Bird stories

nest-builders, scat-shifters, and spring singers

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One day in late April, two friends and I scrambled up a steep stream-side slope to a perch on a cliff below a waterfall. We hoped to locate a nest of American dippers, which have nested in this spot for many years. Although a dipper sat near the pool below the falls, it eventually just flew up over the falls, and we were no wiser about a possible nest location.

However, as we surveyed the pool and falls, another bird was busy, attending to a clump of moss on a spruce branch above us. A male Pacific wren (formerly known as the winter wren) zipped back and forth, carrying twiglets to that mossy clump, which was obviously intended to become a nest. Male wrens commonly build more than one nest, which are inspected by females during the courtship process. When a female selects one of these male-built nests, she adds a little threshold to the entrance, claiming that nest as her own. If a male builds several good nests, he may attract two or even three females who will raise his chicks.

arnie-dipper1
American dipper. Photo by Arnie Hanger

This nest- building male became disturbed at our presence, fidgeting about while peering at us and then finding an elevated perch from which he sang loudly, as if to make sure we knew we were not welcome (songs are how songbirds advertise ownership of their territories). Birds really do not like to be observed when nest-building—egg- and chick-predators such as Steller’s jays are always on the watch for tasty morsels, and the busy activity of a bird carrying nesting material gives away a prospective nest for the jay or other predator to raid.

We go the male’s message and backed away a little. Although he was still nervous, he resumed carrying small twigs and fibers to the growing nest in the ball of moss. Suddenly, the entire bottom of the nest ball fell out! Apparently, the scrawny twigs of the spruce branch weren’t sufficiently substantial to support the structure or all the in-and-out visits of the builder. The wren vanished into the forest.

A couple of weeks later, I returned to this site. Now the tattered remains of the wren’s nest were tipped catty-wompus, barely clinging to the frail spruce twigs. The wren had clearly abandoned this effort and decided to build elsewhere. I could hear him singing, a little deeper into the woods.

On this visit, however, I did see the dippers in action. They were not building in their traditional site in the cliff beside the falls, but under a mid-stream log, instead. These dippers were a bit late in getting started; dippers on some other streams were already incubating clutches of eggs, the incubating females sometimes fed by the male.

In the middle of May, Gold Ridge still had lots of snow, attracting brave or foolhardy skiers up the trail. Ravens were soaring and cavorting, as usual, over the end of the ridge, sometimes peeling away from the group to roll and tumble acrobatically or to chase a passing eagle.

Two ravens perched on a rock outcrop. Both birds picked up something lumpy and white and moved behind another outcrop just uphill. They came back to the first outcrop without the white lumps and picked up two more. They flew downhill a little way, and there they deposited these objects, carefully placing them in nooks and crevices of the rock. Then they flew away.

This time I could see where the white lumps were placed, so of course I went to look. The lumps were the old scats of a wolf and perhaps a bear, all dry and winter-whitened. What in the world did these ravens want with these old scats? Were they playing some kind of game?

Robins and fox sparrows were singing all over the shrubby slopes above the tram. Above the cross, snow still covered much of the ground, and ptarmigan had left the digested remains of their dinners in the places where they had burrowed under the snow in winter. A flock of pipits flew in and began to forage for insects and perhaps a few seeds in the snow-free patches. Pipits look more slender than sparrows and they typically walk and run instead of hop. They sometimes nest high in the alpine tundra on the ridges.

On my home pond, the mallard battles are over. As many as four males hang out amicably, eating seeds that drop from the hanging feeder and sleeping next to each other. No need to fight now; all the females are incubating clutches of fertilized eggs. This is a big contrast to early-season relationships, when each male fiercely defended his female from the attentions of other males. That doesn’t always work, by the way—the interlopers are sometimes successful. Meanwhile, up on Gold Creek, a pair of harlequin ducks was consorting and foraging. She will nest up there somewhere, and when the clutch of eggs is complete, she will incubate them and he will go back out to sea to lollygag with his chums on some rocky point. That’s the way of it, with ducks!

Winter explorations

little snow stories, a fungophile squirrel, and long-leg aggregations

Wonderful snow! Brightening our short December days; under that full moon, it was spectular.

All that glorious snow drew me out, day after day, looking for little stories writ there. There were all the usual perpetrators: deep, winding furrows made by wide-bodied, peripatetic porcupines, lots of snowshoe hares (especially near the visitor center), a mink bounding over a frozen rivulet, red squirrels tramping back and forth between trees, a deer or two—or lots in some places, an ermine, some good otter slides, a few voles and shrews (and a couple of mysteries that I shall gloss over).

There were also a few real highlights. Out near Peterson Creek, after watching a hungry dipper searching for some open water, my friend glanced up and spotted something odd-looking about ten feet up a spruce, right next to the trunk. This looked like a mushroom, stuck in a tuft of twigs. Really? So my friend climbed up, to look more closely. Indeed, not just one but five or six mushrooms were wedged in a tight stack, in among the twigs. Ha!—a squirrel cache. Red squirrels are known to store mushrooms in dry places, such as the tops of well-drained stumps or logs (but cones are usually stored in damp places, so they don’t open and drop the seeds). This squirrel clearly thought that the twiggy tuft was good enough to warrant stashing several valuable food items there.

The sloping base of a huge spruce in Amalga Meadows had been an active site. Small prints of a critter that could bound six or eight inches decorated the trunk up about three feet, as well as all the surrounding snowy ground. Hmm, not a vole, which usually scuttles along, nor a jumping mouse, which hibernates, but probably a deer mouse.

We looked out over the wind-swept open area of the meadow, where the snow had been draped over tussocks and small conifers. We saw immediately that these looked like sea lions lunging up from the water. There was a big, thick-necked bull, and a whole squadron of juveniles, not far behind. No great imagination needed to provide some sound effects as well!

Some friends like to explore old mines in the Juneau area and recently explored one near the base of Thunder Mountain. The adit was barricaded by stout icicles, but a few were persuaded to break, allowing human entrance. Not too far back in the tunnel, observers spotted a number of harvestmen (a.k.a. daddy longlegs) on the wall. Near the end of the eighty-foot adit, many of these were clustered into a close group, with their long legs sticking out in all directions.

Harvestmen are related to spiders, but not very closely. In contrast to spiders, they are not predatory; they feed chiefly on bits of plant and animal debris. They are also not venomous and cannot bite you with their weak jaws. They are often gregarious, gathering in bunches, but why? One suggestion is that they are behaving like what is known as a ‘selfish herd’. Each animal tries to put as many others as possible between itself and the edge of the group, where the risk of predation is highest. For these harvestmen, the most likely predators are spiders, or possibly mice.

Beavers in winter

what’s it like inside a lodge?

On an October exploratory excursion, we encountered a well-built beaver lodge, one we hadn’t known about before. The sides were freshly packed with mud, effectively waterproofing and insulating the lodge for winter. I needed to refresh my failing memory on what it might be like inside a beaver lodge in winter, so back to the literature I went.

Beavers seldom venture into the open air outside the lodge in winter, when ice covers their ponds, so for months a family of beavers breathes ‘indoor’ air, using oxygen and generating carbon dioxide. Beaver lodges have underwater entrances, and mud seals the walls, so air exchange is effected through a ventilation hole in the roof. Apparently this roof vent is sufficient to keep carbon dioxide from building up and allow an influx of oxygen, because when researchers measured the levels of those gases inside an occupied lodge, they stayed nearly constant.

 

Temperatures inside a well-built lodge also do not vary much. For example, when outside temperatures drop to minus twenty degrees centigrade (about minus four degrees Fahrenheit), inside temperatures remain just above freezing. Thick walls obviously conserve more body heat than thin walls, so inside temperature varies more if the walls are thin.

If beavers had to live outdoors in winter, for example at an air temperature of minus twenty degrees centigrade, their metabolic rate would almost double, compared to that at normal lodge temperatures. They might not be able to eat enough to stay alive under those conditions.

Beavers don’t hibernate, so they need a supply of energy throughout the winter months.

Although beavers make a pile of cut branches in front of the lodge as a winter cache of food, the cache does not contain enough food for a whole family of beavers (adults, yearlings, and kits) if they eat as much as they do in summer. Instead of eating lots of cached bark and roots, wintering adults reduce their energy demands by lowering their metabolic rate and body temperature and conserve energy by not moving around very much. The adults put on large amounts of fat in fall, partly in the body cavity and under the skin, but especially in the tail: the amount of fat in the tail in winter can be ten times what it is in summer. This stored fat is used up over the winter, so the adults lose weight.

In contrast, the kits and yearlings maintain their body temperature and metabolic rate, which is higher than that of adults, and they keep on growing. So they eat a lot, and the adults often bring the sticks into the lodge for them to eat.

Just inside the entrance of a lodge is a ledge to which beavers bring sticks from the cache—the winter dining room, so to speak. Here a wet beaver drip-dries as it eats the bark from the branch. A slightly higher ledge is a dry sleeping place where the family spends most of its time in winter. Adults, yearlings, and kits all huddle on the sleeping platform, dozing and occasionally grooming, and sometimes ducking outside to retrieve a cached stick or to defecate and urinate.

lodge-XS-hocker
illustration by Katherine Hocker

If one is very quiet, and the winds aren’t howling nor the rains pounding down, it is sometimes possible to stand next to an occupied lodge and hear the residents chewing on retrieved sticks.

Jays

raiders, cachers, and helpers-at-the-nest

There is a gang of four Steller’s Jays that constantly visit my seed-feeders. I assume (on no real basis whatsoever) that this Gang of Four are siblings, progeny of the pair that brought them to my feeders in the first place. Back then, they were scruffy, clumsy youngsters, with short crests and the remnants of a pinkish flange at the corner of the bill. Then, one day in October, the noisy foursome was joined by two others, perhaps their parents. According to official accounts, Steller’s Jay families often stay together into fall and winter. On the other hand, sometimes rich food sources attract numerous jays; a friend who puts out peanut treats has recorded over a dozen jays at a time.

There are over forty species of jay in the world (every continental area except southern South America, Australia, and of course Antarctica), occurring mostly in wooded habitats. Many of them have not been studied very much. Two of the better-studied North American types are several kinds of scrub jays, in southern U. S., and the distantly related Gray Jay, which is widespread in boreal forests. These two offer striking contrasts to the family relationships of Steller’s Jays.

Scrub jays are known to be ‘cooperative breeders’, meaning that young birds commonly remain on the parental territory and help care for the next year’s broods. So, many scrub jays don’t mature and breed until they are two years old. Gray jays were long thought to lack such helpers. A dominant fledgling drives out its subordinate siblings two or three weeks after they leave the nest, and the dominant stays on the parental territory until the early in the next nesting season, when it too is driven out by the parents. Both dominant and subordinate siblings then must find their own mates when they are about one year old. However, later observations showed that sometimes the dominant young bird helps the parents rear the next year’s brood, but doing so only after the young chicks leave the nest. Then they may feed and guard the fledglings for a few weeks. Thus, some Gray Jays mature at age one, as previously thought, and others wait until age two.

Steller’s Jays are less well studied than Scrub Jays or Gray Jays. But as far as is known, the family breaks up over the winter, the young birds do not help raise the next year’s brood, and they mature and mate at age one.

What determines these differences in family arrangements? That’s a subject of considerable debate. One important factor is probably the size of the population in relation to the amount of available habitat: when habitat is limited, it is harder for dispersing young birds to find their own space, and then it pays for them to stay home and help rear their young siblings.

All North American jays cache food, on the ground or in a tree. They use landmarks, such as a tuft of grass, a stone, or a clump of lichen on a branch, to re-locate food they have hidden. They are good at remembering these landmarks and have high retrieval rates if the landmarks are not disturbed. Gray Jays can cache several hundred food items per day. These jays generally gum down their stashes with sticky saliva and use the stored food through the winter and even into the next nesting season. They are unusual in that they often carry large food items in their feet; they can carry items weighing fifty or sixty percent of their body weight (sixty to eighty grams). Other jays apparently do not do this, although Steller’s Jays have sometimes been observed to attack and grab small songbirds with their feet, and then transferring the catch to their bills.

Because of their extensive food caches, Gray Jay can start nesting very early in the season, in February and March when snow is still falling. I haven’t found much information on food caching by Steller’s Jays (beyond the fact that they do so), but we do know that they are somewhat early nesters too—but not as nearly as early as Gray Jays.

The reasons for early nesting have been debated, with no resolution in sight. One interesting suggestion is that both Gray Jays and Steller’s Jays often feed on the eggs and nestlings of other birds, so they produce their own chicks in time for the season when those food sources are plentiful, in late spring and early summer. Here in Juneau, we found that Steller’s Jays seemed to concentrate their nest-raiding while their own chicks were still in the nest, and did so less after their chicks had fledged.

june-4-jay-babies-1-kerry
Young Steller’s jays. Photo by Kerry Howard

In Atlin, we watched Gray Jay families, with young fledglings, moving through the shrubbery as a group, as if they were searching for nests to raid, or at least teaching the young how to do so. A gang of jays jumping around in the foliage would certainly tend to flush any incubating or brooding songbird parent from its nest, exposing the contents and calling attention to the nest area.

However, I don’t know if they are really searching specifically for nests—a study of Steller’s Jays in Washington suggested that they find nests opportunistically, not as a result of a concerted search just for nests. There is always more to be learned!