Very hungry caterpillars

It’s almost a pity that we introduce children to caterpillars so young. The magic of the transformation of a squishy, unimpressive tube into a living, fluttering creature apparently made of stained glass gets muddled up with the rest of the magic of childhood and is too easy to forget when we grow up. Everyone knows about caterpillars turning into butterflies, but almost no one really thinks about it.

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Photo by Andrea Westmoreland, reproduced through a Creative Common license from Flickr.

Even before they turning into butterflies (or moths), caterpillars are impressive. They hatch tiny, into a bird-eat-caterpillar world, and their one crucial job is to grow big in time to metamorphose. This isn’t a particularly complex task—there’s a reason caterpillars are basically just digestive systems on legs—but it isn’t necessarily easy, either. They need to find the right food and eat it quickly without being eaten themselves.

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Learn about speciation from that one weird duck at the park

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Every park has at least one weird duck. It’s the wrong colors—all white, or patchy white; its bill bright storybook orange or its face weirdly red and lumpy. Next to the other ducks it looks oversized and bulky, like a linebacker in a crowd of quarterbacks.

How new species form, and what determines whether they last, is one of the major topics in evolutionary biology; and much of this topic is embodied by that one weird duck.

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Bathtime, carefully

For birds, cleanliness is not optional. They rely on their feathers for flight and insulation, and only replace those feathers once or twice each year. In between molts, they need to keep their feathers as whole as possible.

Feathers, like our hair, are made of protein; and like all organic things, they degrade over time. Sunlight hastens this degradation, but certain aspects of the feathers themselves can slow it: dark feathers colored with melanin last longer in sunlight, for example. Of more concern, though, are the many creepy-crawly things that like to eat protein, and will happily hang out in a bird’s feathers, munching and laying eggs.

To combat these parasites, birds coat their feathers in protective oil from the preen gland located at the base of their tail, and they bathe.

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But they have to be careful. Small wild birds are lunch for everything from feral cats to Cooper’s Hawks, and no bird wants one of these sneaking up on it while it is obliviously scrubbing behind its ears. So they bathe in bursts, a plunge into the water followed by a quick look around.

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Did anybody see that?

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Saving individuals

Planet Earth II, the new BBC documentary narrated by Supreme Voice of Nature Sir David Attenborough, devotes one of its six episodes to animals living in cities. It’s unsurprisingly great. (Even if the ultimate masters of urban living, pigeons, who you might expect to be celebrated in this context, instead spend the episode getting unceremoniously eaten.) The “Cities” episode has to walk a delicate line, heralding animals’ ability to adapt to human landscapes without failing to acknowledge that humans overwhelmingly destroy habitat rather than creating it. It mostly leans to the optimistic side of the line; one segment makes New York City seem like a wildlife paradise.

The darker side of cities is represented by a segment on hatchling sea turtles. The turtles use the shine of moonlight on water to guide them from their nest in the sand into the ocean. Unfortunately, we humans love to shine lights even brighter than the moon, and more than half of the tiny turtles are drawn away from the ocean by the city’s lights.

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A hatchling Hawksbill sea turtle in Planet Earth II.

As Attenborough narrates, footage rolls of the baby sea turtles gamely clambering across sidewalks and onto busy streets, heading for the ocean that isn’t there. The bodies of roadkilled turtles are visible in the background. One turtle makes it across the street, then tumbles halfway into a storm grate and gets stuck, lost to view save for one forlornly-waving flipper.

As soon as the episode ended, I began typing into Google: “planet earth 2 did”—at which point Google helpfully autocompleted the rest of the sentence: “planet earth 2 did they help the turtles“. Everyone else who had seen the episode wanted to know, too.

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Scarred

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Like elephants or dinosaurs, male Northern elephant seals on land are massive past the point of useful reference. A 5000-lb animal falls off our everyday mental scale; it’s just enormous.

Yet, lounging around on the sand at this time of year—their mating season—these beasts look like they need some band-aids and Neosporin. Their thick, strong hide is marred with new gashes laid over old scars. Titans they may be, but even titans can fall when they square off against other titans.

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Two males facing off. The male on the left has blood on his nose.

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Why do birds flock in winter?

If you live in a temperate climate and pay attention to your local birds, you have probably noticed that their preferences for companionship change with the seasons. In spring, pairs stick close by each other and three’s a crowd—any third-wheel interloper is likely to be chased off in a flurry of angry wingbeats. But in fall and winter, the birds suddenly become community minded, travelling around in flocks of dozens of their fellows. In Chicago in the winter you can find trees liberally decorated with the round orange forms of fluffed-up American Robins, bearing more than a passing resemblance to Christmas tree ornaments. Even in the Bay Area, not generally known for its seasonal variation, huge flocks of quietly chirruping Dark-eyed Juncos make it clear that (mild, occasionally rainy) winter has arrived.

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Not pictured: about fifteen of this robin’s winter friends.

Why flock in winter? Or, why flock only in winter?

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“Rare” birds at the banding station

“Rare” is context-dependent. My Collins Bird Guide lists the Dark-eyed Junco as a “rare vagrant,” but that is, of course, because Collins is a bird guide to Europe. Common birds where you don’t expect to find them are exciting. We have our own rarities at the banding station, birds that may be common in the general region but rarely grace our nets; and although no one else would consider them remotely remarkable, we still get excited.

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Dark-eyed Junco

Juncos flock in huge numbers all around the area, but for whatever reason, they do not like the specific patch of riparian land that the banding station monitors. The banding station catches only around five juncos every year, making them rare by our very particular standards.

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