The Best American Science and Nature Writing 2014 Read Online Free Page A

photographer passed through. I could feel my eyes go wide, and I know his were as he looked back at me. They sent him through again, and this time the alarms were silent. “Just a little glitch,” the guards manning the exit assured us, and this time I could feel my eyes narrowing. But “Just a glitch,” I repeated to the photographer as we sped back toward the casino-hotel in Las Vegas where we were staying. The desert whipped by the windows in a blur of russet and gray-green. I had my foot down on the gas because, well, I was in a hurry to get back.
    â€œYou know,” I said casually as I hopped out of the car, “I think I’ll just go take a shower.” As I recall, I said it to his back because he was already on his way. When we met for dinner, we were both shiny from soap and water. Over the chicken, though, he decided that he was still so stressed out he might just try relaxing in the glitter of the casino. That night, playing blackjack, he lost every dollar we’d brought to cover our expenses.
    But that, as they say, is another story.
    D EBORAH B LUM

KATHERINE BAGLEY
Mixed Up
    FROM
Audubon
    Â 
    â€œI LOVE GETTING huge boxes of blood,” says the genetic ornithologist Rachel Vallender as she pulls open a drawer full of small plastic vials in her laboratory at the Canadian Museum of Nature in Ottawa, where she’s a visiting scientist. Each tube, carefully labeled and organized, holds a blood sample from a single warbler. Whether the bird is actually a hybrid is the question Vallender seeks to answer.
    Hybrids of golden-winged and blue-winged warblers are increasingly popping up across the Northeast and into Canada. The physical differences between the mixed progeny and their pure counterparts can be subtle. A bird might, for instance, have the distinctive yellow patches on its wings, the golden head, and the jet-black collar of a golden-winged warbler but with the yellowish belly of a blue-winged warbler. So individual scientists and conservation groups, including Audubon North Carolina and Bird Studies Canada, are gathering samples from across eastern North America and sending them to Vallender, who analyzes mitochondrial DNA in the blood to determine the birds’ genetic history. She examines the shipments she receives in free moments—on nights, weekends, and vacation days from her full-time job with Environment Canada, a government agency. The research is revealing how prevalent this intermingling of genes is and helping bring to light some of the potential dangers it poses.
    Records of blue-wingeds spreading into golden-winged territory, hybridizing with them, and gradually replacing them extend back to the early twentieth century. Such mixing isn’t unusual in the avian world: nearly 10 percent of all bird species are known to occasionally interbreed. But the genetic work of Vallender, who has been studying warbler hybridization for more than a decade, backs up the observations of birders and scientists who, during the same time period, have reported growing numbers of hybrids while conducting population surveys. She’s found that in many places across the United States and Canada, hybrids now make up as much as 30 percent of golden-winged warbler populations. “This isn’t just some sporadic event anymore,” she says.
    This shift, says Vallender, correlates with the onslaught of climate change. Biologists have long known that habitat loss is a major factor driving blue-winged warblers to expand their range. The bird’s preferred scrubland habitat is disappearing as abandoned farmland reverts to forest. Warming temperatures might be adding additional pressures, causing blue-wingeds to move north in search of cooler climes and into habitat already occupied by golden-wingeds.
    For reasons unknown, the golden-winged warblers seem to suffer more from the interaction. While blue-winged populations are experiencing declines, golden-winged