Signs of Spring Update: March 7, 2003
When Walden Pond is still frozen, the northern states are still covered with snow, and the thermometer is dipping down to zero at night, sometimes northerners like to think about the tropics. Imagine the lush green and steamy heat of a tropical rainforest, and all the colorful birds and frogs! One of the beautiful birds feeding on fruit in Central America right now is our good old Baltimore Oriole.
The Baltimore Oriole spends its life living in two different worlds. Babies hatch in the eastern forests of the United States and Canada, where they grow up with their family. Then in late summer they join flocks and migrate to the tropics, where they remain all winter. Birds that move between North America and Central or South America are called neotropical migrants. Right now most Baltimore Orioles are still in Central America. No one knows exactly why, but a few Baltimore Orioles spend the winter in the north. One came to a feeder in northern Minnesota this winter! But most of them move south.
Bullock's Orioles, which are hatched in the western United States and Canada, spend their winter in Mexico and in the American southwest. Like Rufous Hummingbirds, they arrive on their breeding grounds before Baltimore Orioles or Ruby-throated Hummingbirds come back. Make sure you tell us when you see your first oriole!
What is life like for Baltimore Orioles in Central America? Many live in Costa Rica, along with more than 800 other species of birds. More different kinds of birds live in tiny Costa Rica than in all of the continental U.S. and Canada combined! How can such a tiny country feed so many birds? Do you think it's always warm where orioles spend the winter? Join the orioles and find out here:
Oriole Food Chains
Whether they are in the tropics or the north, orioles have to eat to get the energy they need to stay alive. Sometimes orioles eat fruit. Plants get the energy they need to make fruit from the sun. When an oriole eats a raspberry, the energy from the sun goes straight from the fruit to the oriole. This is a very simple food chain.
Sometimes orioles eat animals such as spiders. Spiders usually eat insects. Insects eat other insects or plants. The food chain gets longer.
Sometimes orioles get eaten by predators. Then the oriole itself becomes food in a food chain.
Think about the different foods that orioles eat. And think about the predators that eat orioles. Then answer this week's Challenge Questions. Before you do, here's a good place to find helpful information:
Current Happenings: Walden Pond Frozen, But Birds Are Warming Up!
If you entered our Ice-Out Contest, you'll be interested in this update on Walden Pond in Masachusetts. Michelle Dumas, Assistant Park Director, wrote on March 4, "Walden Pond is still in the deep freeze!! Today we are about 15 degrees with the promise of seeing the 30's and 40's later in the week. In some years past the ice has already left Walden...but not this year. We currently have about 12" of solid ice covering the entire pond. It will take some warm days with the help of some wind and rain to melt what we have." Stay tuned!
Frozen water may be part of winter, but there are exciting developments in the bird department. "This morning at 9:15, I spotted what may be the first Kildeer of the season at Muddy Creek at the Wheatley Harbour. Spring is upon us," writes Dean from Wheatley, Ontario. And from Mansfield, Ohio, Linda reports "courting wild tom turkeys with full tail-feather display, stutting amongst a large group of turkey hens who were feeding in a corn field."
Taking Their Sweet Time: Discussion of Challenge Question #7
Last time we asked, "Why do you suppose bluebirds take longer to fledge than their larger cousins? Try to come up with at least two reasons."
Robins are larger than bluebirds, so you'd think they'd develop more slowly than bluebirds. But robins nest in an open cup-shaped nest while bluebirds nest in protected tree cavities and bluebird boxes. The whole time baby robins are in their nest they're vulnerable to crows, jays, and other nest predators that have trouble stealing baby bluebirds. So one reason robins are faster is that they speed up the process to limit the time their babies are vulnerable to predators. Another reason bluebirds take longer to fledge is that they eat smaller food items than those huge nightcrawlers baby robins eat, so if parents make the same number of feeding trips to the nest, it takes longer for bluebird babies to get as many calories as robins get.
How to Respond to Today's Challenge Questions:
1. Address an e-mail message to: email@example.com
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North. All Rights Reserved.