Featured paper: five warblers, lots of tornadoes, and a mystery

Male Golden-winged Warbler. Photo by Mark Peck*

Male Golden-winged Warbler. Photo by Mark Peck*

This story begins when Streby et al. (2015) decided to track Golden-winged Warblers during their annual migration. We know that lots of birds migrate, but for most of them, we know surprisingly few details about that migration. Often we know generally where they go (to a specificity of, say, “somewhere in South America”) but not exactly where; rarely do we know what paths they take to get between wintering and breeding grounds. This kind of information is especially important for birds of conservation concern, since to protect a migratory population, you need to protect its wintering grounds and migration route as well as its breeding grounds.

The researchers relied on technology to tell them where the warblers went when they migrated. There are several different ways to track animal movements; in this case, researchers used light-level geolocators, which record the amount of light hitting the geolocator. Collected over time, these light intensity measurements allow researchers to calculate where the geolocator was, based on things such as day length. This location information isn’t as accurate as the data you would get from a GPS logger, but the light-level geolocators have a big advantage over GPS loggers: they can be much smaller, so you can put them on tiny birds like Golden-winged Warblers. A Golden-winged Warbler attached to a heavy, clunky GPS logger would not be migrating anywhere.

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Hurray for California rain

California is in the middle of a severe drought. Winter is the rainy season here, and the last two winters weren’t rainy. The drought’s major human impact has been agriculture-related: California grows a hefty portion of the US’s fruits, vegetables, and livestock, all of which require water. The drive to my field sites takes me through the agriculture-heavy Central Valley, and the drought was clearly apparent this summer. The fields were all cracked dry earth and yellow grass, with the rare irrigated green square standing out like artificial turf. One afternoon late in the field season, a light rain sprinkled as we drove through the valley, and we rolled down the windows and cheered.

The Central Valley is thirsty.

The Central Valley is thirsty.

Concerns over agriculture affect everyone; but beyond them, and more personally, I can’t help seeing the drought through the lens of a field biologist.

I have colleagues who slip and slosh through mud all summer to study Black Rails—or who hope that there will be mud to slosh through, anyway, because the small, secretive Black Rail relies on the existence of marshes in which to hide from predators and hatch its comically large-footed chicks. Less rain means fewer and smaller marshes for the Black Rails.

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Bats are cool (and generous, and selfish, and fuzzy)

I’ve become more-than-usually interested in bats recently, for extremely serious scientific reasons.

Okay, no. It’s because of this video:

But bats aren’t just cute (and really, what animal wouldn’t be cute wrapped up like a burrito? I challenge you to think of one; even a cockroach would look big-eyed and winning). They are also intelligent, social, and adept hunters.

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Does food taste the same to animals as it does to us?

Every day, I feed my cat small, round, hard pellets that look about as appetizing as old gravel, and she gets so excited about them. I tasted one (for you, dear readers!) and I would describe the taste as falling somewhere between the meh of cardboard and the bleh of rancid fish. Not recommended. For her part, the cat flinches if I consume an orange anywhere near her; you can tell she thinks I am disgusting for eating them. It seems pretty clear that she and I have different tastes in food. Are such differences simply matters of individual preference, or is there a biological basis for them?

As in all things, I am right and you are wrong about this.

As in all things, I am right and you are wrong about this.

It’s hard to know what something tastes like to someone else. My personal experience of peanut butter (disgusting) is likely to differ from yours (mmm, yum), despite our belonging to the same species. However, we can say with some certainty that both of us can taste peanut butter, and that it will not taste like lemons to either of us. Humans have five major types of taste receptors: sweet, umami, bitter, sour, and salty. Sugar is sweet, hamburgers and mushrooms are umami, coffee and India pale ales are bitter, lemons are sour, and salt is salty.

And mice are micey.

And mice are micey.

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Let’s talk about bird tongues

Ferruginous Hawk. Photo by Nathan Rupert*

Ferruginous Hawk. Photo by Nathan Rupert*

You don’t have to look at many birds to realize that they are very variable in appearance: hawks look different from hummingbirds, and both look different from peacocks. You can spend a lot of time looking at birds, though, before you realize that they are hiding a lot of variation inside their mouths: long tongues, short tongues, spiky tongues, curly tongues, forked tongues, frayed tongues, brush-like tongues.

Like bird bills, bird tongues are specialized to each particular bird’s way of feeding. Birds that feed on nectar have tongues specifically adapted to nectarivory, often with many little protrusions at the tip of the tongue, giving it a frayed or brush-like appearance. This brushiness increases the surface area of the tongue, making it better at picking up nectar.

Rainbow Lorikeet. Photo by Alan (Kaptain Kobold)*

Rainbow Lorikeet using its brush-like tongue to feed on flowers. Photo by Alan (Kaptain Kobold)*

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