Every morning as I stand at my kitchen sink drawing water for coffee, I look out the window and see one or two squirrels sitting atop the fence waiting for me. They are often joined by birds who are waiting for me, too. The other day, the squirrels were bookends on the fence and between them were three House Finches, two Dark-eyed Juncos, a male House Sparrow, three White-crowned Sparrows and two Mourning Doves.
They were all communicating the same message: “Hey, where’s our food?!”
What started out with me putting a handful of sunflower seeds on the fence’s 2” x 4” support beams to distract the squirrels and keep them out of my bird feeders instead produced the opposite of what I intended — the squirrels hang out on the fence alright, but so do the birds. And I now have an avian conga line every morning waiting along with the squirrels.
That got me to thinking: How do birds find food?It seems obvious, right? The Cedar Waxwing at the top of this post, for example, landed on a tree branch full of berries and voila, instant meal.
But how did the waxwing find that tree with the berries? Did it see them? Smell them?
Take another example, one a little more vexing — the robin. Most of us have seen robins pulling up earthworms out of the ground. How does the robin find worms? Does it smell them? Hear them moving underground? Does it feel with its feet the vibration of the worms moving? Does it see them?
The answer may surprise you. Many people think birds most likely smell food or prey. In fact, birds have very poorly defined olfactory glands. While most birds seem to lack much power of smell, there are some groups of birds that can locate food using their olfactory glands. Extensive research into bird senses has shown that vultures, seabirds, kiwis and parrots have well-developed olfactory glands, giving them some sense of smell and taste.
But birds rely on vision more than any other sense in locating food. Birds are blessed with acute vision, and it's the primary way they find food. Colors attract them to berries, and shifts in movement indicate insects. Water birds watch for fish to jump and then swoop in. Due to their quick metabolisms and high level of activity, birds must eat nearly all of their waking hours for energy. They spend most of their time searching for food, so they become quite good at it.
(Before I go further, be sure to check out the links I’ve included at the end of this post. The first is an exceptional short video from the Cornell Lab of Ornithology on shorebirds’ food-finding techniques and the second is a fascinating Audubon article on bird vision.)
Birds also listen to the calls and coos of other birds, which can tip them off about a source of food. When birds cock their heads, they're listening for clues as to where their next meal will be. They hear other birds call and know food is nearby. Night predators, such as owls, listen for the familiar sounds of the rodents, insects and small birds they prey on. Most birds use both visual and auditory clues combined to locate their food.
Every morning when I put out food for the squirrels and birds, the first California Scrub Jay to arrive (usually within 15 seconds of my setting down a few peanuts) lets off a series of squawks and shrieks, clearly alerting the other jays around that Kestrel has finally come out of the damn door and put out the peanuts.
A little more about bird vision from the Audubon article (included in full in the second link):
Compared with mammals, birds have relatively large eyes. In simple terms, a bigger eye means better vision, and excellent vision is essential for avoiding collisions in flight or for capturing fast-moving or camouflaged prey. Birds’ eyes, however, are deceptive—they are bigger than they look.
The size of eyes is important precisely because the larger the eye, the larger the image on the retina. Imagine watching a 12-inch television screen compared with a 36-inch screen. Bigger eyes have more light receptors in the same way that larger TV screens have more pixels, and hence a better image.
You’ve got to have some pretty good vision and quick moves to snag a dragonfly right out of the air!
That’s it for me. Be sure to check out the links below and feel free to use this as an open thread. I can’t stick around today; an unexpected trip has popped up so maybe another regular (Ocean Diver? Nookular? etbnc?) can keep things moving along. Happy Sunday to all and good birding!
academy.allaboutbirds.org/…
www.audubon.org/...