[CT Birds] Birds of spring: tales of caution and the top 5 most misidentified (long)

Thomas Robben robben99 at gmail.com
Wed Mar 21 20:28:32 EDT 2012

Dear CT birders,
If you have not seen this interesting article, posted in Mass and NH
tonight, it is worth the time and effort to scan it….
Tom Robben
Glastonbury CT

Subject: Birds of spring: tales of caution and the top 5 most misidentified
From: Marshall Iliff <miliff AT aol.com>
Date: Wed, 21 Mar 2012 14:04:04 -0400

As we all know by now, we are experiencing a record-breaking spring.
Perhaps the warmest spring and winter on record, we are now seeing a
record-early spring arrival for many species. Although arrival dates for
migrants have been kept for many years, these have done a good job
documenting just the endpoints of migration...not the whole bell curve.
eBird, for the first time is now documenting the entire arc of migration,
so I'd like to personally thank everyone who is reporting to eBird and
providing such valuable information to actually quantify how exceptionally
early this year's arrival dates are.

As just one example of this full illustration of migration, and a very
simple one, look at this eBird graph for Eastern Phoebe (showing 2012 in
progress compared to 2011 and 2010). It shows not just when the first
phoebes are reported, but when they reach their peak occurrence and when
they become widely reported enough to be considered "arrived" (maybe 10-20%
of their max frequency, for example, where the bell curve gets steep). You
can do these graphs for any year, and only 2010 even comes close to this
year's arrival curve for Eastern Phoebe, which is shifted a full 2 weeks
early! Note that the frequency peak (i.e., % of checklists with phoebe)
that was reached during the week of 15-21 March 2012 was not reached until
8-15 April in 2011!

*http://tinyurl.com/79lnssm [*Try clicking on "March" from the bar chart
(seasonal histogram) at the top of this page to restrict the date instantly
to just March 2012]

As spring continues to heat up and more and more birds start to arrive, I
thought this was a good time to remind birders to be cautious with their
identifications, especially for their "FOY" birds. Jeremiah's post a few
weeks ago did a great job highlighting how even carefully-studied rarities
-- like Pacific Loon -- can be repeatedly misidentified when people chase
birds with an "expectation bias" (i.e., that we know it is present, because
so-and-so reported it, so they expect to find it). In spring, this problem
can be even worse, since new migrants are arriving and being widely
reported and people might think "well, Pine Warblers showed up just
yesterday so reporting a Magnolia Warbler is not that surprising...". In
fact, even in the warmest springs Pine and Magnolia arrival dates are apt
to be separated by up to a month.

Caution: I will be talking about misidentified birds here. I don't intend
to single out any individuals at all, just to acknowledge that we know that
birds are sometimes not identified correctly and that the error rates vary
from species to species. This is a reality of birdwatching and of any
project that uses field identifications as data. I truly don't mean to

Below are some bird species that I have a lot of concern about with eBird
data, but they apply to birders statewide (and countrywide!) regardless. It
is frankly quite easy for eBird's data quality processes to prevent January
Acadian Flycatchers and misidentified Pacific Loons from making it into the
public data output. They tend to be errors that are easily caught but
processes like (show all Pacific Loons East of the Mississippi; or show
 all January Acadian Flycatchers for the USA [there are none!]). Two common
species, like Song and Savannah Sparrows, surely have high
misidentification rates, but that backgrund of error does not adversely
affect the status as shown in data except at very fine and local scales.
But the real issues comes in for species where one is much more common than
the other, or where seasonal transitions involve switches in the species.
In these cases, keeping the edges of the dataset clean is a real challenge.
In the below cases, I think a refined understanding of seasonal,
behavioral, and even molt (eeek!) patterns can be really helpful to
becoming a better birder and reporting more consistently correct
identifications to eBird, Massbird, or wherever.

The first tow issues are primarily winter problems that are fading out now;
the other three are issues that are likely to arise within the next month.

COMMON MERGANSER -- In Massachusetts, Common Merganser and Red-breasted
Merganser are both very common, but they separate out almost entirely by
habitat with Commons preferring fresh water and Red-breasteds preferring
the open ocean and large estuaries. In Middlesex county, Red-breasted is
actually rare, occurring regularly only on the lower Mystic and Charles
Rivers. The eBird process works well in allowing us to carefully check any
Red-breasted in an inland county. Where it fails almost entirely is in
defining the eastern limit of Common Mergansers. Seeing a Common Merganser
on salt water is extraordinary, and when it happens, they are usually
displaced migrants. It is probably true that almost all eBird reports of
Common Mergansers on Boston Harbor, open waters of the Atlantic of Cape Cod
Bay, or other decidedly saltwater or estuarine environments are actually
misidentified Red-breasted Mergansers. Please think about habitat when
reporting Common Mergansers coastally. Tasting the water might be an easier
clue to the merganser's identity than the field marks, since females are
very tough to tell apart. Look for the well-defined white throat and sharp
division between the reddish head and gray chest on Common, as well as
Common's thicker bill and less shaggy crest. If you are unsure, eBird has
"merganser sp." for just these types of situations.
          I think the majority of saltwater records on the eBird map are in
fact misidentifications. You may have to zoom in the map and click "show
points sooner" to see the points. click the points to see the observation


DOUBLE-CRESTED CORMORANT -- Here in Massachusetts, cormorant identification
is a major issue. Specifically, understanding just how common
Double-crested Cormorant is in winter is a real challenge. Great Cormorant
clearly predominates, but a few Double-crested Cormorants winter (or
attempt to winter) in sheltered harbors. This year, one or two last until
early February at least in Gloucester Harbor, and each year a few persist
in Plymouth Harbor, at harbors on Cape Cod, and in southern Bristol County.
How many of these successfully overwinter is unclear. A good tip for
cormorant identification in winter is that if you think you have an adult
Double-crested, double-check yourself. Almost all overwintering birds are
pale-breasted immatures. Another tip is that although they like such
habitats in summer, winter Double-cresteds rarely (if ever!) use rocky
headlands or offshore islands, which are areas preferred by Great
Cormorants. Unfortunately, the eBird data quality system is overwhelmed
with winter Double-cresteds from both plausible and implausible locations.
          I strongly urge extreme caution in reporting winter and FOY
Double-cresteds to help us sort through the significant ID issues with
cormorants in Massachusetts. I currently do not trust the eBird output on
maps like this one:
Since Double-cresteds will be arriving en masse in a few days, the
identification issue will be swamped by the real arrival of tens of
thousands of Double-cresteds. When they arrive, notice that the fresh
arrivers are the all black adults; immatures do not arrive until several
weeks (or maybe a month) later, so an immature seen in late March could
well be an overwinterer. Properly aging your cormorants should be the first
step in any identification of them, in winter or summer. If you are unsure,
"cormorant sp." is always available.

EASTERN WOOD-PEWEE -- Every single year, in most eastern states, Eastern
Wood-Pewee is reported up to a month earlier than any documented record.
Here in Massachusetts, the species should be reported with extreme caution
anytime before 1 May (or even 5 May). The primary culprit? European
Starling. Singing starlings mimic Eastern Wood-Pewee a lot and birders who
are good with bird sounds, but not aware of this problem, regularly get
ensnared by starlings singing Eastern Wood-Pewee songs. A good rule of
thumb, track down your FOY pewee ad check it visually!
         The other problem though is the very real challenge of telling
Eastern Phoebe from other flycatchers. Lets face it, when April and May
roll around, we are all rusty on our flycatchers, since they have been gone
for the whole winter. Eastern Phoebe does wag its tail a lot, has no face
pattern at all, has a stubby black bill, and pretty dull wings and
upperparts. It behaves like a phoebe too, and is conspicuous and often
around bridges and eaves of houses.
         This issue is not limited to pewees either. This year has already
had a few reports of Willow Flycatchers (which never arrive in Texas before
20 April...and never arrive here before 15 May at the earliest!). Empidonax
should be identified with care always, but first establish that it is an
Empidonax. Focus on the strong wing bars, inconspicuous behavior except
when singing, timing, and habitat. Frnakly, there is just one flycatcher
likely to be seen before May -- Eastern Phoebe. In the very last days of
April, three others (Great Crested, Least, and Eastern Kingbird) become
possible, but almost any other flycatcher would be extraordinary. In fact,
Scissor-tailed is MUCH more likely in mid-April than an Eastern Wood-Pewee!

YELLOW WARBLER -- Yellow Warbler seems like one of the easiest warblers to
identify, but every year we get reports well before the actual arriving
front of Yellow Warblers. These are almost invariably misidentifications
involving either Pine Warbler (males are very bright yellow)  or, ore
likely, Yellow Palm Warblers. Since Yellow Palms usually arrive in early
April (and are sure to hit the state in late March this year), we should be
ready for them. They wag their tails a lot, have white tips to the outer
tail feathers, rufous caps, and patterned faces. But when seen poorly, they
ofte get recorded as Yellow Warblers, especially by people who aren't
paying attention to migration timing. In a "normal" year, Yellow Warblers
arrive two weeks after Palm Warblers, hitting the state about 22 April or
even a bit later.If you think you see one earlier than that, please
double-check yourself and ask why it isn't a Palm or Pine. If it is March
or early April, a photo would not be overkill and might be required for
acceptance! To make sure you are getting your Yellow Warblers right, be
sure to look for a short yellow tail (the tail spots are actually yellow on
Yellow Warbler) and a blank face, with no eyeline or eye brow. the songs
help too, with Pine and Palm giving trills and Yellow giving its ringing
"Sweet sweet I'm so so sweet" song. Every year we see these
misidentifications occur, so please consider them as you go out.

CHIPPING vs. AMERICAN TREE SPARROW -- The seasonality of these two species
means that we can effectively filter them quite well (i.e., only let valid
records through) during 9-10 months. In summer we have Chipping Sparrows,
and in winter we have American Tree Sparrows. Although Chippings sometimes
overwinter, this is rare and away from expected spots (like Marconi Beach,
Cape Cod), it is fair for us to require convincing documentation for all
winter Chippings. Summer American Tree Sparrows are almost unheard of, and
it is likewise fair for us to require documentation then. But in the
transition zone (April and October), defining the beginning of Chipping
sparrows and the end of American Tree Sparrows is much harder. In a typical
year, the first Chippings are seen in the first week of April and the last
American Trees in the last week of April. Spring American Trees change
their plumage to get brighter caps and paler chests, so impatient observers
regularly report them earlier than they should. And eBird is powerless to
catch some of these, since both species occur commonly during a narrow
April window.
                   In the past week or two there have been a number of
Chipping Sparrow reports from areas where they did not winter, and I am
concerned that American Tree Sparrow was not fully eliminated. The eBird
map for Chipping Sparrows in March 2012
shows the arriving front of Chipping Sparrows, and they are clearly "in" as
far north as northern New Jersey and maybe the first birds are reaching
southern Connecticut.
                  One tip on these is to carefully check bill color. Spring
arriving birds tend to be in full breeding plumage (this applied to almost
all species, not just Chipping Sparrows). A breeding-plumaged Chipping
Sparrow will have an all black bill, while all Tree Sparrows have bicolored
bills. If you are unsure, and can get a good look, this should almost be
diagnostic in April in Massachusetts, but it is good to back it up with
other field marks like song (long trill in Chipping, musical melody in
Tree). The oft-cited field marks of cap color and supercilium strength
(whiter in Chipping) are good, but can lead people astray as the familiar
American Trees acquire breeding plumage. Better is to make sure your FOY
Chipping has a black line all the way through the eyes and including the
lores (this works in winter too)!
                 I would very much like for the Massbird and eBird
community to help define exactly when Chipping Sparrows arrive this year.
It is sure to be record early and coud happen in the next few days if
patterns appearing within Eastern Phoebe and Pine Warbler (i.e., 2+ weeks
ahead) hold true. The above eBird map shows the advancing front...which
will soon be upon us! If you get one of the earliest ones, please please
provide some notes with your report to ensure that we now you considered
and eliminated American Tree Sparrow, and why.

These aren't the only issues, of course. I have posted before about
Accipiters (our collective tendency to identify Cooper's Hawks as
Sharp-shinneds and to "want" Northern Goshawk and misidentify actual
Cooper's as goshawks). Here are a few others to think about this spring:

- Greater and Lesser Scaup -- The Tufted Duck on Manchester Reservoir last
year was an indication that many scaup are being misidentified, since many
reports came in of Greater Scaup in the flock with the Tufted. When in
doubt, please use Greater/Lesser Scaup; these birds are REALLY hard!

- Broad-winged Hawk -- Be careful with identifying Broad-wingeds before
mid-April when they come back. Immature Red-shouldereds and even other
hawks are regular sources of confusion.

- Murres -- Although murres can sometimes be seen from shore in
Massachusetts (regularly off Race Point recently), many reports seem to
pertain to Razorbills, including birds in Gloucester Harbor and
Provincetown. Murres should always be identified with great care in
Massachusetts. Check tail length in addition to bill structure and plumage;
murres don't cock their tails!

- Pectoral Sandpiper -- Actually pretty scarce in spring; should be
identified with care.

- Catharus thrushes -- These are the spot-breasted, brown backed thrushes.
A major issue. Hermit Thrush migrates in April, but most other thrushes
don't migrate until the very end of April. Any report of any spotted thrush
before 25 April should very carefully eliminate Hermit and Swainson's and
Gray-cheeked Thrushes should not be expected before 5 May. timing helps
here, so use it, but also use "Catharus sp." if you have any doubt.

- Rusty Blackbird - Although they passing through now (March to early May),
many records pertain to misidentified grackles. Identify with car and focus
on the slender bill, square tail, and calls of Rusty; iridescence can be
hard to assess depending on lighting.

- Purple Finch and House Finch --  A perennial and major data quality
concern with birder data. Think twice about urban Purples or House Finches
in the deep woods; otherwise, please study your field guide, learn the call
notes, and use Purple/House Finch if unsure. But if you find these hard,
you are not alone--this is perhaps the most confused species pair in North

I hope this preparation is helpful for people and prompts us all to take a
bit of extra time to think about our reports and to do our best to make
them as accurate as possible, and to use the "I don't know" categories --
like peep sp., Buteo sp., Greater/Lesser Scaup, Catharus sp., Accipiter
sp., warbler sp., and Purple/House Finch liberally.

I'd very much like to hear other's thoughts for identifications to be
careful about as our summer birds return.


Marshall Iliff

Marshall J. Iliff
miliff AT aol.com
West Roxbury, MA
eBird/AKN Project Leader
Cornell Lab of Ornithology
Ithaca, NY


More information about the CTBirds mailing list