American Dipper (AMDI)

American Dippers (AMDI) are a decidedly western “water bird.”  CO ranks 5th among U.S. states for breeding populations, with 7% of the population.  These amazing birds typically breed along fast-running streams and rivers; their loud wren-like chatter (often referred to as a buzzy “jik”) and extremely varied jumble of a bell-like song, individual and repeated notes and intermittent “jiks” ring out clearly over the sound of the river.  North America’s only aquatic passerine, they “fly” under water, often bucking very strong currents and using their wings to propel themselves to capture aquatics insects.  Their common name “dipper” comes from their habit of bobbing or “dipping” on the shore or a rock in the stream while they are looking for prey.  An old name for them was “water ouzel,” a name for several species of European thrush (there, spelled “ousel”).  However, although its body shape suggests some of the plumper species of that family of birds, the AMDI is most definitely not a thrush.

Below is a photo that perfectly captures how we typically see dippers in this area—a black, bobbing blob on skinny legs in the shadows on a rock in the river.  Although the photo doesn’t do the bird justice, it accurately reflects our less-than-ideal glimpses.  Luckily, dippers are easy to identify from afar by their “dipping” behavior; their rapid, shallow wingbeats as they fly low across the river; and their wren-like chatter.  Although they don’t use nest boxes, they do sort of build their own cavities.  So I’ve included them as part of our nest box monitoring effort.

20090410_amdi_2rcr

We’ve been monitoring this site since we found it in 2007, atlasing for the 2nd Colorado Breeding Bird Atlas. (Others have known about the site for years; we were just a bit late to this particular party.) Dippers build very interesting dome-shaped nests of grasses and twigs very close to water; the entrance hole typically faces the water. Our priority block included a 2-lane bridge spanning the Arkansas River, so in early April we stopped by just to see if anything might be there. Much to our surprise, tucked into the corner of one of the bridge girders over the north bank of the river, was not only an AMDI nest but a lively, noisy group of nestlings clamoring to be fed.  Our first species documented for the BBA—and it was a “confirmed” breeder.  Score!!

2008

amdi_2rSince we had missed the very beginnings of nesting behavior in 2007, we decided to try to catch it earlier the next year (2008).  In early March, we found a AMDI nest under reconstruction in the same spot.  (Some bird seemed to have built a nest on top of last year’s AMDI nest.) The photos here are of that nest; if you click on either of the photos, you’ll see a couple for red twigs at the entrance.  We continued to check on the nest untilamdi_3r about 3 weeks later, we found it smashed on the river bank.  Since eggs were still in the nest, I can only assume it was the work of human vandals—any wild animal that might have taken it down would surely have eaten the eggs.  (The spot was easily accessible to anyone by foot and indeed was just above a popular path of fishermen and teens intent on partying by the river.)  Hoping against hope, I continued to check the bridge each week.  About 2 weeks later, I found that the female was constructing a nest on a girder a bit further downstream and on the opposite side of the river—a spot much less easily accessible for humans.  We continued to check weekly for a couple of weeks more; however, the winter’s record snowpack began to melt and the river rose rapidly.  After 2 weeks, we could no longer get to the spot, so we left them in (hopefully) peace.

2009

This year (220090410_amdi_5r009), I began checking the bridge again starting in mid-February.  No sign remained of the 2008 nest, but I heard 2 AMDIs singing.  I saw no evidence of a nest until 4/1; a brief check showed a new half-dome of grasses started on a girder on the north side of the river (photo on the left).  20090410_amdi_4rIt’s on the “dangerous” side of the river again—and with such late start, it will again be in jeopardy of vandalism from warm-weather party-goers, I fear.  On 4/10, we checked again—now a completed nest (photo on the right). Interestingly, with this year’s nest, we can again see 2 red twigs at the entrance—in the same place and in nearly the identical position.  Sort of reminds me of a baby gate.  I haven’t read about dippers routinely doing something like this.  So perhaps this is the same female as last year, adding her characteristic touch?

We checked back on 5/1.  The river was on the rise, but the site was still accessible on foot.  As we approached, an adult flew from the area of the nest.  Zell moved under the bridge to take a photo and realized that a bird was staring back at him from the recesses of nest.   He took some quick photos up close.  (And look—there’s the 20090502_amdi_3r“baby gate,” still in place.)  This bird is much lighter than any  adult I’ve seen. For a time, we thought it must be a nestling that just suddenly appeared this mature.  But given the dates of nest construction (an incomplete nest on 4/1), it just seemed much too quick.  We solved that mystery when we stopped by the nest on 5/11.  This bird was in this exact position again, but we could hear a chorus of tiny squawkings coming inside the nest.  That mystery was solved–indeed, the female had been incubating the eggs, which had pretty recently hatched.  We haven’t solved the mystery of such a light adult.  Even outside the nest, she appears a much light taupe color than her mate.  Just a fluke, perhaps.

Unfortunately, that last monitoring stop is probably the last chance we’ll have.  On 5/11, the river was running at about 1010 cubic feet/second (cfs).  The path was walkable, but just barley.  The river is now rising fast due to extremely warm weather melting the snowpack and filling the upstream reservoirs to capacity.  We stopped by on 5/16 (river at  ~2300 cfs) and the path was under water.  Much safer for the birds; disappointing for the humans.  (Dipper nestlings all yelling from the entrance hole would have been a great photo.  And it would have been fun to see if the “baby gate” remained through such wear and tear.)  Alas–we leave them in peace.

© 2009 Tina Mitchell

6 Responses to American Dipper (AMDI)

  1. Mary Weyand says:

    Thanks for interesting suggestions…great to have a sculptor in the family! I’ll give it a try. Warm Regards, Mary Weyand

  2. Tina says:

    I responded to Mary directly. But perhaps others might be interested in our thoughts on this. Here’s what I wrote back to her.

    I asked my husband, who is a sculptor and who has been the photographer of the dipper nests. He thought you could probably use something like papier mache (or even those cloth strips impregnated with plaster that are used for casts) molded around a balloon (which later could be popped to remove it) to fashion the dome-shaped structure. It would make sense to build it in 2 parts–the top part, a half-round, and the bottom, flat with sides reaching up to meet the dome. (The dippers we’ve monitored have built nests that are actually flat on 3 sides, because they use the corner of a bridge abutment and a concrete bridge girder. Those not building under bridges brace their nests against rock ledges–again, therefore having flat bottoms and possibly sides too. You could make the nest even sturdier by placing it on similar wood structures or fashioning a rock ledge for it.) Lots and lots of grasses and leaves glued around the inside and out would resemble the nest. (The birds in our area also use thin willow branches.) We don’t know what the inside looks like, since it’s an enclosed dome. But Birds of North American Online (http://bna.birds.cornell.edu/bna/) describes it this way.

    Nest is a 2-part domed or ball-like structure with side entrance. Canopy of dome may overhang entrance hole to keep out water. Outer shell of moss with small amounts of interwoven grass (both stems and roots) and leaves. Inner chamber globular with woven cup; composed of grass and leaves, sometimes bark. If moss not available for outside shell, bird uses grass and leaves. Uses leaves of streamside deciduous trees, including birch (Betula), alder (Alnus), and cottonwood (Populus), and even ponderosa pine (Pinus ponderosa) needles.

    Outside diameter 20–25 cm. Diameter of inner chamber about 14 cm; diameter of inside cup 5 x 7.5 cm . Entrance 7.5 cm wide, 5 cm high during early stages of nesting, but enlarges as season progresses; 10 x 10 cm by end of nesting season.

    Does this help in any way?

  3. Mary Weyand says:

    Thanks for the pictures and info on American Dipper nests. I wish to construct an example of an American Dipper Nest that would be suitable for demonstration. This would accompany school visits based on my book, Sequoia Then and Now. One of the chapters covers the presence of American Dippers 100 years ago in the Sequoia National Park, and their continued use of the park in present-day. The tricky part is getting the demonstration nest accurate – and durable to withstand being used over and over. Do you have any ideas? Mary Weyand

  4. Tina says:

    I responded directly to Dave, but perhaps others might be interested in what little I know about this subject.

    I don’t have any direct experience with this myself. Loegering & Anthony’s (2006) article in The Wilson Journal of Ornithology entitled “Nest site selection and productivity of American Dippers in the Oregon Coast Range” described what they built for AMDIs. (I’m not the builder in the family, so I’m not sure if the info they provide is enough to be helpful). Their study also found that American Dippers eagerly took to their artificial nest sites. Here’s what they wrote.

    Created nest sites.—In August 1993 and 1994, we constructed nine nest structures (five nest boxes, two log cavities, and two cliff ledges; hereafter referred to as ‘‘created’’ nest sites) along a segment of Drift Creek (9,480 m long) and compared dipper nest abundance to that along a comparable portion of Lobster Creek (7,800 m long)—an unaltered control—to assess nest site availability and saturation. Both reaches were similar in size, gradient, geomorphology, and adjacent land use. We constructed nest boxes (Loegering 1997) similar to those used by Hawthorne (1979) in California and Jost (1970) in Europe. The open cavities were made by using a brace and bit in the ends of two, nearly horizontal logs extending over the stream (minimum dimensions were 15 x 19 x 15 cm). We used a hammer and chisel to construct two ledges on sandstone cliffs lacking a mossy covering. Two of the five nest boxes were glued to the underside of flat-bottomed, concrete bridges (1994); one was glued to the wall of a fish ladder one was screwed to the inside top of a 3-m-diameter culvert; and one was screwed to the bottom of a stream-spanning log. All structures were >500 m from known nest sites. (p. 284)

  5. Dave Bengston says:

    I really appreciate your article and the photographs. Since you have been monitoring them, I thought you might be able to help us.
    I am the Edc Chair for Peregrine Audubon Society, which is a chapter located in Mendocino County, California. I just did a nestbox building workshop today. I received a question from a birder friend about building artificial structures for A. dippers. I have not been able to locate any or any specific information other than articles mentioning that they will use artificial structures and sometimes swallow nests. Do you know of any specific plans or ideas that have worked? We would like to help them in our area since they are so uncommon.

    Thank you in advance if you can help.

  6. Charlene Anchor says:

    Keeping my fingers crossed too. Wish there was a way to protect the nest.

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