Posts Tagged ‘Northern Harrier’

I was walking along the edge of a plowed field along the Clarksberg Branchline Trail in West Sacramento a couple of days ago when I saw a hatch year Northern Harrier quartering back and forth, low over the ploughed earth. The raptor was not very far from the edge where I stood, so I was able to get a really great view as I watched it coursing along and staring at the ground intently as it hunted for its breakfast. Suddenly, it made a sharp turn, almost flipping over itself, and dove for the ground. It landed on something and after a moment standing on the ground, it took off. As it did so, I saw a small, brown object in its talons. I assumed at first that it was a small mammal, and that the Harrier had made a successful hunt, but when the bird was about 20 feet off the ground, it dropped the brown object. As the thing dropped back to the earth, I was able to see that it was not an animal at all, but was actually a clod of dirt.

What had happened here? Did the Harrier make a mistake and attack a mouse-shaped bit of dirt thinking that it was, in fact, the makings of a meal? Given how amazingly keen the eyesight that raptors possess this seems unlikely. And it seems especially unlikely given that the bird was only about 20 or 30 feet off the ground when it started the dive. Making that big a mistake at that close a range is hard to believe. So what was the hawk doing? Was it practicing? This was a young Harrier. Perhaps, not seeing any actual voles or mice at that moment, it decided to do a little target practice. I don’t think of raptors needing practice, but of course that is probably kind of silly. Young songbirds need to practice their song, and often sound amusingly bad at first. However, of the course of a few weeks, they practice and hone their vocal abilities and end up producing songs that sound like the other adults of the species. So, raptors practicing their hunting skills seems pretty understandable. The amount of skill required to be a predator is rather impressive, and even when you consider that many of these skills are hard-wired instinct, that still leaves a lot of room for learning and improvement: practice. Here was a raptor that, perhaps, just picked a particular earth clod on the ground and wanted to see if it could hit it at high speed, just to see if it could. It did, so that practice run was successful! Practice does make perfect!

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There is a post doc working for my adviser who is from Glasgow, Scotland, named Lindsay.  She and I have been comparing birds in North America to their counterparts in Europe.  One especially interesting example to me was the Northern Harrier of North America and the Hen Harrier of Europe.  These birds are considered different species by some and different subspecies of the same species by others.  The reasons for having some kind of distinction between the two populations usually rests on the fact that they are separated by an ocean and also on slight differences in size.  However, we being students of behavior, Lindsay and I were talking about behavioral differences between the two, and there was one that really jumped out at us.  She was surprised to see so many harriers in the agricultural land around the town of Davis.  In Scotland, the Hen Harrier generally keeps to more natural landscapes of moor and meadow.  Here in the U.S. The Northern Harrier is a common sight in human dominated landscapes such as empty lots and agricultural fields.  In fact, they even breed in these fields fairly frequently which was quite a surprise to my Scottish friend.  This demonstrates how important the study of behavior can be.  The outward, physical differences between birds from these two populations are slight, but they have these distinct behavioral differences in where they hunt and where they breed.  Surely this kind of information could , and should, be used when defining species!

I want to collect such differences in behavior between different populations, so do you know of any?  They can be from any continent or any combination of continents, and involve any species.

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