September

delights of a season of slowdown

In September, the natural world slows down. The days get shorter and shorter, bird song diminishes to next to nothing, marmots are hibernating and the bears soon will be. Most of the wildflowers are done blooming, although a walk above the tram in the middle of the month revealed the last few flowers of six species. And the alpine zone is where we find our best fall colors: various shades of red on dwarf dogwood, avens, and lowbush blueberries, gold and russet on deer cabbage.

Nevertheless, on one day in mid-September, I enjoyed sightings of two kinds of critters that I don’t see very often.

Rusty-Blackbirds-by-bob-armstrong
Photo by Bob Armstrong

There were three rusty blackbirds on the shore of Mendenhall Lake, foraging over the wet sand and in the shallows. Rusties breed all across the boreal forest of North America and winter chiefly in the southeastern states. Even though Southeast Alaska is hardly on a direct route to the usual wintering area, I see them during the spring and fall migration seasons, sometimes by the ponds in the Dredge Lake area, occasionally elsewhere, but always in small numbers. Sadly, those numbers are likely to get even smaller: the number of rusty blackbirds has dropped dramatically in recent years, probably for several (undetermined) reasons.

Rusty blackbirds in Alaska often nest in wetlands and near ponds in dense, small black spruces, where nesting success is good, or in willow shrubs, with less success. Unlike their marsh-nesting relatives (such as red-winged blackbirds), they are usually monogamous. But similar to the other blackbirds, females do the tasks of incubating eggs and brooding young chicks. Blackbird males pitch in to help feed the chicks (but polygamous males commonly help mostly at the nest of a primary female; secondary females get less help).

In the nesting season, rusty blackbirds feed mostly on aquatic insects, including dragon and damselflies. During the rest of the year, the diet also includes seeds of many kinds and fruit. I was fascinated to learn that rusties sometimes kill and eat other birds.

The other critter I don’t see very often was Milbert’s tortoiseshell, a beautiful butterfly whose deep brown wings are banded with orange and yellow and adorned with red spots on the leading edge. All the color is on the dorsal surface, visible when the wings are spread. The ventral surface of the wings, visible on the folded wings, is more camouflaged, looking perhaps like dead leaves or bark. The one I saw was foraging on yarrow flowers—the only flower still in bloom in that area.

This butterfly overwinters as an adult, tucking into crevices in houses or trees, and emerging again in early spring. Batches of eggs are laid on nettles, which are the chief food of the caterpillars. (We could use more of them on the lower reaches of the Granite Basin trail!) Young caterpillars often forage in groups, but older ones are more solitary. They pupate in a folded leaf. When they metamorphose to the adult stage, they forage on nectar of many flowers, as well as sap and rotting fruit. In parts of North America, there may be two broods of caterpillars each year, but I doubt that there is more than one per year in Alaska. The one I saw was surely getting ready to hibernate, filling up the tanks, as it were, to last through the winter.

Addendum: As I strolled down to the beach below the pavilion near the visitor center, I stopped to watch the bear called Nicky and her little cubs. They trotted along the lowest pond on Steep Creek, where a few coho were jumping, waiting for enough water to allow them to ascend the creek. I don’t get to see Nicky very often either, so this was a happy sighting. The cubs looked pretty healthy but still very small…they will need their mom to catch some of those coho, so they can get fat enough to last the winter. But even Nicky, an expert fisher, can’t catch very many until there is enough rain to raise the water levels so the fish can get up into the stream itself. I have to hope for rain!

Early butterflies

four species of early Southeast fliers

Starting in mid-April this year, we began to see a few species of early-flying butterflies. In general, Juneau is not blessed with a great diversity of butterflies, for whatever historical and geographic reasons. I also suspect that butterflies in Southeast Alaska have not been as well studied as those in the Interior or, certainly, in the Lower Forty-eight. In any case, it was a treat to see these four kinds of early fliers in April.

milbert's-tortoiseshell-on-beach-strawberry
Milbert’s tortoiseshell. Photo by Bob Armstrong

–Milbert’s tortoiseshell. Arguably the most colorful of the early fliers, this butterfly has broad orange bands on the upper surface of the spread wings and some red spots at the leading edge of the forewing. On some individuals, however, the orange and red marks are not bright. The undersides of the wings are brownish and much less conspicuous. Males and females are similar. This species overwinters as adults, tucked into crevices of tree bark and buildings. After emergence from hibernation, females lay eggs, which produce a new generation of adults in summer. The larvae feed on stinging nettles, good stands of which are found here in several locations.

Adults like to bask in the sun as they perch on branches or grass or the ground. They visit flowers for nectar and can serve as pollinators by carrying pollen from one flower to another. We saw this species visiting the ornamental coltsfoot the Arboretum in mid-April.

–Mourning cloak. This is another beautiful butterfly that overwinters as an adult. The upper surface of the wing is dark, rich brown, bordered by a wide yellow band on the wing margins. Males and females are similar. A favorite larval food in Alaska is willow leaves, but other hosts are included in the diet elsewhere (and perhaps also in Alaska).

Adults often bask in the sun as they perch. They can be seen visiting the sap wells that sapsuckers carve on willows and other trees, and they also feed on animal dung and decaying organic material. They may occasionally go nectaring and serve as pollinators.

–Blues. There are several species of small bluish butterflies in Alaska, and I don’t know which one(s) we have here. Although the ‘Butterflies of Alaska’ by Philip and Ferris indicates that blues usually emerge and fly in late May or June, at the earliest, in late April this year, hikers were treated to a small, bright blue butterfly flitting along the trail. When it perched with folded wings, the brownish undersides of the wings made it nearly invisible; upon take-off, the brilliant blue was again exposed. This was a male; the females lack the bright blue and are more camouflaged in mottled brownish-gray.

Some blues hibernate as pupae, on the way to transforming from larva to adult, but some pass the winter in the egg stage. Host plants for larvae are varied, and for some species, unknown for Alaska. Eggs are commonly laid in flowers, and the larvae eat the flowers or, in some cases, seed pods of the host.

Blues belong to a taxonomic family (Lycaenidae) in which a number of species are well-known to be part of an interesting symbiosis that may occur in Alaskan species too. The larvae are tended by ants, which guard them from would-be predators. The ants benefit by feeding on excretions from the larval digestive tracts. Juneau, however, does not seem to be home to many ants—I see them only in a few places—and therefore it is uncertain if this symbiosis occurs here.

–Whites. Bigger than blues, but smaller than mourning cloaks and tortoiseshells, they come in a range of whitish-ivory-pale yellow hues. Females are duskier than males. Our whites are currently classified as margined whites; taxonomists call it a ‘species complex’, meaning that they are not sure how many, or which, species are here. I saw several in late April, earlier than the dates given in ‘Butterflies of Alaska’.

The larval host plants are plants of the mustard family. They are presumed to overwinter as pupae. Adults visit many flowers and can be effective pollinators.

All of these species exhibit a particular behavior called ‘puddling’. Butterflies of many species visit moist soil, decaying material, and places where an animal has urinated, sometimes gathering in large, spectacular aggregations. In most cases, these are males. For some species the big attraction is salt, specifically sodium; for others, it is nitrogen. At least in some species, males can transfer the nutrients to females at the time of mating, and this leads to better reproductive success, but we have no information on this from Alaskan species.

As summer comes, there will be more butterflies to see, some of them residents, some of them vagrants. Climate-warming is likely to permit more species to visit or live here–more fun for butterfly watchers.