Tunnel Vision II

What species of bird is this? If you are new to birding this may feel like a difficult question. Surprisingly, the choices are fairly limited. There are primarily two candidate species.

They are a Ruby-crowned Kinglet (RCKI) or a Hutton's Vireo (HUVI). We'll come back to this in a minute.

This week a friend and I ran into each other in the Arboretum. As we walked downhill, towards the Japanese Garden, we heard a bird song that I did not immediately recognize. (This happens most often in early Spring - when many months have passed since the last time I heard the male of some species doing his Spring song.) A moment later we saw this bird which resembled a Ruby-crowned Kinglet.

The sound had come from high over our heads, while the bird was low and in front of us. I did not immediately assume a connection. To my credit, as the bird moved about the understory, I began to get an odd feeling. It was not moving with the extremely energetic pace of a Kinglet. 

Kinglets flutter and dart from one feeding opportunity to the next.  

In fact, the bird we were watching did not appear to be intensely searching for food. The slower pace helped me to realize that it might be a Hutton's Vireo. I started looking closer. I even wondered if the bird was looking for nesting material although I did not see it collect anything.

Here is a frontal comparison of the two species. (Since facial recognition is a critical human skill set, I have often wondered if a face-first approach to distinguishing bird species might be useful.)

On the left is the Hutton's Vireo and on the right is a Ruby-crowned Kinglet. If you look close you can see a faint hint of the ruby color on top of the Kinglet's head (and also in the previous photo). These tiny marks of red indicate they are males.

Between the eyes the Vireo is much lighter in color, plus, it has a wider and lighter colored bill and its eyes are offset on the side of the head rather than pinched-in and closer to the bill like the Ruby-crowned Kinglet. 

I checked a number of Ruby-crowned Kinglet (RCKI) photos with this same angle and the positioning of the eyes is consistently tighter than the Hutton's. This gives the RCKI an intense, hyper-focused appearance that fits well with its behavior.

By the way, both of these species are considered foliage-gleaning insectivores. I suspect their specific feeding methods may relate to the positioning of their eyes. Hutton's seem more likely to spot insects to their right or left while the RCKIs seem to be more focused on finding food directly in front of them.

This thought might even be extended to humans. Perhaps the many things we overlook happen in part because our eyes are forward-focused. We even have a common phrase that describes the concept, i.e. Tunnel Vision.

When we look at these two species from the side there are a few other distinguishing characteristics that become obvious. Here is a HUVI.

Here is a RCKI. 

The most conspicuous field mark is the location of the dark wing bar. On the HUVI the dark bar is between its white wing bars, while on the RCKI a similar dark mark is relatively farther from the head i.e. below its larger white wing bar. Less obvious is the break in the HUVI's white eye-ring, which is only broken at the top of the eye, while in the RCKI there are breaks at both the top and the bottom. Technically, we could call them eye-arcs instead of eye-rings.

The two bird species are very different in terms of migration and range. In Washington State the Hutton's live to the west of the Cascades year-round, while the Ruby-crowned Kinglets winter in our area but breed in the mountains - especially on the east side of the Cascades. 

In the big picture, the RCKIs migrate north and south all across North America while the HUVIs are primarily West Coast birds that migrate very little, if at all. Click on the following links to see dynamic weekly sightings from eBird.

Ruby-crowned Kinglet

Hutton's Vireo

Returning to the bird in our initial photo we now notice the light-colored bill (not black like a RCKI) and the eye-ring, broken only on the top. The dark bar on the wing is not as obvious as it could be, but it certainly does not exist below the lower white wing bar like a RCKI. Since the Hutton's Vireo is the only Vireo in our area which has an eye-ring with a gap at the top, this must be a Hutton's.

I wonder if this particular bird is just reaching maturity. Its eye-ring seems narrower than the other Hutton's (pictured above) and its dark wing bar is a bit faint. While this could be individual variation I wonder if these markings become more defined as Hutton's Vireos mature.

Zooming in for a very close look we can see one more difference between these two species.

The upper bill of the Hutton's Vireo is hooked at the end...

...while the tiny, black bill of a Ruby-crowned Kinglet is not.

The question that really stumps me is, Why do these two species look so much alike? We could guess that their coloring makes great camouflage but there are many other well-camouflaged birds with different color schemes. Plus, having similar wing-bars and eye-rings implies to me that there must be some additional value to a very close resemblance. The only idea I can think of is the slower and slightly larger HUVI might gain a slightly faster reputation by looking like a RCKI. Still, I doubt many predators are going to avoid a feeding opportunity just because their prey looks fast. I guess this is just one of nature's mysteries that is waiting for a brighter mind than mine.

While discussing this with a friend, his insightful reply was, "Have you asked Dennis Paulson?" My response was, "Ah, That is a great idea!" Dennis is a renown, life-long ornithologist, the instructor for Seattle Audubon's Master Birder Class, and has an amazing worldwide knowledge of birds. 

Here is Dennis' thoughtful reply to this line of inquiry,

"Hi Larry,

If you look through the kinglets of the world and the vireos with wing bars of the world, I think you'd see that they all look somewhat similar, little olive-green to gray birds with wing bars (and there are similar birds in some other families-how about Empidonax? (i.e. Flycatchers)). So both groups have fixed on the color pattern over evolutionary time. And of course quite a few vireos have eye-rings or spectacles along with their wing bars, so that is a commonplace color pattern in this family. However, of the six kinglet species, five have black stripes of their head and a visibly colored crown except the Ruby-crowned, and that is interesting. So to me the kinglet is more likely to have evolved to resemble the vireo than the reverse.

On the other side of the coin, the vast majority of the kinglet's range is not inhabited by Hutton's Vireos, so I can't imagine the bird diverged from the other kinglets (the four Old World species aren't called kinglets) just to look like a Hutton's, as it is still moderately different from the other wing-barred vireos.

So my conclusion is that it is just a coincidence that they look so similar. Olive-green for camouflage and eye-rings to call attention to the eyes for social interactions, but as far as I know, no one has explained the evolution of wing bars.

But to cogitate a little further, there is a hypothesis that some passerine birds have evolved to look more similar to some other species, in others words a convergence of appearance by two unrelated species, when they are part of a multispecies feeding flock. I'm not sure if this posited anywhere outside of the neotropics, though. The idea here is that you're more likely to be inclined to flock with another bird that looks similar to you. This could be stretching it a little, as many, many species in these flocks are quite distinctive and look nothing like the others, so the hypotheses is not supported extremely well.

I think no one, brighter than either of us, can really speak with confidence on why they are so similar! It makes a good story locally, at least, definitely worth calling attention to.

Dennis

The rich and varied mysteries of nature surround us. Maybe the similarities of these two species are purely coincidental or maybe there is some unknown hidden subtlety waiting to be revealed via creative inspiration and meticulous research. 

By the way, the song that we heard was very similar to the first recording you can hear when you follow - This Link. This HUVI song is fairly unique and unlike a RCKI. It may be your easiest way to locate a HUVI in the Arboretum. Singing males are a sign that Spring, nest building, and eventually fledglings may be in our future - a welcome thought indeed!

Have a great day on Union Bay...where nature lives in the city and Black Birders are welcome!

Larry

ps: Maybe the scientific method is primarily a methodology for overcoming our Tunnel Vision. I sure hope it works.

Update:

A reader just contacted me to say she just found a Robin, who died in her yard, and appeared to be suffering from salmonella which can be spread via bird feeders. Please read the following from the Cornell Wildlife Health Lab: Salmonella. Cornell suggests, during outbreaks, removing bird feeders is to the greater benefit of the birds.

Going Native:

Each of us, who breathe the air and drink the local water, needs to watch and protect our local environment. Native plants and trees encourage the largest diversity of lifeforms because of their long intertwined history with our local environment and native creatures. I have been told that even the microbes in the soil are native to each local landscape. I hope we can inspire ourselves, our neighbors, and local businesses to respect native flora and to support native wildlife at every opportunity. I have learned that our most logical approach to native trees and plants (in order of priority) should be to:

1) Learn and leave established native flora undisturbed.

2) Remove invasive species and then wait to see if native plants begin to grow without assistance. (If natives plants start on their own, then these plants or trees are likely the most appropriate flora for the habitat.)

3) Scatter seeds from nearby native plants in a similar habitat.

4) If you feel you must add a new plant then select a native plant while considering how the plant fits with the specific habitat and understanding the plant's logical place in the normal succession of native plants.

My intention in my weekly post is to include at least one photo each week and visually challenge us to know the difference between native and non-native lifeforms. 

(By the way, my friend Tom Brown pointed out that the application named 'Wildflower Search' is extremely helpful. Click on the highlighted link to see for yourself.
Also, Jane Lundin has created a small package, with a lot of critical information that looks quite handy, and light, for backpacking in the mountains in Springtime. It is titled, Mountain Wildflowers of Washington.)

What type of plant is this? Is it native to Union Bay? 

Scroll down for the answer.

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Clematis: An invasive non-native vine that covers-over and shades-out native vegetation. I may not have the precise name for the seed heads shown - regardless the impact on native vegetation is obvious. This photo was taken on the southeast corner of Montlake Cut below Monty and Marsha's Bald Eagle nest. (By the way, good things are currently happening in the nest!) 

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The Email Challenge:

Over the years I have had many readers tell me that Google is no longer sending them email announcements regarding my posts. Even more frustrating when they go to 're-sign up', hoping that will enable them to once again start receiving the announcements, they get a message which says 'Sorry, you are already signed up.' Google has not responded to my requests for help with this issue. 

My functional workaround is to set up my own email list and each week I manually send out a new post announcement. If you are experiencing the issue and would like to be added to my personal email list please send me an email requesting to be added. Something like:

                Larry, I want to see more of nature. Please add me to your personal email list. 

Thank you for your patience and interest!

My email address is: LDHubbell@Comcast.Net

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A few more photos:

HUVI or RCKI?

HUVI