Wednesday, August 10, 2011

Willows mess everything up (6/4/11 - 6/10/11)

With curlew activity dwindling, days in the field began to truncate, allowing more down-time for everyone.  After dinners of burritos or Alaskan sausage that capped-off our daily 4,000 calorie budgets, I spent most evenings observing Savannah Sparrows' territorial behaviors or trying to catch up on photography and recordings.  On one such evening, as I made a beeline for camp after photographing stands of Arctic Tundra Grass, I flushed a large bird from a tussock mound, its identity initially alluding me in the low evening sun pouring directly into my retinas.  I assumed a female ptarmigan, and braced for an aggressive attack to my face (these birds become extraordinarily fierce while incubating!).

No sooner had my cerebral cortex processed the distinctive wavelengths of light emitting from the bird's rump that it began belting out a series of shrills and cheuit calls -- a curlew!

He don't take kindly to my type 'round here

We were well aware there was likely a curlew nest in this area (no more than 200 yards from camp), as the birds insisted on displaying and vocalizing vigorously the minute we zipped-up our tents every single night (as distracting as this was to attempts at sleep, this behavior made for a truly pleasant wake-up call most mornings).  Even so, I found myself completely dumbfounded at my discovery, clumsily fumbling over my camera in attempt to photograph the bold behavior of this male bird, who was now performing convincing broken wing displays and audacious mob-flights directed towards me.  After realzing that my flustered mind had failed to change the macro setting on my camera from my botanical exploits, I decided I had disturbed this fellow enough, snapped a couple pictures of him and his nest, marked the location with a GPS, and eagerly fled for camp to tell the crew.

The genetic future of a remarkable pair

Having scoured the entirety of the core study area for nests, Kristine and I opted to continue our search at the western edge of the Nulato Hills -- a truly unforgettable experience that led to a repeat, more extensive trip the following day with the entire crew.  Just before abruptly transitioning to flat, pond-dappled tundra for some 60 miles to the Berring Sea, the westernmost hills of the area shoot up some 1,000 ft above sea level, offering spectacular views of the region, as well as a rare glimpse at a (near) sub-alpine ecosystem.

The Nulato Hills/Coastal Tundra divide

The steep ascent to the final ridge of the hils was an experience in itself.  The graminoid hummocks and sedges of the mid-slope landscape gave way to smooth carpets of light green and black lichens.  Anemone, Wooly Lousewort, Alpine Azalea, and Purple Oxytrope were sprinkled along the slope in vibrant clusters, or, in the case of the Anemone, loose stands that hugged the southern light.  Among these dwarfed meadows, an occasional Old World Swallowtail could be found, clinging for precious life in the face of indifferent summit winds.  Two small passerines (likely redpolls) bounced over the very summit, teasing me with the anticipated display of American Pipits that claim these hilltops.

Alpine Azalea and Purple Oxytrope

As we neared the summit, I caught my first glimpse at the flat expanse of tundra that one recalls from Discovery Channel documentaries highlighting the rich diversity of the Alaskan tundra's avifauna.  From an incredible distance, several ponds holding unidentified waterfowl (spare for two obvious Tundra Swans) were visible, leaving me lustfully speculating at breeding loons, wagtails, turnstones, and all the other species unable to colonize the Nulato Hills.

A view much closer to Russia than Sarah Palin's backyard

To my east lie a dark, unintelligible view of the great Andreafsky Wilderness, home of Arctic Warblers, Boreal Chickadees, and Grizzly Bears -- a wilderness I so long to visit.

Waaaay back there -- 'God's Country', as the locals know it

On the 'campside' of the slope, in a thicket of alders and willows that marks the start of the 'P' drainage -- a drainage containing a curlew territority -- Fox Sparrows and Orange-crowned Warblers contributed great notes towards my content, ridding me of woe over the absence of eiders and reassuring me of the richnesss of my home for these final weeks...the flock of ten Long-tailed Jaegers dancing about the hilltops and our first Grizzly Bear sighting certainly helped this matter as well...

The 'P' Drainage

With one important exception that I will address shortly, the above picture, specifically the right side, is a textbook example of prime curlew estate.  The two slopes meet at a snowmelt drainage that begins at the very top of the hill, visible in the foreground.  For whatever reason, these drainages are a must for curlew habitat, and the birds spent a great deal of time in early spring displaying over them, seemingly utilizing the natural boundaries created by the drainage and the willows on the slope to define their territories.  As you'll notice, the entire left slope is entirely covered in willows and alders, whereas the right slope has a few large lichen mat meadows that are divided up by willows lining the smaller drainages running perpendicular to the main drainage.  These open meadows are where the curlews breed, roughly from low to mid slope.  One of the concerns for future curlew conservation is the rapid expansion of willow and other woody shrub species across the Nulato Hills in recent years -- a phenomenom attributed to rising temperatures and subsequent reduction of permafrost, allowing larger shrubs to take root easier.  A good indicator of shrub expansion has been the recent appearance of moose in this area of the hills, as moose are completely dependent on these shrubs for food and shelter to rear their young.  Indeed, during the last curlew study at Allen Creek (1989 - 1991 -- roughly?), Brian McCaffery's crew saw something on the order of three moose throughout the entire season -- a much different scenario than our daily moose sightings in several distinct locations.

While on the topic of willows, I must admit that I found myself extremely fascinated by them after, what I found to be, a very interesting observation.  The sharp-eyed soul will note that in the above photo of the hill/tundra boundary, there is still significant standing snow.  Such snow deposition areas were fairly sparse by mid June, but common at the bottom of a north-facing slope.  Allen Creek, which runs roughly east-west near our camp, is bordered by both south-facing and north-facing slopes, both of which contain willows bordering the creek.  I noticed that willows on the north-sloping side were well behind the willows on the south-sloping side in terms of budding and "leafing-out", sometimes by as much as two or three weeks.  These conditions initially struck me as having interesting potential for sympatric speciation between the willows on opposite sides of the creek.  Given that the life spans of tundra insects are very short, even a difference of a couple of weeks can see a noticeable shift in the species composition of potential pollinators flitting about.  Assuming that the mentioned phenological differences exist between the two groups of willows most years, it seemed reasonable to assume that there could be potential for adaptive divergence via differential "recruitment" of pollinators, not to mention different physiological demands on the plants based on the different lengths of time the two groups are buried in snow (though I'm less confident about that).  This idea came quickly to an abrupt hault when I realized that willows elsewhere in the area, based on their local environment, had intermediate "phenological clocks" between these two groups, serving as a sort of "bridge" to gene flow between them...and that willows hybridize like crazy.  Oh well.

A failed attempt at illustrating the above 

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