Friday, November 30, 2012


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

Tuesday, November 27, 2012


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

Tuesday, November 13, 2012


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

Friday, November 9, 2012

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:

Peter Wimberger

Tuesday, November 6, 2012


The simple answer is "no," if you value the little critters that make up so much of wildlife. First, cats are not just bird killers; they are a threat to all small animals, including shrews, rodents, frogs, salamanders, lizards and snakes. Nonbirds may outnumber birds in the average cat's diet. But they still catch and kill enormous numbers of birds.

The statistics don't lie. Sixty pet kitties in Athens, Georgia, were provided with Kitty Cams that recorded everything they did for weeks at a time. The results were disturbing: cats bring back to their owners only a fraction of what they catch. Therefore, predation estimates based on observed captures were way low. Extrapolating from their predation rate and the number of cats out in nature, they probably kill at least 4 billion small animals annually in the US.

What can we do for the small native creatures that we have already put at such risk by taking away much of their natural habitat? Clearly, the best answer is to keep all pet cats inside and to have a rigorous control program for feral cats. TNR (trap, neuter, return) programs, supposedly to control cat numbers humanely, have usually led to increases in local cat populations.

Short of that, I think it is still possible to make your yard a little safer for birds in an urban setting. The most obvious way to do this would be to stop feeding them, as any congregation of birds is irresistible to feline passersby. Oh, so you don’t wish to stop feeding birds? I share that feeling, so in our yard we feed them only at certain points, usually near thickety plantings so they have some chance to escape the ever-present Sharp-shinned Hawks. The adjacent shrubbery is surrounded by chickenwire fencing at least three feet high so cats can’t hide in it and rush out on feeding birds. Even here, you have to be careful that the seeds that fall to the ground don’t fall within the fence line, attracting birds within reach of pussycat paws. Vegetation can be used to hide the fencing, so your yard doesn’t look like a prison camp.

We let our cat into the back yard on a regular basis, but only when we accompanied him. Fortunately, he had no interest in scaling the wire fence that rings the yard (perhaps getting outside was a sufficient treat in itself), and we watched him closely enough to discourage him from hanging out by the feeders. Unfortunately, of course, the perimeter fence doesn’t keep neighbor cats out of the yard.  It helps if people are home enough to be vigilant catwatchers. Our solution any time we see a cat is to run from the house at it, screaming like a banshee, and subsequently all we have to do is open a window for the intruding cat to disappear like magic. We wouldn’t dream of hurting a cat, but we don’t let them know that.

What troubles me is that there are many cat lovers who are not willing to restrict their pet’s activities, and who are willing to accept whatever level of wildlife mortality that entails. Kitty is considered just one of the family, not a killing machine unleashed on the neighborhood.

Dennis Paulson
Nature Blog Network