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Frequently Asked Questions about Robins in Autumn

Image: Shelley Powers

Q. Do all robins migrate south?
A.
Robins are a migratory species, but their migration is far more complicated than simply a shift southward. There seems to be a great deal of individual variation in how far they go and where they spend winter. Males are far more likely to remain in the north than females. for some very good reasons. Come spring, the male’s main job is to find and defend a territory. The females’ main job is to create and lay the eggs. This requires a lot of good nutrition and food energy, so females go where they are sure of good food supplies in winter. Yes, they have to use up food energy to migrate north. But migrating and laying eggs are easier for well-nourished birds. 


Q: Why do robins migrate?
A: Robins migrate because the ground freezes, locking them out from their favorite food, earthworms, and because winter weather makes it impossible to find juicy caterpillars and other insect food. Robins switch their diet to fruit in winter, but there is not enough fruit in the north to feed all the robins that live in the north all summer. That's why most robins move south.

Q. Why don't they stay in the south, but instead migrate north again in spring? A. Robins are very often stressed by heat, and areas where robins winter often have hot summers. Soils in the South can even get so warm and dry that worms retreat deeper into their burrows during hot, dry spells, making them harder for robins to find. Also, a careful look at a map of North America shows a vast landmass with frigid winters but pleasant summers, where earthworms and other robin food thrive. Robins evolved to take advantage of that huge food resource.
Q: How do flocks get started in the first place?
A: When a brood of baby robins fledge, they are taken care of by both parents for a few days. Then the female gets ready to lay more eggs. When she starts incubating the next clutch of egge, the male continues to take care of the first brood. At nighttime, he leads them to a nice, well-sheltered stand of trees or shrubs to sleep. Other male robins are also leading their babies to this area, which is called a roost. The young birds get used to sleeping in a big group (flock). When the new eggs hatch, the father leaves his older babies to help feed and care for the new nestlings. The older babies are fine on their own, hanging out with other fledglings. They learn that being in groups, or flocks, is normal. Robins ARE territorial on their summer breeding territories, but not at their roosts, nor in feeding trees. Flocking is a behavior that serves robins well when it's not breeding season. Advantages to being in flocks are that more eyes can search for food sources, and more eyes and ears can be watchful for predators.

Q: How do flocks of mixed species get going?
A: Mockingbirds, waxwings, Pine Grosbeaks, and other fruit-eating birds that join up with robin flocks usually get going when the birds are searching for fruit trees. Hearing fruit-eating birds attracts other fruit-eaters, of the same as well as different species, because they all need the same food.



Q. How do robins prepare for winter?
A. In October they start seriously adding down feathers to improve their insulation for winter. Also, summer food supplies have diminished; there are still plenty of berries around to eat, but robins get seriously on the move in search of plentiful food supplies for the coming winter. They start seriously moving in October. Back on October 1, 1988, birdwatchers counted over 60,000 robins migrating over Duluth in northern Minnesota, so that's serious migration.
But in fall and winter, robins don’t stay in a single spot for long — they wander about searching for new sources of still-fresh fruits.


Q.How do scientists learn where the robins from one state or province migrate for the winter? Can we find out where our own backyard robins migrate?
A.
Scientists study bird banding data to learn where robins go. They put thousands of numbered bands on robin legs, but they know they will only recover data from a few of these birds in the future. So it takes a long time to amass enough data for them to draw accurate conclusions. Meanwhile, robins can change some of their migration patterns, making the research even more complicated. To see the U.S. Fish and Wildlife Service's robin banding data to learn where robins from your area go in the winter, see our Bird Banding Data Study.


Q: When the robin migrates, does it travel in small groups or large groups, or does it migrate alone?
A: All of the above! Robins often associate in flocks, and sometimes these are huge. I once counted 60,000 robins flying along Lake Superior in just 5 hours! And sometimes robins fly alone. But over the years that I counted migrants along Lake Superior, most of the robins were in flocks of about 10-50 birds.

Over the course of a year, robins each lead two entirely different lives. In spring and summer, they're territorial worm-and insect-eaters. In fall and winter, they switch to berries and other fruits and live in sociable flocks. Robins migrate and spend the winter in flocks to make it easier to spot predators.

Q: I live in northern Illinois and see many robins during the summer. They rarely fly more than a few feet above the ground. It is now November and when I've seen robins lately, they are in groups and still flying close to the ground. Do they migrate by flying so close to the ground, seemingly flying from neighborhood to neighborhood? Do they rest overnite?

A: When robins are flying short distances, between fruit trees and roost trees in a neighborhood, they fly below tree height. When they make major movements, they fly much higher, though lower than hawks and other birds that use thermal air currents. I live in Duluth, MN, on a major robin migration flyway, yet from my own yard, I never see the higher flying flocks. I have to stand on one of the ridges in my area to see the large, high-flying flocks. So I believe it's more an issue of vantage point than anything. They rest overnight in large numbers in trees.


Q: Do robins from different areas in the north travel to different areas in the south? (i.e. Do robins from Massachusetts travel to Florida and Georgia, while robins from Illinois travel to Mexico and Texas?)

A: Nope. Robins are “nomadic,” meaning they wander irregularly. The same individual robin may winter one year in Texas, one year in Florida, and one year in Wisconsin! You just never know with robins.
Q: How long does a robin's migratory flight usually take? Does it depend on different conditions? If so, what kind of conditions may apply?
A: The spring migratory flight depends entirely on weather, since they follow the 37-degree isotherm. It can take anywhere from a few days to several weeks for a robin to go from Texas to Minnesota, for example. Fall migration never really ends, since robins wander throughout the autumn, winter, and early spring.


Q. What can I do to help robins in autumn and winter?
A.
You can make your backyard bird-friendly. That means don’t rake too much. Dead leaves left under trees and shrubs are ideal spots for birds to forage for insects as iweather gets colder. You can also provide cover. Birds need shelter from harsh conditions, and vegetation in your yard will help provide it. Don’t prune back dead vegetation like vines and stalks, as these provide both valuable winter cover and nesting material for birds in the spring. If you have berry bushes or fruit trees, don't pick them bare because those fruits are food sources for robins migrating through, or overwintering in your area.

The best thing you can do is to plant native fruit trees and shrubs that will provide robins with fresh, wild food. To feed them in winter, one Journey North friend set out fruit and mealworms in a heated birdbath filled with sphagnum moss rather than water.

Q. Why do robins molt just before they are about to migrate south?
A: They molt so they will have fresh feathers for their flight. These fresh feathers will also be very good for insulating them from the winter cold. Robins start molting their flight feathers in mid-June, and have finished molting them by early September. They molt their body feathers from late July into October. One by one, each feather is pushed out by a new one. Most feathers last for a whole year. If a feather gets pulled out when the robin isn't molting, that feather gets replaced fairly quickly.

Q. Do baby robins migrate by themselves? How do they know where to go?
A: After a brood of young robins fledge (leave the nest), the mother starts building a new nest and laying new eggs even as she still spends most of the time each day attending to those fledglings. The father spends all day with the fledglings and leads them to a roost at nighttime, where they join with other fathers and fledglings. When the mother finishes laying a new clutch (which takes usually four to six days after her new nest is built), she starts incubating and leaves the fledglings to their father’s care. When the new eggs hatch, the father leaves the fledglings on their own and returns to feeding the new nestlings. Those fledglings hang out with the other fledglings from their nighttime roost, finding fruit trees and worms and being sociable, and every night the fathers join them in the roost. As the last broods are done being raised, the mothers join these flocks. So by the summer’s end, robin flocks contain birds of all ages that start to wander, looking for new feeding areas that provide some worms and fruit. The young birds hang out with these restless flocks, moving from place to place in search of food, mostly headed in a southerly direction. They don’t have to know where to go on their own because of their need to associate with other robins.
Q: How do robins know which way to migrate?
A: There is a powerful instinct that makes them grow very restless in spring and fall. And that instinct includes telling them which way to head. After wandering during winter--and individual robins can go to entirely different places from one winter to the next--robins often find their way to the exact backyard they nested in year after year. As daytime migrants, they may well find their way by using the angle of the sun to guide them. Some birds have tiny bits of magnetite in their brains that helps them know which way is north--I'm not sure if robins have been analyzed for this.

The trickiest migration to understand is fall migration. How does a baby robin that has never migrated before know which way to head? Again, more research is needed. But it's quite possible that part of their migration is learned, because young robins tend to join with adults in big migratory flocks. But as with many robin behaviors, it's probably a mixture of instinct and learning both.


Q: Have humans had any effect on how long the robins will stay before migration?
A: Before migrating south, robins often gather in areas with abundant food. The kinds of plants humans grow affect robins because of this. The impulse to migrate is strong in most robins, so even while food is abundant the majority of robins in the north suddenly move on. But when a great amount of food remains, individual robins and groups of robins often remain.


Q: I was wondering if there is some change in the environment, weather, migration path, etc. or have I been seeing a usual pattern of change? I live in a rural, southeast corner of Orange County, Orlando, Florida. I have seen robins begin to pass through our neighborhood as early as November through February in years past.
A: During winter, robins are very nomadic. In some exceptional places they may appear year after year, but their wandering may also change dramatically sometimes because of weather and food patterns farther north. For example, if fruit is unusually abundant in Georgia and Tennessee in one fall and winter, the bulk of robins might not bother to migrate as far as Florida. As temperatures grow milder, more robins may winter farther north. But as of now, the biggest February flocks of robins are usually in the St. Petersburg area of Florida, according to the Great Backyard Bird Count.



Q: Why don't birds sleep in their old nests in the wintertime?
A:
Nests are nurseries, not homes. Even if they were not, the nests that served robin families so well in the summer are built to last a single season and aren't in the best shape by now. Most nests were built on branches of deciduous trees and shrubs, and autumn's leaf fall exposes those nests to both elements and predators. But one creature that appreciates an empy bird nest is the deer mouse. These tiny mammals will build a roof over an old cup nest and stay warm all winter!


Q: I understand that Robins that do not migrate in the winter from NH eat berries from shrubs and trees during the winter. My question is: Is there enough food for these birds that do not migrate? And how can berries replace worms in regards to nutrition? Wouldn't worms have more protein? With all of the birds that stay in NH over the winter, it would seem like all of the berries, etc would be eaten up during the Fall and early Winter.
A: You're exactly right that worms have much more protein than berries. But some birds manage to achieve a "balanced diet" over an annual cycle rather than day by day. Robins require protein especially when females are producing eggs and when both sexes are molting-these activities occur only during the time of year when they're eating worms and insects. During winter when they switch to a diet of fruits, they are getting plenty of vitamins, and the carbohydrates give them plenty of energy to sustain their bodies. Winter is the time when their activity is limited and they aren't growing new plumage or producing young.

Regarding berries, there are many different species, and some have a bitter taste until winter. So some berries are avoided during late summer and fall, and these are the ones that remain for winter food. Robins also eat crab apples. There is clearly not enough fruit to sustain as many robins in winter as live in New Hampshire in summer, but there is enough fruit to maintain a small but robust winter population. And robins aren't like some birds, especially neotropical migrants, that maintain winter territories. When one food source becomes depleted in winter, a robin flock will move to another place. The only time robins are sedentary, remaining in one fixed place for weeks at a time, is during the nesting season when they are in their territories.


Q: I saw a robin eating the suet, which was so strange to see. Is this normal?
A:
It's unusual, but not unheard of. A robin's warm-season diet is full of high-protein insects and worms, and suet is another source of protein. This robin seems very smart, as he's taught himself a new feeding trick by watching other birds at your feeder!


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