American Robin Migration Update: May 2, 2000
Robins in Alaska! Today's Migration Maps and Data
To everyone's delight, the robins are sweeping northward and eastward into their far northern range. Just in time for today's map, Terry Slaven sent happy news from Palmer, AK (61.68N,-148.00 W): "Robins have arrived! My neighbors reported hearing and then seeing them Friday, April 28. At last!" (Terry.Slaven@MSB.Mat-Su.k12.ak.u)
In Anchorage (61.18 N,-149.19 W), Mike Sterling reports: "We're hearing more and more robins every day here in Anchorage, but so far nobody has seen any pairs. I think the male vanguard is all there is. We'll report when the first big wave arrives."
But Still Waiting for Songs
Compare this week's migration maps and the Northern Observation Posts. When will the newest northern arrivals be singing on territory? Here's more news from the North!
Shageluk, AK (62.67 N,-159.57 W)
On April 27, Joy Hamilton wrote: No singing Robins here yet, it's still pretty cold. We had a warming spell last week (in the high 40's) and by Thursday, April 21 our first Robin was spotted 3 miles from our village. Our temps have gotten colder again, in the 20's this week and we haven't seen any more Robins. Last night 3 of our students were out jogging on the dirt road going up to our runway and saw a group of about 8 of the first Tundra Swans for the spring. More Robins will be on the way for sure. Happy Birding from the Students at the Innoko River School!" (email@example.com)
Homer, AK (59.63 N,-151.52 W)
This report came from Voznesenka Village at the head of Kachemak Bay near Homer on the Kenai Peninsula. From Voznesenka school, Mr. Stan White wrote: "We heard our first robin singing near the school on the morning of Monday, April 17th. From that date until Wednesday, April 26 it was the only robin we heard, and it sang every morning all by itself. There is now another one singing, although quite a ways off. We saw a pair of robins at a slightly higher altitude on Sunday, April 23, but there are still none singing in that area." (firstname.lastname@example.org)
Denali National Park, AK (62N, -148 W)
And Mitch Knobbe just sent greetings from Healy, Alaska, saying: "I can confirm our first robin sighting at Denali National Park on April 30th. I guess spring is here!" (email@example.com)
Robin Attitudes at Different Latitudes
Depending upon where you live, robin families in your region are at a particular point in the cycle of males arriving and setting up territories, females following a week or two later, pair bonds forming, mating, nest-building, egg-laying, and incubation. Did you know that the timing of these activities varies with latitude? A general estimate is that the timing varies by 10-15 days for every 5 degrees north in latitude. (Remember: this rule is intended for comparing points located at the same longitude. You couldn't use it, for example, to compare timing in California and a location on the East Coast, since the seasons are so different at these places.)
Try the challenge question below for a chance to use this "rule" about the timing of spring's advance:
Early Bird Contest: Announcing the Closest Calls!
If you read our April 24 Signs of Spring report, you already know who came closest to predicting the arrival date of the robins in Anchorage. In case you missed the news, here's Mike Sterling's announcement from Sand Lake Elementary School in Anchorage:
"Ok, so I send in my 'no robins' message on Monday, April 17th before school. Then I'm riding my bike to work and I hear this strange 'music' in the background! I slow, look toward the source, and see a plump robin sitting way in the top of a cottonwood tree singing its 'come hither' song! On Tuesday, I hear--and see--the same robin. Ditto Wednesday. I ask my students: "See any robins yet?" They're all nodding their heads. "Where?" I ask. The answers vary, but they've been spotted in backyards, in parks, and (the kids claim) in the woods between Sand Lake School and the lake that is its namesake. Bottom line: I think the robins are here."
Three cheers and congratulations to the students whose predictions came closest!
Mrs. Voelker's Fifth Grade Class at Pymatuning Valley Middle School in Andover, Ohio, said, "We predict that the robins will come back to Anchorage, Alaska on April 15. We based this on when our robins appeared and previous sightings in Alaska." (WVoelker@excite.com)
Mrs. Nelson's science class #2 from Madelia Elementary in Madelia, MN predicted that "the robins will reach Anchorage, Alaska on April 20th." (firstname.lastname@example.org)
A great big thanks to EVERYONE who sent predictions for this year's Early Bird contest!
Eat. . .and Beware of Being Eaten
We all know that hawks are predators, rabbits are prey, and vultures are scavengers. But most animals fit into more than one of these categories. Bald Eagles are predators of live fish, but they're also scavengers on dead fish, road-killed animals, and other carrion. Screech owls are predators of mice, but are prey for foxes, cats, and larger species of owls. Crows are all three: predators of small birds, mice, and insects, prey for Great Horned Owls, and scavengers on carrion. What about robins?
Robins lead the lives of both predator AND prey. Robins are predators on worms and insects. But adult robins are tasty prey for cats, hawks, raccoons and foxes. Baby robins are eaten by all of those plus jays and crows. Robins have to be adapted to finding enough food AND to keeping themselves from being eaten!
Robin as Predator: The Early Bird Catches the Worm
Robins are perfectly designed for hunting and eating soft-bodied worms and insects. This is lucky, because it takes a LOT of worms to give them the calories they need each day when an average worm has 0.7 calories. A 55-gram adult robin requires 18.9 calories a day just to keep breathing, and probably almost twice that amount to keep active. A 100-pound, eleven-year-old child requires about 2200 calories per day. That leads us to ask:
(To respond to these questions, please follow
the instructions below.)
Robin as Prey: Breakfast of Champions
The primary mammalian predators of robins (including eggs and nestlings) are cats, dogs, and squirrels. Crows and jays eat robins mostly at the egg and nestling stage. Raptors--those champion hunters--that have been recorded killing robins include Cooper's Hawk, Sharp-shinned Hawks, Goshawks, Northern Harriers, American Kestrels, Merlins, Peregrine Falcons, Gyrfalcons, Great Horned Owls, Barred Owls, Eastern Screech-Owls, and Snowy Owls.
How do robins protect themselves from being eaten? They make sounds to warn fellow robins to fly to safety, and they can fly with some speed. But here's a curiosity: Many researchers have observed that robins nesting in forests are very timid during nesting. These forest-dwellers fly away when a person approaches from a much farther distance than backyard-nesting robins would. Think about some of the differences between forests and backyards. There are usually MORE predators in backyards, counting cats and dogs, than there are in forests. Doesn't that make you wonder. . .
Is the Nursery Rhyme True?
Cats, dogs, and squirrels haven't been the only mammalian predators. Bird expert Laura Erickson tells us that people used to eat robins, too. The early American colonists ate them in abundance, and people continued to legally catch and eat them until they became protected in 1918. That's when the Migratory Bird Treaty Act was signed into law. Renowned birder John James Audubon wrote in 1841 that winter robins "are then fat and juicy, and afford excellent eating." Our American Robins are very closely related to the European Blackbird, so those "four and twenty blackbirds baked in a pie" probably tasted a lot like Audubon's robin pie. Do you think there was some truth to that Mother Goose Nursery Rhyme? What causes people's attitudes and practices to change? (For the sake of our valuable robins and songbirds, we're glad they did!)
Listen carefully to the robins in your yard. You're almost sure to hear them respond when crows, cats, bluejays or other predators are nearby, looking for a nutritious meal. Notice the variation in the robin's voice: a quick, nervous "tck, tck, tck" in cases of possible danger; and a longer, louder "teeeeek" when actually sounding alarms. When you hear these sounds, see if you can figure out what's bothering your robin.
Laura Erickson says, "Robins have one call for low-level danger, such as someone mowing the lawn; a more agitated-sounding call for cats and other more serious threats; and a high-pitched call when a hawk is flying overhead. In fact, Robins have been timed in flight at 20-36 miles per hour--and may go even faster in an amazing burst when being pursued by a speedy hawk."
Keep Baby Robins Safe
If you find a robin nest, study it at a safe distance! Don't make it easy for your neighborhood crows and other predators to discover the nest. And make sure to keep cats indoors during robin nesting season. When the baby birds fledge, they are like little toddlers--clumsy and inexperienced--and they spend a lot of time of the ground where cats hunt. Learn more about Cats Indoors.http://wildlife.wisc.edu/extension/catfly3.htm
Robins Finally Find Frisco: Response to Challenge Question #16
We asked, "Why do you think it took robins so long to reach Frisco, CO (39.57 N, 105.96 W) when robins have been at the same latitude in other areas for many weeks?"
Frisco, CO is high in the Rocky Mountains. According to our Frisco observer, Mr. John Kejr: "At 9,100 ft. elevation, we have snow on the ground well into April, which makes digging for worms not too much fun. Because of that, our first Robins come much later than those at lower elevations."
This is an example of "vertical migration." Just as we watch migrations move northward across a continent, there are many examples of vertical movement up mountains. Because temperatures are lower at higher altitudes, it takes time for spring to climb up the mountains. According to naturalist Edwin Way Teale, spring advances up the United States at the average rate of about 15 miles per day, and spring ascends mountainsides at the rate of about 100 feet per day.
Go Lay An Egg! Answer to Challenge Question #17
"If you add up all of the time a robin egg is incubated, how many hours do you estimate that it takes for a robin egg to develop properly?" (Assume the egg is incubated for 13 days and that there are 15 daylight hours. Don't forget to subtract the time a mother robin takes for "breaks"!) See how we figured our answer of 279.5 hours. Does it match your answer?
13 days X 24 hours = 312 hours, but NOW SUBSTRACT Mrs. Robin's "breaks."
10 minute break per daylight hour per day X 15 daylight hours (6 am to 9 pm) = 150 minutes
150 minutes of breaks per day X 13 days = 1,950 minutes (divided by 60 minutes per hour) = 32.5 hours of breaks
312 hours total time - 32.5 hours of break time = 279.5 hours to incubate a robin egg. WHEW!
Thanks, Rachel Carson: Response to Challenge Question #18
Our Earth Day question asked: "If people weren't spraying robins directly with pesticides, exactly how did these chemicals kill the robins?" Hooray for students from Iselin Middle School 7A in Iselin New Jersey, who sent these answers:
Jessica, Kristy, Anthony and Kostas said: "When they sprayed the pesticides it seeped into the ground and the plants absorbed it. The worms ate the dead plants and dirt and the robins ate the worms, ingesting the pesticide, and therefore died. The robins also ate the sprayed berries on the plants, which would have also killed them."
John and Eric further explained: "The reason why the robins are dying from the pesticides is because the robins eat the insects that get on them and the plants that are sprayed. The robins, which are on top of the food chain, ingest a large amount of the pesticide and therefore die."
The use of natural, safe, Earth-friendly, bird-friendly ways to control insect and weed pests is an important one. Thanks for spreading the word and helping protect birds!
How to Respond to Today's Challenge Questions:
Please answer ONLY ONE question in each e-mail message.
1. Address an e-mail message to: email@example.com
2. In the Subject Line of your message write: Challenge Question #19 (or #20 or #21 or #22).
3. In the body of EACH message, give your answer to ONE of the questions above.
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The FINAL Robin Migration Update Will be Posted on May 16, 2000.
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