PINE SISKIN—INVASIVE NATIVE

The winter of 2012-2013 has seen record number of Pine Siskins (Spinus pinus) in the Pacific Northwest. Numbers in the thousands have been reported on some Christmas Bird Counts. What's going on? It turns out that siskins are cyclic, on the average peaking in a given area in alternate years, and the peaks on occasion are very high. Thus they have a two-year cycle. The cause of this cycle is usually thought to be food availability, which varies in both space and time.

Siskins are among our smallest birds. They are members of the finch family Fringillidae, a family of interest because of its adaptive radiation into the seed-eating niche. The biggest species eat large seeds, the smallest very small seeds, and so forth. Pine Siskins eat a great variety of seeds of weedy herbaceous plants in the summer, but in winter in the Pacific Northwest they are strongly associated with red alders (Alnus rubra).

Alders bear their seeds in small conelike structures, and the slender bill of the siskin is well adapted to extract these seeds. Flocks of siskins visit alder trees and spend quite a bit of time working through the abundant cones. These flocks can be of surprising large size, up to and over 100 birds, but are usually smaller.

Pine Siskins also eat a variety of other seeds, from dandelions to hemlocks, and are frequent visitors to bird feeders, especially preferring thistle seeds. Unfortunately, this can be their undoing, as they seem very subject to infection from salmonella, which is spread in their feces. Birds may defecate while at feeders, and thus the salmonella bacteria are spread from bird to bird. Most winters, people who feed birds report sick and dead siskins at their feeders, sometimes dying right on a feeder.

Pine Siskins are very aggressive little birds. Perhaps they have to be because they go around in flocks, and a bird has to defend its feeding site against others. But they are also aggressive toward any other species, and at feeders, it is an impressive sight to see a siskin chase away a larger finch or sparrow. Siskins often have yellow in the wing and tail, and larger yellow patches may enhance a bird's success in driving away others.

Dennis Paulson

SHRIKES, SONGBIRDS OF PREY

We are all familiar with hawks and owls, raptorial birds with strong feet and long, curved talons for capturing and carrying prey and a strong, sharp-edged, hooked bill for tearing that prey into bite-sized morsels.

But there is another group of common birds that are just as predatory, although with somewhat different anatomy. These are the shrikes. Shrikes are members of the perching bird order Passeriformes, and although that order is full of insect eaters (shrikes do this), it's not so full of birds that eat small vertebrates such as lizards, songbirds and rodents (shrikes do this too).

Loggerhead Shrikes (Lanius ludovicianus) are widespread breeders in interior sagebrush habitats in the Pacific Northwest. With us only in the summer, they feed primarily on large insects such as grasshoppers and beetles, but they also eat small vertebrates whenever they can capture them, including voles and birds right up to their own size.

Northern Shrikes (Lanius excubitor) breed in the boreal forest and drop down to the PNW in the winter. They are more widespread than Loggerheads, occurring throughout the region in open country. Although they take many insects on their breeding grounds, Northerns are bird and mammal eaters in the winter. Voles are among their most common prey, but they will chase and capture small birds of any sort.

Shrikes have typical perching-bird feet, not raptorial, and they don't capture or kill their prey with their feet, but they do use their feet to carry prey, especially heavy items and even up to their own weight; otherwise prey is carried in their bill.

Although not just like a hawk's, the bill is strong and hooked at the end. It has a pair of toothlike structures near the tip of the upper mandible (tomial teeth) that are important in prey-killing. The shrike bites a vertebrate just behind the head, and the "teeth" apparently sever or injure the spinal cord sufficiently to kill or paralyze the prey, which then cannot struggle and possibly injure the predator.

Not having feet to hold a prey animal down while tearing pieces of flesh off, shrikes have evolved a substitute. They carry their prey to something on which they can position it. In nature, this would involve impaling on thorns or hanging from crotches where two branches diverge. They can then begin to dismember the prey.

Having evolved this behavior and often taking prey much too large to be eaten in one session, shrikes further evolved the behavior of leaving the prey hanging and returning later to eat some more. Wherever shrikes occur, such prey are liable to be found. Nowadays, we can watch for shrike prey caches on barbed-wire fences!

Dennis Paulson

WAXWINGS, THE SMOOTHEST BIRDS

Anyone who looks closely at a waxwing usually exclaims "how smooth it is!" What is there about waxwing feathers that gives this impression? They really do seem smooth, perhaps in part because the body is uniformly colored and the individual feathers thus difficult to make out. Maybe that's all we need to know. Their jaunty crests, black face masks, and yellow tail tips make waxwings unmistakable birds.

Cedar Waxwings (Bombycilla cedrorum) are very common in the Pacific Northwest. Small numbers of them spend the winter, especially in the interior, but many more arrive in spring to breed throughout our deciduous and mixed woodlands. Because they are confirmed fruit-eaters, they breed later than many other migrants, so the young when just off the nest can find plenty of fruit. Many native trees and shrubs flower in early summer and have mature fruit in late summer, if you didn't know.

Waxwings are really tied to fruit and can survive on a fruit-only diet longer than other temperate zone songbirds. Males offer berries to females for courtship feeding, and the young are fed fruit more than is the case in most of our birds. Of course this diet is augmented with insects, which are better sources of some nutrients. Waxwings spend much time around water looking for emerging aquatic insects such as dragonflies, which they often catch in the air.

You can see waxwings hawking for insects above the treetops in late summer, but they are still seeking fruit at that time, and any plant fruiting in September may harbor small flocks of waxwings. In October, most of them take off for lower latitudes.

The "waxy" tips on wing feathers in waxwings are merely modifications of the feathers. Imagine the individual feather barbs becoming thicker and thicker, fusing, and becoming bright red. As a waxwing matures, it develops more of these tips, and their size and number are a sign of maturity. Birds with more red tips tend to breed together and breed more successfully, so more "wax" may be a sign of a bird with higher fitness.

Bohemian Waxwings (Bombycilla garrulus), bigger and more colorful, visit the Northwest only in winter from their breeding grounds in the boreal forest. They are more common on the east side of the Cascades, where flocks may be encountered in fruiting trees, many of them non-natives and often in cities and towns.

There is only one additional waxwing, the Japanese species (Bombycilla japonica). It looks much like the other two but has red tail tips; I wish I had a photo to share, but I've never seen one.

Dennis Paulson

PSYCHEDELIC ROBIN OF THE NORTHWEST

Some people, seeing their first Varied Thrush (Ixoreus naevius), wonder if they are having vision problems. This psychedelically colored thrush looks more or less like an American Robin (Turdus migratorius) and feeds on the ground or in fruit trees like a robin, but the similarity is only superficial.

Male Varied Thrushes are vividly colored in gray, black and russet, much more brightly patterned than robins. Females are more subdued, with less conspicuous facial markings and breast band, but they still show the vivid wing markings typical of the species. Note also their black instead of yellow bill.

While robins run about our yards looking for earthworms that have surfaced, Varied Thrushes are foraging for a much greater variety of invertebrates. A robin is a visual forager, cocking its head to scan for worms, but a Varied Thrush gets down and dirty, pulling leaf litter up and hopping backward to examine the ground exposed. The complex web of life beneath the litter furnishes up dietary items one after another to the thrush.

In addition, Varied Thrushes take fruits and seeds of all kinds, even acorns, from the ground. They often visit bird feeders to take seeds or suet, something robins never do. Both species are attracted to fruiting trees and shrubs, where they may gobble berry after berry, jumping up or briefly hovering to pull them from branches to small for a comfortable perch.

Varied Thrushes breed in wet conifer forests in the mountains of the Pacific Northwest, and they are present in the lowlands only in winter, when they come down from the mountains. In some winters, probably the colder and snowier ones, they are more common than at other times, numerous enough to be called an invasion. At intervals they wander much more widely than their usual range in the far West, turning up as far east as the Atlantic coast.

The call note of a Varied Thrush is a sharp 'tup,' much like that of a Hermit Thrush, but the song is magical. It is a series of drawn-out notes at different pitches, sometimes with overtones. Note after note comes out of the bird with an ethereal quality that seems well suited for our dark evergreen forests. Fortunately for us, they sing commonly in the spring before they depart for the mountains, so you may hear this song in your suburban yard.

Watch for the psychedelic robin; it's that time of year!

Dennis Paulson

THE ANT-EATING WOODPECKER

Most of us think of woodpeckers as black and white birds that forage on tree trunks, hitching their way up, down and around to probe into bark crevices for insect larvae. Not finding any on the surface, they are supremely adapted to chiseling their way into the wood to extract burrowing beetle larvae from their hidden galleries beneath the bark.

One woodpecker stands out against this generality. It is a typical woodpecker in anatomy but not in color or foraging habits. This is the Northern Flicker (Colaptes auratus), a common breeding species over much of North America. The brown plumage, heavily barred and spotted with black, is distinctive, and, as in many other birds that feed on the ground, serves as camouflage. Males are easily distinguished by their red malar stripe.

Flickers are the only ground-feeding woodpeckers in North America. They nest in holes that they excavate in tree trunks, but their primary diet of ants, among the most abundant insects, has them nesting at woodland edges and foraging in open country when they are not breeding. Watch for flickers flying up from the ground, their contrasty white rump and red wing linings almost startling at first sight.

Flickers are still common everywhere they occur, and in the Pacific Northwest they are becoming more common in urban and suburban habitats. Every ant-filled lawn is a feeding station for them, and they quickly learn to come to bird feeders with either suet or seeds. Watch a flicker at a seed feeder sticking its tongue into the seeds. The seeds stick to the sticky tongue just like ants in an anthill and are slurped in with gusto. Bits of suet are chipped off with the powerful bill, while squirrels wait below to get all the pieces dislodged.

Ants stay underground when temperatures drop below freezing, and flickers wintering at high latitudes change to a diet of fruits of all kinds. Poison ivy berries are among the most common, and they illustrate an interesting fact of nature: poison ivy toxins are harmful only to mammals. If mammals are deterred from eating the fruits, then much wider-ranging birds will eat them and disseminate the seeds at greater distances from the parent plant.

Although common in towns and even cities, flickers are declining slightly overall. European Starlings often outcompete them for nesting holes, but there is no definitive proof that that interaction has caused the decline. Another good possibility is the general decrease of snags, dead standing trees in which the birds can excavate nest holes. One possible reason for the surprising increase of flickers in some cities is that they can excavate in utility poles!

Dennis Paulson

BALD EAGLE - HERO OR VILLAIN?

The Bald Eagle is the national symbol of the United States of America. It seems appropriate for a country to have such a majestic bird as a symbol. Long-lived, monogamous, good parent, characteristic of wild places, Bald Eagles excite awe and admiration wherever they fly.

There have been notable dissenters from this view, including Ben Franklin, in a letter to his daughter 20 June 1782: "For my own part I wish the Bald Eagle had not been chosen the Representative of our Country. He is a Bird of bad moral Character. He does not get his Living honestly. You may have seen him perched on some dead Tree near the River, where, too lazy to fish for himself, he watches the Labour of the Fishing Hawk; and when that diligent Bird has at length taken a Fish, and is bearing it to his Nest for the Support of his Mate and young Ones, the Bald Eagle pursues him and takes it from him."

Yes, Bald Eagles are inveterate kleptoparasites, robbing Ospreys and other raptors of their prey. Like all birds, they have terrific vision and are aware of what goes on all around them, even at some distance. Not even a swift and strong Peregrine Falcon can withstand the attack of an eagle determined to wrest a recently captured bird from it.

In the middle of the 20th Century, Bald Eagle populations were decimated by ingesting DDT along with the fish and fish-eating birds that they preyed on. DDT compromises calcium transport, and the eggs laid by the eagles, with inadequate calcium, were thin-shelled enough to crack under the weight of an incubating female. Reproductive success fell and populations declined along with it.

DDT was banned in the US in 1972, and eagle populations have been rebounding ever since, to levels greater than any previously documented. Their numbers have skyrocketed in particular in the Pacific Northwest, which must be optimal eagle country.

Unfortunately, the consequences of this are dire for some other bird species. Eagles are opportunists above all, and they have learned to make a living, at least in spring and summer, by hanging around bird colonies. With present eagle numbers, colonies of Great Blue Herons, Caspian Terns, and Common Murres on and near the coasts have been hit hard by these predators, sometimes just single birds taking advantage of the prey concentration.

The nesting birds have no way to withstand eagle predation, losing eggs, young and even adults to the predators. Even though eagles may eat a small percentage of the birds in a colony, their presence causes nesting to be disrupted to the point of complete colony abandonment. Because of this, numerous Great Blue Heron colonies have failed, and even huge colonies of thousands of murres and terns have been abandoned.

In the coming years, wildlife managers will have to figure out how to deal with this dilemma. Bald Eagles are not on the endangered species list any more, but they are still protected. The birds whose colonies they are destroying are also protected and of concern, and what should we do when one valued species affects another one so severely?

Dennis Paulson

Ice Worms. Yes, They're Real!!!

   

 That’s what Ben Lee told me years ago when I looked at him like it was April Fool’s Day. Although I think he said, “damn it, they’re real!,” Ben was looking for an organism that would allow him to spend time in the mountains AND do some summer research. Ice worms are annelids, in the same group as earthworms, and endemic to the coastal mountain glaciers from central Oregon to south-central Alaska. These little denizens of the snow and ice are small – usually no more than an inch long, and 1-2 mm wide.  They look like a thick-ish hair on the snow surface, or a piece of stout, fruticose (gotta love that word!) lichen. Ice worms typically emerge onto the glacial surface to feed on algae and bacteria in the late afternoon and will stay out until the surface starts freezing over. On warm nights they party all night.  

 Ben Lee with ice worms.

     Ice worm distribution is likely limited by their narrow temperature tolerance – they survive between about -6 - +6 C.  Coastal glaciers (in the Olympics, Cascades and up the coastal ranges of BC and Alaska) are “temperate” glaciers, meaning that their internal temperature always hovers around freezing.  We don’t find ice worms in glaciers on the Rockies, presumably because it gets too cold during the winter, or the prolonged cold season leads to a lack of food; we don’t find them much above 10,000’ on Mt Rainier, probably for the same reasons. 

 photo by N. Takeuchi

      Ben and I examined the population genetic structure of ice worms in the Olympic Mountains. Previous work done by Paula Hartzell, Dan Shain and colleagues showed that there were two distinct evolutionary lineages, a northern lineage in Alaska (and probably into BC) and southern lineage that ranged from somewhere in BC to Sisters, Oregon. We predicted that the Olympic worms would be most closely related to the Cascade Mountain (southern) worms. But when Ben started getting his DNA sequencing results, all of the first worms examined (from the Olympics east of the Elwha and Mt. Comox on Vancouver Island) belonged to the northern lineage. And then the story got more convoluted.  On the last collecting trip of the year, Ben collected worms from Mt Olympus and Mt Carrie (west of the Elwha drainage). The worms in those collections were a mixture of worms from the southern and northern lineages! 

  Ali Garel and Peter Wimberger collecting ice worms. Photo: Holden Sapp    

    That leads to a number of obvious questions:  1)  how did the northern worms get to Vancouver Island and the Olympics?  2)  Why do both lineages coexist in the western Olympic Mountain glaciers?, and 3) Do the northern and southern worms make wormbabies together?  Think about it and I’ll post our thoughts next week!

To watch an old clip of Ben Lee and me on Oregon Field Guide:

http://www.opb.org/programs/ofg/segments/view/1653

Peter Wimberger