Friday, August 24, 2007

Dust bowl weather...

... but no dust storms.

I have many disagreements with the standards and practices of early 21st Century large-scale agriculture. But I am happy to admit that there have also been some significant advances in the last 50 years in agricultural practices. The drought we are having now may or may not have some contribution from global climate change; only another few decades of climate data will sort this out. But it has reached a magnitude where it clearly belongs among the great droughts of the Dust Bowl Cycle. A Special Weather Statement from the Nashville NWS this morning rightfully reminds their readership that extreme heat waves and droughts are a well-known part of natural variability of our climate here. They list other periods that have had summers of comparable brutality to what we are experiencing now: the 1930s, 1950s, 1980s, and now the mid 2000-aughts (this is actually our third consecutive year of summer drought; this year is however far more extreme than the previous two). Anybody else detect a periodicity there? The 1930s and, to a lesser extent, the 1950s were the great dust bowl eras; even in the early 1980s I remember a few episodes of dust clouds that travelled across multiple States. So far in the Aughts, this hasn't been happening. I'm happy to credit the lack of a Dust Bowl this decade to the half-century-plus of work by the Soil Conservation Service, Extention Agencies, Ag Colleges, and every one else who has developed and taught soil conserving tillage and management practices.

The skies may be scorching and desicated, but at least they are blue, not red!

Sunday, August 19, 2007

The Brown-eyed Vireo Problem

I was just treated to the best impression of a Bell's Vireo that I have ever seen a White-eyed Vireo pull off. Not only did this bird (presumably a juvenile male) have nice dark brown eyes and faintish whitish spectacles with no trace of yellow, but he was singing a song that, with only a little effort and selective listening, was easily interpreted as a mumbly version of the classic Bell's "wheedlewheeedlewhee wheedlewheedlewoo." So why wasn't this a Bell's Vireo, you might ponder? Well, because other than looking and sounding like a Bell's, it didn't look and sound like a Bell's. By this I mean its size, proportions, actions, "flickiness" or lack thereof, were all typical White-eyed Vireo. Its wingbars were a bit too crisp, its head, bill, and tail shape didn't look un-WEVIish in any way. Plus, if you listened more objectively, you had to admit that his mumbly song had a few chips and some "chickaparea" like phrases thrown in, and honestly, well, it was just the juvenile babblings of a baby boy who hadn't learned to form proper words yet.

I see these Brown-eyed Vireos every year in late summer and early fall, of course; anyone who lives amidst an abundance of nesting White-eyed Vireos does. Every year there are one or two like this bird that really tug on the temptations to make it into a BEVI not a WEVI. But I considered this bird blog-worthy for one particular reason: I decided out of curiosity to see what the major North American field guides had to say about this particular ID problem. I was astounded and profoundly disapointed to discover that they do not address it at all! I grabbed the four guides I had handy, and here's a case-by-case breakdown:

Eastern Petersons: Illustrates the head of a young WEVI with a bold glowingly yellow set of spectacles. No mention of jizz or behavioral differences. Dark eye and white eye-ring listed as marks for BEVI.

Robbins: Illustrates young WEVI looking exactly like adult except for dark eyes. Mentions that yellow spectacles will distinguish it from Bell's. No mention of jizz or behavior; indeed it references the two species as "counterparts" which could be taken to suggest there's little difference.

NGS (an older copy): Juvenile WEVI not illustrated. Text says only that is is duller with "gray or brown" eyes. BEVI not even compared with WEVI in text; but (finally!) the distinctive shape, jizz, and behavior of the BEVI are mentioned.

And finally, the current state of the art, Eastern Sibley: "First winter" WEVI is illustrated with dark eye but flaming yellow spectacles and flanks. "Bright yelow spectacles" are listed as a distinguishing mark "for all" WEVIs. No mention is even suggested of the white-spectacled juvies of late summer and fall. Entry for BEVI is extensive including behavior, jizz, shape, and several distinguishing marks that might eventually let a novice or overeager intermediate birder realize that their dark-eyed, white-spectacled WEVI is NOT actually a BEVI, but not very quickly.

So the gist is this: The popular American field guides would leave most any birder who relied on them thinking that any dark-eyed, whitish-spectacled, wingbarred, smallish vireo is a Bell's Vireo, unless they are very dilligent in investigating the subtler aspects of bird ID. Why no guide even bothers to mention that some Juvenile WEVIs can be very drab and appear to have whitish spectacles, hence other field marks must be examined, is a mystery to me. Just another argument for learning to bird primarly from other birders and then only secondarily from field guides, but not everyone has that luxury.

Saturday, August 18, 2007

Farm life...

It's hardly news to anyone in the North American continent that it is hot out there. We had a nice week away from home in Colorado, where we enjoyed balmy beach-weather at 8500 feet above sea level. In a dramatic break from tradition, even the nights were mild.

Back at home, the year of climate extremes continues. On the heels of our devastating spring freeze, we are in the midst of a wave of heat and drought that is bumping against the boundaries of historical precedent. The latest drought monitor shows us having finally crossed the threshold to "exceptional drought," the highest category. Temperature records are of course being broken left and right. At our place here, there have been about a dozen days this month that have been hotter than any day I recorded in the previous five years. Yesterday was a comparatively mild 103F, down from two consecutive days of 107F. I'm managing to keep the vegetable garden watered enough so things aren't dying, but heat like this puts an end to ripening of tomatoes. They just sit there and gradually get sort of bleached looking. I've harvested some of these and put them inside in paper bags with apples, which seems to be getting them to redden up.

Who can say what is going on with this? The worldwide scientific community hs reached concensus that global warming is happening. However, the line between climate variability and climate change is very hard to resolve at the local, year-by-year scale. The records we have been matching and breaking this year are mostly from 1952 and 1954, the height of the dust bowl. Most of what is happening lately is probably due primarily to ordinary drought cycles, with perhaps some additional nudge from long-term warming. We've not seen the truly, qualitatively unprecedented yet. Native vegetation is stressed but it is not showing wide-scale die-offs and shifts; at least not as of the present. Until we finish breaking all the records from the 19th and 20th Centuries, and start breaking records that were just set a few years previously, it is hard to say that our climate has actually shifted to an ecologically and sociologically meaningful degree.

We may not be far off, though. So far as I understand it, even if the weather in Nashville reverted to climatological averages starting today, August 2007 would still work out to be the hottest August in 137 years of records. Given that in fact the short- and long-range forcasts are for persistence of the extreme heat and drought into the indefinite future, well...

Friday, August 17, 2007

Another musical interlude


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