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You’ve done it—you created the perfect outdoor oasis. Now lilting birdsongs are your alarm clock; your double-decker birdhouse seldom has a peak-season vacancy; and “the restaurant”—otherwise known as the feeding station—practically requires a reservation. Things couldn’t be better. Then disaster strikes: a sobering thud against the window; a hawk with a just-fed goldfinch in its talons; a cat with a tuft of feathers dangling from its mouth; a house finch with conjunctivitis splashing around the birdbath. How can you prevent such backyard blunders? Our expert ornithologist covers everything you need to know.

Windows

Collisions with glass are the single greatest threat to the birds visiting your yard. It’s not that birds have bad vision; an American kestrel, for instance, can spy an insect no bigger than a pea from 60 feet away and sees a broader range of colors than humans do. But glass presents a novel obstacle—a transparent, unyielding wall—and nothing in a bird’s evolutionary past has prepared it for such face-to-glass encounters. Windows kill indiscriminately, taking both healthy and ailing birds in every season, day and night. Researchers with the Cornell Laboratory of Ornithology’s found that window collisions might account for the deaths of between one and ten birds per building, per year. Daniel Klem Jr., an ornithology and conservation biology professor at Pennsylvania’s Muhlenberg College, estimates that as many as a billion birds die this way each year in the United States. His research indicates that feeders placed within three to 30 feet of a window are especially dangerous, because this gives flushed birds enough distance to build momentum for a fatal crash.

Objects stuck to the glass are often considered an acceptable safeguard, but unfortunately, such decorations usually don’t work. Even the classic falcon silhouette sold for this purpose has next to no benefit unless the silhouettes are just two to four inches apart and cover most of the window. One promising new product is . Available with static backing, these decals, which come in leaf, butterfly, snowflake, or hummingbird shapes, effectively break up the large, reflective surface with a frosted-glass effect. To increase your chances of success, attach the stickers to the outside of windows. By putting them about three inches apart, you will create a nearly transparent, decorative look indoors while helping to break up the mirrorlike surface from the outside. The glass’s reflective nature can also be blocked with a one-way surface film, which masks the exterior with a solid silver-gray color that’s transparent from inside.

When birds repeatedly hurl themselves at the same pane of glass in spring and early summer, they are likely battling their own likenesses. This behavior arises from an attempt to chase a rival from a nesting territory. Try hanging mobiles, wind chimes, or Mylar streamers outside. (Objects attached or suspended inside windows offer little benefit.)

Windows that result in chronic collisions can be fitted with mesh netting. Fruit tree netting (available at most garden shops) is ideal. Stretch the netting over the outside of the window, securing it in place with molding, or ask a local screen and glass shop to make fitted screens with the netting. For smaller windows, one of the simplest solutions is to leave screens in place throughout the year. Commercial bird-bouncing devices are also available for large windows. One such is secured to the window with suction cups.

If a head-on collision with glass doesn’t do a bird in, other factors might. Stunned birds become more vulnerable to predators, and a feathered traveler with a concussion won’t likely have all the faculties it needs to fly and feed during an already arduous migration. (Find my tips for helping a stunned bird .) If you haven’t yet witnessed a bird meeting glass, don’t assume that your windows are safe. Strikes often go unnoticed because scavengers like cats and raccoons make quick work of the feathered corpses. Look at your windows closely for telltale feathers stuck to their surface or the powdery outline of wings, and take the proper precautions.

Cats

Got a Sylvester stalking your feeder hoping to snag himself a Tweety Bird? Between 1970 and 1990 the number of domestic cats in the United States doubled, from 30 million to 60 million, according to the U.S. Census Bureau. Taking into account stray and feral cats, more than 100 million cats are likely prowling the United States. Although birds make up only about 20 percent of the prey killed by cats (mice and other rodents are mainly taken), felines kill hundreds of millions of birds each year. Many of these are migratory songbirds that are already under pressure from habitat loss and other threats, including collisions with buildings and cell phone towers. Most bird fatalities happen near homes, where house cats come and go and where birds are concentrated at feeders. Fledglings are acutely vulnerable, since some spend a few days on the ground before they can fly.

The best way to reduce the risks to birds is to keep cats indoors—particularly if there are active bird feeders nearby. This protects not only birds; it could save the cats from untimely deaths on the road. Indoor cats are also safer from feline leukemia and other diseases, parasites, attacks from predators, and fights with other cats. Additionally, cats that roam at night are more likely to come into contact with raccoons and skunks, the primary transmitters of rabies in the wild. The average lifespan of an outdoor cat is just five years; by contrast, indoor cats can live more than 15 years.

Putting bells on a kitty’s collar is largely ineffective in preventing bird predation, because by the time the bell rings, it’s usually too late for the prey to escape; fledglings are unable to fly away in any case. Kittens are easiest to train to a life indoors, but even older cats can learn new ways. It takes the attention of your entire family to keep your cat within the safety of your home. Providing toys, games, activities, and other forms of “environmental enrichment” can help minimize boredom and keep indoor cats fit and alert. Bird feeders near windows—even videos of bird feeders, mice, and fish—can entertain indoor cats for hours. Or try interactive cat games that provide exercise, play, and problem solving. One source is the new book 101 Cool Games for Cool Cats (Rockwell House, 2007), by Elissa Wolfson. Also consider a fenced-in cat enclosure that offers fresh air, sunshine, and climbing perches. Commercial pre-built enclosures are available from online retailers. For those who have neighborhood cats near their feeders, one device that may prove useful is the . This battery-operated product has a motion/heat sensor that triggers a startling noise and a blast of water to scare predators. If you need proof that a neighbor’s cat is stalking your feeders, catch him in the act with a weatherproof camera like the Wingscapes BirdCam, which snaps photos with a motion-detecting lens.

Diseases

The unusually crowded conditions at bird-feeding stations increase the likelihood of spreading contagious diseases, especially where uneaten food and bird droppings accumulate. Such a consistent food source may also enable diseased birds to survive longer than they would without supplemental food—and the longer they reside at feeders, the more likely they are to spread disease to healthy birds. To keep your birds fit, feed fresh seed, stored in watertight containers and, in the summertime, out of the heat, which can turn oils rancid. Avoid feeding suet to birds once summer temperatures peak, because it will melt and then oil feathers, possibly ruining waterproofing.

Moldy food can transmit a respiratory disease called aspergillosis. If seed goes bad, bury it or otherwise dispose of it in a place where birds will not gain access. Seed can also turn moldy in feeders, so scrub them out in the spring and fall and more often if they are used during the humid summer months. Use a long-handled bottlebrush, scour with environment-friendly dish soap, and rinse thoroughly. You can also prepare a solution of 10 percent non-chlorinated bleach and fully immerse the feeders for two to three minutes; scrub and rinse with fresh water. In early spring rake up spilled grain and hulls from under feeders. Wash and rinse hummingbird feeders every three to five days and change the nectar solution daily in hot weather.

Hawks

Nature will be nature, but bird feeding shrinks the predatory playing field, particularly if you’re a raptor like a hawk or an owl. That’s because large concentrations of songbirds at backyard feeders commonly attract Cooper’s hawks, sharp-shinned hawks, American kestrels, and goshawks. Screech and great horned owls also take backyard prey, but their bird-snatching ways are seen less often, since they hunt at night. In addition to being hunted by predators, birds of all sizes often die from slamming into windows in their panic to escape. Sometimes pursuing raptors suffer fatal collisions as well.

When predators do come calling, you can prevent songbirds from getting picked off by holding back the seed and letting the feeders go empty for a few days. With their prey dispersed, hawks will soon move on. Healthy birds can usually evade predators if there are suitable trees to serve as escape cover within 15 to 20 feet of a feeder.