Birds on wires

Out in the flat prairies, marshes, and agricultural fields surrounding Pelican Lake, there are few structures from which a hunting bird can search for its prey.  Power lines and poles are the most convenient perches, and narrow dirt roads lined with short, mowed grass make excellent hunting grounds.

Within a 1/2 mile stretch of one such dirt road, I saw a male Harrier (marsh hawk) making its huge sweeping forays across the fields, a huge (female?) Red-tailed Hawk perched atop a power pole, and an American Kestrel, and a Loggerhead (I think) Shrike perched on power lines.  Of course, I scared all of them off with my exuberance in jumping out of the car to take some photos, but I spied a couple of them again on a return trip to the same dirt road when I returned a couple of hours later.

This male American Kestrel was very intent on searching a particular piece of the mowed strip, and kept coming back to the same site on the power line.  This time I shot photos from the car window and crept slowly toward him without too much disturbance.

Flaring his wing and tail feathers for  maximum braking, an male American Kestrel comes in for a landing.  He was very intent on searching a particular piece of the mowed strip below him, and kept coming back to the same site on the power line. This time I shot photos from the car window and crept slowly toward him without too much disturbance.  I love all the color in his wing and tail feathers.

Every now and then, he would look over his shoulder to check on what I was doing...and then return to the search.

Every now and then, he would look over his shoulder to check on what I was doing…and then return to the search.  His breast feathers look a little ratty, as if he had been moving around on wet grass while tackling his prey.

A Loggerhead Shrike perched on the opposite side of the road from me, but was so small and so far above me that I couldn't really see his head.  They are a little smaller than a robin.

A Loggerhead Shrike perched on the opposite side of the road from me, but was so small and so far above me on the power line that I couldn’t really see his head.

Getting a better view (from farther away) I could see his large head with its black mask, hooked bill, and white breast -- all indicative of Shrike-ness.

Getting a better total view of the bird (from much farther away), I could see his large head with its black mask, hooked bill, and white breast — all indicative of Shrike-ness.   The mask extends in front of the eye as well as behind, which means this is most likely a Loggerhead Shrike.

Loggerhead and Northern Shrikes are very similar in appearance, but Northern Shrikes spend the winter in MN and then migrate north to northern Canada and Alaska to breed. Loggerhead Shrikes spend the winter down south, and migrate to the northern U.S. and southern Canada to breed.  Unfortunately for birders, the two species overlap during their migration through Minnesota in April, making it difficult to determine which species you’ve seen.

Both Kestrels and Shrikes are sit-and-wait predators, preferring to hunt from a high perch, looking down on their insect, amphibian, reptilian, or even small mammal prey. Birds of prey, like the kestrel, are known for their keen eyesight, which results from the high density packing of light sensitive rods and cones in their retinas.  Kestrels, for example, are said to be able to see a 2 mm insect from the top of a 18 m (~50 foot) tree! I don’t know if anyone has measured eyesight in Shrikes, but they probably have excellent vision as well.  An additional difference in predatory birds is the forward placement of their eyes, enabling binocular vision that gives them depth perception. Although Shrikes are technically songbirds and not raptors, they also appear to have more forward placement of the eyes to promote binocularity.

Hawk-eyed, a synonym for visual acuity, is a product of high density of photoreceptors and two (not one) foveas for focusing incoming light.

Visual acuity (being “hawk-eyed”) is a product of high density of photoreceptors and size of the fovea (focusing center  for incoming light).  Raptors have 6-10 times the number of photoreceptors that humans do, and two (not one) foveas, which allows them to focus looking straight ahead as well as down (while perching or flying).  (Photo from Wikipedia)

Hawk-eyed sounds better than Shrike-eyed, doesn’t it?

6 thoughts on “Birds on wires

    • There do seem to be a lot of hawks flying around just now, most are passing through the area on their way north. The spring migration has really just begun in the northern US, so hopefully you’ll be seeing many more and colorful feathered friends on your walks in the next month.

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