Welcome
Back, Red-Winged Blackbirds!
Every spring
as the ice in cattail marshes starts to decay (the term for soft, melting
ice), Red-winged Blackbirds return to their posts, flashing red epaulets
and calling "Okalee!" to
defend their patches of territory. Males return first, often before
any open water is available, but females bide their time farther south
until the weather and food supplies are more steady. Male and female
red-wings look completely different. Many people have trouble believing
they're really the same species! Why do you suppose males and females
look and act so very different?
Changing
Meal Plans
Red-winged Blackbirds have been spending the winter eating mostly plants. But
the moment they settle into their marshy breeding grounds, they'll switch their
diet to mostly animals, because that is exactly when insects will suddenly
become available.
Female redwings wait to come north until warmer, more predictable weather makes
insects more reliably available. Females need a LOT of bugs to provide the
protein and calcium necessary to lay eggs. Redwings start breeding earlier
in southern marshes than in northern ones, except for a small population breeding
all the way down in Central America. They won't start breeding until June in
Costa Rica, even though they'll lay their eggs all the way up in Saskatchewan
in mid-May!
Changing Boundaries: Where Are They?
When male redwings first return, it takes a while before they work out the
boundaries of their territories. When females return, and again during the
nesting season, these boundaries move. If a male gets so busy courting or feeding
babies that he doesn't pay attention, another male might start moving in on
him!
One way ornithologists figure out exactly where territory boundaries are is
to make a precise map of a section of the marsh. This section, called the "study
area," can be any size, just so the scientist (or student, like you!)
knows exactly how big it is. Then the ornithologist watches crows or hawks
flying over the marsh. The male blackbird makes alarm calls as the predator
flies over.
It's an easy matter to locate the redwings making the alarm calls. Each male
redwing sits conspicuously on cattails, watching for predators and keeping
other males off his territory. And when he's agitated, he exposes his red epaulets.
Whenever the ornithologist hears one of these alarm calls, they mark the map
exactly where the male made the call. It doesn't take long to see where the
most calls take place. These clusters of marks on the map show the territories. Another
way to figure out a Red-winged Blackbird's territorial boundaries is to make
a Red-winged Blackbird "Action Figure" (decoy) and set it near
a marsh. You'll know if you've placed it in or near a territory if any Red-winged
Blackbirds try to chase it off! If your classroom is near a red-wing marsh,
make some paper maché action figures that look just like red-winged blackbirds
and try it!
Try
This! Journaling Questions
- Red-wings
arrive in marshes just before (or close to) the time when frogs start
calling. Why do you think the arrival of Red-winged Blackbirds on
marshes coincide with frogs starting to call? (Learn more about frogs
and toads here.)
- When
a redwing dies, it usually happens over the winter. That means some
redwing territories won't have an adult male to return them this
spring. If a good territory isn't claimed by last year's owner, what
will happen to the empty territory? Try to think of three different
possibilities for
what happens to a red-winged blackbird territory that isn't taken
over by last year's male.
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