Friday, May 20, 2011

Hermit and Porcupine

A bright male hermit warbler was a highlight of yesterday's birdwalk in the Valley. He was in a black oak in the company of several yellow-rumped warblers, a black-throated gray warbler and a Wilson's warbler. We love these springtime collections! Orioles have been silent and invisible this week- did they leave the Valley for lower elevations?
As part of their training on Wednesday park ornithologist Sarah Stock had interpretive rangers out in Ahwahnee Meadow looking at peregrine falcons coming and going from their eyrie up on the Rhombus Wall. She's teaching a terrific "Hawks and Owls" Yosemite Outdoor Adventure program, June 3-5, in the company of great gray owl specialist Joe Medley.
The river and waterfalls are below average volume now but will surely creep back up with a couple warm days here. More clouds come in late Saturday = more waterfalls still flowing in July.
Nearly two feet of new snow fell in the high country this past weekend. NPS road crews have plowed up to Porcupine Summit on Tioga Road. This is beyond Yosemite Creek, before the drop to the long straightaway near Porcupine Flat Campground. It's still many miles and several avalanche zones to Olmsted Point, Tenaya Lake and Tuolumne Meadows. At Glacier Point there's still so much snow it doesn't seem possible to open that area for Memorial Day weekend because water and septic systems won't be on line. It'll be a busy holiday weekend a week from now with all visitors concentrated in Yosemite Valley.

Tuesday, May 17, 2011

Towhee and Frazil

Cold and snow chill Yosemite. We had frazil ice in Yosemite, Sentinel and Ribbon Creeks yesterday morning; a bit late in the season, but not unheard of. The Merced River has dropped just below the average flow rate for mid-May; it has been running at above-average volume since the big storms got started in November. Though average, the falls are still big, but they'll get bigger, and they'll still look good in July. Fire season gets delayed, though the moisture likely means more growth of small fuels like grasses.
A highlight on yesteday's birdwalk was seeing Superintendent Don Neubacher dash out of his office with binoculars in hand to stalk a seldom-seen green-tailed towhee outside the Administration building. He was accompanied by ace ranger-naturalist Karen Amstutz who spotted the unusual bird out her window and had the inspiration to pull the park's boss (a dedicated birder) away from his desk to see the towhee. I'm glad to know that our park is being looked after by such people. My group was surprised to see a second green-tailed towhee a short time later near Yosemite Creek.
Ranger JT reports snowplant emerging near Sentinel Bridge. I've seen a couple in the west end of the Valley, too. Along with new birds and plants, it's exciting to see the seasonal increase in park staffing as more interpretive rangers return to duty or start their first summer as seasonal rangers. Park visitors are lucky to have all these people leading walks and campfire programs, answering questions in the visitor centers, conducting tram tours and cultivating another 24,000+ Junior Rangers.
There is still room in the Yosemite Conservancy's 3-day "White Wolf Botany" course in early July. This is going to be some terrific field time for casual botanists in a special part of the park. We also have space for people to join us for the two "Family Camping Jamborees" in late-July in Tuolumne Meadows.

Friday, May 13, 2011

Warm then Storm

Last weekend's overcast and rain caused the Merced volume (and the tributary waterfalls) to drop back down to near average flow. One might think that rain would raise the river level, but, in fact, the cloud cover and cooler temperatures reduce the snow melting rate much more than a bit of rain can increase the runoff. Warm sun brought the flows up again through the week. Again this weekend we expect a cool storm to bring a bit of rain (and snow -which, of course, reduces the near-term runoff much more than rain does), so the waterfalls will be smaller at the start of next week than they are now.
On most days, the river (and tributary) volume exhibits a nice 24-hour cycle of rise and fall. The hottest part of the day is when the most snow melts up at 7-13,000'; this surge of melt doesn't reach the two Yosemite Valley river gauges until many hours later. It's odd that our highest water flows in the Valley happen after midnight - about 12 hours after the hottest part of the day. That's the lag time for high country runoff to make it down to 4000'.
It was cold enough in the Valley this past Tuesday morning (9 May) for people to observe frazil ice in Yosemite Creek and in Ribbon Creek. A deposit outside the eastern channel at Ribbon Creek persisted into the next day, looking like an anomalous patch of snow.
NPS road crews have reached Glacier Point, and they've reached the White Wolf area on Tioga Road, through average snow depths of 8' and 10' respectively.
The bizarre red snowplant is emerging from the ground in Yosemite Valley. Bracken fern is tall and unfolding its fiddlehead fronds. Dogwoods are fully alight now. Western Wood Pewees arrived this week in the Valley. The concentrations of yellow-rumped warblers and some other birds have dispersed from the Valley to higher elevations a bit. I've been seeing 1-2 bears a week in the Valley, more than has been my usual experience.
If you're up early and have a good eastern view, check out the concentration of planets in the east before dawn.

Monday, May 2, 2011

The burst of spring

I encountered my first Western Tanager of the year on Monday's Conservancy bird walk - just moments after a participant asked about them. It was a stunning, bright male in the black oaks in front of the visitor center - lots of exclamations from all present. Since then, more males have arrived and are singing in Yosemite Valley. This morning we had the triple feature of the bright neo-tropicals when within a short time we also saw the male Black-headed Grosbeak and Bullock's Oriole. Surprises on Monday were the Lark Sparrow feeding on the gravel trail along Cook's Meadow and the Western Kingbird sallying out from the black oak canopy over the meadow. This morning we had a decent look at Vaux's Swifts.
Those black oaks are pale green with dangling flowers now and a few leaves are starting to emerge. The early dogwood below the former diversion dam site, along 140 has 'blooms' almost 3 inches across which are almost fully white. Most Valley dogwoods are still pale green - they're more than a week behind an average spring schedule.
The Merced River has leapt in volume with the warm weather this week; it's doubled in volume in the past five days. This morning it had already exceeded the average springtime peak - and there are still a few weeks of potential increase to the average high flow date. Low-lying Valley trails are starting to get wet, but there's no real flooding yet. (Last year peak flow reached 2.5 times what it is now!)