Sibley Guides

Flycatcher identification by the calendar

David Sibley — Fri, 12 Apr 2013 17:54:47 +0000

Here are some eBird maps showing all records for the month of April for several species of small flycatchers in eastern North America. A glance at these maps will show which species are possible in your area in the next few weeks, and this greatly simplifies flycatcher identification. For most of the east, through most of April, small flycatcher identification can be summed up in one short phrase – ”It’s a phoebe” (see Eastern Phoebe map at the end of this post below).

Anything is possible, of course, and spring migration is getting earlier each year, but if you think you have found, for example, an Alder Flycatcher in Pennsylvania in April, you’ll need some photo or audio documentation to verify it.

Alder Flycatcher records in the month of April – very few!

Yellow-bellied Flycatcher records in the month of April – very few!

Willow Flycatcher records in April. Only a handful of records scattered north and east of Texas. Assuming that these are correctly identified, the fact remains that any Willow Flycatcher in those areas in April is an extreme rarity.

Least Flycatcher records in April. The second-earliest Empidonax (after Acadian), and getting farther north by the end of April. This map was made on April 10th, the orange markers indicate records in the current year (i.e. the first ten days of April), blue markers show records from past years. Virtually all of the blue markers shown represent records from late April.

Acadian Flycatcher records in the month of April – this species arrives on its southern breeding grounds in mid- to late-April, and is generally the earliest Empidonax.

Eastern Wood-Pewee records for the month of April, showing as purple rectangles because there are over 2000 total records in view. Note that there are very few records north of about Missouri, southern Ohio, and Maryland. North of there any April reports of this species should be very carefully identified.

Eastern Phoebe records in April. This species is the earliest flycatcher by far. Many winter in the southern US, and spring migrants arrive as far north as New England during March, with a big influx there in early April. This map represents a nearly fully-occupied breeding range in April.

The white eyelid of American Dipper

David Sibley — Tue, 09 Apr 2013 22:21:25 +0000

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.

References

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] http://bna.birds.cornell.edu/bna/species/229

Pairs as an aid to hawk identification

David Sibley — Mon, 04 Mar 2013 15:44:16 +0000

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.

Sibley eGuide for Kindle Fire HD coming within days

David Sibley — Thu, 14 Feb 2013 16:29:21 +0000

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.

A video bird quiz

David Sibley — Thu, 14 Feb 2013 15:19:20 +0000

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.

Dark heron/egret

David Sibley — Tue, 05 Feb 2013 15:04:28 +0000

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: http://www.hipikats.com

It should be immediately obvious that this photo shows two species of dark herons, and their overall slender shape and uniform grayish color, with no distinct markings on head or neck, reduces the options to two: Little Blue Heron and Reddish Egret.

It is rare to see these two species side-by-side, so we rarely get to appreciate the much larger size of Reddish Egret. This kind of grassy freshwater pool is normal habitat for Little Blue Heron, but Reddish Egret is almost always found on expansive shallow saltwater lagoons.

It’s also a great opportunity to compare the differences in overall color, as well as details of the color of bill, lores, eye, legs, etc.

This is an immature Reddish Egret, less than a year old, based on its lack of plumes, drab grayish color overall and slightly paler and brownish tips on all of the wing coverts. Compared to an adult Little Blue Heron the immature Reddish Egret’s paler ashy-gray and mottled color is easily distinguishable. An adult Reddish Egret would be even more distinctive in color, with clean gray body and shaggy reddish neck.

Updated app for iPhone

David Sibley — Mon, 04 Feb 2013 21:38:13 +0000

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

Quiz 54: Head patterns

David Sibley — Wed, 02 Jan 2013 20:29:57 +0000

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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Congratulations - you have completed Head patterns.

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Question 1

The lateral throat stripe is labeled:

A	A
B	B
C	C
D	D
E	E

Question 2

The lateral throat stripe is labeled:

A	A
B	B
C	C
D	D
E	E

Question 3

The lateral throat stripe is labeled:

A	A
B	B
C	C
D	D
E	E

Once you are finished, click the button below. Any items you have not completed will be marked incorrect. Get Results

There are 3 questions to complete.

Posture and shape distinguishes male and female Dark-eyed Juncos

David Sibley — Wed, 19 Dec 2012 18:36:22 +0000

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.

That one bird really did stand out in posture and behavior among the three or four juncos on the ground, but I realized that the others were all males. Soon another female appeared, and while it wasn’t quite as obvious as the first one, the two females still shared more posture and behavior in common with each other than they did with the males.

Watching and sketching for the next hour or so revealed consistent and fairly obvious differences. I could watch a bird with my naked eye, guess the sex, and then check plumage through the binoculars, and it worked!

A big factor is that males are generally the dominant birds. They tend to sit still and defend one spot as they feed, and will chase away a female that gets too close. The males spend a lot of time in the center of the feeding area and in a “macho” posture, crouching and looking aggressively around, while the females are flitting nervously around at the edges, alert and always ready to fly when challenged.

Besides the females’ more upright posture, more active behavior, and lower rank in the pecking order, I also noticed that they seemed to have thinner necks and a very slight crest.

The more I watched and sketched the more obvious this seemed. The males have a “ruff” of feathers on the back of the neck, smoothing the contour of the crown into the back, and looking particularly broad and “swarthy” from behind. This is enhanced by their crouching posture, but did not seem to be solely caused by that. The neck of the females is more normally proportioned, with a subtle constriction between head and body, appearing narrow when viewed from behind and leaving a sharp corner (a slight crest) on the rear crown.

In summary:

Females tend to stand more upright, with head held high and body higher above the ground
Females have thinner neck, lacking the male’s bulging neck feathers
Females tend to show a very slight crest, while males’ head profile is more rounded
Females are lower on the pecking order and are often chased by males, leading to more active and fidgety movements

This is based on just an hour of observation and about a dozen birds in one situation, but it has worked just as well here on subsequent days. It may not work so well under other circumstances, or in a different flock. There may be situations where some females are higher-ranking socially, and that would negate a lot of the behavioral differences. I will be watching for these differences in the future, and would be interested to hear of anyone else’s experience with it.

Video

I took a few minutes of video, which is very poor quality due to the low light and snowfall, but is still helpful to show the differences described above.

Can you find the Cackling Goose?

David Sibley — Fri, 16 Nov 2012 15:07:40 +0000

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.

When looking for Cackling Goose among Canadas I find that it’s best to focus on the body size of the birds and just scan for one that looks smaller or less bulky. You’re looking for a bird about two-thirds the size of the standard Canada Goose.

It’s tempting to scan the flock looking for a bird with a small bill, since that is the most reliable distinguishing feature emphasized in all of the field guides, but the differences are hard to see, and bills are often hidden, and therefore this is not a very good way to find a Cackling Goose. Unless you’re very close to the geese it’s better to ignore bill size until you’ve located a good candidate based on other features.

Once you’ve found a bird that looks smaller, check the overall color. A typical Richardson’s Cackling Goose is slightly darker and warmer brown on the breast, and slightly more grayish or silvery on the back. If you scan through any big flock of Canadas you can find birds that match each of these features, and plumage color by itself is almost useless for picking out a Cackling Goose, but any bird with smaller size and these plumage colors is likely to be a Cackling. None of that is absolutely diagnostic for Cackling, but it will tell you that you’re on the right track and then you can work on studying the bill.

On some individuals (like the one shown above) the warm brown color of the breast blends to darker and more rusty at the upper edge just below the black neck, and this darker breast color helps to set off a small white collar (also only on some individuals). A similar white collar is only rarely shown by Canada Goose.

If you’ve actually found a small goose that looks slightly more golden on the breast and grayer on the back, then it’s time to confirm the identification by studying bill size.

Pitfalls

Judging size is harder than it sounds, since the geese are usually moving around, and standing at varying angles on uneven ground. A bird facing away and standing in a furrow will always look smaller than a bird in profile standing on a ridge. In addition, males average larger than females, and size is quite variable overall. You will have to watch a goose move around for at least a few seconds while comparing it directly to other geese to be sure you’re getting an accurate impression of size, and you can expect a lot of “false alarms” of birds that look small at first and then transform into more normal size. If it still looks small from several angles then it is worth closer study.

It’s a little easier to judge the size of birds that are swimming, since they are all on the same level. The best opportunity to judge size is when something alarms the geese and they are all in alert posture. Scan quickly then for smaller birds.

When comparing sizes within a flock, keep in mind that geese (unlike most birds) often stay together as family groups through the fall and winter. If you find a bird that really looks small, but a few of the geese around it look about the same size, it is worth making some extra comparisons to see if that whole group is smaller than the average of the flock.

I haven’t mentioned neck length above because I don’t think it’s very useful as a distinguishing feature. The neck length of an individual bird can change dramatically depending on stance and alertness. It is true that Cackling Geese average shorter-necked than Canada, but there is just too much variation, and too much overlap, to recommend this as a field mark.

When there is less variation in neck posture – in flight, in alert posture, or when grazing with head down – neck length is more reliable and worth studying, but in most situations it’s just too variable.

Answers

In the first photo the Cackling Goose is the bird in the left foreground with head down; in photo 2 right foreground; in photo 3 second from right foreground with head up; in photo 4 right foreground. All of the other geese are Canadas.