LITHOSOLS AND THEIR SPRING BEAUTY

In the Miocene, about 17 million years ago, great lava flows spread across the interior of the Pacific Northwest, year after year and flow after flow, reaching depths of 6000 feet in some places. As the molten rock cooled, it left very extensive areas of basalt. Some of these rocky areas remain as cliffs, too steep to support soil. In the flatter areas, breakdown of the bedrock produces shallow volcanic soils supporting steppe and shrub-steppe habitats.

Where the soil remains shallow and rocky, there is a rich and diverse plant community, often dominated by scabland sagebrush (Artemisia rigida) and grasses. Even though they remain hot and dry for much of the year, in the spring these lithosols come alive with wildflowers, as do the sandy soils around them dominated by big sagebrush (Artemisia tridentata).

Two of the most showy lithosol species are Simpson’s hedgehog cactus (Pediocactus simpsonii) and bitterroot (Lewisia rediviva). Both of them can be locally abundant on rocky soils in the Northwest interior, adding splashes of pink or red to a landscape that features all the flower colors of the rainbow.

The cactus is typical of its group, with a deep taproot that gathers limited water and nutrients, a succulent stem protected from herbivores by fierce spines, and no leaves. The showy flowers are produced in spring when the bees that pollinate them are most likely to be active in this hot, dry environment. Many other small insects feed on the pollen and/or nectar but are probably not effective pollinators.

Bitterroot is stemless and leafless, the clumps of flowers growing up from a fleshy taproot that anchors the plant firmly among the rocks. This may be another strategy to avoid herbivory—put most energy into reproduction without supporting photosynthetic leaves that are attractive to plant-eaters. The only thing edible on the plant, the succulent root system, is well protected in the soil, but Native Americans ate it as an occasional delicacy. During the Lewis and Clark Expedition, Meriwether Lewis ate bitterroot and brought back specimens; he was honored by its generic name.

Bitterroot survives without apparent chlorophyll by utilizing CAM (Crassulacean Acid Metabolism) photosynthesis, in which leaf stomata open only at night, when water loss is reduced, to take up CO₂ that is then released the next day and converted into sugars by chemical pathways that do require light energy.

These flowers and their habitats are best seen in April and May. As the air heats and the soil dries, this large part of the Columbia Basin seems to retreat back into dormancy.

Dennis Paulson

BLACK-BELLIED PLOVERS - NOT ALWAYS BLACK-BELLIED

Many of the common names given to organisms are descriptive, but sometimes the description is valid for only some of the individuals. Take the Black-bellied Plover (Pluvialis squatarola), for example. Forgetting for a moment that the undertail coverts, which some might take as part of the belly, are snow-white, the males of this species have lustrous black bellies, and in fact almost entirely black underparts.

Female Black-bellied are similar to males but duller above, more brownish in comparison with the males' more spangled black and white look. They also may have some white intermixed with the black of the underparts. Nevertheless, they are clearly black-bellied Black-bellied.

However, this is true for only half the year; the underparts are black only in alternate (breeding) plumage, from April to August or September. For the rest of the year, in basic (nonbreeding) plumage, the underparts of both sexes look entirely white at a distance; brown streaks and bars are apparent at closer range. the upperparts are light brown, with slightly darker markings at this time.

Furthermore, most birds don't get black underparts until they are at least two years old. Juveniles fresh off the Arctic breeding grounds look much like basic-plumaged adults but are a bit darker above, with light markings on the feathers. These birds get increasingly faded and worn during their first winter and spring, then molt into a plumage much like the adults' basic plumage for their second year of life. In their second spring, their plumage is identical to that of the adults.

Even more fun, if confusion can be fun, it takes the birds about a month to molt between these plumages, so there are black-and-white-bellied plovers present during one-sixth of the year. This is mostly in March and September, but not all individuals molt on the same schedule, so these intermediate birds can be present at other times.

One of the most interesting aspects of the plumages of this species is the sexual dimorphism. Males conduct aerial displays on the breeding grounds, so it is understandable why they are black below to be more visible against the sky. But why then should females share the color? They are duller than males, but their plumage change at breeding time is still quite substantial. Perhaps different plumages just function for sex recognition, as they do in so many birds, but then why aren't all shorebirds sexually dimorphic?

Black-bellied Plovers are abundant migrants on the Washington coast and also winter in some numbers, both on the outer coast and in protected estuaries in the Strait of Juan de Fuca and Puget Sound. They are usually in flocks, and an observer with a good spotting scope can study all of these plumages at different times of year.

Dennis Paulson

COLONY-NESTING SWALLOWS

Finally, a swallow that nests only where it is supposed to. Bank Swallows (Riparia riparia) nest in sand banks, usually in colonies, sometimes in very large colonies. These vertical or near-vertical banks are typically along rivers but may be in dry areas as well, even sand quarries and piles of sand thrown up by construction and then abandoned. Thus like all other swallows, their nest sites can be augmented by human activities.

Bank Swallows are common breeding birds across northern North America. They winter mostly in South America and are common migrants in between. Breeding also all across Eurasia, they are one of the most widely distributed songbirds (like the Barn Swallow).

Bank Swallow colonies range from just a few birds to up to 1,500 active nests. The burrows can be quite near to one another but stretch for hundreds of feet along a bank.

At new sites, males begin excavating burrows as pairs are forming. A male with a burrow will fly after a female and attempt to attract her to the burrow, where he lands at the opening. If she is interested, she will accompany him inside, where copulation takes place.

Although Bank Swallows are socially monogamous, males constantly attempt extra-pair copulations. When a female leaves the nest, her mate often flies right on her tail to keep other males from attempted mating, and this is successful most of the time. These flights, usually with three or more birds, can be seen constantly around colonies early in the season. One researcher found that males could actually distinguish heavier females, apparently receptive to breeding, and preferentially chase them.

The burrow is dug with beak, feet and wings. The excavation takes about 4 or 5 days, and then the female begins to gather material for the nest at the end of the burrow, taking another few days. The four or five eggs are laid one each day, and incubation, mostly by the female, ensues for about two weeks after the last egg is laid.

Both adults gather food for the brood, and it has been estimated they bring about 60 prey items/visit and feed the entire brood about 7,000 insects in total. If you're worried about bugs, it would seem to pay to live near a Bank Swallow colony. 500 nests x 7,000 insects = 3.5 million fewer insects in three weeks! But what would the Society for the Prevention of Cruelty to Insects say about that?

The young leave the nest at about three weeks of age and gather in communal perching areas, where they are fed for up to another week. Adults recognize their own young vocally among the clamoring of many individuals, much like the case in a tern or gull or penguin colony.

Dennis Paulson

A HERONRY TO WATCH

I recently learned of a Great Blue Heron nesting colony in Kenmore, Washington, only 10 minutes from my house. But the colony, at the edge of a park and ride lot, was at some distance from the vantage point, so it would take a long telephoto to get good photos of them. So I went up there with my new Canon PowerShot SX50 HS camera with its 50x zoom lens.

The colony has about 50 obvious nests, although not that many pairs were present during my two morning visits. Activity levels were low, consisting mostly of birds flying out to gather additional nesting material. But that activity had birds flying in with twigs and branches often enough to be photogenic, and a few birds even landed in the nearby Douglas-firs to tug on live branches. Otherwise the herons stood quietly at their nests.

The nests are reused for many years, birds sometimes changing nests between years. I don't know what happens when a bird chooses a nest and its previous owner returns soon thereafter! You do see sparring in the colonies.

Males procure the nest material and females remain at the nest to put it in place, and I saw numerous such exchanges. The sexes can't be distinguished, so all one can do is make assumptions that are supported by previous research. The first eggs should be laid in March, according to the literature, so presumably in early April some of the birds had clutches already. Indeed, some birds were flat on the nest, presumably incubating.

Copulation takes place both before and during egg laying, and one such act was observed during a two-hour visit. Both sexes incubate, alternating during the 24-hour period (females more at night), and the total incubation period is about 27 days. Hatching is asynchonous, as incubation begins when the first egg is laid, so the youngest bird may be several days younger than the oldest.

Once the eggs hatch, the young remain in the nest 7-8 weeks, so there will be plenty of photo opportunities to come. One thing I will be looking for is siblicide, where a young bird attacks and actually kills a nestmate. The prey is often dropped into the nest in the midst of the young, and especially when the items are small, the young are more likely to fight over them. When food is limited, it makes evolutionary sense for the brood to be reduced, so the remaining young will have sufficient food to grow and fledge.

Great Blue Herons have had a hard time of it in the Seattle area, as Bald Eagles, which have increased tremendously in recent years, visit their colonies as they are forming and take eggs, young or adults if they can catch them. A few such disturbances will usually cause the adults to desert the colony. They can either move elsewhere or just fail to breed. The next season they try again at another spot, and there is a fair likelihood that eagles will find that spot as well.

I keep hoping that the eagles won't destroy this colony. It has been established for a decade at least, so there is hope. On occasion, herons nest very near an eagle nest, and apparently that keeps other eagles away from the heron colony. I don't know why the resident eagle doesn't take its toll.

Dennis Paulson

FROM CAVES TO BARNS

Just as Cliff Swallows adjusted to the push of humans (and their structures) across North America, so did Barn Swallows (Hirundo rustica). This species, virtually worldwide in distribution, has been known to be associated with humans for over 2,000 years in Europe. But it may have had a limited breeding range in North America, thought to be primarily in the mouths of caves. Needless to say, these were very limited nesting habitats.

Nowadays, however, Barn Swallows nest throughout southern Canada and the United States, excepting the southwestern deserts and peninsular Florida. They are so successful because they nest on just about any structure provided by humans—houses, barns, overpasses, bridges, even small culverts. Drive across country, and there will be Barn Swallows nesting under just about every bridge you cross. But look for them in vain on natural substrates!

Like Cliff Swallows, Barn Swallows utilize mud for the foundation of their nest, and they gather it in the same way from the water's edge, although singly rather than in groups. The mud walls are usually about an inch thick. Rather than retort-shaped, their nest is cup-shaped, so the young spend their time looking out at a broader world, although still constricted by the ceiling of their nest site.

Some people think having Barn Swallows nest on their house brings good luck. Others are turned off by the mess they make. The parents collect fecal sacs from the nest for the first 12 days after the eggs hatch, but after that the young just stick their rear end over the edge and let fly. That's a lot of incremental excrement in the subsequent 8 days before they fledge.

With clutch sizes averaging around five eggs, the nest of a Barn Swallow fills up fairly rapidly with growing young, so the young need to leave the nest as soon as they can fly. The adults "park" them on nearby tree branches or fence wires and feed them for up to a week more. Then they are on their own.

Barn Swallows have been much studied in Europe, especially their mating behavior and sexual selection. Birds of both sexes with longer and more symmetrical tails have greater reproductive success, parental effort, annual survival, ability to withstand parasites, immunocompetence, and other measures of fitness. Thus an individual has a fairly good chance of judging the true quality of a prospective mate.

So Barn Swallows nested in caves, and Cliff Swallows nest on barns. Care to guess where Cave Swallows nest?

Dennis Paulson

SWALLOWS ON CLIFFS AND BRIDGES

In this era of human domination of the world, a successful animal or plant may be defined as one that has adapted in some way to human presence, even benefits by it.

Cliff Swallows (Petrochelidon pyrrhonota) may be one of those animals. They build mud nests that they attach to vertical substrates overhung sufficiently to provide shelter from rain. They were able to evolve this nesting habit because of the widespread abundance of rocky canyons in western North America. Cliff Swallows are still abundant in that habitat.

The species was probably restricted to western canyonlands until barns and bridges built by settlers advancing across the Great Plains a few hundred years ago provided nesting substrates comparable to those provided by nature. The birds took advantage of these newly furnished nest sites and moved eastward, encountering more and more artificial cliffs and canyons as they went. Today they nest through much of the East as well, on buildings but mostly under big bridges across rivers.

Cliff Swallows are among the most social of land birds, with colonies of up to 3,500 pairs reported. Their closely packed nests extend over lengthy sections of cliff walls and can fill up the sides of barns and bridges wherever there is overhead shelter. Because they nest so densely, they are more subject than most birds to ectoparasites, especially swallow bugs and ticks, in their nests. Because of high chick mortality from high densities of these parasites, whole colonies are sometimes abandoned and the birds settle elsewhere.

Their other "enemies" include House Sparrows, which take over Cliff Swallow nests and even kill their young, and automobiles, which take their toll of birds nesting adjacent to roads. Recent research has shown that Cliff Swallows in such situations are evolving shorter wings, making them more maneuverable and less likely to be struck down by a car.

Swallow nests are somewhat messy, because after about a week old, the young defecate off the edge of the nest. A pile of poop can build up rapidly below the nest, sometimes even blocking the entrance! Swallows that nest where people live and work aren't always well loved because of this, and whole colonies are sometimes removed from highway overpasses because of the mess they make. Living around humans brings mixed benefits.

Dennis Paulson

SWALLOWS LOVE PEOPLE, AND WE SHOULD LOVE THEM BACK!

For some reason, purely by accident, it turns out that many of the world's swallow species now nest primarily in structures built by humans.

One of these species is the Violet-green Swallow (Tachycineta thalassina). Its breeding distribution lies mostly in extensive mountain ranges of the West. Originally the birds must have nested in natural crevices in trees and cliffs as well as holes excavated by woodpeckers, chickadees or nuthatches. Some of the swallows still nest in such places, and they remain common as montane birds.

However, fast forward to the early Twenty-first Century, and one of the best places to find Violet-greens is in our cities and suburbs. When I first moved to Seattle in 1968, there were nesting swallows all over the city. Some of them nested in houses, even more in commercial buildings, for example all over the University District. As I drove and walked around, I saw them all over the place. Any little opening into a building often had a pair of these beautiful birds nesting in it.

Nowadays they are still present in Seattle, but in reduced numbers. I have heard of no place where they are increasing and many neighborhoods from which they have disappeared. When I moved into a house in Maple Leaf, a wooded section of town, in 1991, I could dependably see and hear Violet-greens overhead on a daily basis each summer. A decade later, they were scarcely to be seen, and by 2010, they had disappeared from former haunts in many parts of the city.

A possible cause of this decline is the tidying up of our human habitat. The crevices in buildings that are used by Violet-greens and some other urban/suburban birds are presumably decreasing in number as people find them and seal them up. Who could argue with someone who wants to keep rats and mice out of their house!

Perhaps more significant, all swallows are aerial insectivores. In other words, their diet consists almost entirely of flying insects. Because of habitat destruction and pollution, primarily the use of insecticides on so many of our crops, we have brought about a widespread decline in such insects. Violet-green Swallows are decreasing generally as breeding birds in the Pacific states, although Rocky Mountain populations are doing well.

Even with local declines, swallows are thankfully still among our most common and visible birds.

Dennis Paulson