Monday, March 31, 2014

Geotripper is for the Birds: Life persists in the midst of horrific drought

It was on my morning stroll that I realized that Dry Creek was flowing. The creek has its headwaters in the Sierra Nevada foothills, and drains a region about thirty miles long before joining up with the Tuolumne River in downtown Modesto. It might seem extraordinary to be impressed by such a thing, but Dry Creek in recent decades tends to flow all year, from winter and spring rain runoff, and from irrigation overflow during the rest of the year. We had about two-thirds of an inch of rain yesterday, and in this drought year, that was finally enough to stop just infiltrating into the ground in the headwaters and begin flowing down the channel. In the twenty-five years I've been here, I've never seen such dry conditions. The rain is welcome, giving a last bit of moisture to fuel the growth of vegetation before the long dry season sets in. But it does little to alleviate the drought; we'd need something on the order of a foot of rain in the Great Valley and many feet of snow in the mountains in the next few weeks to fill the reservoirs.

As many of my readers know, I got a new camera a few months ago, and the powerful zoom lens has allowed me to explore a world that has been largely hidden to me until now: birds. Living in the Great Valley is wonderful for the access it provides to the incredible geological wonders of the Sierra Nevada, the Coast Ranges and the Cascades, but during the winter months when most field studies aren't happening the valley can seem a boring place. But not for the birds; for the birds, the valley is life itself. Millions of migratory birds winter on the valley floor, primarily in the federal and state bird refuges that have been established up and down the San Joaquin and Sacramento Valley floors. Over the last few months we have been frequenting some of the wildlife refuges, and the variety and number of bird species has been stunning to me (the neophyte birder). But the lingering drought is going to have an effect on their populations.

In some ways, the most surprising aspect of the bird-watching has been the variety of species I've found in my local neighborhood.  I documented some of them back in January in this post, but I have seen some more as the rain has finally come, and a few migrants have arrived back in the valley for the spring and summer. Here is a selection of the birds I have seen in the last week or two.
Cooper's Hawk (Accipiter cooperii)
The nicest discovery from this morning was a pair of Cooper's Hawks near Dry Creek (they could also have been Sharp-shinned Hawks, a closely related species; I invite corrections!). Even with the zoom lens, the raptors have been surprisingly shy about getting photographed. The hawks this morning were paying more attention to each other.
Western Bluebird (Sialia mexicana)
I saw quite a few Western Bluebirds during January and February, but I thought they had migrated higher up into the mountains, having not seen any for weeks. But here was one that was hanging out in the cow pasture a few blocks from my house. I love his colors.
Lesser Goldfinch (Carduelis psaltria)
There has been no lack of Lesser Goldfinches around my house. They are one of the most common visitors at our birdfeeders. This morning was the first time I've caught them foraging in the wild (the wild in this case being the grass along the highway north of my little farm town). The flowers in the background are Fiddlenecks and Purple Vetch.
Black Phoebes (Sayornis nigricans)
I love the little flycatchers in our area called the Black Phoebe. They are a western species, found commonly only in California, Arizona, and New Mexico, and many points south as far as Argentina. The Great Valley seems to be the northernmost end of their range. I'd never noticed them in the past, but I've seen dozens of them in the last three months.
Western Scrub Jay (Aphelocoma californica)
It's hard to miss the Western Scrub Jays around here. They're obnoxious and loud sometimes, and they're always chasing the other birds away from our feeders. On the other hand, they are one of the most colorful birds in our area. I always enjoy getting a close look at one.
Barn Swallow (Hirundo rustica)
One the recent arrivals in our area have been the Barn Swallows. They winter in Central and South America and migrate into our region for the summer. I photographed one for the first time just a few days ago. I'm seeing flocks of them lately building nests under the bridges around our irrigation canals.
Nuttall's Woodpecker (Picoides nuttallii)
I was very surprised to find a species unique to California living in my neighborhood. I thought "rare" endemics are hard to find. The Nuttall's Woodpecker hangs out in oak woodlands of California and nowhere else. I've now seen them several times in the walnut trees next to the cow pasture (and on telephone poles).
Great-tailed Grackle males (Quiscalus mexicanus)

The Great-tailed Grackles just recently arrived on the CSU Stanislaus campus. They arrived raucously, with one of the loudest calls I've heard during my bird travels of late.The males are dark black (above), while the females are brown (and much smaller).
Great-tailed Grackle females (Quiscalus mexicanus)

Yellowlegs Sandpiper (Tringas species); I don't know if it is the Greater or the Lesser.
I found the Yellowlegs Sandpiper in the slowly filling irrigation canal a few blocks from my house. They winter in our area before heading north into Alaska and Canada.
Yellow-rumped Warbler (Setophaga coronata)

I've briefly seen the Yellow-rumped Warbler flitting about in the grass on my campus, and even  chasing insects on my back porch one morning, but I walked out of my classroom on the third floor of our new Science Community Center the other day, and there was this little one right there in front of me. He politely waited until I had taken a few pictures before flying off.
Yellow-billed Magpie (Pica nuttalli), a Central Valley original

The Yellow-billed Magpie is endemic to the Central Valley. I see them all the time, and they are beauties. They are also in grave danger. The West Nile Virus reached our region in 2004, and the Yellow-billed Magpies were particularly vulnerable to the infection, with something like a 95% fatality rate. The population dropped by half in two years when the infection began. According to some web sources, they are rebounding somewhat from the disaster. I hope so; they are one of the prettiest of our local species.

So why all these birds on my geology site? Well, mainly because it's my blog, and I write about whatever interests me at the moment. But in the larger picture, the native species of a region are shaped by the geological forces acting on that area. These birds are adapted to the Mediterranean climate of the Great Valley and the riparian areas (rivers) and grasslands found within. They have survived hundreds of droughts in the past, and presumably are equipped to survive those of the present and the future. They have persisted through the vast floods which sometimes turn our valley into a vast lake. They are products of the geological forces shaping our valley just as surely as the rocks and sediment beneath our feet. And like so many of the wonderful geological sites in our state, they are interesting and often beautiful.

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