Who doesn’t like a cheap and easy meal? I guess that is a rhetorical question since microwaves, TV dinners, and fast food drive-throughs are commonplace today. No doubt about it, a cheap and easy meal is a way of life for many folks. While some would argue that this reflects an unhealthy societal trend, I’m not going there today, as I sip on my fountain drink and crumple up a candy bar wrapper.
Actually, most critters have adapted to take advantage of food that is easy to find one way or another. Non-mobile animals may use a gimmick to attract food towards them. For example, alligator snapping turtles use their tongue to lure in fish, just to turn the tables on the unsuspecting hungry finned friend. On the other end of the spectrum, waterfowl are highly mobile and migrate cross country to take advantage of food that seasonally becomes abundant on the other side of the continent. In the last week, we’ve seen what happens when those once abundant food resources suddenly become no longer available. The ducks move on for the next easy meal because breaking their bill on ice or digging through the snow is just not worth it.
The ducks that have stayed have become consolidated and another critter’s dining strategy has come into focus. Bald eagles can be seen following the annual waterfowl migration and their numbers increase in Missouri as our duck numbers soar. Essentially, as lakes and other wetlands up north lock up with ice, the eagle’s kitchen also closes up shop. Fish, which can be their primary diet, are no longer available and their secondary option, waterfowl, start to diminish. Consequently, they go with the flow or the next front and are often seen as unwelcome sentinels watching over the uneasy dabbling ducks concentrated in our mid-latitude wetlands.
As temperatures dip below freezing here and ice begins to close in across the marsh so do the eagles. With the options for open water reduced, ducks become concentrated. Their predators move in, conserve energy on their perches, and wait for the right moment. Occasionally, they taunt the feathered flocks by sweeping over the milling masses to stir them up and see if there are any stragglers or cripples ready for the taking. If you sit and watch, you can almost feel the anxiety on the rise as one of the large raptors sweeps low over the open water hole, temporarily spreading ducks flying to and fro. While it isn’t surprising, you may see the occasional coot being hauled off to be devoured on the ice nearby. However, it isn’t always the birds that are slower to launch into flight that end up on the sharp end of an eagle’s talons. Mallards, snow geese, and other fowl also suffer this same fate. At times the scene can become quite grisly as the edge of the ice turns from white to crimson.
Then again, that is what eagles do. They take advantage of an opportunity to fill their bellies, stay warm, and live another day. Who can blame them? This is what optimal foraging theory is all about. Just think next time you roll into Mickey D’s or zap-fry a pop tart; for an eagle it might be just as easy for them to grab that next coot burger or catch mallãrd filléts to go.