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American Robin Migration Update:
April 26, 2005
American Robin Migration Maps and Data
Initiation of "Song" is the clearest pattern we expect to see as we track the spring robin migration. Printer-friendly format: Robins have surged
northward. They are singing in some of the farthest reaches of their
range. We always feel excited when they get farther
north. But just as important are the robins filling in the gaps in
states and provinces where the first arrivals were earlier. Some of
you have already reported babies hatching! “Ever since we started
composting to fill in a small ravine, the Robins have visited us,” writes
an observer. “This year, the nest is in our photinia mature bush.
It's lovely to spy on them as the birds have now hatched and can hop
about in the branches.” Hatching
Babies: A Robin Cam Lets You Peek
Meanwhile, one student produced a video showing the baby robins at every stage from incubating the eggs to fledging. You’re invited to watch! See the babies hatch. See the mother feeding the tiny nestlings. See the babies growing, feeding, preening and pooping! See them getting feathers and finally getting crowded and leaving. We give you guiding questions with each clip. It’s all here:
Baby robins remain in their nest for about 13 days. Just about every time the nestlings gulp down some food, they poop. Let's see--that's 13 days x 4 babies x 356 insects and worms on average each day--that's a LOT of poop! How on earth do robins keep their nest clean? How can the nest and other babies stay clean when one baby poops? To see how adult robins deal with baby bird poop, see: After you enjoy this lesson, come back and send us your answer
to:
(To respond to this question, please follow the instructions below.)
Just like a recipe for baking a cake, a robin egg must be warmed for a specific length of time. It must also be kept at a specific temperature. A robin egg must be incubated for 12-14 days to develop normally. Except for about a 10-minute break per hour during daylight hours, the female robin sits on the eggs all day long. Sharpen your pencil and tell us your answer to this question:
(To respond to this question, please follow the instructions below.) Photo Study: How Much Can a Photo Tell You?
Family Album: How Many Offspring? How many offspring can a pair of adult robins potentially produce if they survive a 10-year lifetime? You’ve learned that robins make 2 to 4 nests a year, with 4 babies per nest. It’s easy to figure out how many babies they raise in a season. But remember: these same two adult robins are responsible for the hatching of grandchildren, great grandchilden, and more! In his book The American Robin, Roland Wauer cites L.A. Eiserer, who points out that if there were no mortality, a pair of robins has the potential to produce 19.5 million descendants by the end of a ten-year life span. Surprised? At the end of a mere 30 years, the original pair of robins would have 1.2 billion trillion descendants. Wow! Robins, like all birds, experience a high death rate, so this number is purely theoretical. Robins must produce plenty of babies to keep the robin population high enough to replace all the robins that are killed each year. Many robins are claimed by hawks, cats and other predators, pesticides, accidents, ice storms and other bad weather, and all the many other hazards they face. And many robin nests fail. Robin nests are fairly conspicuous--that's why we're lucky enough to see robin nests more often than most other birds' nests. But that means they're also pretty easy for jays and crows to discover, and jays and crows feed robin eggs and nestlings to their own hungry babies.
This year’s Early bird Contest (and the answer to CQ #4) is now history! Anchorage teacher Mike Sterling reported: “I saw one April 12. I do a 25 mile bicycle commute from my house on the Anchorage Hillside down along a bird sanctuary, and right in along the coastal bluffs above Cook Inlet I come across what is apparently some pretty prime robin habitat. I say apparently, because a big, fat, presumably male robin comes and claims the same tall cottonwood every year right about this time.” No contest entries named this date, but Bryan and Ryan were watching the isotherm. Does the latest isotherm map (below) support the April 12 robin in Anchorage? News from the NOPs: How Are Your Predictions Holding Up? On April 19, Stan White in Homer, Alaska reported: “Snow? Yes. Cold? Yes. Geese? Yes! Robins. No.” How many NOPs are still waiting to see their first robin, or to hear the first robin song? Find out the latest robin news or other spring news from our NOPs, and see how your own predictions for NOP robins are holding up: Tracking Temps and Robins: This Week’s Isotherm Map We’ve invited you to test the theory that robins follow the 36- or 37-degree isotherm during migration. (The isotherm is an imaginary line that connects places having the same AVERAGE temps.) So, how’s the theory holding up in YOUR region? Here’s the latest isotherm map:
Go Lay an Egg: Discussion of Challenge Question #8 We asked, "If we estimate a 2-week delay for every 5 degrees north in latitude, and we assume robins in Jackson, Mississippi are now beginning to lay eggs, when would you expect robins in Madison, Wisconsin to begin laying their eggs?" Jackson is at 32.32 N, and Madison is at 43.08 N, so that's a difference of about 11 degrees. A two-week delay for every 5 degrees north means robins will probably lay eggs in Madison about 4 weeks later than robins in Jackson. Fun to know! Something Eggstra: Discussion
of Challenge Question #9 Spring Comes to Alaska: Discussion of Challenge Question #10 "Why don't robins go even further north? What factors influence the northern limits of their nesting range?" Some of you said it’s too cold and robins would lose weight trying to stay warm. At these far northern latitudes, permanently frozen ground is the limiting factor. Robins are hardy enough to breed wherever they can find what they need, which is food and nesting sites. BUT, permanently frozen ground means no worms. It also means few if any plants, berries, insects, or trees for nesting. Folks in Point Hope, Alaska, a village at the tip of a peninsula on the Chukchi Sea, have never seen robins in their area. Even Kodiak Island has been waiting for 10,000 years for robins to fly the mere 15 extra miles from the mainland across Shelikof Strait to their island. Robin habitat on this island was probably eliminated by ice and snow in the last glacial period. The island has far fewer plant and animal species on it than the nearby mainland. It's rare, but islanders sometimes hear a singing male. Hopeful folks say all it will take is for one female to find that male, and then Kodiak Island may have robins, too. How
to Respond
to Today's Challenge
Questions: The Next Robin Migration Update Will Be Posted on May 3 (Data only).
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