If you’ve ever driven across the United States of America, you have passed beneath the wings of a courageous songbird — smaller than your palm, light as your change pocket, feathered in bright blue and yellowish-brown — called the cliff swallow (崖燕). Where other animals flee the human footprint, cliff swallows don’t. They should properly be called the bridge swallow, for our steel spans have furnished it with more nesting sites. Once a bird of the western mountains, in the last century cliff swallows have spread onto the Great Plains and across them, making their mud nests under bridges, works of birds’ engineering no less impressive than our own.

For the last four decades Brown has paid annual visits to more than two hundred nesting sites in Nebraska, trying to figure out what makes swallow societies success or fail. “Ninety-eight percent of cliff swallows in western Nebraska,” Brown said; “are within fifty feet of a road.”

Near a road, of course, is the most dangerous place an animal can live. When Brown began studying swallows in the 1980s, he often picked up dead swallows on the roads, wings broken and heads crushed (压变形). However, Brown found swallow roadkill had been decreasing. By 2011 it had dropped to four. Somehow swallows had become harder to kill.

He found his answer. When he stretched a tape measure from the birds’ shoulders to their outermost feathers, he found car struck swallows had longer wings than the average bird he caught in his nets. Brown immediately understood the significance. Traffic was weeding slower long-winged swallows from the population and favoring the quicker, short-winged ones -Darwinian selection in action.

“Centuries ago ... cliff swallows had existed largely beyond human influence; now they were so involved in our world that our infrastructure (基础设施) had influenced their DNA,” Brown said. Cliff swallows were rare winners of concrete and steel. Yet their success had come at a cost — to the long-winged swallows erased from the population and to the birds’ altered genes themselves. They had been shaped by the road.

Swimming alongside wild dolphins has long been on the Hawaii vacation list. However, scientists are concerned that increased human activities may do bad to the animals by disturbing a very important period of their rest. “We have seen changes in their action,” Ann Garrett of NOAA’s National Marine Fisheries Service said. “They will be more active with people around.”

After feeding in deep water at night, dolphins return to sheltered, shallow (浅的) water to rest during the day. The problem appears when swimmers draw them out of their resting state, a change in behavior that NOAA points out “may cause disturbance”.

“Disturbing their resting behaviors can actually affect their long-term health and the health of the population,” Garrett said. This summer, NOAA is set to put forward its new rules. “NOAA is considering a lot of measures. These measures may make some people angry, but they will undoubtedly do good to those dolphins,” Garrett said.

Today, a small number of Hawaii tour companies willingly join in a NOAA program called Dolphin SMART. Designed to lower the disturbance that dolphins suffer because of human activities to the minimum (最低限度), the program encourages tourists to stay 50 yards away from dolphins and to move away carefully if they feel the animals are disturbed.

NOAA’s new rules, however, would not be allowed to be chosen to follow or not, and could affect over 200 dolphin-related businesses as well as swimmers and other ocean users. Garrett said that new rules would keep tour companies from disturbing dolphins. “The final goal of the changes,” she said, “will be to provide more protections for dolphins while still offering a chance for tourists to have a pleasant wildlife experience”.

About a billion birds die from flying into buildings each year in North America. Suspicions have been that birds may regard the open areas behind glass as safe passageways. Or they may mistake the reflected trees for the real thing.

Researchers would like to reduce collisions, which requires a solid understanding about what makes a bird more or less likely to die by crashing into a building in the first place.

“There was relatively little known at a broad scale. Previous studies were at one small study site.'' Jared Elmore, a graduate student in natural resource ecology and management at Oklahoma State University. So he and his colleagues used a previously created data set of building collisions for birds at 40 sites throughout Mexico, Canada and the U.S.

The first finding was obvious: bigger buildings with more glass kill more birds. But the details were more remarkable. "We found that life history predicted collisions. Migrants(候鸟), insect-eaters and woodland-inhabiting species collided more than their counterparts(同类).”

Most migratory species travel at night, when lights near buildings can distract or disorient(使迷失方向)them. And Elmore thinks that insect-eating birds might be attracted to buildings because their insect prey(猎物)is attracted to the lights. He suspects that woodland species get tooled by the reflections of trees and bushes in the windows. The results are in the journal Conservation Biology.

By understanding which birds are more likely to collide with buildings, researchers can perhaps determine the best way to adapt buildings, or their lighting, to help prevent such accidents. And by knowing risks, along with migration timing and behavior, building managers can better predict when birds are at their greatest danger - and improve lighting strategics accordingly.

Elmore's next project will use radar to help predict bird migrations. " I think that would maybe go a long way in terms of providing information to people, to the public, to building managers, on when they can get the most benefit in terms of lights-out policies."