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Bird Migration: Top 10 Questions

October 2009

Thanks to Jay Carlisle, Research Director, Idaho Bird Observatory; and Vicky Runnoe, Conservation Education Supervisor, Idaho Department of Fish and Game for the answers.

1: What is the biggest bird?

The Emu is probably the largest living bird. Emus are big in part because they don't fly. By not having wings, they can put on extra body weight. If they had to fly, they wouldn't be able to carry that weight. (From Kenton at Hayden Meadows Elementary School in Coeur d'Alene)

2: How many birds migrate a year?

Millions and millions of birds migrate every single year. It's hard to put a number on it. However, on each continent there are millions of birds migrating between the temperate and tropical zones every year. (From Grace in Mrs. Dransfield's class at Mary McPherson Elementary School in Meridian)

3: How come some birds don't migrate?

A lot of it depends on what they eat. If they eat insects and the insects die off during the winter months, they will need to migrate in order to eat. However, if they are a bird who eats foods that are around in the winter, like eating seeds for example, they won't have to migrate and will stay locally. (From Ben in Mrs. Dransfield's class at Mary McPherson Elementary School in Meridian)

4: How do birds flap their wings so they don't get tired?

Birds utilize oxygen very efficiently, allowing them to exercise (or flap their wings) more efficiently than we may be able to. Also, they store a lot of fat. Fat is their migratory fuel. This fuel allows them to keep going as if they had a battery. Some species can even fly for 72 hours continuously! However, scientists believe that there is evidence that birds really are tired when they land. Flapping a lot and being tired may go hand in hand. (From Jake in Mrs. Gris' class at Horizon Elementary School in Boise)

5: Where do the birds from Idaho mostly go?

It depends on the kind of bird. Our Mountain Bluebird migrates to the southern United States. The Osprey goes to South America. Central Mexico seems to be the area that hosts the highest number of Idaho species during the winter. (From Jenna in Mrs. Schweitzer's class at Riverside Elementary School in Boise)

6: What birds are adapted to living in winter instead of going south?

There are several birds that can live in winter weather conditions. For example, there are raptors, like the Red Tailed Hawk, that eat small mammals, and Bald Eagles that eat fish. These birds don't need to migrate as far. Black-capped Chickadees can switch their diet from eating more insects to eating more seeds and fruit, allowing them to stay here. Also Sparrows, the more common wintering birds in the Treasure Valley, feed on seeds through the winter. (From Elise in Mrs. Boyer's class at Mary Nelson Elementary School in Boise)

7: Do birds carry diseases?

Birds do carry diseases. Some areas have a higher prevalence of disease than others. In southwestern Idaho, we will see migrating birds carrying a virus called avian pox. This is not a fatal disease, but sometimes it can cause them to lose a toe or something like that. This is not a dangerous disease or really prevalent among the population, but there are other areas where a disease like that can be more dangerous to bird populations. (From Haven in Londeen's class at Christine Donnell Elementary School in Boise)

8: Do owls migrate?

There are some owl species that do migrate and some that don't. Northern and Flammulated Owls eat mainly insects, so they migrate to the southern United States and west central Mexico for the winter months. Saw Whet Owls rely on small mammals for food, so their distance of migration is much shorter (200 or 300 miles). The Great Horned Owl, another common resident here, eats from small mammals up to raccoons or skunks. They do not migrate at all and can eat year-round right here. (From Calen in Mrs. McCoy's class at Donnelly Elementary School in Donnelly)

9: Why can't birds hibernate? Do they do anything like bears?

They don't hibernate but there are some birds that will voluntarily lower their body temperature. For instance, Chickadees can do this at night where they can store up fat from the food they eat during the day. Then, they lower their body temperature at night so they don't have to keep their body as warm, using less energy. However they still have to shiver to keep some baseline level of warmth so their body organs won't fail. In the morning, they turn it back on, and in about half an hour their body warms back up again and is ready for flight. There is a bird that is related to the Night Hawk that will do this for longer periods. (From Leah in Mrs. Hunt's class at Cynthia Mann Elementary School in Boise)

10: Why do birds travel as a group in a "V" formation?

It has to do with saving energy. If birds can travel in a group like that and save energy while flying, they can travel further and more efficiently during their migration. So, the lead bird takes some of the brunt of the wind in the front and then they trade out over time. Those traveling in the back will eventually be up in the front, but while they are in the back, they can save energy by drafting off the lead birds. (More than 20 students from all over the state asked this question)


October 2006

1: Bats fly too; do they migrate?

Yes, they do. Bats are mostly insectivorous. There aren't many insects around in the wintertime. So they have to migrate to continue eating. (From Dylan in Mrs. Lane's class in Grangeville)

2: How did the first bird get the bird flu?

Probably just the same way the first human got human flu. Some flu viruses occur naturally in birds, just like some viruses in humans. At some point in the past, those viruses changed in some way, mutated, and birds started getting sick. Some die. The virus continued to spread from bird to bird. So far, it is difficult for a human to catch bird flu. (From Skylar in St. Anthony)

3: What can you do to help the birds that do decide to stay here?

We recommend putting out bird seed that comes from a good source, like one of the bird stores in town, where they know what species are here during the winter and which kinds of seeds those species will need. Typically, most of the birds that we'll have in our backyards during the winter are small songbirds that are seedeaters and that's the main food we need for them. And don't forget that birds need water-especially in the winter, when it's freezing and natural water supplies may freeze up.

4: Why are wildlife refuges important to bird migration?

The term "refuge" means an area that we have protected. We have put areas aside and are trying to conserve the habitat there, because habitats are really important for the birds that migrate through that area. They land at those kinds of places during their migration to eat and refuel, gain energy, and gain strength to help them on their way to wherever they're going. (From Miss Whitman's class in Idaho Falls)

5: How do birds know where to come back to?

I don't think we really know all the answers. Birds use a combination of methods to migrate and to know they're going in the right direction. There's actually a small element in their brain that, basically, allows them to use the magnetic earth and to navigate-almost like a compass in their head. They use the stars. They use landmarks. They use familiar mountains and rivers and drainages, but birds' navigational ability is still a mystery in many ways.

6: Do birds migrate back to the same place where they were hatched as babies?

Certainly many do. In fact, some birds will leave from somewhere here in Idaho, where they might nest in a tree, and fly into Central and Southern South America for the winter. Then they'll come all the way back the following Spring and go straight back to that same tree in Idaho. So, many times they come back to the nest or at least the area in which they were born. Others come back to the general area, but not necessarily to exactly where they were born-although a lot of birds will return to exactly the place where they were born. (From Mrs. Fryer's class, Clearwater Valley Elementary)

7: What is the bird with the longest migration route?

The bird that we're aware of that has the longest migration route is the arctic tern. That's a species that literally flies from the North Pole to the South Pole, and then back again later in the year. It's about a 22,000- to 24,000-kilometer journey-one that almost literally goes around the whole world. (From Wade, in Mrs. McCoy's class in Donnelly)

8: How do birds know the right way to go?

They just seem to know. Birds that are born in a particular spring don't migrate with their parents, the adults. They just know how to go. By the way, they don't all make it. We notice that the young often end up along coastlines and other barriers to bird migration. They actually get blown off course and have to find their way. (From Haley and Sara)

9: How do birds know when to migrate?

The most obvious sign is that winter is on its way and therefore food becomes scarce. So the birds need to migrate to be able to keep eating through the winter. But we also think that when the length of day shortens, that triggers the birds' brains and tells them that they need to migrate. Often, birds start migrating while there's still plenty of food available. So we think it's the length of the day-when the day's length shortens-that lets them know it's time to migrate. (From Tristan in Hailey)

10: Do all birds migrate?

No, absolutely not. Not all birds migrate. Many species of birds are not migratory. They're resident birds that don't migrate. (From Sonny at Cynthia Mann Elementary in Boise)


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