American Robin Migration Update: February 18, 2003
Today's Report Includes:
- Winter Robin Roundup: A Clear Pattern
- Song Is the Key!
- Detectives Wanted: Interpreting Robin Wintering and Migration Maps:
- Challenge Question #1 and #2
- This Week's Migration Maps and Data
- Toxic Lunches: Too Much of a Good Thing?
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Overwintering Robins |
Winter Robin Roundup: A
Clear Pattern
Thanks to everyone who joined the Winter Robin Round-up! The results are
in, and here's the map with your sightings. This winter American Robins
have been very common in the southeastern states, especially along the
Gulf coast. They followed an interesting diagonal line that ran parallel
to the Appalachian Mountains from the south-central states up through
New England. Very few robins were reported from the middle of the continent,
where conditions are drier, winter weather more severe, and fewer fruit
trees provide food.
With all the snow in the East this year, how can robins possibly be wintering all the way up to the northeastern states? Remember that robins don't have any trouble at all surviving in cold conditions as long as they have food. In winter, their diet switches from mostly earthworms and insects to almost entirely berries and fruits. As long as there are fruit trees, robins can easily survive even severe winter conditions. Isn't that a relief after the huge February snowfall in Maryland and Virginia.
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| These American Robins fill a tree right outside the Bridge School in Lexington, Massachusetts. Photos by Fran Ludwig. |
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During some periods in January, after days were already getting longer, robins in the northeast were observed still moving south. That is because migration is more complicated than we humans would like it to be. Few bird species have a single breeding range, a single wintering range, and a simple migration from one to the other. American Robins are especially tricky. They eat fruit, and like many fruit eaters, individuals and flocks wander widely. A robin flock may stay in an area for days, weeks, or months. As one flock goes another may come. And as food gets scarce and weather conditions get worse, robins often move where they will find better conditions and more food. Isn't it fascinating that such a common, homey backyard bird leads such a complicated life?
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Are these American Robins a wintering flock or a migratory wave? |
During spring's journey north, we collect data and prepare maps about three different kinds of American Robin sightings:
- First Robins Seen
- Waves of Robins
- First Robins Heard Singing
The "First Robins Seen" map shows when and where our observers see their first robin, and so it includes wintering robins as well as migrants. During the season, you can see how the dot colors shift as robins move.
"Waves of Robins" that are actually migrating are very tricky to recognize. On October 1, 1988, Journey North robin expert Laura Erickson counted over 60,000 robins migrating along Lake Superior. This was a genuine wave--a huge migratory movement of many birds. But hardly anyone gets to see that kind of migratory movement except along the shores of large lakes and rivers and the coast. What most of us see from day to day during winter and spring are flocks of robins. Some of these flocks are huge, and they move from one feeding area to another, looking very much like they're migrating, and some are actually migrating, but they look exactly the same! So the "Waves of Robins" map tells us where people are seeing lots of robins, but not necessarily where migration is happening
But tracking robins first heard singing is the simplest method for tracking spring migration.The "First Robins Heard Singing" map probably tells us the most clearly about when and where robins are switching from winter feeding and flocking behaviors to spring migratory restlessness and territoriality. As an Alabama observer notes,
Montgomery, Alabama has good numbers of American Robins throughout the winter. That makes "first song" the relevant information for us to provide to your round up. While I have heard song fragments earlier, today, 2/3/03, was the first day on which I have heard American Robins giving their full songs - and I had at least three singing on a 2-block length of street. Throughout the winter, there has been considerable calling and chattering. When they switched to song, the difference was dramatic and clear.
Singing or Calling?
Can you remember how to tell a singing robin from a calling one? Five common robin
vocalizations are listed below. Only the first is the true song. All five have their
own meaning, according to Lang Elliott, an authority on bird vocalizations. While
you wait for your robin to arrive, learn to recognize its true song. That's how you'll
know YOUR robin reached the end of its migration.
- The robin's "song" is a territorial declaration.
- The "peek" and "tut" calls are heard in alarm situations.
- The "whinny" is heard in mildly alarming situations.
- The high-pitched "Seeeee" call is given in response to the presence of an aerial predator.
- The "Zeeeup" call is a contact note heard mainly during migration.
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Song |
"Peek" and
"Tut" calls |
"Whinny" |
"Seeee" call |
"Zeeup!" call |
Detectives Wanted: Interpreting Robin Wintering and Migration Maps
From Towson, Maryland (just north of Baltimore) we hear,
"For the past few weeks, we have had daily visits of a flock of about 200 robins in our yard and the adjacent 3 yards. They hang around for a while, picking through the leftover leaves and leaving a polka-dotting of droppings all over our driveway. The yard behind us has a number of holly trees which are also an attractant. There are robins in Baltimore County year round. I don't know if they're the same birds all the time, or if our summer birds go south and are replaced by northern robins in the fall."
How could we find out if these winter robins are the same birds as the summer ones? Can you think of a way ornithologists could learn the answer?
Challenge Question #1
"Name at least one way that ornithologists could find out if the robins wintering in Towson, Maryland, are the same individuals that spent the summer there."
(To respond to this question, please follow the instructions below.)
If American Robin migration is so complicated, how can we possibly track it? Do all those dots on the Journey North migration maps leave you stumped? Learn some easy ways to interpret the maps and make sense of a bewildering migration with the following lesson, and then answer the following Challenge Question::
Challenge Question #2
"How many variables can you name that affect where, when and how many robins you might see in the winter time?"
(To respond to this question, please follow the instructions below.)
This Week's Migration Maps and Data
Now try your new map detective skills with this week's robin migration maps!
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Toxic Lunches: Too Much of a Good Thing?
Imagine watching robins staggering and flopping around, crashing into branches and buildings. This is what happens sometimes in winter, when robins eat toxic berries. In late December, Thomas DeBray in southwest Florida reported seeing very large groups of robins. "They fly in large numbers, flock and eat the berries on the Brazilian Pepper trees only to get intoxicated on the berry juice and then fly weirdly."
Do robins really get intoxicated? Why does cold weather make it worse? How can we protect birds from toxic berries? See:
Even when berries haven't fermented or become toxic, robins gathering in feeding flocks sometimes are so focused on eating and on interacting with one another that they don't notice other things in their surroundings. We got a sad report this week from Bill Hilton, Jr., about a major bird kill in Raleigh, North Carolina, where the ground was littered with dead robins and cedar waxwings near and on a major highway. This time of year, as food becomes more and more scarce, desperately hungry robins gather wherever they find fruit, and so planting large numbers of fruit trees along a highway is very dangerous for birds.
How to Respond to Today's Challenge Questions:
IMPORTANT: Answer only ONE question in each e-mail message.
1. Address an e-mail message to: jn-challenge-robin@learner.org
2. In the Subject Line of your message write: Challenge Question
#1 OR #2.
3. In the body of your message, give your answer to ONE of the questions above.
The Next Robin Migration Update Will Be Posted on March 4, 2003
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