Tag Archives: biology

Vampire birds

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The vampire strikes again! Photo by Ian White*

The vampire strikes again!
Photo by Ian White*

In honor of Halloween, let’s talk about vampire birds.

I am using “vampire” loosely here, the same way people do when they talk about “vampire” bats. These vampire birds are hematophagic (blood-eating!), but do not follow other items of vampire lore: they have reflections in mirrors, can enter your house without an invitation, do not shape-shift, are mortal, and do not sparkle in the sunlight.

Sharp-beaked Ground Finch, Geospiza difficilus

This is one of the famous Darwin’s Finches of the Galápagos Islands. This species is a vampire only on two of the islands, Wolf and Darwin; everywhere else it eats bugs and seeds like a regular finch. Even on Wolf and Darwin, it mostly eats bugs and seeds, but sometimes it craves something a little… richer…

Dum-dum-DUMMMM. (Sharp-beaked Ground Finch. Photo by budgora*)

Dum-dum-DUMMMM.
(Sharp-beaked Ground Finch. Photo by budgora*)

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Featured paper: cheating Common Yellowthroats, or, the world is more complex than you think

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There is a thing that happens a lot in biology, especially in animal behavior: one set of researchers finds an interesting relationship, like, say, “Birds prefer to eat bugs off of cows with lots of spots, and don’t like to eat bugs off of cows with no spots.” (This is a made-up example.)

Starlings flying near a cow; Pt Reyes, CA.

Blackbirds flying near a cow, Pt Reyes, CA.

Then, some other researchers do a study and say, “Hey, our birds prefer to eat bugs off of cows with no spots! That’s the opposite!”

Then still different researchers do another study and say, “Our birds don’t care at all about the number of spots, they just care whether the spots make a shape like a smiley face. You guys must all have made a mistake. The Smiley Face Rule is the new Lek Paradox! #nobelplease”

To put it less ridiculously: scientists get different results sometimes, and it can be hard to figure out why. Did someone make a mistake? Who is right? Today’s featured paper takes an example of this confusing scientific disagreement and elegantly makes sense of everything, with the help of this handsome little bird:

Common Yellowthroat (male). Photo by Dan Pancamo*

Common Yellowthroat (male).
Photo by Dan Pancamo*

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Our regular programming will resume shortly

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I’ve been neglecting my blog-writing duties lately, preoccupied with the annual Big Grant Proposal Deadline. My grant proposal is on sexual selection in juncos. What part of juncos is sexually selected, you ask? Why, that flashy tail, of course! They’re practically peacocks!

LANK showing off his sexy tail

LANK showing off his sexy tail

You're not quite there yet, little one...

You’re not quite there yet, little one…

I’ve also been TAing a class on animal behavior, so while I don’t have many extra words to spare right now—I need them all for that grant proposal—I do have a wealth of animal videos that have been brought to my attention by my fellow animal behavior fans. Please accept some videos in lieu of words.

Here is a video of a bird even drabber than a junco who attracts females with his sexually selected aesthetic tastes in things like flowers, shiny beetles, and slightly… er… less attractive items as well: the Vogelkop Bowerbird.

And here are some flies that—well, you should just watch it to believe it. It starts with them gulping air bubbles into their heads, and that’s not even the weird part.

Why are they like that? Sexual selection! Females in this species prefer their males as hammerheaded as possible.

Hey, why not?

Velella velella! Or, falling off the edge of the world

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They were strewn all along the beach, these transparent, tripartite things. At first glance they looked like plastic trash, but they felt organic in my fingers.

velella5

Fortunately I happened to be beachcombing with a world expert on marine invertebrates. “Ooh,” he said, “Velella!”

Velella velella, or by-the-wind sailor: a living sailboat, a jellyfish on a stiff frame. In their preferred state, i.e. when not washed up on beaches, these animals float on the ocean surface with their tentacles just below the water, to catch food, and their upright sails above the water, to catch the wind.

velella8

 

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Avian flight III: hummingbird flight

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Hummingbirds are amazing fliers. They fly forward at up to 26 miles per hour; they fly backward; they hover. They beat their wings 50 times a second, so all you see is a blur, with that enameled little body floating serenely in the middle. They are flight acrobats. They are flight artistes. How do they do that?

Rufous Hummingbird. Photo by M. LaBarbera

Rufous Hummingbird. Photo by M. LaBarbera

It helps that they are quite small. The amount of power that you can get out of your muscles increases as muscle mass (size) increases—bigger muscles, more power—but the amount of power increases less quickly than mass does. That is, if you double the size of the muscle, you get less than twice the amount of power out of it. This means that as an animal gets bigger, its ratio of muscle power to muscle mass decreases. An ant can carry enormous things for its size. A small bird can generate enough power with its muscles to hold its own body aloft and still in the air—to hover. A California Condor? Not so much. Hummingbirds’ small size means that they are, relative to their own body mass, very strong.

Rufous Hummingbirds are small. Photo by M. LaBarbera

Small size is a Rufous Hummingbird’s secret weapon.
Photo by M. LaBarbera

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Ducklings with superpowers

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Everyone knows ducklings: yellow fuzz, big flat bills, big flat feet, cute little waddles all in a line after Momma, and superpowers.

Photo by Farrukh*

Photo by Farrukh*

What, didn’t you know that last part?

Death-defying leaps!

Several duck species nest high above the ground in tree cavities. This is safer than nesting on the ground, predator-wise, but it also means that the ducklings hatch very, very high up. And then they have to get down.

When they hatch, the ducklings weight very little, which helps: the less you weigh, the less you are hurt by falling. Terminal velocity—the fastest that gravity will make you fall—depends on weight, so small creatures are essentially safe from falling no matter how far they fall. The cushiony leaf litter on the ground helps the ducklings too. And notice how they flatten out, spreading their little legs out behind and their wing stubs out front, their bodies as spread out as possible: they are gliding—albeit not as well as a true glider like a flying squirrel, but nevertheless slowing their descent so that they can land safely.

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Safe behind these castle walls, eggs: how birds’ nests protect their precious contents

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Recently I was lucky enough to spend some time in Spain, where the land is dotted with hilltop castles and the winding narrow streets of the old cities are encircled by sturdy stone walls. I crouched behind crenellations, pretending to be a bowman awaiting attack, and climbed dark winding staircases glad that no defending army waited at the top.

Winding staircase in the Olvera castle. Photo by Q. Stedman

Winding staircase in the Olvera castle.
Photo by Q. Stedman

It’s exciting and romantic to imagine castles and walled cities in the flush of functionality, but it’s hard to ignore that the motivating force for those structures was real, unromantic, gut-knotting peril and fear. The people who lived in those cities put up thick stone walls with their hands because they thought other people were going to come and unromantically kill them—which they sometimes did.

Gulls standing guard over Tarifa.

Gulls standing guard over Tarifa.

When birds build nests, they’re responding to that same threat. Eggs and baby birds are easy targets for anything from mice to snakes to deer to toucans. To keep them safe, birds too rely on stout walls, secret passageways, and defending armies.

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What we know about one nest

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On July 1, 2013, we caught a female junco who we banded MABY.

MABY

MABY

An already-banded male, ARKM, seemed very upset about this. Sometimes juncos do hang around when we band their mates—it’s rather sweet to see them reunite when the banded birds are released—but ARKM’s behavior seemed different to me, so after we released MABY, I lurked behind a tree and watched.

Sure enough, ARKM went down to the ground: he had a nest.

ARKM and MABY's nest, just under the rock.

ARKM and MABY’s nest, just under the rock.

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Seeing through scales and walking with six legs

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There are a lot of scientific journals out there. There are the big shots (Science, Nature), the bird journals (The Auk, The Condor), the topic-specific (Behavioral Ecology), etc. And then there is The Journal of Experimental Biology, or JEB. I love JEB. It claims to be the journal for “comparative animal physiology” but that doesn’t cover the half of it. JEB is about crazy, wonderful strangeness—strange animals and strange scientific methods. Following are two characteristically odd JEB studies: snake eyes and how walking sticks walk.

Leucistic (lacking pigment) black rat snake is looking at YOU.

Leucistic (lacking pigment) black rat snake is looking at YOU.

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