are long, dark, cold and wet and hard not only for birds but for
people too especially birders and banders waiting for spring which
at times seems like it's never going to arrive!
Our winter banding
program was rained out on countless occasions which pleased some
VARC team members who were able to turn alarm clocks off on the
weekends and sleep-in. We promised we'd make up for all that sleep
as we began to gear up for spring migration banding!
loosened its grip in March and birds began to move responding to
increasing daylight and hormonal changes. The sound of skeins of
geese flying over the banding station finally convinced us that
spring really was just around the corner!
impossible to believe looking out across the old field habitat where
we band which is virtually bird less at this time of the year that
it can be transformed in to such a critical oasis for breeding and
migratory birds come spring and summer.
And talking of
tough environments for birds it doesn't get much tougher than being
an overwintering Hummingbird in Vancouver!
This stunning adult
male Anna's Hummingbird somehow managed to endure sub zero
temperatures by visiting a single feeder we kept under the eaves of
the banding pagoda.
Even though the
nectar periodically froze, amazingly this tiny bird found enough
food resources to survive and kept us all amused by its constant
chipping tik as it buzzed backwards and forwards to the
At this time of
year our species diversity is limited to resident birds like the
Black-capped Chickadee (BCCH) below which choose to stay and tough
out the winter rather than risk the high stress, energetic costs and
risks of migration.
Ageing BBCHs was
discussed at length in a whole photo essay in our January 2011 blog
which can be viewed here:
This second year
(SY) bird of unknown sex shows a discernable molt limit in the
greater coverts -
the outer two greater coverts are identified as
retained juvenal feathers due to their much more worn, washed out
and lightly pigmented appearance versus the replaced inner greater
coverts. As mentioned previously, in members of the tit family (Paridae)
retained greater coverts will sometimes (but not always) show a step
out (or down) being longer than replaced ones (indicated with the
red arrow) as in the example below.
The blue arrow points to a
pseudo limit which is the result
of a natural colour contrast within the inner greater coverts and
can simulate a molt limit but is NOT the result of feather
replacement. Feather wear is another important clue for banders when
ageing birds - retained juvenile feathers which are of poor quality
start to show signs of wear in spring having been worn throughout
the entire fall and winter months.
The tail of the same bird (photo below right) also shows wear to the
retained juvenile feathers. Tail shape
is another helpful clue to ageing
birds in the hand but it is important not to use tail shape alone
as it is generally not very reliable due both to individual
variation and the possibility of accidental loss and replacement
(called adventitious molt)
Chickadees often lose and replace tail feathers as was the case with
this bird which at some stage over the winter had lost and replaced
just the two central retrices (R1).
Had this bird lost and replaced
all of its retrices the tail would appear uniformly adult and lead
us to make a wrong age determination, again emphasizing the
importance of ageing using molt limits on the wing.
A much more
uncommon bird for us was this handsome Chestnut-backed Chickadee
(CBCH). Unlike Black-capped Chickadees, Chestnut-backed Chickadees
prefer the tall coniferous trees to the open old field habitat at
similar molt patters to BCCH - this second year (SY) bird of unknown
sex again showing a distinct molt limit in the outer greater coverts
and the step out between retained and replaced feathers and tapered
outer retrices with little or no white to the outer web.
Blackbirds (RWBL) are partial migrants meaning that within a
population not all birds migrate; some do and some don't. Last
winter we didn't find a single RWBL in the park whereas this winter,
being milder for the most part, lots of birds stayed and more
arrived back earlier than last year.
Ageing male RWBLs
is easy at this time of the year as second year (SY) males do not
have the brilliant red epaulettes (lesser coverts) of adult birds
prebasic molt can be complete in RWBLs, underwing coverts are often
retained in the first PB contrasting
markedly with the adjacent blacker feathers (indicated by the red
arrow pointing to replaced feathers in the photo right).
The first prebasic
molt can include all flight feathers although some remiges
(primaries and secondaries) can be retained as was the case with
this bird showing a contrast in rachis colour between retained and
altogether more difficult to age not having the contrasting glossy
black plumage of their male counterparts. Although underwing coverts
can be retained in second year birds they are extremely difficult to
see even under magnification often leading us to make a safer age
determination at this time of year of after hatch year (AHY). The
lesser coverts of adult females normally show mixed bright orange
and blackish feathers forming an indistinct shoulder patch or
epaulette. This bird was therefore aged as an AHY female but noted
as 'leaning towards ASY' or after second year in our notes.
are primarily altitudinal migrants moving from colder, higher ground
to lower, warmer elevations in the winter. The flashy white outer
retrices of Juncos are a welcome sign of early spring as large
numbers of birds move back through the park.
There are six subspecies groups in
North America of which ours is Oregon Junco (Junco hyemalis
simillimus) hence the alpha code of ORJU.
The first prebasic
molt in ORJU is partial and includes 3-10 inner greater coverts,
sometimes 1-2 tertials and very occasionally central retrices. This
second year (SY) male had replaced 8 inner greater coverts and
retained the two outermost (indicated with the red arrow) the molt
limit between GC's 2 and 3 and the two innermost tertial (S8 & 9)
indicated with the green arrow. Primary coverts (blue arrow) are
always retained feathers in all these examples of partial first
prebasic molts and show the thin, tapered and somewhat worn
appearance of retained juvenal feathers.
This bird had not
replaced any retrices all of which were showing wear typical of
retained juvenal feathers.
The odd tiny pin
feather visible on the head of this bird is the result of its
prealternate molt discussed later in the blog.
Ageing and sexing
some birds is very easy with 'smack you in the face' molt limits.
The very dull eye of the male Spotted Towhee below almost doesn't
require a molt limit to determine its age but a quick look at the
wing reveals a very obvious limit (red arrow) between the glossy
black replaced lesser, median and greater coverts and the retained
juvenile primary coverts, primaries and secondaries (this bird had
also replaced all 3 tertials), the retained juvenile feathers again
showing a high degree of wear (blue arrow).
The first of a long
list of scheduled visitors this year was a group of Fish, Wildlife
and Recreation students from the British Columbia Institute of
Technology (BCIT) who came out in early March ahead of exam finals
to get some practical, hands on experience at the station.
arrived in April and as always we forgive Vancouver the long, cold,
dark, wet winter months as the rhododendrons and azaleas bloom
in the community gardens in the park and Vancouver looks its
stunning best on a sunny spring day with fresh snow still on the
north shore mountains.
arriving with two Nashville Warblers (NAWA) banded in addition to
good numbers of Wilson's (WIWA) and Orange-crowned Warblers (OCWA).
The first wave of
these returning neotropical migrants consists almost entirely of
adult males - the OCWAs with extensive orange crowns which can
easily be seen when the feathers of the crown are parted, the WIWAs
with glossy black crowns extending far to the back of the crown
(photo below right) and the well defined crown patch of the NAWA
Ageing and sexing
wood warblers in the spring requires a complete understanding of the
molt cycle of the individual species being studied. All of these
birds will have undertaken a prebasic molt following the breeding
season last year when adults replace all body and flight feathers.
In species where the annual 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 a SECOND molt that occurs prior to the next
prebasic molt called the prealternate molt which occurs in the late
winter / early spring. This 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 but
only two generations of feathers between adult prebasic and adult
The after second
year (ASY) male Myrtle Warbler below is showing such a molt limit
(shown with red arrow) between the outer four greater coverts
replaced as part of the birds definitive adult prebasic molt last
year and the six inner greater coverts replaced as part of its adult
prealternate molt this spring.
This prebasic molt
occurs in many species of passerines but is often restricted to
feathers of the head and throat as is the case with the WIWA, OCWA
and ORJU mentioned earlier.
Although tail shape
is not reliable for ageing Setophaga (formerly Dendroica)
warblers as all age classes can show rounded retrices as mentioned
in previous blogs the extent of white on retrices r2 to r6 of this
adult male and the extensive black centers to the uppertail coverts
are all reliable indicators to confirm our age determination.
Hermit Thrushes are
relatively short distance migrants wintering in the southern US and
south to Central America but some remain further north along the
pacific coast and they are always the first of the Catharus
thrushes to return.
This second year
(SY) bird of unknown sex is showing the typical buffy tear-drop
pattern of retained juvenal greater coverts in this genus. Note the
molt limit between the 7 retained outer greater coverts (red arrow)
and 3 replaced inner greater coverts (black arrow) which have
chocolate brown edging and lack these buffy tear drops. These buffy
tips can easily be seen on the closed wing indicated by the green
arrow (photo below left).
The blue arrow
points to primary 10 (P10) which is a vestigial feather in
Catharus thrushes, the characters having lost their original
function through evolution. This tiny feather which has probably
little use to the bird is of great use to banders in making their
age determinations. In addition to the molt limits on the wing
mentioned above the length and shape of this feather varies with age
being longer and more rounded in first year birds and shorter and
more sharply pointed in adults.
Although listed as
'common' birds of western forests we rarely see or even hear a
CASSIN'S VIREO so we were delighted when one showed up in our
nets and was a new bird banded for the station.
together with Blue-headed and Plumbeous Vireos as the Solitary Vireo
it is now split as a separate species.
This after second
year (ASY) bird of unknown sex shows the pale lores and eyering
which gives the bird the quintessential field mark of its bold white
A very late
AMERICAN TREE SPARROW (ATSP) was banded on the 21st
April. ATSPs are annual but uncommon winter visitors to Vancouver
breeding in the tundra of the far north.
The rusty crown and
eyeline, bi-coloured bill and dark spot in the centre of the pale
breast distinguishing it from other Spizella sparrows.
This second year
(SY) bird of unknown sex is showing a strong molt limit between the
replaced outer greater covert and retained inner primary covert and
thin, tapered and worn retrices.
This stunning adult female
Sharp-shined Hawk (SSHA) had everyone racing back to the station
when she was brought in from a net round.
She was one of 5 SSHAs banded this month!
We were very happy
to receive notification from the Bird Banding Laboratory this month
of a significant recovery of one of our banded birds.
A Cedar Waxwing
banded at Colony Farm on June 12th, 2010 as a second year male was
recovered in Santa Clara County, California at the southern end of
the San Francisco Bay area on March 8th this year!
recovery was as a result of a window strike and the bird was found
We hosted our
Bird Identification Workshop
on the last weekend of April with lots of people and lots of birds!
Our Sunday field session at the banding station enables participants
to see birds up close and personal, to study field marks and to use
the skills and practice the techniques they have learned at the
Everyone had a
great time and we were really overwhelmed with the feedback we
received from workshop participants and thank them all for their
very kind and generous course evaluations which can be viewed here:
We banded our first
DUSKY FLYCATCHER of the spring this month along with two
Hammond's Flycatchers. We have spoken about the biometric
measurements we use to separate these two very similar Empidonax
Flycatchers in the hand in a previous blog
(May 2011 Blog)
but thought we'd take a moment to pass on some useful tips to
birders which may help with identification in the field.
These two very
similar Empids both have greyish throats, yellowy bellies,
narrow bills and almond shaped eyerings but as can be seen from the
photographs below Hammond's (photo left) has a short, steep forehead
and long, flat crown and the longest primary projection (distance
between the tips of the tertials and tips of the primaries).
Dusky has a fairly
rounded head (photo right), short primary projection and the outer
edge of the outer retrices (r6) is contrastingly white.
It's still much
easier to be a bander than a birder when it comes to identifying
these confusing Empids as we can look closely at primary tip
spacing and wing morphology which is quite different between the two
species and take wing, tail and primary projection measurements to
make an accurate determination but hopefully this information will
This After Hatch
Year (AHY) HOUSE WREN was a nice surprise this month and only
our second record for the station.
House Wrens are
larger than the more common Pacific Wren, lack the short, buffy
supercilium, have longer bills and tails and barred undertail
And finally, we
were delighted to receive notification from the North American
Ornithological Conference (NAOC) that the abstract “The
importance of old-field habitats to birds in a suburban-urban
landscape” submitted by VARC was evaluated by the scientific
committee and accepted as a Poster Presentation from some 1230
VARC will be
hosting field trips and workshops for the conference which will be
help at UBC from the 15th - 18th August. The 4 day scientific
program will include Plenary Speakers, presentations, symposia,
contributed papers, poster sessions and scientific and ENGO
Thanks to Mark
Habdas, Kerry Kenwood, Carol Matthews, Jason Jones, Jerry Rolls,
Debbie Wheeler, Sarah Gray, Mike Nutter, Kyle Norris, Eric Demers,
Celia Chui, Louise Routledge, Monica Nugent, Marg Anderson, Todd
Heakes and Dev Manky for their help with banding this month.