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Ecology

Q. What is the range of the American robin?

A. The American robin is found over most of North America. See its range map

Q. What is the robin's habitat?

A. Robins can be found in a wide range of habitats. You can find them in marshes, fields, forest borders, orchards, hedges, cut-over woods, gardens, urban, suburban, and rural yards, and parks.

Q. What is the robin's role in the ecosystem?

A. Robins are omnivores. They serve as predators mostly of insects and worms, but also of small snakes and other small reptiles and amphibians. They are also fruit and berry eaters. Sometimes they eat a berry in one place, and then fly away. When they poop, their droppings often contain the seeds of these berries, so the robins can "plant" them in new places.

Robins are in turn eaten by foxes, bobcats, hawks, shrikes, and owls, and crows and blue jays often take their eggs and babies. These are all natural predators. House cats, which are not natural predators because they are fed by humans and maintained at an artificially high population, kill exceptionally large numbers of robins because cats mostly stalk creatures where robins do their feeding--on the ground.

Q. What are a robin's enemies?

A. Some of the natural predators named above are enemies of the robin, though some are also the robin's natural friends. Jays and crows eat baby robins during the nesting season, but when they aren't stalking a robin nest, they are very helpful to robins by alerting them of even greater dangers, and sometimes chasing away hawks and owls. Robins may also consider mockingbirds, waxwings, and other birds that compete for fruit to be enemies--they often chase these birds away. Humans who leave cats outdoors and/or use lawn pesticides are probably a robin's greatest enemies, endangering both the robins and, especially, their newly-fledged babies.

Q. What do robins eat?

A. Robins eat large quantities of worms and other invertebrates, and berries and fruits.

Q. What happens to robins when worms are in scarce supply?

A. Robins can easily switch from eating a lot of worms to taking almost entirely fruits, so when the ground starts getting cold in fall, robins change their diet. During droughts and other periods when worms are temporarily hard to find, robins can eat fruit. If pesticides kill most of the worms in an area, robins may stop nesting in that area.

Q. How do earthworms migrate?

A. In areas where the ground freezes, one sign of spring is the appearance of the first
earthworms of the season. This is called a "vertical migration." Earthworms, in the fall, migrate deeper into the earth, below the frostline. Sometimes they ball up to reduce moisture loss--as many as a hundred worms being bunched together--and thus spend the winter in inactivity. When spring comes and frost leaves the soil, the earthworms become migrants again, tunneling upward. They appear at the surface, leaving the first castings of the new seasons, as soon as the average temperatures of the ground reaches about 36 degrees.

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.


How can we participate in Journey North's Robin Migration Study?

A.You can

Q. Do robins really migrate along the 37-degree isotherm? How can we test this?

A. Yes, the huge bulk of male robins follow this migration pattern in spring, though there is a wide amount of variation among individuals. To test this theory, try our Spring Fever Lesson

Q. How do weather patterns influence robin migration?

A. Robins often move ahead of warm fronts, arriving just before or along with rainy weather. This means they arrive right when earthworms must emerge from their tunnels or drown.

Q. How do we tell whether a robin in our yard in early spring is a migrant or a territorial bird?

A. It's usually impossible to tell by their appearance unless they have been banded or color-marked, except for one lucky thing. Male robins from Newfoundland and Labrador are darker than other robins, with almost black backs, brighter red underparts, more noticeable striping on the white throat, and a bolder eye-ring. People farther south in Canada and the U.S. may notice the difference when they spot one of these, and then they'll know for sure that these are the northern race rather than their own breeding robins. Many magazine photos of winter robins show these brightly colored ones, which make a lovely contrast against snow-covered branches and orange berries.

But there is another difference between local and migrant robins. Male robins that intend to remain in your area will sing their territorial song. Robins that are passing through will occasionally sing, but not as often, especially at dawn, and usually they remain fairly quiet.

Q: Where was THIS robin yesterday?

A. Robins migrate at a speed of about 30 miles per hour, and can migrate during day or night. They average 38 miles per day, but some days they don't migrate at all, and other days they can go many times that. So it's impossible to be exactly sure where your robin was yesterday unless it was wearing a satellite transmitter.

Q. Which returns first: males or females?

A. Male robins arrive on the breeding grounds a few days to two weeks before the females return. You can tell male robins because their head and tail feathers are very dark black and bright orange in comparison to those of the female. When the first females arrive later, you'll notice their plummage appears faded and drab in comparison to that of the males.

Q. W
hat do robins eat when getting ready for their migration?

A. At winter's end, robins eat a lot of berries. They also eat as many worms as they can find at the start of spring migration. In late summer and early fall they prepare for migration by eating a lot of fruit and insects as well as worms.

Q. Do robins travel together when they migrate?

A. Yes, they form loose flocks for both feeding and flying during migration.

Q. What might be some advantages for robins to migrate in groups?

A. While feeding, the more robins there are, the more likely that at least one of them will notice a predator and warn the rest. During migratory flights, hawks have trouble singling out one robin to strike when faced with their fast-moving, tight migratory flocks. With a large flock, some individuals may be more familiar with an area than others, and the experienced birds will show the others the best places for feeding and roosting. Since the robins are all moving together, no individual will know all the best places, and most of the flock members will both help and benefit from flock membership.

Q. Do all the robins leave at the same time?

A. No. Immatures hatched in the first nesting of a season will be ready to join migratory flocks before their parents or later siblings. Adults who nest three or more times in a season won't be ready as quickly as those who nest only twice.

Q. Where do robins spend the winter?

A. Some robins retreat all the way to southern Texas and Florida, but others winter as far north as they can find berries. So robins have an enormous winter range.

Q. How far is the robins' migration?

A. Some robins fly thousands of miles, such as the individuals that migrate from Vancouver Island to as far south as Guatemala. Others don't migrate at all, such as robins that breed in southern Mexico and Baja California. Most robins migrate intermediate distances.

Q. Do robins migrate by day or night?

A. Although robins occasionally migrate at night, they mostly migrate during daytime.

Q. When do robins leave their wintering grounds?

A. Robins typically start moving northward from Florida and the Gulf states, and tend to follow the 37-degree average daily isotherm.

Q. Many neotropical migrants have a fairly regular migration from year to year. Why don't robins depart at almost the identical time each spring?

A. Neotropical migrants have no way of knowing what the weather may be like across the Gulf of Mexico when they leave their wintering grounds. Most of them migrate much later than robins, and time their migration by daylength. Robins are very dependent on availability of worms on their nesting territories. By following the 37 degree isotherm, they tend to migrate in the kind of weather systems that bring rain, snow melt, and enough warmth to thaw the soil so worms will emerge in large numbers. But weather conditions vary enormously from one year to the next, so robin migration varies, too.

Q. How do robins prepare for the journey north?

A. Robins put on some fat when food supplies permit during late winter and early spring, and again in late summer and early fall, which helps fuel their flight. Adults molt, growing new body and flight feathers, in summer after they've finished breeding: these feathers will be fresh for fall migration, provide maximum warmth in winter, and still be in good enough condition for spring migration.

Q. When do the robins arrive in their breeding (summer) home?

A. Male robins arrive about the time that the average daily temperature is 37 degrees. Females arrive a few days to a couple of weeks later, when both worms and mud are easy to find.

Q. What do the robins do first upon arrival back on their territories in the spring?

A. During fine weather, male robins spend their time singing, investigating their territories, and feeding. During cold or very wet weather, the males grow more silent and concentrate on feeding and taking shelter in thick conifer branches. Female robins investigate their territory, begin nest building, and feed when they first arrive.

Q. How fast do robins fly during migration?

A. Robins fly about 30 - 36 m.p.h. during migration

Q. How far do robins usually fly each day when they migrate north?

A. Robins can fly for many hours each day, so on days with good migrating conditions, they probably cover roughly 100-200 miles per day.

Q. Why is the timing of robin migration so important?

A. In fall, robins wander and migrate when food is abundant but with a patchy distribution. Their migration is irregular, allowing individuals to be in a broad range so food is abundant for all. (If their migration was more uniform, too many birds would be in one area at the same time, and they would deplete the food there while other food went ignored. In spring, the timing allows them to migrate right when worms are emerging and are most conspicuous. And females return to their nesting areas when mud is available so they can start nesting almost immediately after arriving.

Q. What are the best weather conditions for robin migration?

A. In many areas, high pressure systems with northwesterly winds are best for migrating during fall. In spring, robins follow warm fronts.Cool conditions are better than warm.

Q. What are the least favorable weather conditions for migrating robins?

A. Hot weather gets them overheated.Rain and snow are hard to migrate in. Ice rain and hail are much worse.

Q. What do migrating robins do during bad weather?

A. If the robins have a reliable food supply, they hunker down near it, and sometimes become very territorial, keeping other robins away. When not actively feeding, they usually hunker down in a thick coniferous tree to stay as dry, warm, and protected from wind as possible.

Q. How do robins find their way when storms blow them far off course?

A. Robins figure out their location on the planet in much the way sailors on the high seas once did--using the angle of the sun in relation to the time of day. If blown off course, they fly to where the sun will be at the proper angle.

Q. Do all the robins survive the migration?

A. No! Scientists estimate that only 25% of fledging robins survive until November. And many experienced adults die during migration, too.

Q. What are some of the hazards that robins face on their long migrations?

A. Being in so much unfamiliar territory, robins are more vulnerable to predators during migration than when they are on a breeding territory. They only rarely hit communications towers, because they migrate by day. During the time that DDT was used, robin deaths usually took place during migration, because DDT collected in robin fatty tissues in summer and in winter. When the birds migrated, their bodies "burned up" this fat, releasing huge amounts of the DDT into the robin's blood.

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