

3. Common Raven: Wolf Ridge, flying overhead at the Superior overlook
4. Bald Eagle: Wolf Ridge, flying overhead at the Superior overlook
5. White-breasted Nuthatch: Wolf Ridge, Education Building bird feeders (this was exciting - WBNuthatches are not very common around here this time of year. I haven't seen one since).

6. Common Redpoll: Wolf Ridge, Education Building bird feeders

7. Hairy Woodpecker: Wolf Ridge, Top of the North Stairs

1/4/13:
8. Red-breasted Nuthatch: Wolf Ridge, chickadee landing

1/6/13:
9. Pine Grosbeak: Wolf Ridge, above Korppi's enclosure

1/7/13:
10. American Crow: Finland, MN, across the street from Zion Lutheran Church

1/11/13:
11. Rock Pigeon: Duluth, MN, on the telephone wires above the Duluth co-op

1/12/13:
12. Blue Jay: Isabella, MN, at the eco-home bird feeders

1/14/13:
13. Pileated Woodpecker: Wolf Ridge, trees between dining hall and West Dorm

1/26/13:
14. Ruffed Grouse: Finland, MN, dog-walking trail behind "Ragged Ass Road" (walking two golden retrievers, all three of us jumped a foot in the air when a ruffed grouse flew out of the trees right over us and perched in a tree on the other side of the trail).