Journey North Red-winged Blackbirds

Red-winged Blackbird

Neighborhood Watch: How Redwings Protect Their Babies

Background
Have you ever seen a small black bird chasing a hawk or a big black bird through the sky? It happens a lot in spring and early summer. It's part of the red-winged blackbird's "Neighborhood Watch" program. Whenever any red-winged blackbird spots a potential predator flying anywhere near its nesting marsh, it calls out a warning and flies off. Although redwings chase hawks, they spend more of their energy chasing crows. This is because most hawks don't raid nests, but crows DO! The redwing usually stays behind the crow, dive-bombing it from above and behind. Once Journey North science writer Laura Erickson even saw a redwing pull out a crow's tail feather! This lesson will explain why red-winged blackbirds chase crows, and give students a chance to conduct their own field studies about crows and redwings.

From the Crow's Point of View
During spring and summer, crows raise three or four babies. These babies need a lot of protein while they're growing. To get this protein, crows pay a lot of attention to robins and blackbirds. Adult songbirds can defend themselves against crows. Songbirds are usually faster fliers so have no trouble escaping crows. But nestling songbirds--and their eggs--are completely helpless. Tiny birds like hummers, warblers, and sparrows often build their nests on branches too skinny for a crow's big feet to grasp. But larger species, like robins and blackbirds, make a sturdy nest that is easy for crows to perch on while pulling out the babies. Baby robins and blackbirds are a very important food source for nestling crows.

How Robins Deal with Crows
Robins nest on fairly large territories with a lot of trees blocking their view. And robin nests are usually covered from above by a branch or the top of a window case. Because of this, crows don't notice robin nests while flying over, and robins don't notice flying crows until they're right overhead. Crows are more likely to spot a robin nest when hanging out in the area and paying attention to the adult robins coming and going. So when a pair of robins starts nesting, their strategy for dealing with crows is to be very quiet and inconspicuous around the nest in hopes that crows won't discover it. If a crow DOES come close, the robins squawk loudly. They dive-bomb the crow and do everything in their power to drive the crow away. Their loud calls attract other robins (and blue jays and other species), which come to help them "mob" the crow. Sometimes this drives the crow away.

How Redwings Deal with Crows
Photo Courtesy of Ann Cook

Red-winged blackbirds nest in big colonies in marshes. Usually there are no trees to block a wide view of the sky. Each male redwing has a small territory in the marsh, like a human backyard, but the neighborhood has a LOT of nests. Many of these are at least a little visible from above. To defend their territory, male redwings spend a lot of time perched at the top of cattails. If one spots a crow in the sky, a male redwing will instantly fly up and dart at the crow rather than risk the crow getting close and noticing nest locations. The crow may still fly directly over the marsh, but the distraction of the redwing flying at him may very well keep the crow from noticing where the nests are. Any redwing who notices the crow will take action, and overall this helps ALL the redwings to protect their eggs and babies from crows.

Try This! Discussion and Field Experiments
1. Discussion Questions
What are some advantages and disadvantages for redwings using their time and energy to chase crows? List as many as you can, then compare your list to the one we came up with. If you came up with some good ones we missed, let us know!!

2. Field Experiments

Sit or stand in the schoolyard, your own yard, or a redwing marsh with a clock, stopwatch, or wristwatch and your field notebook. Count every time you spot a crow. If the crow is perched or flying over, only count it once. It must leave your field of view for at least 10 seconds for you to count the same crow again. How many crows do you see in 5 minutes? If different students try this at different times of day, how do the crow numbers compare?
Sit at the edge of a redwing nesting marsh for 15 minutes with your field notebook. Try to keep track of what the redwings are doing, and what things in their world are important to them, and take notes. While you're watching, pay attention to any crows flying overhead, and see what happens if a redwing notices a crow. Try to write down everything the redwings do. Be careful to distinguish between the birds' actions and what you think these actions may mean.