One of the joys of biology lies in appreciating how strange and varied the world is. When humanity starts to feel claustrophobic, you can imagine the life of an albatross, aloft over the ocean for most of her life, searching out schools of delicious fish by their scent; or a cuttlefish, flashing colored signals at his companions as he shoots through the currents, flexible tentacles waving. When the world feels narrow and limiting, you can remember that clownfish change sexes depending on their place in the dominance hierarchy, with males becoming female when they advance to the position of top dog.
Yet—amazingly—biology used to be even wilder. Before satellite tracking and genetic analysis, before “biology” was a recognized science at all, natural philosophers looked at a perplexing natural world and invented some truly outside-the-box explanations for what they saw.
Some of these are fairly well known: for example, the idea that there is a “homunculus”—a tiny human—inside the head of each human sperm cell.
To be fair, we now know that sperm (and eggs, etc.) contain the genetic blueprint for building a human, which isn’t all that far off from containing a tiny human.
But my favorite old science myth involves—of course!—birds.
The sun dips low over the bay, its fading rays gilding the avocets as they swish their heads through the water. The egrets eye their own reflections as if in profound self-contemplation. A willet flashes past, its black-and-white wings an exclamation in the dusk.
Faced with such beauty, two words come irrepressibly to mind: niche partitioning.
Hummingbirds wear a public image of fragile, ethereal beauty: tiny jewels whirring through the air, occasionally pausing to drink daintily from a flower. Their unusual appearance supports this: the iridescent feathers, the long dainty bill, the near-invisible feet all make them seem quite apart from the everyday world of animals who don’t shimmer in the sun and do have feet.
80% gemstone, 15% fairy from a storybook, only maybe 5% actual bird. He doesn’t even have feet! (Yes he does.)
But hummingbirds, like all birds, evolved from dinosaurs. Hidden under that glimmering exterior is a tiny, fierce raptorial dinosaur.
Egrets are beautiful, especially in their breeding plumage, when they sport long curved plumes and dramatically colored faces.
Great Egret displaying breeding plumes and a green face.
Snowy Egret with similar plumes and a red face.
Those breeding plumes are so beautiful that demand for them—for decorating women’s hats—almost drove egrets to extinction, and concern for the heavily persecuted egrets is what gave rise to the bird conservation movement in the early 20th century.
Egrets earn those luscious plumes. Before they get to be adults in breeding plumage, egrets must survive a cutthroat childhood in considerably less impressive dress.
Yikes, THAT’S what our chicks look like??
I was supposed to be done with field work after summer 2015, but you know how it is. The birds call. You realize that a few more blood samples would put the patterns you’re seeing in context in an illuminating way. You miss those feathery little dudes.
The small amount of field work I did this year took place much earlier than my usual field work because I was sampling juncos at a much lower elevation. Down here, the juncos are breeding in mid-March. Up at my usual sites, they wait until late May. That early start happened to be convenient for me, since I needed to analyze any data I got in time to file my dissertation in mid-May.
We all know about food webs—or we think we do. Herbivores eat plants, then predators eat herbivores, and if one part of the web is affected, other parts are impacted too. Seems pretty simple—except that the threads in those webs sometimes connect things you would never expect.
For example: trout and a songbird, the Gray-crowned Rosy-Finch, in an alpine habitat. The fish are in the water and the birds are on land—how connected can they be? If the birds were Bald Eagles or Ospreys or Great Blue Herons, sure, they would be connected because the birds eat the fish. If the birds were ducks, maybe the trout would be an occasional threat to the ducklings. But this is a Gray-crowned Rosy-Finch:
Photo by Blake Matheson*
They’re not going to be eating fish, and their babies definitely don’t float about on the water.
The reason that we need to worry about what threads on the food web those trout might be tugging at is that the trout are introduced, nonnative species. Alpine lakes often don’t have any fish in them naturally. In the Sierra Nevada and many other mountain habitats, however, people have stocked these lakes with fish so that people can come and fish them for fun. This has been a problem for aquatic species such as frogs, which get gobbled up quite happily by the new fish, but nobody was particularly worried about the effects on songbirds.
It turns out that we should have been.
Ranitomeya imitator giving his tadpole a piggy-back ride. Photo by John Clare*
You can find poison frogs at zoos, aquaria, and some museums now: tiny and colorful, often hard to see in the vegetation-rich tank until— oh! all those little blue things, that’s them! They’re so pretty! You watch for a while, and they sit on their leaves unmoving, doing accurate impressions of the plastic toy frogs being sold in the gift shop, until you get bored and move on to the next exhibit.
They have a secret: they have rich lives full of interesting behaviors. They just aren’t interested in doing those behaviors in front of you.