|As everyone who lives in Vancouver knows winter
2016/17 was one of the longest, snowiest and wettest in memory (I
also didn't mention darkest!).
Preparing the station for spring migration banding was a maintenance
nightmare as the heavy weight of compacted snow had brought down
tree limbs and flattened
elderberry and blackberry bushes across net lanes some of which had
to be entirely re-cut.
Nevertheless, we got underway on schedule on April 1st although
more sessions were cancelled than completed in the early part of the
month due to the incessant rain. We delayed opening our far field nets
which were completely underwater until the second weekend of April but the very
first bird on the very
first net round to these nets was this Hammond's Flycatcher.
Silent Empidonax flycatchers are the
birder's nightmare but Empids in the hand although confusing, are
less of a challenge as we have the opportunity to take biometric
measurements and examine wing morphology which usually allows us to
make the correct identification.
and Dusky Flycatchers are all very
similar and all three species occasionally turn up in our nets.
Least has a whitish throat and whitish belly whereas both Hammond's
and Dusky have greyish throats, yellowy bellies, narrow
bills and grey heads usually contrasting with greener backs and both
have almond shaped eyerings (photos below).
Hammond's has a short,
steep forehead and long, flat crown although this can be somewhat
arbitrary when you have nothing to compare it with and when the bird
like this one has a slightly raised crest!
But one of the
diagnostic field marks for Hammond's
is that they have a very long primary projection as can be seen in the top photo
|Hammond's bill is small and short with
straight sides, the lower mandible varying in colour (photo below
In addition to a very long primary projection, wing
morphology shows a long gap between primaries 5 and 6 with a short
gap on each side (photo below left).
|In contrast Dusky Flycatcher has a long tail and short wing
with a short primary projection and the primary tips are
So, when you're out birding and see that silent
Empid and think Least, Hammond's or Dusky you'll know what it is!
Here's one to test your ID skills! (answer at the end of the blog!)
|An early sign of spring for anyone interested in
birds in North America is the transformation of American Goldfinches
from drab winter (non-breeding) plumage to bright yellow summer
This second year (SY) male is undertaking this
dramatic change molting of all of its body feathers but no flight feathers.
And it's not just the body feathers on American Goldfinches that
undergo a dramatic change - their bill colour does too!
they have dark mandibles that change to bright pinkish/orange in the
spring. Bird's bills are comprised of keratin, the same hard
material which human hair and fingernails are made of. But if
keratin is non-living, then how can a goldfinch's bill change to
bright orange during the breeding season? The answer is that keratin
makes up only the hard outer sheath of a bird's bill, beneath which lies
living skin tissue with active blood vessels.
Birds really are
Ageing American Goldfinches in the hand is easy. First year (hatch
year/second year) birds show a buffy tip or fringe to the carpal
covert (photos below). Adults (after hatch year/after second year)
lack this buffy tip and often have a bright yellow shoulder (this is
not the shoulder often referred to in field guides but actually the
Banders should be aware that adults can show a
white tip to the carpal covert but it is usually off to one side and
never buffy as in the examples below.
Sexing AMGOs is easy too as
males have jet-black remiges (primaries and secondaries) whereas
female's wings are never jet black and vary from brownish black to a
subdued black that contrasts less obviously with the white tips of
the greater coverts (photos below).
Another clue to ageing AMGOs in spring and summer is that they are
the only birds where we can use the prealternate molt to age as
only second year (SY) birds molt their inner greater coverts as
part of their prealternate molt in late winter/spring.
leave you to age and sex the wing below! (answer at the end of the
|One of the reasons we all love spring as birders and
banders is that many birds are in alternate plumage giving them
their bright summer breeding plumages. That especially applies to
Setophaga warblers like this stunning adult (after second year) male
Ageing and sexing
wood warblers in the spring requires a complete understanding of the
molt cycle of the individual species being studied. Adult birds like
this one will have undertaken a definitive prebasic molt following the breeding
season last year when all body and flight feathers are replaced.
In species where the prebasic molt is the only molt occurring
annually breeding occurs in basic plumage and the result (when
looking at an adult bird, which has undertaken this complete
definitive prebasic molt) in the spring is that there are no
discernible molt limits on the wing between replaced and retained
However, in many
species there is the SECOND molt referred to above that occurs in the late winter/early spring prior to the next prebasic molt. This prealternate molt occurs in both adults and first year birds so that
in the spring first year birds will show three generations of
feathers but adults will also show molt limits. In adults however
there are only two generations of feathers, definitive basic and
definitive alternate feathers.
The wing of the
above adult male Audubon's Warbler is showing such a molt
limit (shown with red arrow) between the outer three greater coverts
replaced as part of the birds definitive adult prebasic molt last
year and the seven inner greater coverts replaced as part of its
prealternate molt this spring.
|And speaking of Yellow-rumped Warblers it looks as
though we are going to see a return to Myrtle and Audubon’s Warblers
according to a new study which says Yellow-rumped Warbler may be at
least three separate species.
Myrtle is the form that birders in
the eastern U.S. and most of Canada see with with a white instead of
yellow throat. It also has a longer migration, and a distribution
that stretches farther north than the other forms.
Audubon’s is the form familiar to birders in the western U.S. and
parts of BC and Alberta. Males have yellow throats and gray on the
head, back, and breast and are shorter distance migrants.
So what about the hybrid zone that swayed scientists to lump the
species back in 1973? According to the research, it’s relatively
narrow, just 80 miles across and hasn't moved or widened in 50
years, but in SW BC we're not sold on that as during spring we see
and band equally large numbers of Myrtle (photo below) and Audubon's
warblers suggesting that the hybrid zone could be considerably wider.
|Nashville Warblers are uncommon birds for us in the
Vancouver area so they are always welcome additions to species
diversity on our net rounds.
|The wing (below) of the after second year (ASY) male
above is a good
example of what definitive adult plumage, with no discernible molt
limits among the coverts or alula, looks like in spring. Notice the
uniformly adult wing coverts with prominent greenish edging and broad, truncate outer rectrices
with a corner to the inner web diagnostic of adult birds.
|Correctly sexing a bird depends on correctly ageing
it first always remembering that young (HY/SY) males can look a lot
like adult (AHY/ASY) females.
This second year (SY) male Wilson's
Warbler had a fairly extensive, shiny black cap which showed only
feint greenish, mottling towards the hindcrown.
|The wing however confirmed our age determination
with a clear molt limit between the outer greater covert and
adjacent inner primary covert and between the alula covert (A1) and
lower main alula feather (A2) show below with red arrows.
also the extensive wear and fade to the visible remiges (primaries
and secondaries) and extensive wear to the rectrices particularly
the central rectrices - all of these feathers are retained juvenile
feathers. The central rectrices are bilaterally symmetrical and are
raised above the plane of attachment of the remaining rectrices
ensuring that they cover the closed tail.
The feathers absorbing the brunt of the exposure to the elements
are the tertials, the coverts, in particular the greater coverts, and
central rectrices. Because of the protection they provide for the
remaining flight feathers and because of their extreme exposure to
wear, the tertials and central rectrices are the only flight
feathers likely to be included in partial preformative molts.
|We hosted the first of two
Bird Monitoring and
Banding Workshops in May and had a full house
with another great group of people. Participants came from as
far away as Alberta and Washington sacrificing their entire weekend
to learn about molt and ageing of NA landbirds in the hand.
|We then had 30 odd parents and kids for the first
VARC Family Day of the season.
We see public outreach and education to raise awareness of
environmental issues as they relate to birds as a very important
part of the work we do at VARC. Parents and children are introduced
to the research techniques required for monitoring migratory birds
and the population ecology and ecosystem dynamics of wild bird
populations, in an age specific way. They learn about bird
migration, the various habitats and communities birds depend on
during migration and the breeding season, and the conservation
actions required to protect these habitats to ensure the long term
survival of bird species.
|Special thanks to Jason Jones who was interpreter for the
morning and to Martine Cutbill who continues to come up with the
most amazing arts and crafts for the event - this time owls for the
kids to make out of pine cones, googly eyes, felt and feathers!
|It certainly made this little girl's sixth birthday!
Thanks to everyone for their help in making these events at the
station such a success.
|And a YELLOW-BELLIED SAPSUCKER! ok, ok, not a
Yellow-bellied Sapsucker but a second year Red-breasted Sapsucker
but it DID have a yellow belly! (photo below right)
Note also the
zygodactyl toe configuration of woodpeckers. Toes are
numbered 1 to 4, 1 is the hind toe or hallux, toes 2 to 4 are the
front toes numbered inner to outer. The usual arrangement of toes in
passerines is 3 toes in the front and 1 in the back in a
configuration termed anisodactyl.
In some species (Owls, Cuckoos and Woodpeckers) toe 4 has shifted
to back with 2 toes forward and 2 toes backward - an adaptation for
|By the end of May the station was looking fantastic
and although 4 am seems awfully early when the alarm goes off, it's
worth it when you get out there on a gorgeous morning with the mist
rising over the old field habitat where we band.
The preformative molt in Orange-crowned Warbles normally includes
all median and greater coverts but this second year (SY) male had
replaced just a few lesser coverts and was showing extreme wear to
all of the retained juvenal feathers - notice the wear to all of the
visible remiges (primaries and secondaries) in the photo below as
well as the coverts and contour feathers.
Possible a late hatching
bird or second brood with insufficient resources to undergo the
normal preformative molt following the breeding season last year and
unlikely to be a successful breeder this year.
|That wasn't the case with this gorgeous pair of
second year (SY) Yellow Warblers, the male on the left showing
extensive red streaking to the breast and the female right with no
breast streaking. Caught side by side and almost certainly a breeding pair,
she was however shy and refused to look at him for the photo!
|The photo immediately below of the wing of the
female is showing three generations of feathers. In the preformative
molt following the breeding season last year, she replaced lesser,
median, inner greater coverts and the carpal covert and stopped
molting, preformative molt limits shown with red arrows between the
greater alula covert (A1) and lower main alula feather (A2) and
between the carpal covert and adjacent primary covert.
first prealternate molt during the late winter/early spring she
replaced some median coverts, 7 inner greater coverts (some or all
of which may have been replaced in the preformative molt) and all 3
tertials (blue arrows) which may also have been replaced in the
preformative molt. Hence, the three generations of feathers are
formative (carpal covert and greater alula covert), first
alternate (some median coverts, inner 7 greater coverts and all 3
tertials) and retained juvenal (outer 3 greater coverts, primary
coverts, lower 2 main alula feathers and primaries and secondaries).
|The male had undertaken a similar molt sequence but
had replaced all 10 greater coverts in his preformative molt, the
preformative molt limit shown clearly between the outer greater
covert and adjacent primary covert, between the carpal covert and
adjacent primary covert and greater alula covert and lower alula
feather (red arrows). He had similarly replaced the inner 7 greater
coverts and all 3 tertials in his first prealternate molt (blue
In both examples notice the wear to the remiges
(primaries and secondaries) which are retained juvenal feathers.
|And a nice study of adult, after second year (left) and second year
(right) male Black-headed Grosbeaks.
|In members of the Cardinalis family
(Grosbeaks and Buntings) where males have such contrasting and
distinctive plumages, there is often an extensive molt including all
greater coverts, carpal covert, alula, tertials, and in buntings
especially, additional inner secondaries and outer primaries.
These can be very easily seen and are helpful in learning molt
patterns in these species and can also be helpful in looking for
molt limits in females of the same species.
The wing and tail of the SY male above is showing such molt -
what we call 'smack you in the face' molt limits! :o)
|The wing of the above ASY male is another good
example of what definitive adult plumage, with no discernible molt
limits among the coverts or alula, looks like in spring. Notice the
uniformly adult wing coverts and extensive white wing patch and broad, truncate outer rectrices
again with extensive white to the outer rectrices (R6) and compare
to the SY male wing and tail photos above.
|And finally another confusing looking Empid looking
more like a Myiarchus with it's raised crest than an
Empidonax - an adult Willow Flycatcher!
|Thanks as always to all of our intrepid volunteers
who sacrifice their weekends and set alarms for ridiculously early
hours during the spring and summer, mostly on their weekends off, to
help with banding operations - again thank you all!
|Answers: The answer to our question ageing and
sexing the American Goldfinch wing above is second year (SY) male -
the right wing of the bird shown in the photo!
Can you also see where the prealternate molt limit is within the
The Empid in the ID challenge photo is a Dusky Flycatcher
Mike Tabak - thanks Mike!)
Please note: All images are copyrighted and are not to be used