Larcenous lichens

A big tide-stranded log on the wetlands was studded with lots of little tufts of ‘moss’. It didn’t look a bit familiar to any of us, but I should have looked more closely… a couple of experts later let us know that those tufts are not moss at all. Rather, they are composed of one species of lichen growing on another species of lichen.

Juneau folks see lichens almost everywhere—they drape gracefully from tree branches, form crusts over bare soils, decorate tree bark, boulders, and cliffs with a variety of colors and designs. They can colonize roof shingles, long-abandoned clothing, foam insulation, and other un-natural substrates. And, we just learned, they can grow on each other, too!

Lichens are composite organisms, commonly consisting of a fungus with a green alga, but sometimes associated with a cyanobacterium, or even with both. A given species of algae or cyanobacteria may associate with different fungal partners.  A lichen develops its characteristic shape when the fungus associates with its partner; otherwise, the fungus exists just as a mass of filaments. Does it need the additional input of nutrients from the partners to develop that morphology and to produce spores? Occasionally, other organisms such as yeast (another type of fungus) and bacteria may join the association in some way.

These associations are generally thought to be mutualistic: the fungus provides housing as well as water and nutrients from the atmosphere and sometimes also the substrate, while the other partners provide carbohydrates (by photosynthesis) and cyanobacteria fix nitrogen from the air. In the nutrient exchange between partners, an alga or cyanobacterium is commonly destroyed, but the remaining ones reproduce fast enough to replace the destroyed ones.

Some lichens grow exclusively on other lichens; they are called ‘lichenicolous’ (meaning living on lichens). There are hundreds of species with this specialization, from a variety of evolutionary lineages. It is thought that most of these lichens are parasitic (the fungal partner is presumably the larcenous agent), but some may be pathogens or simply harmless co-habitants.

I had thought to write a whole essay about lichenicolous lichens and their fascinating way of life. I rapidly found out that the arcane taxonomy of unfamiliar names and terminology left me bewildered, so I must content myself with calling attention to an interesting phenomenon that was entirely new to me.

In the case of the tufts on the beach log, a species of Xanthoria was overgrowing a species of Physcia. (But in other regions, different species of Xanthoria may be colonized by a lichenicolous lichen, being the host instead of the invader).  Locally, some other lichen invades the spore-bearing structure of common leafy lichens called lettuce lung (Lobaria oregana) and lungwort (L. pulmonaria), making the structure black. Is the invader hijacking the spore-dispersal mechanism of the host?

Here are a few short stories:

–In a grove near the Boy Scout beach, a friend and I heard a strange, repeated sound. We finally located the source: a porcupine was slowly backing down a fairly tall spruce tree, mostly stepping on small dead branches but occasionally slithering a bit from step to step, moaning every few seconds. Finally it reached the ground, shook itself, and trundled off, still moaning.  Had it been sampling spruce needles near the top of the tree?

Northern Waterthrush. Photo by Bob Armstrong

–One sunshiny morning in mid-May, I happened to look out a window to my pond at just the right time, and there was a northern waterthrush, foraging along the edge. (Despite its common name, this little brown warbler is not a thrush.) I hadn’t seen one for years; later, I heard their loud song, over in the Dredge lake area. They are uncommon nesters here, usually making a cup-nest on the ground, in wooded areas near ponds, where they like to forage in the shallows.

–Later that day, on the lower part of the East Glacier trail, a little group of friends stopped to admire a fine display of small white flowers, several patches of it on a cliff. This species has the very silly common name of Sitka mist-maiden, but bears a more stately name of Romanzoffia sitchensis. It usually blooms a little later than the more famous purple mountain saxifrage, which was still blooming on some cliffs along the trail.

–At Eagle Beach, on one of those sunny days, we saw a nice variety of dabbling ducks, not many of each type, but all clustered in one area near the river. There were gadwalls, green-wing teal, blue-wing teal (not common here), American wigeon, mallards (of course), and a pair of northern shovelers. All these ducks feed on invertebrates and vegetation, often by tipping upside down to reach under the water. Shovelers, however, have an additional way of feeding with a very specialized, broad, flat bill. The relatively large bill is edged with a row of comb-like structures that the shoveler uses to catch small invertebrates and plankton as it sweeps its bill from side to side.

Thanks to Chiska Derr for consultation about larcenous lichens.

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Tree sparrows and bluebirds

In the early part of April, there were sometimes two dozen mallards on my mostly-icy home pond. There was one male who was not fully ‘dressed’—while all the other males in the group had long since acquired their glossy green heads, rusty chests, and so on, this one was only part-way into the typical breeding dress. Was he just a very late hatchling last fall, lagging in maturation, or did he have a metabolic deficiency of some sort?

By late April, the mallard mob had dispersed, leaving one pair in charge of the now-ice-free pond. The male was seriously aggressive toward a visiting solo male, defending both his female and, perhaps, the seed-fall from the feeder hanging over the water.

Out at Eagle Beach, a mixed crowd of six species of waterfowl moved offshore, as a gamboling puppy approached along the water line. A scattering of American pipits foraged over the tideflats, readily distinguished from other small, brown songbirds by their characteristic gait—they walk and run, rather than hop. At the edge of a mown grassy area, I found a mixed flock of juncos, both Oregon and slate-colored, and American tree sparrows. They were all scouring the turf for food and flitting hastily to the surrounding brush when startled. I hadn’t seen a tree sparrow for ages, so this was fun.

Tree sparrows nest way up north, on open tundra with scattered shrubs and thickets of willow, birch, or alder. The nest is usually on the ground, and the female incubates the eggs for about twelve days. Nestlings are fed by both parents and stay in the nest only about nine days, then hopping out to follow the adults on foot. Tended by the parents, they begin to fly when they are about two weeks old. Tree sparrows feed on the ground and also by hopping up to grab seeds from the seed-heads of low-growing plants. In season, they also feed in trees, to eat small berries. This species has not been very thoroughly studied, so there are lots of details to discover.

Through much of April, there were reports of migrating mountain bluebirds on their way north, seen now here, now there, and in some other place. I tried several times in several places to find them, but they continued to elude me. Then, the day after finding the tree sparrows, I strolled out toward the Boy Scout beach. In addition to seeing a fox sparrow, two Townsend’s solitaires, some Bonaparte’s gulls, and a flock of snow geese, I encountered two friends who were intently watching a patch of dead cow parsnip stalks and a few little spruces. They had found a male bluebird, which was foraging in classic bluebird style: watching from an elevated perch, just a few meters above the ground, then dropping down to the ground to pick up an insect and flying back up to an observation perch. Later, I spotted a female bluebird in the same area, and she too was foraging in the traditional way. So, at last, I had found them.

Photo by Kerry Howard

Bluebirds have other foraging techniques too. Sometimes they hover a couple of meters above the ground to scan for bugs or occasionally chase bugs in the air. In the non-breeding season, they add seeds and fruits (of many species) to the diet. To augment calcium in the diet, egg-laying females may eat bits of egg shell or snail shell to help build the shells of developing eggs, and nesting females may feed shell bits to the chicks to help develop good bones.

Mountain bluebirds nest primarily in the mountains of Montana, Wyoming, and so forth, but some of them range more widely, coming in small numbers to northern B.C., Yukon, and interior Alaska. They are cavity nesters, loving old woodpecker holes but also nesting in cliff crevices, nest boxes, and sometimes other human structures. They favor habitats with short grass and scattered trees or snags offering nesting cavities. They are reported to arrive early on the nesting ground, probably because suitable cavities are limited in number, so the early arrivals get the best choices.

Male bluebirds are territorial, defending an area around potential nest sites, and females can then choose among them. Nests are built primarily by females, often guarded by their mates against potential predators and intrusions by other males. Females incubate for about two weeks, usually fed by their mates, and they brood the tiny hatchlings. Both parents feed the nestlings, which stay in the nest about three weeks, and the fledglings.

Mountain bluebirds are socially monogamous, meaning that they form pairs but both partners may go philandering–seeking occasional matings outside the pair bond. This arrangement turns out to be rather common among species that were once thought to be strictly monogamous. A bluebird pair bond typically lasts for a season, including replacement nests or second nests, but a pair does not necessarily stay together the following year.

That blue color that we love is not produced by pigments but by the micro-structure of the feather barbs; both UV and blue wavelengths are reflected. Males within a population differ in the amount and reflectance of their plumage. Now things get more intriguing: In two studies, done in two different geographical areas, brighter males were more likely to go philandering, engaging in more extra-pair copulations, than less-brightly colored males. Their brightness was not related to age or body condition. In one of those two studies, the more colorful males sired more of the chicks in their own nests and more extra-pair chicks. In the other study, the more colorful males were also early nesting and achieved more extra-pair copulations, but the paternity of chicks in their own nests was not enhanced, compared to less colorful males nesting later. Thus, in both cases, the payoff for bright coloration was greater numbers of offspring sired, and potentially greater evolutionary fitness, although the size of the payoff differed between the two areas.