Signs of Spring Everywhere Signs of Spring Everywhere
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Signs of Spring Update: April 23, 2001

Today's Update Includes:

Going Buggy
A few Barn Swallows were sighted in Florida and Texas in January and February. In March more and more of them appeared in the south, but suddenly they're surging north! One sure sign of spring is the appearance of insects. And it's no coincidence that swallows appear soon after.

The first individual swallows to return are sometimes called "scouts." With Purple Martins, which are colonial swallows, the scouts may actually be checking out nesting areas in advance of the rest of their colony. But with more territorial species like Barn Swallows, the scouts are probably more like the first robins, simply individuals most eager to return and take over a territory. Donald and Madeleine Forgie report from Orillia, ON, "On one occasion we let the Barn Swallow scout overnight in our garage, the weather was so bad. He was quite appreciative. While it may seem unusual, these swallows are quite good communicators. If a cat is in the barnyard, they come and fly past our sun room window in great swoops seeking support. A pair usually nests over our back door, and are great friends. So I hope the scout this year will check in, as usual, on arrival, and I will let you know."

Photo by Gregory K. Scott for W.S.O.

Photo Courtesy Wisconsin Society for Ornithology

Barn Swallows DID arrive in Cannon Beach, OR. Brian Godfrey reports, "Today we saw our first returning Barn Swallow. It was molting so bad that we had to examine it closely in the scope to be sure that's what it was! He sure did look uncomfortable." Since Barn Swallows normally molt during winter, before migration, we wonder if that particular bird has a parasite, had just been bathing, or was molting unusually late.

And Darrell Lee from Alameda, CA, reported "On the Dry Tortugas 4/16-18, there were several dozen Barn Swallows hanging around. Some were apparently exhausted from their long overwater flight and were sitting on the ground where they could be approached within 6 feet. I found one dead on Loggerhead Key. There were at least three Merlins and half a dozen Kestrels in the area at the same time, and I witnessed a couple of Merlin attacks on Barn Swallows during those three days when all were in the area. Almost all of the Barn Swallows left the evening of 4/18 to continue their migration. When the Barn Swallows left, so did the Merlins." (snorkler@juno.com)

Big waves of swallows rush through in spring a week or two before big waves of warblers, even though both groups eat insects. That's because swallows eat flying insects, while warblers usually eat crawling insects. Let's figure out the difference between them.

Aquatic Insects

Mayfly Nymph

Mayfly Nymph

Most people know that a butterfly starts as an egg, hatches out as a larvae (caterpillar), pupates into a chrysalis, and emerges from that as an adult. But that's not how all insects progress through their lives. Dragonflies, damselflies, and mayflies are entirely different. Their eggs are laid in water, and when they hatch, the young are called "nymphs." Nymphs have beautifully complex body shapes, with gills for breathing underwater, and no wings.

Some nymphs live underwater for three years or more. As they grow, they periodically shed their outer skin. The last time they do this, they don't pupate. They simply climb out of the water and as their outer skin splits and sheds off, their wings unfold. As adults, their main job is to mate and produce eggs, which will hatch into babies that live in the water for most of their lives. Dragonflies and damselflies live for a whole season or more as adults, snatching up smaller insects with their amazing hinged jaw that literally snaps out to grab things. One lovely aquatic insect, the mayfly, emerges as an adult with no mouth! It never eats even a single meal as an adult, and dies within a few days of emerging, after using all its energy to find a mate. The mayfly family name is Ephemeroptera.

Challenge Question #22:
Find a word in the dictionary that is related to "Ephemeroptera." How do you think the Mayfly family got its name?

(To respond to this question, please follow the instructions below.)

Mayfly Adult

Mayfly Adult

Many species of aquatic insects emerge very soon after ice-out, as people who've already gotten mosquito bites know! One Journey North science writer drove through northern Wisconsin this week, where there is still ice on many lakes. She had to stop at a gas station to clean her windshield, which was spattered with dead bugs. And sure enough, she saw her first swallows on the same day.

Caterpillars
Many moth and butterfly eggs synchronize their hatching with leaf-out. Leaves sprout out tiny-on oak trees they're called "mouse ears." They not only look like tiny mouse ears--they're just about as soft as them, too. Plants have cell walls that protect the nutritious insides. Many tiny, newly hatched caterpillars would have trouble eating through the cell walls of full-grown tree leaves to get at the nutritious food inside, but right when the leaves emerge, before the cell walls are firm and strong, these tiny caterpillars can munch on them easily. As the leaves grow and get tougher, the caterpillars are growing, too, their jaws becoming stronger.

Warblers fuel their migration in part on hatching caterpillars. If they arrive a day or two before leaves have emerged and caterpillars hatched, they concentrate near water, where the abundance of emerging aquatic insects can sustain them as they wait for their real food supply. But most warblers arrive just as trees are leafing out.

Exceptions to the Rule

Photo by Laura Erickson

The first warbler to arrive each spring, the Yellow-rumped Warbler, usually arrives over two weeks before leaf-out, and the first swallow to arrive, the Tree Swallow, often arrives when there are hardly any insects about. Fortunately, they can both eat small berries when insects aren't available. These two exceptions are exceptional in another way-they each have longer intestines than the other members of their families.

Challenge Question #23:
How do you think longer intestines help Yellow-rumped Warblers and Tree Swallows?

(To respond to this question, please follow the instructions below.)

Swallowing Signs of Spring
The Barn Swallow is one native American species that has become very dependent on humans. It's very difficult for anyone to find Barn Swallow nests that are not on houses, barns, bridges, or other structures made by people. They construct their nest out of mud pellets that they shape and carry in their mouths.

Barn Swallows are lovely to watch, whether perched on their nests or flying about. Their long tail helps them maneuver. They weigh less than an ounce, and fly anywhere from about 17 -46 mph. Their graceful, speedy flight is lovely to watch as they dart every which way, snatching insects in mid-air. During migration, some Barn Swallows travel from Argentina to Yukon and Alaska, about 7,000 miles. This isn't much more work than their normal daily flights back and forth in one area, since just catching flying insects area they can fly 600 miles a day.

Sometime around 330 B.C., a great philosopher named Aristotle wrote, "One swallow does not make a summer." He was probably thinking about the Barn Swallow, which nests throughout Europe and Asia as well as North America. Our birds winter in South America.

Challenge Question #24:
Where do you think European and Asian Barn Swallows spend their winter?

(To respond to this question, please follow the instructions below.)

Amphibian Advertising: Discussion of Challenge Question #16
"Why do you think a female might be more attracted to a louder, faster call? Is there some strategy in the call? What might it tell the female about the male?"

"I think that a spring peeper can call loud and fast if he is strong," said Mariah from Sterling Elementary in Sterling, AK. "I think that weak and sick spring peepers' calls would be slow and quiet. Females would go for the loudest calls because that frog is strong and healthy." (shepner@kpbsd.k12.ak.us)

And the Grammy Goes to... Discussion of Challenge Question #17
We asked, "Why do the male frogs stay in the breeding ponds after they have already fertilized a female's eggs?"

For most frogs, the females are in the breeding ponds for a very short time--just long enough to lay their eggs. In contrast, the males stay in the ponds longer, because they hope to mate with other females that are attracted to the breeding chorus.

Calling All Frogs! Discussion of Challenge Question #18
Last time we asked you to tune your ears and take the Frog Call Quiz:
"If you were a Spring Peeper, which of the above calls would you listen for: Frog Call A, B, C, or D?"

Mrs. Nunnally's second grade class in Bedford, NH would listen for Call C if they were spring peepers. (NUNNALLYR@sau25.net)

"If I were a spring peeper, I'd find frog C," said Mariah from Sterling (Alaska) Elementary.

"Frog C" was the answer from Rachel.

Keeping an Eye to the Sky: Discussion of Challenge Question #19
This was the question: "Which of these bird migrations do you think are timed to coincide with the return of frogs? Give one or two reasons why you think so."

Bird expert Laura Erickson sends this answer: Broad-winged Hawks and Northern Harriers are two hawks that eat a LOT of frogs. Also, Sandhill Cranes and Bitterns enjoy eating frog legs and their other parts, too (By the way: Most birds that eat frogs swallow them whole!)

Please Report "Signs of Spring" From Your Part of the World!
Report your "Signs of Spring" sightings to Journey North.
Remember to share your sightings of first frogs, earthworms, red-winged blackbirds, barn swallows, emerging leaves, flowing sap, melting ice and other spring events.

Your observations will be incorporated into "Signs of Spring" updates according to the schedule above. Thanks for sharing!

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-spring@learner.org
2. IMPORTANT: In the Subject Line of your message write: Challenge Question #22 (or #23 or #24).
3. In the body of the message, answer ONE of the questions above.


The Next Signs of Spring Will be Posted on Monday, May 7, 2001.


Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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