Fall's Journey South Update: September 18, 1998
Today's Report Includes:
Living Off the Fat of the Land
Imagine if your teacher suddenly, in a matter of weeks, doubled his or her weight! What effects would this
have on her or his skin? Legs? Heart? Would you be able to notice a difference?
What if YOU suddenly doubled your weight? It would take a long time for you to adjust to the new size, and the
extra weight would slow you down. You'd get out of breath a lot faster when running or going up a hill or staircase.
Small songbirds called Blackpoll Warblers double their weights twice a year, in preparation for the flight of their
life. The added weight is all fat, but it doesn't clog their arteries and veins and doesn't slow them down. The
amount of fat on their bodies will determine whether they live or die, but it's virtually impossible to notice
any difference in their appearance without holding them in your hand! Their feathers cover them up, and air sacs
keep them looking plump even when they're starving.
Even though it's migrating for the first time in its life, the young Blackpoll Warbler pictured to the left
will fly farther than almost any other songbird.
Fueling Up
Every fall, Blackpoll Warblers pig out on insects and spiders as if their lives depended on it. As their bodies
become fat enough, they take off on their own personal marathons.
But before striking out over the Atlantic, they wait for a low pressure system. Trace the blackpoll's flight path
on a map and you'll see why: The wind blows from the northwest after a low pressure system. These winds carrying
the blackpolls southeast, toward the Bermuda Islands. Once they reach that area of the ocean, they meet air currents
called "trade winds". These winds push them southwest toward the coast of South America.
Use the map's scale to calculate how many miles a Blackpoll would fly if :
- It took off from Nova Scotia tonight and flew in a straight line to the Bermuda Islands.
- How many more miles would it go before it reached South America?
- How much shorter would it be for a blackpoll warbler to fly a straight line from Nova Scotia to South America?
Loose Weight in Only 80 Hours
We've seen ads promising rapid weight loss, but for blackpolls it's true. Imagine running three four-minute miles.
Now imagine running 1,200 four-minute miles, keeping up that high speed the whole way, for 80 hours. That's how
one ornithologist calculated the exertion involved in a Blackpoll Warbler's migration. If all goes well, the blackpoll
is back to its pre-migration weight by the end of the trip.
Where They Are Now
Right now many Blackpolls are still in Canada and Alaska, but a lot have been trickling south. American Birding
Association secretary Blake Maybank, an active birder in
Nova Scotia who leads birding tours, says 7,000 - 8,000 pairs of Blackpolls breed in Nova Scotia every year, and
that there are a LOT more in Newfoundland--too many to census. He told Journey North that Gros Morne National Park
(49.5N -57.5 S) has half a million breeding pairs!
Blake told us that in Nova Scotia, local birds start moving as early as late July, and by early September it's
not hard for someone to see several in a day. But by late September and early October you can find 100 in a single
day.
Fascinating Facts
- Number of miles the Blackpoll Warbler will fly to avoid a North American winter: 2,000
- Number of Blackpoll Warblers you could mail (if you had any reason to do so) for one 32 cent stamp: 3 (They
prefer airmail.)
- Number of Blackpolls you could mail for a 32 cent stamp after they've bulked up for their migration flight:
1 (and a few would require an extra stamp).
- Altitude at which the Blackpoll Warbler will fly to catch favorable winds on its way to Central America: 16,000
feet.
- Relative rate at which a human would have to run to match the non-stop exertion of the Blackpoll Warbler: 4-minute
miles for 80 hours.
- Pitch of song: 8-10 kilohertz, the highest pitch of any warbler song. Listen!
(Sounds by: Lang Elliott, Stokes Field Guide to
Bird Songs)
- Number of times lost Blackpoll Warblers wandered all the way to the British Isles: 35 (that we know about).
Most of these sightings were in September and October.
Which leads us to this week's--
Challenge Question # 3
Using a map, figure out the minimum distance between North America and the British Isles. How many degrees off
course would a Blackpoll Warbler have flown if it ended up there rather than the Bermuda Islands? Can
you name three possible reasons why a warbler might fly so far off course?
How to Respond to Today's Challenge Question
1. Address an e-mail message to: jn-challenge-fall@learner.org
2. In the Subject Line of your message write: Challenge Question # 3
3. In the body of the message, answer the Challenge Question.
Discussion of Last Week's Challenge Question #2:
What evidence could you give to show that dragonflies and kestrels migrate together? Frank Nicoletti's graph
shows the numbers of kestrels and dragonflies every day in September. Every day with a bug number of dragonflies
has a big number of kestrels, and every day with a low number of dragonflies has a low number of kestrels. It's
easy to see that the graph's peaks and valleys for both species happen on the same days. Scientists say these numbers
are correlated.
The Next Journey South Update Will Be Posted on September 25, 1998
Copyright 1998 Journey North. All Rights Reserved.
