Thursday, September 6, 2007

Two to Watch...

The Ohio Breeding Bird Atlas II is in full swing, and now through its second year of data collection. Three more field seasons await, and much more information will come in, but some possible trends are showing up already. One fascinating and very useful feature of the website is the ability to pull up maps that show all of the records for a species, and also maps that show what records the first atlas (1982-87) produced. Go here to jump to their results page.

I've lamented the apparent decline of American Kestrels before. I travel far and wide all the time, all over Ohio, and have been for a long time. I surely see less of these beautiful little falcons, and common sense says there would be less, given all of the development and bird-unfriendly farming practices. Plus, they need suitable cavities in which to nest and that further compounds troubles in the world of the kestrel.
Here's the distribution map of American Kestrel resulting from data collected from 1982-87 and published from the first atlas. They are everywhere, as you can see. Every county, and about 90% of the 800 some formally sampled priority blocks.






Here's what atlasers have found thus far - the past two seasons. Not good. I know there is still three seasons to go, but a few points are worth consideration. One, there are probably more birders out there turning in data than there was the first go-round, and two, kestrels are very obvious birds. They sit out in the open on telephone wires, and hover like little helicopters over fields. They're easy to find. I hope many more dots sprinkle this map after next summer.



Here's the second bird to think about. Whip-poor-will. Above is the map from Atlas I, when it was found in 187 blocks. Whips are birds of scruffy second-growth woods, and that habitat is most plentiful in the rough topography of the unglaciated southeastern portion of Ohio.

Here's the current situation. This does bear out anecdotal reports that I've often heard in recent years, "where did the Whip-poor-wills go?" Maybe we just haven't made a strong enough push on nocturnal species in the atlas yet, but I don't think that's the whole story. No nighttime bird is easier to find than a whip if one is around and singing it's loud, impossible to mistake and incessantly repetitive song. Two likely factors at work to cause declines in this nightjar are the maturation of Ohio's forests to stages where the habitat is no longer suitable for Whip-poor-wills, and possibly on a localized level, spraying for gypsy moths. Pesticides used for the latter are not selective and kill most of the moths, and whips eat lots of moths.

One thing to think about in both these cases that is somewhat philosophical: neither bird would have been in Ohio in most of the areas where they now occur prior to European settlement. Then, the landscape was mostly cloaked in old-growth woodlands not suitable for either kestrel or whip. We created their habitat. And now it looks like we are taking it away.

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3 comments:

Anonymous said...

A comparison of old and new atlas range maps shows the same "range collapse" for Mallard, Rock Pigeon, Horned Lark, Savannah Sparrow, Baltimore Oriole, and other common species. Additional species, Barred Owl and Acadian Flycatcher, for instance, appear to have shifted their ranges. Wilson's snipe has moved into Ohio since the original atlas.

I suggest that these results are an artifact of the research designs of the two atlas projects. The first atlas assigned observers to randomly selected blocks across the entire state. The new atlas, instead, allows the volunteer participants to self-select the blocks to be included in the project.

Not surprisingly, participants have selected blocks either near their homes (Ohio's Cleveland-Columbus-Cincinnati population axis is obvious on the new atlas maps) or with attractive birding destinations (parks, forests, marshes, etc. are emphasized--Wilson's snipe is "in"; rural, low-population and agricultural areas, second-growth and shrub land are all selected against--American Kestrel is "out").

Jim McCormac said...

Thanks for your theories, Anonymous, but that's just not the case. Both of those species have been well documented as declining elsewhere, and as anyone who gets out and about much in Ohio knows, habitat for the two species that I emntioned - and many more- has decreased dramatically in recent decades. So have the birds.

As for picking blocks near one's home, that'd be no different than Atlas I. The data certainly doesn't support your position, but I really hope that I'm totally wrong and kestrels and Whip-poor-wills are doing just fine.

Jim McCormac

Anonymous said...

I heard a Whip-Poor-Will last night. I have heard them in Hocking Hills and in Shawnee State Forest but never near my home. I live in Northern Brown county near the Indian Creek Wildlife area. I am going to keep my ears open but I am betting that it was a migrant passing through. We do have a lot of young woods but most of the area is farm land.