American Dipper... North America's only aquatic songbird

American Dipper at Hagg Lake, Washington Co., Oregon on 24 November 2010 by Greg Gillson.

 

Some birds are very difficult to photograph. At least, I've had some trouble. One of those is the American Dipper. These gray aquatic songbirds live along rushing streams with steep banks edged by dense forest. So they are often in shade, with bright reflections off the water. The shade requires a slower shutter speed. Any shafts of sunlight are over-exposed. Slow shutter speed also means the bird must be still. And dippers got their name for their constant dipping, bouncing 40-60 times per minute on their legs even when standing in place.

On November 22 we got our first snow of the season. It wasn't much, as typical for western Oregon, just a bit as rain showers all week were pushed south by a cold front and the dry air behind it. By November 24 the roads had dried, the icy roads had mostly cleared. I went up to Hagg Lake at the edge of Oregon's Coast Range about 30 miles west of Portland.

At the upper end of the lake I stopped briefly to see if the resident pair of American Dippers were present at the Scoggins Creek Picnic Area, where this creek enters the reservoir. The birds were there, swimming and diving in the water, so I got my camera out. The leaves of the maples and alders were gone, and the quarter-inch of snow brightened up the creek under the western red-cedar and Douglas-fir. So I sat on a rock at the edge of the creek about 20 feet from the ledge where two birds were diving for caddisfly larvae--their favorite food.

Then something wonderful happened. The bird pictured here began his long, warbling, high-pitched song. It wasn't as loud as it will be in a couple of months, but clearly heard above the roar of the creek. It is not unusual to hear dippers singing throughout the year. But the bright cascading trills and sweet notes brightened the cold overcast winter day, when most other birds were silent.

Another thing that can ruin a good photo of a bird is the inner eyelid, the nictitating membrane. In some birds it is transparent, but is opaque in the American Dipper, as seen in the photo below, creating a vacant-eyed "Little Orphan Annie" appearance.

 

The nictitating membrane, or inner eyelid, covers the eye of this singing American Dipper at Hagg Lake, Washington Co., Oregon on 24 November 2010 by Greg Gillson.

 

The nictitating membrane is under the eyelids. It sweeps across the eye from its base on the bill side of the eye. It allows light to enter. On birds with clear nictitating membranes they can see through it. It is thought many birds fly with their nictitating membrane closed--to keep the air from drying out the cornea. The well-developed nictitating membrane protects the eye of the American Dipper from the spray of water (The Audubon Encyclopedia of North American Birds, 1980 by John K. Terres).

A year ago I discussed How to find a Dipper nest. There is more information on these fascinating birds there.

Feeding habits of the Northern Shoveler

Female Northern Shovelers, Fernhill Wetlands, Forest Grove, Oregon on 19 October 2010 by Greg Gillson.

 

Many birders are a bit hesitant when it comes to identifying female ducks. The hen's plumage is camouflaged browns. Clues from the brightly-colored wing are often concealed, folded up and covered by the scapulars and breast feathers. It doesn't help, either, that they frequently keep their bills hidden, tucked away in the scapulars as they rest.

But what's this? All those ducks swimming around seem to be feeding with their head half way under the water! Looking around, it doesn't take long to spot plenty of drakes feeding in the same manner--Northern Shovelers all.

Called "spoonbills" by hunters, for their long spatulate bills, Northern Shovelers are the 4th most abundant duck on the Pacific Flyway, following Northern Pintail, Mallard, and American Wigeon.

Shovelers are included in the "puddle ducks" or "dabblers" that primarily feed by upending--head under the water and tail and legs in the air. But not so the Northern Shovelers. They feed more on the surface, pushing their bills through the water, straining out food with the sieve-like lamellae--a comb-like structure on the edges of the bill. All ducks have lamellae, but on the Northern Shoveler it is especially well-developed.

These ducks commonly feed in small groups that circle about, stirring up mud with their feet. They take more animal matter than most puddle ducks, about 65% animals to 35% plants. Snails and water boatmen seem to be favorites, according to John K. Terres in his 1980 reference work, The Audubon Society Encyclopedia of North American Birds.

However, whereas Terres indicated that the feeding groups are "three or four" in size, I have often noted groups of a hundred or more in a tightly packed raft, circling and circling as they feed. As they feed, the males (only?) constantly grunt a mechanical chug-kuk chug-kuk chug-kuk....

 

A whole raft of nearly headless ducks! Feeding Northern Shovelers, Fernhill Wetlands, Forest Grove, Oregon on 19 February 2006 by Greg Gillson.

Photo Quiz

Quiz bird, Jackson Bottom Wetlands, Hillsboro, Oregon on 15 November 2010 by Greg Gillson.

 

Do you know the species pictured here? Are you sure? Can you tell what age? Can you find it in your field guide?

Certain birds can be highly variable in their plumage appearance. An individual may not match exactly the illustration in the field guide. Most field guides show an "average" plumage; some show certain variations, but not all. The plumage above does not appear exactly in any of my field guides.

This is obviously a bird of prey. It has large, broad wings with "fingers" formed by emarginated (notched) primaries. Large yellow feet with sharp black talons, and a short curved bill complete the raptor characters visible.

The mostly black plumage with white base to the tail probably has most people immediately guessing eagle--either Golden or Bald. But which one?

If we only had a view of the upperside....

Well, we do. And it is immediately below. However, if you want to stop here and get your field guide out and make a guess, this is the place to do it. Because immediately after the photo below I will start giving the answer...

[Microsoft Windows tip: Right-click on each photo and "open in a new window" to get the larger image. Then you won't have to wait so long to reload the blog page as you do when you left-click and hit the "back" button to return.]

 



 

So, is it Bald Eagle or Golden Eagle? And what age? Why do we care about the age? We get more clues about the ID if we can determine age.

Let's start with what it is not, shall we?

It is not a juvenile Golden Eagle. Such a bird would have a brighter and cleaner white base to the tail and big white wing patches.

It is not an adult Golden Eagle. They have darker tails and less white on the face.

In fact, the white on the face and yellow on the bill eliminate any age of Golden Eagle. It must be a Bald Eagle. But what age?

The dusky banded tail, dark underparts, and dark back looks a lot like the juvenile Bald Eagle illustrated in Sibley's guide. However, the white on the face and yellow bill are wrong for a juvenile.

Second and third year birds have white wing linings and belly and a white triangle on the back. That doesn't fit. That's odd. And fourth year birds reach adult plumage with white head and tail.

I don't see any plumage age that matches the quiz bird.

Let's try the National Geographic Guide and... oh my God!   It looks just like the juvenile White-tailed Eagle!

---

Wait! Slow down just a minute. While it is possible that I've actually found a rare bird--in fact, I have found several rare birds over the years--it is more likely this is an unfamiliar plumage of a common bird. After all, White-tailed Eagle from Eurasia is not just a rare bird in North America, it is extremely rare with only a few records from Alaska (mostly the Aleutians) and a record or two from the East Coast.

Let's age this bird more accurately to help with the ID.

Juveniles of many species, including eagles have more pointed feathers than older birds. Look at the wings--the primaries and secondaries on the trailing edge of the wing. The trailing edge is rather smooth and even. If this bird was a juvenile each feather would be obviously pointed, the trailing edge would appear saw-toothed.

Unlike smaller songbirds, the wings are so long on eagles that not all the flight feathers are replaced every year. It takes at least 2 years to replace the flight feathers. During this time the longer and more pointed juvenile feathers would contrast obviously with shorter and broader replacement feathers. There would be obvious "steps" (molt limits) every 3-5 feathers on the trailing edge. Such is not the case in this quiz bird.

Based on the state of molt on the wings (none visible) and no juvenile feathers, this bird must be at least 2-1/2 years old. As discussed, 2 and 3 year old Bald Eagles have white wing linings and often a white belly (especially 2-year olds), and a white triangle on the back. This bird does not. It has a more adult-like blackish body.

Not all Bald Eagles reach full adult plumage in 4 years, some birds take 5 years. It is possible, then, that our quiz bird is 3-1/2 (assuming hatched in May, and it is now November), with extensive dark mottling remaining on the tail and head feathers. I do note some white spotting throughout the body and wings.

A paper on aging eagles by Mark McCoullough would seem to indicate the bird I saw was in Basic III plumage.

However, everything we've said for Bald Eagle is also true of its sister species, the White-tailed Eagle. How do we know this is not a 3-1/2 year old White-tailed Eagle?

There are 3 remaining features to separate Bald Eagle from White-tailed Eagle. Rarely does one have to resort to these "supporting" field marks. But in this case it seems necessary.

For comparison, look at this album of White-tailed Eagle photos from Lithuania (isn't the Internet wonderful?). Bird 7 is a juvenile, looking superficially like our quiz bird. However, note the saw-toothed trailing edge of the wing?

Remember that we said that raptors show emarginated primaries? Bald Eagle has notches in the outer 6 primaries, White-tailed Eagle shows 7. On my photos I can only clearly see 6 notched primaries. The 7th? Well, it's hard to tell. Nothing conclusive.

The tail of White-tailed Eagle is short and pointed. My dorsal (back-side) photo above does not show an obvious pointed tail. Perhaps still not conclusive, but this mark seems to favor Bald Eagle.

Finally, Bald Eagles have white undertail coverts and White-tailed Eagles have dark undertail coverts. My ventral (under-side) photo definitely shows extensive dark undertail coverts. There appears to be a couple white feathers on the bird's right-hand side of the undertail coverts--maybe. If we assume this is a 3-1/2 year old bird, when all Bald Eagles should have extensively white undertail coverts, this mark definitely favors White-tailed Eagle.

A mark not mentioned in my meager references on White-tailed Eagles is the upper tail coverts. The uppertail coverts are white on Bald Eagle and mostly dark on White-tailed Eagle. My dorsal photo above shows 2 white uppertail covert feathers over the middle 2 tail feathers. This is exactly like this photo of White-tailed Eagle. This mark favors White-tailed Eagle.

That's it then. I can go no further based on my knowledge and references. Here is a bird that doesn't really match any plumage that I can find of either Bald Eagle or White-tailed Eagle. I believe it is in Basic III plumage, 3-1/2 years old.

Such an inconclusive outcome may happen anytime when we're bird watching. Sometimes birds are too far away, in bad light, or not seen long enough for us to be sure. In such a case it is best to let it go. Odds favor a common bird over a rare bird by, literally, millions to one. The odds are still the same even when photographed. And sometimes photographs--even fairly good ones--aren't diagnostic.

Unless someone can prove otherwise, with additional knowledge and experience I don't have, I have to go with Bald Eagle. But,... okay, take my own advice and let it go....

Oh, and by the way, that bird is probably still around...

What is eBird?

Golden-crowned Sparrow, Forest Grove, Oregon on 21 October 2010 by Greg Gillson.

 

Recently I have begun using eBird and wanted to present some information about this "citizen science" program.

Sponsored by the Cornell Lab of Ornithology and the National Audubon Society, the heart of eBird is a free "real-time online checklist" program. But it is so much more.

On the surface it is as easy as going birding and then submitting an online checklist for each location where you birded that day. Every time you go birding, submit another checklist, or checklists, for the area(s) you visited. Simple. The program keeps tracks of your birding list by world, country, state, county, or birding hotspot, and by life total, year, or month.

The real power comes as it combines your checklists with everyone else's.

"The observations of each participant join those of others in an international network of eBird users. eBird then shares these observations with a global community of educators, land managers, ornithologists, and conservation biologists."

The sharing of many birders' checklists creates a huge database. How big? Big. As of November 2010: 45,000 birders in 200 countries reporting the status of 8665 species.

In North America the numbers of monthly checklists submitted is very large. California birders lead all others. 4211 individual checklists during the first 2 weeks of November. However, British Columbia, in 7th place, with very few birders has 1531 checklists submitted so far this November! Washington State, in 14th place, has 920 checklists the past 2 weeks. Oregon and Idaho are farther down the list. But I think more people should be using eBird. I encourage you to take a look at eBird.org.

So, is it only scientists that can use the data? No, there are things you can "research" as well, in the "View and Explore Data" section. Here are some examples...

• View the worldwide range of Winter Wren (before the split into 3 species)
  
• Create a county checklist, such as one for Lincoln County, Oregon
  
• Look at the checklist of all birds reported at Malheur NWR, Oregon in May 2010
  
• Look at the mapped range of Western Scrub-Jay in Washington State
  
• View the mapped range and click on the location flags to see who reported Oak Titmouse in Oregon
  
• Compare the seasonal range map of breeding Golden-crowned Sparrow with the winter range
  

So, besides entering your own data, you can keep track of other sightings in your local county, prepare for a visit to a birding hotspot at any time of year, track year-to-year (or month-to-month) variation in any bird species in any area.

And with your sightings added to the database, it will keep getting better....

Try it!

One year old Cedar Waxwing

Cedar Waxwing, Forest Grove, Oregon on 21 October 2010 by Greg Gillson.

 

One final post on the many Cedar Waxwings I photographed in a hawthorn tree in October.

Post 1 showed 2 views of a waxwing feeding on hawthorn berries.

Post 2 discussed the molt and aging of this same adult bird.

Post 3 talked about an juvenile waxwing and discussed the waxwing's first description to science.

Today's post goes back to molt.

Perhaps after reading Post 2 you can see the patchy back plumage on this bird and discern a couple of pin feathers in sheaths on the cheek of this bird. Most obvious are the outer tail feathers that are still growing in. So this bird is undergoing a full prebasic molt into its first definitive basic plumage.

Why can we say this bird is attaining its first fully adult-like plumage?

If you look at the wings you will see some fresh dark inner primaries, and some very faded, worn, brown primaries. Those brown primaries are the remnants of juvenile plumage, the first (non-down) feathers this bird ever grew. Those tattered wing feathers are now over a year old. And that is the age of this bird--perhaps 16 months old. Once those feathers in the wing and tail are fully replaced and grown, probably before the end of November, it will no longer be possible to tell how old this bird is by looking at its plumage.

Here is a link that will bring up all my blog posts having to deal with molt.

Juvenile Cedar Waxwing

Cedar Waxwing, Forest Grove, Oregon on 21 October 2010 by Greg Gillson.

 

We discussed the adult Cedar Waxwing and how to age it in two previous posts.

The streaky underparts of today's photo and lack of much crest are ample clues for most people to identify this bird as an immature.

The Cedar Waxwing was first described to science in 1808 by Louis Jean Pierre Vieillot. And this Frenchman had ample time to collect and describe birds in North America.

You see, Vieillot was on a business trip to Haiti when the French Revolution broke out in 1889. So, being on the wrong side of the new ruling class, he fled to the United States. There he began to study birds.

It was not until a dozen years later Vieillot was able to return to France and start working on his book, Histoire naturelle des oiseaux de l'Amérique septentrionale (Natural History of Birds of North America) that he published in 1808. In it was the first description of Cedar Waxwing from eastern North America.

One more waxwing photo is coming with the next post....

More on the Cedar Waxwing

The Cedar Waxwing in the previous post, Cedar Waxwing feeding on hawthorn berries, was not only beautiful, it has a secret. Closely observing the photograph (and the bird in life) can tell us more about this bird.

In this species the sexes are described as "outwardly alike," meaning that the sexes have the same plumage and we can't tell the sex of the bird without some disassembly.*

But we can observe that the bird is in molt and thus tell a bit more about its age.

 



 

In the photo above, note some feather sheaths on the face (A). These are new growing feathers, not yet fully developed. Also notice that the new breast feathers are especially wispy with whiter tips (B) that contrast with the browner feathers of the shoulder. [You can click on the photo for a larger view.]

As these feathers wear and age, the plumage will become smoother and more evenly colored, as in a previous discussion of Cedar Waxwings.

 



 

Perhaps more obvious, we can see in the above photo that the outer tail feather on this bird (C) is short, and has not yet reached its full length. Wing and tail feathers in most birds are replaced sequentially so that the bird can continue to fly during the molt period.

 



 

Again, in the above photo, note that the 9th primary feather (D) is only half the length of the others and has more growing to do. [Waxwings have 10 primaries, but the outermost, the 10th, is always very tiny.] The new yellow belly and side feathers (E) are fresh and wispy. While the plumage of waxwings is naturally fluffy, these tips will wear down as the year goes on, creating a more smooth-looking plumage. The name-sake waxy tips of the secondaries (F) indicate this is an adult.

We thus can tell that this bird is an adult, 2 or more years old, undergoing a full pre-basic molt.

For more on molt and aging see this previous post.

* - Males have, on average, more extensively darker throats. Look at this web page that Mike Patterson alerted me to.