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Bird Health

House Finch Eye Disease

Q. I’m suddenly seeing a lot of House Finches with red, swollen, and weepy eyes. What’s wrong with them?

A. The sick House Finches are probably afflicted with Mycoplasmal conjunctivitis, otherwise known as House Finch Eye Disease. In early fall, the prevalence of this infection increases dramatically, and bird watchers may start to find many more sick birds at their feeders. To read more about this disease and to learn about the citizen science project that attempts to track and understand it, please visit the House Finch Disease Survey.

Bald Birds

Q. I’ve been seeing a bald cardinal at my feeder. Is it sick?

A. In fall, we receive many inquiries about bald birds, especially Northern Cardinals and Blue Jays. In late summer and fall, when a bird molts, it usually grows and replaces all its feathers gradually, but occasionally a bird loses all the feathers on its head at once. The result is a very strange looking bald bird! Don’t worry--usually the feathers grow back just fine.

It is possible that the baldness is caused by environmental or nutritional factors, feather mites, or lice. To read more and take a look at photos of other bald birds, visit the “Bald Birds” page on the Project FeederWatch web site.

Window Collisions

Q: A bird keeps flying into my window. Why is it doing this?
I’m afraid it will hurt itself--what should I do?

A: The behavior you mention often occurs in spring. This is the time of year when most birds are busy establishing their territories, finding a mate, laying eggs, and raising their young. They are very protective of their territory and will attack and try to drive away any bird they view as a possible competitor or a threat to their young. When they see their own reflection in your window, they assume they’re seeing a competitor and so they attack their own image. Both males and females may do this, especially species that often nest close to houses, such as American Robins, Northern Cardinals, Chipping Sparrows, and Song Sparrows.

This territorial reaction may be so strong that the bird may exhaust itself, but it usually doesn't result in fatal injury. Try covering the outside of the window with netting or fabric so the reflection is no longer visible. You can also try drawing soap streaks across the window to break up the reflection. You will probably be able to take down the netting and remove the soap several weeks later, when passions aren't running quite so high.

Other kinds of window collisions can be much more serious. Visit our Window Collisions page for ways to avoid this potentially lethal problem.

Birds and Hurricanes

Q. How do hurricanes affect migrating birds, and is there anything we can do to help the birds that have been negatively affected?

A. Each year, migratory birds cross the Gulf of Mexico during the hurricane season. Birds wait for favorable winds and weather before taking flight, so they won’t try to fly during a hurricane. If a migrant lands at a spot that has been devastated by storms, it will continue onward in search of better stopover areas.

Unfortunately, sometimes migratory birds get caught in bad weather while crossing open water. Although migrants have enough fat (fuel reserves) to make the 600-mile Gulf crossing in favorable winds, they may not have enough energy to survive if they have to fight against headwinds. Preserving critical coastal habitats is important for exhausted migrants.

Resident birds in hurricane areas also suffer when their food supplies, such as fruits and berries, are stripped from trees and shrubs.

Birds and hurricanes have coexisted for millennia, and given the chance, healthy bird populations can rebound from the effects of natural disasters. Unfortunately, humans are making this difficult for some birds because we have destroyed so much of their original habitats. With fewer birds and fewer places where they can live, hurricanes pose greater threats to vulnerable bird populations. For this reason, one of the best things we can do to protect birds from hurricanes is work to ensure that there are enough birds and places for them so they have the opportunity to rebound.

Dead adult bird

Q: I was cleaning out my next boxes and I found a dead adult Tree Swallow in one of them. How can this happen?

A: There are a couple of reasons why you may find a dead adult bird in your nest box. Was the inside of the front of the box (below the hole) rough or grooved? Very often birds get stuck in boxes because the inside walls are too smooth and they can't climb their way out.

Also, Tree Swallows migrate quite a long way--some of them come up all the way from Central America. If they arrive after such a long journey to wet, cold conditions, and a lack of insects (which is what they feed on), they will often die.

To be safe, I would replace the box. Maybe there is something toxic in the wood that you are not aware of.

The Birdhouse Network, a citizen-science project of the Cornell Lab of Ornithology, has a wealth of information for people who have nest boxes. For features of a good nest box, check out the page, "Resources for Nest-Box Monitoring." You might also like to join The Birdhouse Network and let us know what is happening in your nest boxes.

Blind Pelicans

I hear that Brown Pelicans frequently die of blindness because they develop cataracts as a result of their diving behavior. I find this to be preposterous and wonder if you have any light to shed on this subject.

The good news is that pelicans do not become blind from the impact of repeated diving, even though they may plunge into the water from as high as 65 feet. The bad news is that they do sometimes lose their vision for other reasons, including infections resulting from disease or hook and line injuries.

These cases are relatively rare, however, compared with other causes of injury and mortality. Wendy Fox, executive director of the Pelican Harbor Seabird Station in Florida, has seen only several blind pelicans out of some 10,000 pelicans that came through the rescue and rehabilitation center in the past 25 years. Wendy says that about 90 percent of all injuries were caused by fish hooks from fishing lines.

Other causes of mortality for Brown Pelicans include starvation because of scarcity of fish during cold temperatures and the stress of migration, especially for younger birds.

Pelicans have several adaptations to diving, including air sacs beneath the skin on their breast that serve as cushions and floats. While diving, they also rotate their body to the left, probably to avoid injury to their trachea and esophagus, which are on the right side of neck.