Category Archives: other people’s research

Think like a scientist: correlation

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Correlation does not equal causation. Done!

Just kidding. It isn’t enough simply to state that classic phrase because in the real world, we’re often still stuck with using correlations. If you want to know how lifelong exercise habits affect lifespan, you can’t take two groups of people and force one group to exercise and the other not to (“GET BACK IN THAT CHAIR! That is TOO MUCH walking to the corner store for one day!”), while keeping everything else exactly the same between the groups (“I don’t care if you’re not hungry, everyone eats one cupcake on Tuesdays!”), for their entire lives. Even if you didn’t mind knowing that you, too, would be dead before the study was over, it would be completely unethical. Instead, you study people’s natural exercise habits, and try to correlate them with lifespan. Continue reading →

Featured paper: side-blotched lizards play rock-paper-scissors

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B Sinervo and CM Lively. 1996. The rock-paper-scissors game and the evolution of alternative male strategies. Nature vol. 380, pp. 240-243.

(Side note: I don’t want to feature-paper too many Science or Nature papers, since those journals are so high-profile that you’re likely to hear about the work elsewhere, and part of the point of this feature is that papers in “lesser” journals can be awesome too; but this paper is classic and fun, so I’ll make an exception.)

Male side-blotched lizards come in three flavors colors: orange-throated, blue-throated, and yellow-throated. Orange males are highly aggressive and defend large territories. Blue males are less aggressive, defending smaller territories. Yellow males look like females and don’t defend territories at all. All three colors compete to mate with females and have offspring. Throat color is highly heritable: orange males have orange sons, blue males have blue sons, yellow males have yellow sons.

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What the chickadees are saying behind your back

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Black-capped Chickadees may be the easiest birds to identify by ear. Chick-a-dee-dee-dee, they sing, telling you exactly who they are. (I’ve heard that towhees do this too, but the towhees I’ve heard always seem to be saying twee or taree, from which I would not be able to get “towhee” unassisted.)

Don’t you know who I am? I’m Chick-a-dee-dee!
[A Mountain Chickadee, not a black-cap, but I don’t have any photos of black-caps.]

Of course, the chick-a-dee sounds like a vocal nametag to us only because someone had the good sense to name chickadees after their call. But it serves as an identifier among the chickadees too. The “chick-a-dee call complex” consists of four note types (the A, B, C, and D notes in a row might be transcribed as chick-k-ka-dee) that can be given in various combinations. Each note type itself can vary in frequency and duration. The chickadees thus have a lot of potential variation to work with, and they do. The D (dee) notes alone indicate both the identity of the individual bird calling, and the flock it belongs too—rather the same way that an Englishman saying “Hello, my name is George,” might indicate to compatriots both his own identity (George) and, in his accent, the region he is affiliated with. When captive chickadees are put into new flocks, the calls of the new flock members change, converging on each other, to indicate their new flock membership.

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Why birds don’t need GPS

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Imagine you’re an albatross, a large seabird that spends months aloft over the open ocean. Now it’s the breeding season: time to head back to your favorite island, do some amusing courtship dances, and lay an egg. But you’re in the middle of the vast, featureless open ocean. How do you find your way back?

Homing pigeons, taken from their roosts and driven up to 800 km away, can fly home. (Several pigeons have received the animal version of the medal of honor for doing this while carrying messages in wartime.) Arctic shorebirds like the Red Knot will fly from the Arctic to southern South America, over 13,000 km, twice a year. Birds are very good at navigation. How do they do it?

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A conference, a love story

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A conference, a brief vacation, and getting back into non-field-work have conspired to keep me away from the blog for far too long; humblest apologies!

Red-breasted Nuthatch scoffs derisively at your apology!

The conference was the North American Ornithological Conference, which combined the usually-separate annual meetings of many ornithological societies into one gigantic über-meeting with 1500+ attendees, almost all of whom were presenting their research as either a talk or a poster.

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Featured paper: barn owl chicks’ spots

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Melanic color-dependent antipredator behavior strategies in barn owl nestlings. By Valentin van den Brink, Vassilissa Dolivo, Xavier Falourd, Amélie N. Dreiss, and Alexandre Roulin. Behavioral Ecology, 2011.

I’ve been slacking off on the Featured Papers, since it’s the field season and I’ve been reading almost nothing less than usual; but this paper is too crazy not to mention.

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Speeding kills bears

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If you have ever driven through Yosemite National Park, you’ve seen them: distinctive yellow signs with a silhouette of a bear and the admonition, “Speeding Kills Bears.” Although it doesn’t say so on the sign, each sign is placed where a bear has been killed by a car.

On our last trip, driving through Yosemite on our way home, we saw the truth of this first-hand: a black bear lying dead at the side of the road, his blood still red on the asphalt. He was young, no larger than a St. Bernard.  His muzzle was delicate, his ears soft. Like many of the black bears I’ve seen, he was not just black, but had an elegant sweep of blond across his shoulders, like a shawl.

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What do birds see?

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Another great question from James:

When certain birds (not owls) look out at you from their left eye, they can’t see you with their right eye on the other side of its head. So what do birds with eyes on both sides of the head actually see? Two different scenes? Or some sort of panorama distillation?

What does LAGG see?

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Featured paper: nest predation

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Corey Tarwater. 2008. Predators at nests of the Western Slaty Antshrike (Thamnophilus atrinucha). The Wilson Journal of Ornithology, volume 120(3): pp 620-624.

Nest predation is a major worry for most birds. Chicks in the nest are essentially helpless, and parents usually can’t do much to stop predators, although they will try. Losing broods to predation is common. In this study, 79% of nests were lost to predation. If you’re a Western Slaty Antshrike, you can expect 4 out of every 5 broods of chicks you have to get eaten!

Yet actually seeing these—or any—predation events is extremely rare. Dr. Tarwater describes five nest predation events on Western Slaty Antshrikes (small, cryptic brownish birds) in Panama, one she observed in person and the rest of which she caught on video.

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