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Signs of Spring Everywhere Update: May 10, 1999

Today's Report Includes:

Warblers Back in the North!

This migrating Ovenbird took a break on an oilrig in the Gulf during its journey north.

Warbler migration is going at top speed right now. These tiny birds weigh between one quarter and one half of an ounce. They face tornadoes and other treacherous conditions in their northward rush each spring. Many cross over the Gulf of Mexico, and are HUNGRY when they finally reach land. Tiny caterpillars emerging just as leaves pop out provide the perfect fuel for their migration

Setting Boundaries
When Bill Cosby was a boy, he had to share his bed with his brother Russell. The boys had an "invisible black line" running down the middle of the bed, and they had to stay on their own side of the bed to keep from fighting.

Imagine a family of birds that does the same thing. Each species of warbler eats insects in its own small part of the forest, hardly ever crossing invisible borders to enter any other warbler's area. So several different species can all live in the same small stand of trees. Although warblers are shaped pretty much the same, most species are specially adapted for taking insects in one particular area, called their niche. Groups of birds that can live together in the same area like this are called communities. Warblers form an important part of breeding bird communities in North American forests.

The Specialists

Black-and-white Warblers often perch on wide branches.

Some warblers are specialists. These birds virtually always take their insects from one particular part of a tree.
  • Black-and-white Warblers act like creepers and nuthatches, taking their insects from crevices in the bark of large limbs and the trunk.
  • Blackburnian Warblers glean for insects in the canopy of trees, especially on small twigs and leaves.
  • Magnolia Warblers feed at low and medium levels, especially in the understory, and catch many flying insects.
  • Chestnut-sided Warblers take insects from the undersides of leaves, especially in low and medium levels.
  • Ovenbirds feed on the forest floor, probing around and under fallen leaves for food items.

Look and Listen for Warblers
There are about 115 species of warblers in the Americas, of which about 60 occur north of the Mexican border. Many of these are secretive and hard to find, but two species breed over most of the United States and Canada.
  • The Common Yellowthroat breeds in every province and state (except Hawaii). It can be found in weedy, brushy, or marshy habitats. This colorful little "bandit" stays hidden in the dense vegetation, but if you listen for its "witchity witchity witch!" song and have patience, you'll eventually spot the singer!

  • The Yellow Warbler used to have as broad a range as the yellowthroat, but has been extirpated from parts of the Southwest and its range in shrinking in the Southeast. It nests just about anywhere it can find a stream, pond, lake, or river, especially where there are willows. This bright warbler sings "Sweet, sweet, sweet, aren't I so sweet?"

Listen to the Common Yellowthroat
Wait for download; 54 K file.
Recording Courtesy of
Lang Elliott

Listen to the
Yellow Warbler

Wait for download;
42 K file.
Recording Courtesy of
Lang Elliott

Oddly, warblers that live in the highest parts of trees have a higher pitched song than warblers that live closer to the ground. Compare the songs of the Blackburnian Warbler and the Ovenbird.

Listen to the Blackburnian Warbler
Wait for download; 54 K file.
Recording Courtesy of
Lang Elliott

Listen to the

Wait for download;
70 K file.
Recording Courtesy of
Lang Elliott

Challenge Question #21
"Give one reason why warblers that live high in trees sing a higher-pitched song than warblers closer to the ground."

(To respond to this Challenge Question, see below)

Attracting Warblers
Warblers don't visit bird feeders, but there are a few ways that some people manage to attract them.
  • Birdbaths and dripping water
  • Fruit fly feeders (Put some chunks of banana and/or melon in a mesh bag like onions come in, and hang it from a tree outside)
  • Mealworm feeders (Put mealworms in a small can such as the kind tuna comes in, and set it out near a stand of trees. It takes time for warblers to notice.)
  • Oranges or grape jelly feeders (Once in a while warblers will join orioles at these.)
  • Nesting materials: Set out short lengths of binder twine, handfuls of dog or cat fur (from when you clean your pet's brush).

Discussion of Challenge Question # 19
"What is 'plankton'? How is it similar to aeroplankton? How is it different?"
Fourth Graders Heather and Ashley wrote,
" Plankton are tiny plants and animals that are living in the sea and being eaten by sea creatures, such as whales, jellyfish, and other fish. Aeroplankton glide across the sky peacefully. But then again they are eaten just like plankton only they are eaten by birds and other flying insects and animals. Differences would be that aeroplankton floats in the air and plankton floats in the water. Plankton and aeroplankton are eaten by different species. Similarilities would be that they are both the basis of the food chain. They are also both microscopic plants and animals."

Like plankton, aeroplankton is found at all levels of the air, and because these plants and animals are so tiny, they are carried by currents beyond their control. For example, airplane pilots have spotted spiders at high altitudes miles out over the ocean!

Discussion of Challenge Question #20
"Why do we usually find more flying insects over wetlands, lakes and rivers than over fields and forests?"

Many of the insects we see all the time in summer, from mosquitoes to dragonflies, spent the first stages of their life in water, and must return to water to lay their eggs. So water makes a big difference in the number of insects around!

How to Respond to Today's Challenge Question
1. Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question # 21
3. In the body of your message, answer the question above.

The FINAL Signs of Spring Will be Posted on May 24, 1999.

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