American Robin Migration FINAL Update: May 18, 1999
Today's Report Includes:
Robins at Home
From Florida to Alaska, California to Nova Scotia, robins are hunkering down to the serious business of making new little robins. People watch them eating, bathing, singing, fighting, building nests, incubating eggs, feeding babies. And the more we watch them, the more questions we have!
For example, one Journey North writer in Minnesota noticed that the male robin in her yard was suddenly collecting nesting material again. Her friend's robins (in the same area) hatched about 9 days before. Assuming theirs are both on roughly the same schedule, she wondered if her male was beginning to build a new nest "in his spare time" while the first brood was still in the first nest.
She checked Journey North's robin phenology chart on the WWW at:
and it seemed to make sense. If the male feeds the fledglings while the female is on the second set of eggs, that implies that the second nest must be ready before the first fledglings are entirely on their own. But females are supposed to be doing ALL the nest building, while males gather nesting materials to help them. Is this a question of illiterate robins who haven't read the bird books, or is the female doing the work in secret?
Considering how common and conspicuous robins are, there is a lot to be learned about them! If you find a robin nest this spring or summer, see if you can catch the male doing actual building. Let us know what you find! And see what new questions you can think up about YOUR robins during summer vacation!
Made in the Shade
Discussion of Challenge Question #12: "Give at least two reasons why a robin's first nest of the season is usually in an evergreen tree while the second and third are more often in a leafy tree."
Kristen explains: "I think that the reason for the Robins to build their first nests in an evergreen is because the other trees do not have leaves. An evergreen has needles or leaves all year long and robins want to build their nests in safe places."
As Kristen notes, predators would have an easier time discovering the nest without the protection of leaves. Also, the eggs and nestlings would be more vulnerable to weather. Rain, late snow, and wind would be a bigger problem, and so would sun. Before their feathers grow in, baby birds are VERY vulnerable to sunburn. Parent robins just can't afford sunscreen.
He Says, She Says
Discussion of Challenge Question #13: "Which robin vocalizations do you think would be given by both sexes and which by only the males?"
Fifth grader Alisha at Penobscott Elementary School in Penobscott, ME, put it succinctly:
Giving Robins Some Latitude
Discussion of Challenge Question #14: "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?"
Sahar and Adam in Ms. Jones' class explained how their class figured it out: "Our class thinks that the answer for question number 14 is a four week delay. We got that answer by figuring out Jackson, MS, latitude, which was 32 degrees. Then we figured out Madison, WI, latitude, which was 43 degrees. The difference between the two latitude recordings was 11 degrees. We learned that for every five degrees it is a two week delay. So, that is how got the answer, a four week delay until the birds will start laying eggs in Madison, Wisconsin.
Pulling an All-Nighter!
Discussion of Challenge Question #16: "How much do robin songs and calls vary between individuals and at different times of day?"
Amanda at Griswold Middle School explained, "Robins usually sing songs when the sun goes down and when the sun comes up. I used to think that they would sing songs because it sounded pretty. Now I realize that they wouldn't sing for just anything. They sing for mating and different territorial reasons."
Amanda is right that the most intense singing is early morning, BEFORE first light, and late in the evening, near sunset. Since robins find worms by sight, they can use the brightest daylight hours for eating and finding food for their babies, and the darkest times for singing. BUT territorial males will sing any time they darned well feel like it, so we can hear songs any time of day OR night. Journey North's Robin expert stayed up all night once in early July when she was living in Michigan. She listened to a robin singing on a streetlight without stopping until sunrise!"
The Eyes Have It!
Discussion of Challenge Question #17: "If you had the materials Frank Heppner used, how would you design experiments to prove which sense(s) robins use to find worms? Why do you think he used each of these materials?"
Dr. Heppner considered ALL the senses that a robin might use to find worms.
City vs. Forest
Discussion of Challenge Question #18: "Why are American Robins that nest in northern forests more shy around humans than those nesting in towns and cities?"
Predators can lurk behind trees! Perhaps one big reason why robins are more secretive in forests is because of all the secretive dangers they face while hunting on the forest floor. Robins living in towns and cities spend a lot of time out in the open, where they can more clearly observe people and animals from a long distance. Over time, a civilized robin learns that people aren't dangerous unless they're walking straight toward it, and that most dogs are far less dangerous than cats. In the forest, movements and sounds might not be fully visible until it's too late, so robins tend to be much more secretive.
Have a Great Summer!
We at Journey North have had a lot of fun learning about YOUR robins this spring! Thank you so much for sharing your observations and questions with us. This is the FINAL American Robin Migration Update--We hope you learned a lot and enjoyed participating. Have a great summer. We hope to see you in the fall, in time for the birds' Journey South!
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