Pelican-Watching in San Francisco

Fog over Golden Gate Bridge, copyright 2009 Christine Petersen

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I’m standing on the coastal trail just west of San Francisco’s Golden Gate. Fog obscures most of the famed structure, though now and then a blazing patch of red is revealed as a gust of wind pushes aside a corner of the low-lying cloud. My goofy grin and slightly elevated heart rate are reminiscent of the symptoms I used to experience on a promising second date. I indulge the emotions, for they are familiar and sweet. In a way, this city is like a long-lost lover. Although my new sweetheart—Minnesota—is also full of charms, some part of my heart will always remain here.

The Golden Gate Bridge is an iconic structure known around the world, and I never tire of this view. Yet there are countless more delights to be found across the landscape leading into this narrow, rocky passageway. Craggy cliffs, hidden beaches, and patches of woodland are revealed to those who explore the ecotone where land meets sea. Every stretch of the San Francisco coastline offers breathtaking views, and crowds are often minimal.

Brown pelicans, copyright 2009 Christine Petersen

If asked to choose a mascot to represent this landscape, I’d find few rivals worthy of the brown pelican. To the inexperienced observer this might seem an odd choice. Weighing up to eight pounds, with a wingspan greater than 7 feet and a curving neck that culminates in an improbably long, hooked bill, brown pelicans look like make-believe creatures from a child’s storybook: gangly, disproportionate, and comical. Yet airborne pelicans are the epitome of grace—flapping with slow ease; making fast, steep plunges in pursuit of fish; flying in long, curving formations that follow the breaking lines of waves.

In the 1820s and ’30s, while traveling across the nation to study and paint avifauna, John James Audubon had many opportunities to observe brown pelicans. He found them to be “one of the most interesting of our American birds,” and had this to say about pelicans on the wing.

“The flight of the Brown Pelican, though to appearance heavy, is remarkably well sustained, that bird being able not only to remain many hours at a time on wing, but also to mount to a great height in the air to perform its beautiful evolutions. Their ordinary manner of proceeding, either when single or in flocks, is by easy flappings and sailings alternating at distances of from twenty to thirty yards, when they glide along with great speed. They move in an undulated line, passing at one time high, at another low, over the water or land, for they do not deviate from their course on coming upon a key or a point of land. When the waves run high, you may see them “troughing,” as the sailors say, or directing their course along the hollows. While on wing they draw in their head between their shoulders, stretch out their broad webbed feet to their whole extent, and proceed in perfect silence.”

Audubon was not alone in his appreciation of pelicans. Women of the nineteenth and early 20th centuries considered it the height of fashion to festoon their hats with feathers. Many bird species, including pelicans, were hunted to fulfill orders for the millinery trade. Pelicans were vulnerable to other threats, as well, including egg collection and hunting by fishermen who considered pelicans to be their competitors for fish.

Passage of the Migratory Bird Treaty Act in 1918 curtailed these forms of collection. Yet surveys in the 1960s showed that brown pelicans had all but disappeared from California. Only a small nesting population remained on one of the Channel Islands, off the coast near Ventura. The birds’ killer this time was almost invisible—carried on the wind and in water, hidden in the tissues of fish which the pelicans consumed. It was dichlorodiphenyl-trichloroethane—better known as DDT.

First synthesized in 1873, DDT was virtually forgotten until the 1930s when Swiss chemist Paul Müller discovered its effectiveness as an insecticide. In World War II DDT was applied to protect Allied troops from diseases spread by mosquitoes and lice. Dr. Müller won the Nobel Prize in Chemistry for his work, which was seen as a life-saving advancement in the fight against insect-borne diseases. After the war, and through the 1960s, DDT was widely used in agriculture and advertised as a safe treatment for household pests. Human health risks from the chemical were not immediately apparent, but evidence of environmental hazards soon began to mount. DDT has a long life in the environment, as do the products of its chemical breakdown, DDE and DDD. These chlorinated hydrocarbon chemicals move up the food chain from microscopic organisms to fish and thus to pelicans and other piscivorous birds. They accumulate in fatty tissues over time, so that larger and longer-lived animals—such as pelicans—accumulate proportionately greater chemical loads than smaller, shorter-lived species. Humans are also affected by this process, called biomagnification.

Biologist Rachel Carson reported the effects of DDT in her ground-breaking book, Silent Spring, published in 1962. She wrote about the sudden decline among populations of American robins and other ground-feeding birds after DDT was used to treat Dutch elm disease in many communities during the 1950s. Direct exposure to the insecticide caused many of these small birds to die immediately. But Carson was also concerned about long-term effects. She noted that for many years DDT had been sprayed along the Atlantic coast to combat marsh mosquitoes, and knew the effects on marine species, and reported in Silent Spring that “Fishes and crabs were killed in enormous numbers. Laboratory analyses of their tissues revealed high concentrations of DDT—as much as 46 parts per million.”

Carson knew that fish make up a significant part of the bald eagle’s diet, and extrapolated that by virtue of their long lifespan eagles and other fish-eating birds would store proportionately larger concentrations of DDT than small, shorter-lived marine animals. As a consequence, she wrote, “they are less and less able to produce young and to preserve the continuity of their race. (Carson 122)” Declines in the rate of bald eagle reproduction had already been observed. Carson felt certain DDT was to blame, though she could not explain how the chemical caused physiological damage.

Research in the late 1960s revealed the mechanism by which DDT affects bird reproduction. Calcium carbonate is the primary mineral component of eggshells, and serves as a crucial source of calcium for embryonic skeletal development. Calcium carbonate is secreted by the bird’s shell glands during egg formation. It is apparently blocked by the presence of DDE, a chemical that results from the metabolic breakdown of DDT. By the late 1960s, brown pelicans nationwide produced eggshells that were, on average, 20 percent thinner than in years prior to DDT use. Some populations of California brown pelicans were found to have shells only half as thick as normal. Brown pelicans build a stick nest on the ground or in a tree. The male and female of each pair take turns on nest duty, sitting on the edge of the platform and incubating the eggs beneath large, webbed feet. DDE-thinned eggs were delicate and susceptible to cracking under pressure, making pelican reproduction an abysmal failure.

Brown pelicans might have gone the way of their ancient dinosaurian kin. But thanks to a 1972 ban on DDT and protections under the U.S. Endangered Species Act, extinction of the species was averted. The intervening decades have seen a slow but sustainable recovery of brown pelican populations, significant enough to lead the U.S. Fish and Wildlife Service in 2008 to propose delisting of all brown pelican populations from Endangered Species Act protections. That process was finalized on 17 November 2009.

On your next visit to San Francisco, tear your eyes from that big, beautiful bridge for just a few minutes. Watch instead the narrow valleys between cresting whitecaps, and look to the sky at hilltop level. Better yet, wend your way westward and south through city neighborhoods to China Beach, Lands End, or Fort Funston. It won’t be long before an undulating line of pelicans drifts in, skimming silently across the water or plunging-and-plundering in search of fish. Don’t be embarrassed if your heart starts to beat a little faster. It’s appropriate to be thrilled when you witness a miracle.

Golden Gate Bridge in clearing fog, copyright 2009 Christine Petersen


On the Wing

(repost from August 29, 2009 on Intelligence with the Earth)

For weeks the yard has hummed (yes, that’s a pun) with ruby-throated hummingbirds. Throughout the day males, females, and juveniles zipped between feeders, flowers, perches, and hideouts. The chase was always on, and tiny birds whizzed past us, in pursuit or retreat, whenever we ventured into the yard. Actual fights between hummingbirds are apparently uncommon, though they seem to expend endless energy keeping each other from nectar sources.

In Birds of America, John James Audubon described this habit. “They are quarrelsome,” he wrote, “and have frequent battles in the air, especially the male birds. Should one be feeding on a flower, and another approach it, they are both immediately seen to rise in the air, twittering and twirling in a spiral manner until out of sight.”

A few years back I read an article about hummingbirds in Smithsonianmagazine. The author commented how fortunate it is that hummingbirds are not as large as crows. That image has remained in my mind. The ruby-throated hummingbird’s bill accounts for one-fifth of its body length. Expand the hummer to crow-size and its bill would be more than 10 centimeters long. The pileated woodpecker provides a useful model. This bird is of comparable size to the American crow, but its bill is elongated like Pinocchio’s nose after he’s told a series of whoppers. Rather than being chisel-shaped like the woodpecker’s, however, a hummingbird’s bill is rapier-thin and sharp. Our Superhummer would be a Musketeer among birds. Mon dieu!

Pileated WoodpeckerThe total length of this adult male pileated woodpecker may be close to half a meter. Imagine a hummingbird with those proportions!

The dogfights haven’t ended among our remaining hummingbirds, but a sudden decline in population density has reduced the intensity of these interactions. Three days ago I noticed the absence of any males in the yard. Male ruby-throated hummingbirds always leave in August, heading gradually toward the Gulf Coast. Females and juveniles remain somewhat longer, into October if conditions permit. During that time they may share the yard with dark-eyed juncos and pine siskins. These songbirds also travel south after nesting, but because they eat seed (among other reasons) their migration from Canada may end right here in central Minnesota.

I have often wondered whether the same birds somehow return year after year to our yard. Site fidelity is an aspect of migration that is of concern to biologists. But it can be difficult to prove. Banding studies  shed some light on the question for ornithologists. Captured birds are fitted with tiny metal leg bands. Each band is stamped with a unique number, and may also carry a discrete color pattern. Bands allow individual birds to be identified upon sighting or recapture. At Hilton Pond Center in York, South Carolina, biologists banded 3,614 ruby-throated hummingbirds between 1984 and 2007. More than 430 of these birds came back to Hilton Pond the spring after banding. A couple returned several years in a row. Amazing information can be obtained from such simple techniques, but they require funding, staff, and infinite patience.

Hummingbird resting on raingaugeAudubon wasn’t terribly scientific when he described the ruby-throated hummingbird as a “glittering fragment of the rainbow”—but he was utterly accurate. I watch a little female perch atop our rain gauge between bouts of feeding and chasing. Her belly is rotund with nectar and she looks perfectly fit. This wee gem has a long journey ahead. I don’t know if she’ll make it back to this yard in the spring. But we’ll keep the nectar flowing, just in case.

Afternoon Delight

(repost from August 22, 2009 on Intelligence with the Earth)

Rain or shine, subzero or sweltering, around 2:00 p.m. each weekday some internal alarm prompts me from my chair toward the kitchen. Although this is a short migration, it involves a radical shift in habitat. My office is tucked on the north side of the house and flanked by an Entish pin oak tree. Those with an aversion to low light might find the room too solemn, but I enjoy its cool, shady attitude. It feels as though I have my own little bower among the branches of the house. I work here for hours at a stretch, cocooned in a silence that is conducive to concentration but not oppressive. There’s a palpable shift in my awareness when I enter the kitchen, which is flooded with light throughout the day and in all seasons. Wide windows on its east and west walls, and exposure from the south through an adjoining mudroom, make the kitchen open and lively. This is the real heart of our home. Even a quick infusion of its light, color, and space gives me just the dose of energy I need to remain focused through the afternoon. A cup of tea doesn’t hurt, either.

Teatime is not a fancy affair. I don’t prepare food, and never even sit down. But there is a ritual associated with this break. I take down two mugs from the cabinet. One is chosen randomly, though it can’t be too large. The other is my favorite mug, made of thick, cream-colored ceramic with a handle that looks like a twisted twig. Across its surface are painted two of the birds that commonly appear in our yard: the Baltimore oriole and the blue jay. The style of painting looks somehow old-fashioned, like it belongs in a dusty field guide you might find tucked away in your grandparents’ library. I choose a bag of good black tea to go in the first mug. Something fruity or spicy goes in mine—but no caffeine allowed. Finally I fill the burnished metal teakettle and place it on the burner. Now begins my favorite part of the routine. Until the kettle sings I have a few free moments, with nothing more important to do than watch.

Much as I love spending time outside, it’s no exaggeration to say that I could gaze out the kitchen windows for a whole day. The east window provides a view of the hillside meadow and lake that comprise our “backyard.” We don’t live in isolation; I can see houses on the far lakeshore and, at night, lights from the highway beyond. Yet this is something more than the typical sprawling suburban property. It’s just on the edge of wild. We routinely observe loons on the lake and bald eagles overhead. The tame and familiar wildlife—deer, raccoons, and woodchucks—are occasionally joined by minks, coyotes, and huge flocks of turkeys.

Front Yard The expansive lakeview is always tempting, yet today I’m drawn to the smaller, paired windows over the kitchen sink. There’s no grand vista framed here—just the front yard. It’s a yard like many others in our area. There’s a deck and a small, screened cabin where we sometimes take our meals. Several flower patches and bird feeders are scattered across the open space. A big, hundred-year-old boxelder tree throws shade over the grass where my young son plays. A tidy orchard gives fruit of three varieties, and a white picket fence defines part of the property line. This view is appealing not so much for its scale as for its intimacy and the relatively invisibility offered by a reflective window pane. Wildlife—particularly birds—come so close to the windows that it’s breathtaking. At this moment a downy woodpecker clings to a suet feeder half a meter from my face, but the bird is heedless of my presence.  Downy Woodpecker on suet feeder

The woodpecker circumambulates the birchbark feeder in search of a good toehold. I lean over the sink to carefully open the opposite window. Moments later a distinctive sound reaches my ears. It’s the low, whirring drone made as a hummingbird’s wings beat the air more than 50 times per second. A male ruby-throated hummingbird rockets in from the east side of the house. It clears the suet feeder—and my corner window—by a narrow margin of safety. The emerald green bird’s destination is the nectar feeder that hangs from a pole in the deckside flower garden. It hovers before the feeder, dipping down to feed then popping back nervously to look around. Suddenly the hummingbird pivots toward me. The feathers of its gorget (throat)—which had at first appeared black—now flame metallic red. This burst of iridescence occurs when sunlight reflects off microscopic air bubbles located inside each barb of the gorget feathers. (If you’ve never examined a feather closely, there is a long, stiff central shaft with many thin “branches” extending off the sides. These branches are the barbs.) Iridescence is only visible when the bird and observer are face-to-face. The flash of color fades when either party changes angle relative to the sun. And it doesn’t take long for this to happen. The hummingbird holds its position barely long enough for me to complete a full breath cycle. It emits a rapid series of high-pitched chitters that seem out of proportion to its size then lunges forward in a wide, arcing sweep over the deck. I suspect the source of the bird’s annoyance, but it takes a moment for me to locate it. Another male hummer has flown near the feeder.

Hovering male hummerMinnesota lies too far north to support hummingbirds year-round. Their presence is limited to the warmer months, when flowers are blooming and nectar supplies are ample. Even when food is readily available hummingbirds must conserve energy by entering a hibernation-like state called torpor for part of every day. A generalist feeding strategy also aids their survival. Rather than focusing on a narrow category of foods, they feed opportunistically on a variety of items. All hummers are known for their love of nectar, but ruby-throated hummingbirds are especially open-minded tipplers. Due to loss of habitat throughout their range, human-made nectar feeders are a crucial source of food. Where they can get it, however, these birds take nectar from any reddish, bell-shaped flowers large enough to accept their beaks. That includes everything from phlox and Monarda (aka beebalm and wild bergamot) to morning-glory and honeysuckle. In our yard, ruby-throated hummingbirds also go for giant hyssop. The pale lavender flowers of this mint species are tiny, but they form tall inflorescences atop stems that tower over my head. Ruby-throated hummingbirds are known to follow sapsuckers in spring. The sapsuckers drill small, round wells in the bark of maple trees to release sap, and hummingbirds take advantage of the free resource. Throughout the year they also seek small insects and spiders, capturing prey mid-flight or scooping it off surfaces.

Hummingbirds spend at most four months in Minnesota. They show up during the second or third week of May, depending on weather conditions here and along their migratory path from the south. I always try to have the nectar feeders out and waiting, for they a. It seems that a creature so slight must be tossed by the wind like cottonwood fluff. Hummingbirds appear to have turned this liability to an advantage in some circumstances. When possible they wait to fly with favorable tail winds, allowing the gusts to provide a push in the right direction during migration.

Juvenile male hummerTheir imperative here in the northlands is clear: establish a territory, build a nest, and raise a healthy brood of Lilliputian offspring. By early August the breeding season has ended and the birds begin to respond to different internal rhythms. Migrants from breeding populations in Canada and northern Minnesota now join our resident hummers. If mid-August seems a bit premature for migration, consider that by mid-October these wee creatures must cross the Gulf of Mexico to reach their winter ranges in the Yucatán Peninsula and Central America. The birds seem to focus on one goal in preparation for this long journey: getting fat. During the breeding season male ruby-throated hummingbirds have an average mass of 2.5 grams. Balance an American penny on the tip of your finger to get a sense of how insubstantial that mass is. Females can be up to 2 grams heavier—closer to the mass of a nickel. In less the two weeks, through a vigorous program of nectar sipping, a hummer may increase its body weight by 75 percent. No body builder ever took weight gain more seriously. At this time the birds engage in fast and furious territorial battles over access to feeders and flower patches. Females are as just as contentious as males. The bird I’m watching now probably nested in our yard, and is not eager to share resources at such a crucial time. I crane my neck to watch as he chases the interloper away, but the two miniscule green birds are immediately lost among the foliage.

Distracted by the hummingbird drama, I’m startled when the teakettle begins to sing. I pour the water and leave the cups to steep for the requisite three minutes. Delivery of my partner’s steaming tea is the last part of this afternoon ritual. It’s sometimes an excuse for conversation, but more often a simple gesture, a quick and quiet interlude in the midst of our mutual workdays. When I get back to the kitchen my herbal tea will require only a spoonful of honey to make it ready. Allowing myself a last glance out the window, I see that a mean, green flying machine is back at the nectar feeder. Whichever of the two male hummingbirds has prevailed, it wastes no time in savoring the sweetness of its prize. As I return to my quiet work habitat, that sweetness lingers in my mouth as well.