“Want a closer look?” It’s the sixth time I’ve made the offer to peer through my telephoto lens in the past hour, but it’s easier than trying to explain what I’m photographing. This time, it’s a group of Japanese tourists who excitedly ooh and aah at the close-up view of an Osprey on its nest.
Waiting for the Osprey’s mate to fly in, I reflect on what an unlikely location California’s Mono Lake is for a fish-eating bird: a salty, soapy-watered lake utterly devoid of fish! But during two summers here, I’ve found that nesting Ospreys are only one of the avian surprises this magical place offers.
The Ospreys’ bulky stick nest sits on top of one of the otherworldly rock formations known as “tufa towers” that punctuate the shoreline and mineral-rich waters. Arid sagebrush desert surrounds the lake in every direction, while the snow- capped peaks of the Sierra Nevada rise beyond it. Mono Lake draws a quarter-million international visitors annually. Most come for the majestic scenery, but increasing numbers are discovering it’s a great birding spot too.
One early visitor was Mark Twain. He wasn’t impressed. In his 1872 travelogue Roughing It, he declared its “venomous waters are nearly pure lye” and complained “there are no fish in Mono Lake — no frogs, no snakes, no polliwogs — nothing to make life desirable.” Obviously, Mr. Twain was no birder!
In fact, Mono Lake supports North America’s second largest breeding colony of California Gulls (after Utah’s Great Salt Lake) and is a vital stopover location for Eared Grebes and countless shorebirds, especially phalaropes, during fall migration. It was designated as a site of international importance in the Western Hemisphere Shorebird Reserve Network in 1990.
The big draw for the waterbirds is food. That nasty-sounding water teems with tiny brine shrimp, and the shoreline in summer is abuzz with huge swarms of alkali flies. The well-kept birding secret, though, is the variety of landbirds dwelling among the strange tufa towers.
Descriptions of tufa towers always fall short; you really have to see them for yourself. Suffice it to say, they’re bizarre — whitish knobby rocks, some tall and spindly, resembling craggy tree trunks, others fused into enormous masses topped with peaks and spires like surreal mountain ranges.
What the heck is tufa?
Tufa is essentially limestone formed in an unusual way. From springs below Mono Lake’s bottom, calcium-rich freshwater bubbles up through mineral-laden water. Through chemical reaction, calcium carbonate forms and accumulates at the mouth of each spring, gradually building up like an underwater stalagmite until it reaches the surface, as much as 30 feet above bottom. Only when lake levels drop and the shoreline recedes does a tufa tower become visible; towers currently on dry land were formed when the lake level was much higher.
The best place to experience tufa and meet the local birdlife is at South Tufa on the lake’s southern shore, part of the Mono Lake Tufa State Natural Reserve. Take the paved trail leading through the sagebrush to the shore. You will be transported to a strange forest of trees turned to stone. The locals call them “tufa groves.” Since no real trees stand near the shore, tufa offers birds perches, nesting and roosting sites, and in some cases sources of food.
Nooks and crannies in the tufa make great nest sites for hole-nesting birds, of which the most numerous is the lovely Violet-green Swallow. Clouds of twittering swallows swirl around the columns in early spring, vying for the choicest nest sites. Eventually, each pair settles on a location, and the female begins nest building. She shapes a cup of grasses inside the tufa cavity and lines it with soft gull feathers. Meanwhile, the ever-watchful male keeps close tabs on his mate, ready to take flight lightning-fast to chase intruders.
Rock Wrens are regular nesters, but rarely has the opportunity to view them been better than in summer 2010, when a pair took up residence near the much-traveled boardwalk at South Tufa. Just yards from passing visitors, the drab-colored little wrens scurried around the base of the tufa, foraging for insects, spiders, and other small creatures. Every now and then, the male popped into view on a tower to sing brightly, while the female carried nest material into a tufa crevice to build the well-hidden nest.
Bluebirds, phoebes, and Great Horned Owls
Mountain Bluebirds and Say’s Phoebes occasionally choose tufa towers as nest sites, and for several years, one offshore tufa grove hosted breeding Great Horned Owls. Their perching spot was a regular stop (along with the ever-popular Ospreys) on summer-weekend canoe tours run by the Mono Lake Committee, the lake’s primary conservation organization. The owls were hard to spot at times, unless they attracted the attention of the local Common Ravens, whose raucous mobbing calls would give away their location.
None of these hole-nesters restrict themselves to tufa, of course; they nest here because they’re adaptable birds that can adjust to a variety of habitat structures. Whether they need a perch to sing from, a cavity to breed or roost in, or a good lookout spot from which to hunt — a tufa tower fits the bill. The Violet-green Swallow epitomizes these easy-to-please species. Elsewhere in its breeding range, it might breed in a rock crevice, a hole in a dirt bank, columnar cactus, or building, or even in a disused Cliff Swallow nest, as well as the obvious tree hole or nest box.
Osprey first nested at Mono Lake in 1985, but it took five years before they successfully raised young. Since then, the number of active nests has risen to a high of eight in 2010, all of them situated atop offshore tufa towers scattered around the lake. That year, a record 10 young were raised; each one was provisioned with fish that their hard-working parents had to catch elsewhere.
Lisa Fields, an environmental scientist with the Sierra District of California State Parks, has studied Mono Lake’s Osprey population since 2004. She tells me that the birds sometimes catch fish in nearby creeks, but many commute 8-10 miles each way to freshwater lakes such as June Lake or Grant Lake, carrying their catch back to their young.
Surely, a 20-mile round trip undertaken several times daily in the peak of the breeding season must put the birds at a reproductive disadvantage compared with Osprey breeding near freshwater lakes where fish are only a swoop away.
Quite the contrary, according to Fields, whose study area includes freshwater lakes as far north as Lake Tahoe, about 80 miles to the northwest:
“Even though they are traveling farther for food than Osprey that nest elsewhere,” she says, “the Osprey nesting success at Mono Lake is overall slightly greater than at Lake Tahoe, where we annually monitor nesting success following the same protocol.”
A big plus
She explains that one big plus at Mono Lake is that the tufa nests are over open water, safe from ground-dwelling predators (a major source of Osprey breeding failure). Furthermore, human disturbance is minimized; boaters must keep 200 yards away from any active Osprey nest. And compared with a tree, she adds, a tufa tower is a more stable nest location since it doesn’t sway in the wind.
So convenient and safe are the stick nests that they are sometimes taken over by a surprising culprit: the Canada Goose. The geese arrive first in spring — managing to alight in a small space on a 15- to 20-foot-tall offshore tower without crash-landing on their eggs — and often boldly defend the nest against the later-returning Osprey. Sometimes the ousted birds start building elsewhere on the lake, or they simply wait to reclaim the nest after the geese finish with it. Late Osprey nesting can be a problem: Fields recalls that one pair’s young fledged so late in September that the adults had to hold off migration to finish rearing them.
Besides offering nest sites, tufa plays a variety of other roles. Sagebrush-nesting birds such as Green-tailed Towhees and Sage Thrashers sing from tufa perches when their territories border on a grove. I’ve noticed Say’s Phoebe, Loggerhead Shrike, and, occasionally, American Kestrel perching on the craggy spires keeping a lookout for prey. Spotted Towhee, House Finch, and Brewer’s Blackbird use the towers to check that the coast is clear before hopping down to drink or bathe in freshwater springs along the lakeshore. And away from the nest, each Osprey has a favorite tufa perch on which it rests or consumes its fish. Being whitish rock, tufa reflects a lot of solar radiation, making it the perfect spot for sunbathing on a chilly morning. I’ve often seen Song Sparrows, Violet-green Swallows, and Mourning Doves warming up in the sun.
One surprise was the Northern Flicker that I watched two mornings in a row as it basked on top of a tufa tower. What had attracted it to this treeless spot? Although flickers are the most flexible of our woodpeckers in terms of habitat use, especially in the non-breeding season, my sightings were in early summer. Maybe the flicker had roosted overnight in a tufa hole. Perhaps it was even checking out possible nest sites.
On the northwestern side of the lake lies Mono County Park, where tufa formations are found in surroundings quite different from the sagebrush of the south shore. I tag along on one of the morning birdwalks led there each weekend in spring and summer by ranger Dave Marquart. An interpretive specialist with the Mono Lake Tufa State Natural Reserve and 29-year resident of the area, he’s a goldmine of information about the local birds. We head toward the lake past the park’s cottonwood-lined lawn, where we delight in a colorful male Bullock’s Oriole, then onto a wooden boardwalk that winds through dense stands of shrub willow, home to nesting Yellow Warblers.
Suddenly, the habitat opens up, and we find ourselves in the marshy delta of a small creek emptying into the lake. Here tufa towers stand stranded amid the wetland vegetation. Marquart points out a female Brewer’s Blackbird snug in her nest, barely visible in a tufa crevice. To our growing list of tufa birds, he adds Red-winged and Yellow-headed Blackbirds, Northern Harrier, and Great Blue Heron, all of which perch on towers. From overhead comes the winnowing of a Wilson’s Snipe making a courtship flight. And, yes, Marquart tells me, snipe benefit from tufa, too. The towers in the marsh make fine perches from which the shorebirds give their territorial calls before taking to the air to display.
A coordinated, glittering ballet
It’s midsummer, and I’m in a canoe looking for a good spot to photograph Wilson’s Phalaropes. My jaw drops when a flock suddenly takes flight en masse and wheels across the water in a tightly coordinated, glittering ballet. Mono Lake is a major refueling station for phalaropes on their southerly migration. By late summer, as many as 140,000 Wilson’s, along with smaller numbers of Red-neckeds, will sojourn here.
The phalarope flock returns, swirling past me to join others amid a large tufa grove just offshore, in a spot where I’d noticed them several mornings in a row. As my paddling companion and I nose our canoe in among the tufa spires, we’re struck by the numbers of phalaropes clustered on the rocks, resting and preening, while still more bob around on the water.
Did they roost here overnight because the tufa towers offered shelter from the wind? Maybe. Cornell biologist David Winkler (“Wink” to those who know him) has studied Mono Lake’s ecology, especially its California Gulls, for many years. He suggests another reason: food.
He explains that submerged tufa blocks are pupation sites for alkali flies, providing a solid surface to which the aquatic larvae attach as they make the transition to pupae en route to adulthood. Early morning brings a spike in adult fly emergence, so phalaropes that concentrate near tufa have a ready source of breakfast food, lots of protein-rich flies to be picked off the water’s surface.
Furthermore, Wink continues, the pupae themselves get dislodged during strong winds (something for which Mono Lake is famous). In this case, phalaropes use the spinning foraging method for which they’re best known. Swimming in tight circles in the water, each bird produces a miniature vortex that brings the pupae to the surface.
Conserving Mono Lake
The Mono Lake Committee is a membership-based conservation organization located in Lee Vining, a small town located just west of Mono Lake.
Since 1978, the group has employed litigation, legislation, cooperation, and most important, public support to protect Mono Lake from excessive water diversions to Los Angeles.
Visitors will find a well-staffed information center and bookstore, summer canoe tours, educational programs, and restrooms. Open year-round.
And the food chain doesn’t end there. Bartshé Miller, the education director at the Mono Lake Committee, describes his most memorable tufa-bird moment: watching a Peregrine Falcon devour a phalarope while perched on top of an offshore tufa tower — an ironic twist, given tufa’s role as an alkali-fly buffet for the shorebirds.
We have a far greater appreciation for Mono Lake’s importance to birds and a deeper understanding of its ecosystem than when Mark Twain called it a “solemn, silent, sail-less sea — this lonely tenant of the loneliest spot on earth.”
The area’s a lot easier for today’s birders to visit, too. So enjoy the grand vista of the lake with its keening flocks of gulls, its mysterious tufa groves, and the dramatic mountains beyond. Then take your time to look closer at those rocky spires. Let the marvelous forest without trees reveal its avian secrets to you.
I bet Mark Twain would have thought differently if he’d been a birder!
Marie Read is a wildlife photographer and a longtime contributor to BirdWatching. She is the author of the book Secret Lives of Common Birds (Houghton Mifflin, 2005) and the co-author, with Lang Elliott, of the ebook Music of the Birds, Vol. 1. She wrote about photographing a Black Tern colony in our June 2010 issue.