posted April 9th, 2013; last edited April 9th, 2013 –– David Sibley

The white eyelid of American Dipper



American Dipper showing off its white eyelid. Photographed near Cody, WY, March 2013, by David Sibley.

It’s one of the first things people notice when they get a good look at a Dipper – the eyelid flashes white when it blinks! This is so different from any other bird that it begs for an explanation. Understandably, many people assume that the flashing white eyelid must have something to do with the dipper’s unusual underwater habits, related to helping them see underwater, which leads to the common misconception that the white flash is a nictitating membrane.

All birds have a nictitating membrane, a translucent whitish/bluish “third eyelid” that flicks across the surface of the eye from front to back to protect it while still allowing some vision (more info on Wikipedia).

But the dipper’s flash is bright white, and travels from top to bottom and back up (and if you can examine it very closely you’ll see that it’s covered with tiny white feathers). It is the eyelid.

Because the eyelid is white, we notice every time a dipper blinks. They don’t blink a lot more than other birds, it’s just that most other birds have dark grayish eyelids without feathers, and blink more quickly, so their blinking is barely noticeable.

The next question is… Why? Why do dippers have white eyelids and then make a big show of blinking slowly? Nobody knows.

One idea that’s been proposed is that it’s a useful way of communicating with other dippers in the very noisy streamside environment, but that’s just a general idea about visual communication and doesn’t get any closer to explaining what dippers are trying to say with their eyelids. Even the authoritative BNA account by Willson and Kingery offers no explanation.

Maybe the dippers we see – blinking as they pop in and out of the water – are just blinking, and the white eyelid has some other specialized function at another time in their life. It’s a basic question about a relatively common and easy-to-see bird, and it could be answered by just observing and getting to know some dippers. And that seems like it would be a pretty nice way to spend a few months.


Willson, Mary F. and Hugh E. Kingery. 2011. American Dipper (Cinclus mexicanus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: [subscription required]

posted March 4th, 2013; last edited March 4th, 2013 –– David Sibley

Pairs as an aid to hawk identification

Two Red-tailed Hawks in a single tree. Modified photo by David Sibley.

By the end of February, even in cold and snowy Massachusetts, Red-tailed Hawks are courting and forming pairs in preparation for nesting. It’s common to see the male and female of a pair sitting close to each other in a tree, and this provides a very powerful clue to identification.

Hawks are generally solitary and territorial, and will not tolerate another hawk nearby. The only exception is mated pairs. You won’t see two Rough-legged Hawks, or a Red-tailed and a Red-shouldered Hawk, sharing a tree like this on the wintering grounds. Therefore, whenever you see two hawks sitting this close to each other, it’s safe to assume that they are the same species and that they are nesting nearby, which greatly reduces the number of candidate species.

Habitat also helps, and since Red-tailed Hawk is the only large open-country raptor nesting in Massachusetts it’s easy to identify these two birds as Red-tails based on nothing more than their size and their choice of perches.

posted February 14th, 2013; last edited February 14th, 2013 –– David Sibley

Sibley eGuide for Kindle Fire HD coming within days

Some of you had noticed that the Sibley eGuide was not in the Kindle store any more. Apparently the new Kindle Fire HD tablet required changes in the app, but those are now completed, the app has been resubmitted to the Kindle store for approval, and it should be available within days.

Thank you for your patience and support.

posted February 14th, 2013; last edited February 14th, 2013 –– David Sibley

A video bird quiz

The answer is at the end of the video, and in the text below.

It has been a relatively mild winter in Massachusetts, but the blizzard of Feb 2013 put over two feet of snow on the ground, effectively eliminating most of the grassy and weedy habitat sparrows need. In such conditions the plowed edges of roads become an oasis of open ground and exposed seeds, and sparrows gravitate to those edges. Thus a Le Conte’s Sparrow, a very rare visitor to Massachusetts, was found in Concord on 12 Feb. I suspect it had been at this location, somewhere in the acres of weedy and marshy habitat, since at least December, and was only found because of the snow that forced it into the open.

Given its behavior, it’s no surprise that it wasn’t found sooner. Le Conte’s Sparrow is known for being secretive, just like Grasshopper Sparrow and other species in the genus Ammodramus. They rely on camouflage for protection and usually crouch when alarmed rather than flying. The behavior shown in this video – burrowing under matted grass – is something most sparrows simply never do.

posted February 5th, 2013; last edited February 5th, 2013 –– David Sibley

Dark heron/egret

Can you identify the two birds in this photo?

Photographed by William Horden in Big Cypress Preserve, FL, Dec 2012. Used by permission. You can see William's more artistic work at his website:

….Continue reading Dark heron/egret →

posted February 4th, 2013; last edited February 4th, 2013 –– David Sibley

Updated app for iPhone

The Sibley eGuide to Birds app for iPhone has been updated.

This update adds thumbnail images of every species in the scrolling list and in search results, the option to display common names in French, Spanish, or Latin instead of English, the latest AOU taxonomy including splits of Scripps’s and Guadalupe Murrelet, new audio for Bendire’s Thrasher and Cackling Goose, and some minor corrections.

Similar features for Android and other platforms coming soon.

more info here

posted January 2nd, 2013; last edited January 2nd, 2013 –– David Sibley

Quiz 54: Head patterns

The three photos below show a Song Sparrow as it turns its head. Your challenge is to locate the plumage marking known as the lateral throat stripe in each photo.

Photos ©David Sibley. Sep 2012, Concord MA.
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posted December 19th, 2012; last edited December 19th, 2012 –– David Sibley

Posture and shape distinguishes male and female Dark-eyed Juncos

Backyard Bird Discoveries

While watching a small flock of juncos at my bird feeder on December 17, 2012, I noticed one particularly brownish female. Considering subspecies and watching it a little further I noticed that it seemed more active and alert, darting around quickly and holding its body more upright than the other juncos. Could this be a regional difference? Maybe some western Juncos have a previously unnoticed tendency to stand more upright? Unlikely, but worth watching more to figure out what was going on.

Pencil sketches of Dark-eyed Juncos showing female (upper) and male (lower). Differences in posture and shape are described in the text below. Original pencil sketch copyright David Sibley.

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posted November 16th, 2012; last edited November 16th, 2012 –– David Sibley

Can you find the Cackling Goose?

One of the biggest challenges of identifying a Cackling Goose is just finding one, especially in the east where the species is rare and occurs mostly as single birds (of the relatively large and pale Richardson’s subspecies) among big flocks of Canadas. The photos below show one Richardson’s Cackling Goose among Canadas. See if you can pick it out in each photo, then read below for tips on what to look for.

Canada and Cackling Geese, Acton, MA. 14 November 2012. Photo by David Sibley.

….Continue reading Can you find the Cackling Goose? →

posted November 5th, 2012; last edited November 5th, 2012 –– David Sibley

My trick to finding Rusty Blackbirds

Almost every Rusty Blackbird that I see in the eastern United States is in flight, so the simple trick is to look up. In order to do that you need to know what to look for: I use sound to know when to look, then look for flying blackbirds that are solitary or in small groups, with long wings and long, club-shaped tails.

Rusty Blackbird (left) and Red-winged Blackbird, showing subtle differences in shape. Original pencil sketch by David Sibley.

Use your ears

First, listen for a slightly different call. All of the blackbirds and grackles give a low harsh check or tuk call in flight. In Red-winged Blackbird this is a relatively simple and unmusical chek, like hitting two twigs together. Rusty Blackbird’s call is more like chook, it has more complexity and depth. Rusty’s call is slightly longer, slightly descending, and with a bit of musical tone. It reminds me vaguely of the harsh chig call of Red-bellied Woodpecker.
….Continue reading My trick to finding Rusty Blackbirds →