July and August
were two of the busiest months in VARC's history dominated by the
fifth North American Ornithological Conference (NAOC-V) at the
University of British Columbia (UBC) in August. In addition to all
the conference activity we conducted banding and monitoring 4 days a
week and were rewarded with great species diversity, lots of birds
and even more visitors and guest banders to the Colony Farm banding
Swallows are part of the guild of aerial insectivores which have
suffered precipitous declines in recent years with research in
Canada showing that populations of Barn and Bank Swallows have
fallen by 70% and Cliff, Northern Rough-winged Swallows and Purple
Martin by over 50% in the past two decades.
The old field habitat at Colony Farm is critically important to
aerial insectivores and 7 of the 8 species of NA swallow are found
there sometimes in large numbers.
Northern Rough-winged Swallow (NRWS) is one of the less common
swallow species found in the Park nesting in burrows and cavities in
various substrates including pipes and other man made structures.
NRWS gets its name
from the serrations on the leading edge of the primary feathers
which are distinctly hooked in males and smaller and straighter in
females. The edge really is rough to the touch and similar to
running a finger along the edge of a coarse file!
The photos below
show the leading edge of the outer primary of this after hatch year
(AHY) female NRWS at 2 times magnification (left photo) and 5 times
magnification (right photo). The function of the rough wing edge of
NRWS still isn't known.
A large part of
VARC's mandate is public outreach and education to raise awareness
of environmental issues particularly as they relate to resident and
migratory birds and in addition to lots of individual and family
visitors this month we also welcomed 20 youth from the Catching the
Spirit (CtS) Youth Society for their annual field trip to Colony
Farm as part of a weekend outdoor experience to learn all about the
birds and habitats of the Vancouver area.
Mentorvisors from CtS told us that everyone had a great time
and that it was a great learning experience for the kids and one
youth said it was his favourite part of the entire weekend (another
By early July some
birds are already undergoing their annual prebasic molt like this
after hatch year (AHY) male American Robin (AMRO). Although aged as
an AHY this bird was almost certainly a second year (SY) bird and
likely failed breeder undertaking its first definitive adult
prebasic molt where all body and flight feathers will be replaced.
Note the very truncate and blackish replaced primaries with glossy
black rachises contrasting markedly with the brownish retained and
as yet unmolted secondaries in the photo right.
This hatch year
(HY) male Brown-headed Cowbird (BHCO) had already completed its 1st
prebasic molt. In BHCOs the 1st prebasic molt is complete except for
a few underwing coverts being retained. The dorsal view of this wing
shows very fresh replaced feathers - the inner primaries and primary
tips showing the brownish wash contrasting with the blacker
secondaries diagnostic of hatch year / second year (HY/SY) males.
(BRCR) are uncommon birds for us in the old-field habitat preferring
forests with large, mature trees for foraging and loose-barked trees
for nesting. These tiny, cryptically coloured woodland birds have
long decurved bills for probing tiny crevices and long, stiff tails
(photo below right) to help spiral up stout trunks and branches.
This hatch year
(HY) bird of unknown sex was in full juvenile plumage with no
discernible molt limits and still showing a prominent gape.
In contrast to many
birds which have fledged and already completed their 1st prebasic
molt others like this Black-capped Chickadee nestling are still in
natal down being just a few days old and still another two weeks
from fledging. This family had occupied one of our monitored Tree
Doves are common doves across most of North America they are
uncommon for us in the old field habitat where we band at Colony
Farm so the odd one that shows up in our nets is always a surprise.
Adult Males have a
powder blue crown and nape, a well-developed blue-black spot on the
neck, a rosy breast, and a dazzling patch of iridescence on the side
just at the bend of the wing.
Adult females have a brownish cap, the blue-black spot is small,
iridescence is generally lacking, and the overall appearance is more
drab. Females are also smaller, by 5-10%.
Juvenile birds like this one are
uniformly brown and have whitish edging on all of the wing feathers
creating a scaly appearance.
in the 5th North American Ornithological Conference (NAOC-V) held
from August 14-18, 2012, at the University of British Columbia. The
conference was attended by close to 1500 participants from 24
countries. In all, 12 professional ornithological societies from
North, Central, and South America were represented. VARC was an
active participant in maintaining a booth in the Exhibit Hall that
also housed the scientific poster sessions. VARC volunteers provided
complete coverage at the booth from lunchtime until the close of the
poster sessions each evening providing an excellent opportunity to
engage professionals on VARC’s mission and MetroVancouver’s support
VARC submitted a
poster for inclusion in the scientific sessions that was was
accepted by the scientific committee from over 1,500 submissions.
The title of the poster was “The importance of old-field habitats to
birds in a suburban-urban landscape.” The accepted poster can be
(please allow a few moments for it to load).
poster sessions, VARC received numerous comments on how important
our work on suburban-urban ecology was and how lucky VARC was to
have an engaged partner like MetroVancouver.
VARC also hosted a
field trip to Colony Farm to showcase the park and the banding
program. The field trip was attended by NAOC attendees from five
different countries. Many of the attendees were seeing a banding
station for the first time, and others were very experienced banders
who have worked throughout North, Central and South America. The
unanimous opinion of the field trip participants was that
MetroVancouver is displaying admirable foresight and wisdom in their
park management strategies and that VARC’s banding operation is one
of the most professional banding and research operations in North
Finally, VARC played host to Robert Mulvihill and Adrienne Leppold,
two legendary names in North American bird research and banding and
both former banding program coordinators at the renowned Powdermill
Avian Research Center in Pennsylvania, and many of the Powdermill
Both were highly
complimentary of VARC and the banding station at Colony Farm and
especially impressed with the professionalism, organization and
structure of VARC’s banding operation. As huge fans of both of them
we were honoured to have such a strong endorsement of our work form
such highly acclaimed and prominent ornithologists and avian
researchers and even happier that we able to give Adrienne her
Western Tanager and Anna's Hummingbird banding ticks! Thank you
Lots of baby birds
in juvenile plumage made for many gratuitous photographs and lots of
oohs and aahs from banders and visitors alike.
locally hatched Cedar Waxwing, Ring-necked Pheasant, American Robin
and Swainson's Thrush all scoring tens on the cuteness scale!
As can be seen by the photos above
there are lots of characteristics of birds in juvenile plumage
making identification easy - streaked, spotted plumage, prominent
gapes, loosely textured feathers, dull eye colour and lack of
feathering to the tibiotarsus and underwing all help to identify
birds in juvenile plumage.
Another characteristic is the presence
of fault bars which can be see on the rectrices (tail feathers) of
this hatch year (HY) House Finch (HOFI) in the photo below.
The conspicuous growth bars across the
tail of this young HOFI tell us that this bird was probably not well
fed for a number of days after it fledged from its nest.
These so called ‘fault bars’ are the result of environmental or
nutritional stress that the bird encountered while it was growing in
the feathers. Groups of feathers on hatch year birds are grown
concurrently so a stress that results in a fault bar on the feathers
is distributed in an even line as in the photo below right. Adult
feathers are sequentially grown so a fault line on the feathers is
normally distributed in an uneven line.
Fault bars are caused when actively growing feathers cease to grow
resulting in a dark line across the feathers. Young birds begin to
grow their rectrices as nestlings and growth continues after
fledgling. At this time the birds are dependent on their parents for
their nutrition (the food required for the energy and proteins
necessary for feather synthesis) but these adults are typically not
only feeding themselves but also several hungry fledglings. This is
a tremendously energetically taxing time for adults often resulting
in undernourished young and the presence of fault bars.
Fault bars can be useful as an ageing criterion but banders should
be aware that adults do sometimes lose all of their tail feathers at
once accidentally. When such accidentally lost feathers are regrown
adventitiously (outside the normal molt cycle), it is not unusual
for such adult replacement rectrices to have prominent fault bars
like those more often seen in juveniles.
When birds are
extracted from mist nets they are placed in to clean, soft bags and
taken back to the banding station for processing. We use pegs to
attach to the bags to identify which net an individual bird has been
extracted from and this hatch year (HY) female Black-headed Grosbeak
became very attached to hers reminding us that she was captured in
She did finally
release the peg but not until she was released herself!
There's something special about
raptors that both banders and visitors alike love and this gorgeous
hatch year (HY) male Cooper's Hawk had everyone running back to the
station when the radios squawked his arrival.
The photo of Olga (below left) looking very much more comfortable
here than she did when she came across it in the net and
(below right) posing for photos!
We did very well
for wrens this month with both Bewick's (BEWR) and Marsh (MAWR)
Wrens caught for banding including this precocious hatch year BEWR
(photo below left) which seemed totally captivated by the camera
probably attracted to its own reflection in the lens! Like many
species in juvenile plumage wrens can be tricky to separate with
paler plumages and less distinct superciliums than their adult
are a species of special interest to us and one of a number in which
we are conducting long term studies.
Our molt-migration research is attempting to better understand this
phenomena in western subspecies. The term molt-migration is given to
individuals that leave their breeding grounds and head south to find
a suitable location to undergo their annual pre-basic molt before
continuing southward migration. Unlike most other species which molt
either on their summer grounds or on their winter grounds,
Swainson's Thrushes overlap their molt with migration. Birds may
continue to migrate while actively molting or they may initiate
and/or complete their molt in an area south of their breeding
Where arid conditions on the breeding grounds in late summer are not
especially conducive to molting, adults routinely migrate
substantial distances to special molting areas. In general, their
movement away from increasingly drought-stricken breeding habitats
is timed for their arrival somewhere further south where an
abundance of insects and fruit production constitute a bumper-crop
resource for the energy and protein-demanding molt process.
Research on adult Swainson’s Thrushes at Colony Farm shows that many
of the adult birds caught for banding after the breeding season are
in flight feather molt suggesting the old field habitat could be a
special molting area for this species.
Moreover, it appears from VARC data collected during the last 4
years that these birds are not local breeders but birds from further
north based on the fact that post breeding season we see an influx
of unbanded birds many of which are in flight feather molt.
The purpose of this study is to assess the numbers of Swainson’s
Thrushes caught for banding which are in flight feather molt, the
extent of the molt and through additional biometric measurements and
photographs to try to establish a rationale as to whether these
birds are a different subspecies originating further north in Canada
Six subspecies of SWTH are recognized – four in the russet-backed
group, of which the BC coastal subspecies C.u ustulatus is one, and
two in the olive-backed group. Plumage variation between subspecies
are slight but differences in the coloration of the back, rump and
uppertail coverts and colour and density of spotting on the breast
may help separate them.
The study also
provides an opportunity to further examine known ageing criteria
(molt within the greater coverts and shape and length of primary 10)
and to examine the under alula coverts (the feathers under the
largest alula feather A3) to determine whether buffy shaft streaks
on these feathers can be used to definitively determine age in
Swainson’s Thrushes. Buffy shaft streaks on the under alula coverts
indicate a first year (HY/SY) bird but it is uncertain whether lack
of these buffy shaft streaks indicate an adult (ASY/AHY) bird.
The photos below all show hatch year (HY) SWTH - The bird top left
had completed it's 1st prebasic molt showing a clear molt limit
(indicated with the red arrow) between the replaced inner 3 greater
coverts and the retained 7 outer greater coverts. Notice the buffy
tipping or 'tear-drops' on the retained outer greater coverts and
the olive-greenish edging on the replaced inner coverts. Notice also
the replaced feathers are longer than the retained ones producing
the visible 'step-in' between replaced and retained coverts typical
of Catharus thrushes.
The bird top right was in the early stages of its 1st prebasic molt
with the inner GCs (GC8 indicated by the red arrow) still in sheath
- a molt limit in the making! This much younger bird was still
retaining much of its juvenile plumage - notice the buffy tear drops
on the median coverts in this photo.
The bird bottom left had also completed its 1st PB but the molt
limit here is much more subtle - the replaced inner GCs are longer
with olive-brown edging and there is still the step between replaced
and retained feathers but the outer retained GCs lack the buffy tear
drops of the bird above. This illustrates the importance of
understanding what to look for, where to look for it and wearing
'mag-eyes' (head mounted magnification lenses) when looking for molt
The final photo (bottom right) shows a close up of the under alula
feathers of a hatch year (HY) SWTH. By sliding the large alula
feathers (A2/A3) to one side the buffy shaft streaks of the under
alula coverts can be seen (red arrow) diagnostic of first year
This hatching year
(HY) male Hairy Woodpecker (HAWO) left and HY female Downy
Woodpecker (DOWO) below left were in full juvenal plumage, the male
HAWO showing an extensive red juvenal crown patch. As mentioned in
previous blogs Peter Pyle's excellent book the Identification Guide
to North American Birds Part I suggests that both male and female
HAWO and DOWO juveniles have a red juvenal crown but it has been
proven that those with an extensively red juvenal crown are, in
fact, males, while those with a black, or mostly black, juvenal
crown are young females.
During this males first prebasic molt, its red juvenal crown will be
lost and a red nuchal patch (on the back of the head) characteristic
of 'adult' males will molt in.
August saw the
first push of wood warblers through the park with Orange-crowned,
Yellow, Townsend's, MacGillivray's, Wilson's Warblers and Common
Yellowthroats all caught for banding.
Ageing these birds requires close
scrutiny as molt limits can be difficult to see when hatch year (HY)
birds still have very fresh retained juvenal feathers. The hatch
year (HY) Orange-crowned Warbler (OCWA) wing (photo below left) is a
good example of this. Under magnification the contrast between
replaced lesser, median, greater coverts and carpal covert and
retained primary coverts and main alula feathers (A2 and A3) can be
seen the molt limits indicated with red arrows between the outer
greater covert and inner primary covert and alula covert (A1) and
main lower alula feather (A2). Molt limits like this can be quite
subtle with birds in the hand and for this reason, especially after
adults of these same species begin to show signs of approaching the
end of their complete prebasic molt age should always be confirmed
by additional criteria such as skull ossification.
Tail shape can also help being generally more tapered in hatch year
birds (photo below right) and more truncate in adults although
determining the age of birds by tail feather shape alone is
generally not very reliable because of individual variation and the
possibility of accidental loss and replacement (i.e., adventitious
molt). Tail shape should always therefore be used with caution and
only in conjunction with other ageing criteria (e.g. molt limits).
The 1st prebasic
molt in Townsend's Warblers is partial and usually includes all
lesser, median and greater coverts but was much less extensive in
this hatch year (HY) female (photo below right) which had replaced
only the 4 inner greater coverts, the molt limit indicated by the
red arrow. A number of inner median coverts had also been retained,
the replaced feathers showing the wide black streaks through the
white tips (blue arrow) diagnostic of 1st year (HY/SY) females.
(WETA) moved through in good numbers this month with all of the
birds caught for banding hatch year (HY) birds.
the 1st prebasic molt in WETA is partial with normally all lesser
and median coverts replaced and sometimes an inner greater covert
(indicated with the red arrows - photo below right).
Some HY birds can be sexed like the HY male below with bright yellow
rumps and black median coverts with extensive yellowish tips (photo
In some birds molt
limits provide 'smack you in the face' examples of the difference
between retained and replaced feathers.
This hatch year (HY) male Red-winged Blackbird provides such an
example replacing worn, lightly pigmented brownish juvenile feathers
with pale brown rachises with glossy black, truncate feathers with
black rachises. Notice also the replaced orangish lesser coverts of
this HY bird which will be replaced by bright red feathers in the
birds first definitive adult prebasic molt following the breeding
season next year.
Our Hummingbird monitoring continued
during the summer months with mostly hatch year (HY) Rufous
Hummingbirds caught for banding. Hummingbirds are aged by the
occurrence and extent of corrugations on the culmen. In all species
the bills of nestlings are soft and deeply grooved or corrugated
along the rhamphotheca (the horny covering of the bill) lateral to
the culmen. In the first 5-9 months after fledging the bill hardens
and these grooves or corrugations are lost due to wear and the
are easy to see under magnification (photo below), this recently
fledged male Rufous Hummingbird with deep corrugations extending
almost the entire length of the bill.
We commonly catch
two species of NA Hummingbirds at Colony Farm, Anna's (ANHU) and
Rufous (RUHU). The prebasic molt in these two species is complete in
both adults and juveniles meaning all body and flight feathers are
replaced. RUHUs molt on their winter grounds whereas ANHU are
resident in the Vancouver area and molt here as can be seen in the
photo left of a hatch year (HY) male ANHU undergoing its first
complete prebasic molt.
Waterthrush (NOWA) is a rare transient in Vancouver (range map
right) so we were delighted when not one but TWO showed up this
month especially when one of them was on the morning that Bob
Mulvihill and Adrienne Leppold were banding with us. We were doing a
net round together when Adrienne walked up to a net and said "Oh Bob
a NOWA" and then watched the excitement as we did the 'rare bird
dance' - this was a first for Bob and Adrienne who have banded many
hundreds of NOWA but never before seen the 'rare bird dance'
although they did say the dance needed some extra 'bobbing' in it
for this particular species!
Waterthrushes are not thrushes of course but one of the larger,
terrestrial wood warblers which spend most of their time walking on
Ageing NOWA in the
summer and fall is relatively easy as juvenile birds typically have
narrow rusty tips to the tertials (photo below right) and narrow,
more tapered rectrices. Both of the birds caught for banding this
month were hatch year (HY) birds of unknown sex.
(CHSP) are another uncommon species on the coast being much more
numerous in the interior of BC. Adult CHSPs are unmistakable with
bright rufous crowns, white superciliums, dark eyelines and crisp,
whitish underparts. This very worn adult (photo below left) had lost
much of the edges of the buffy feathers of the wings and back.
Definitely fitting in to the category of 'confusing fall sparrows'
was this hatch year (HY) CHSP (photo below right) like many sparrows
in juvenile plumage looking very different from its adult
counterpart. We look very carefully at juvenile sparrows especially
CHSPs as they are very similar to Clay-colored and Brewer's Sparrows
both of which are possibilities for us in the park.
Notice the brownish auriculars and sides of the breast of this bird
and black centers of the median and greater coverts which extend
through the buffy tips of the feathers creating the appearance of
spotted wing bars. The dusky streaking on the head and neck is also
generally more extensive on CHSP than other Spizella
This hatch year
(HY) Warbling Vireo (WAVI) was one of a number caught for banding
this month. HY birds can be separated from adults by a number of
criteria in addition to molt limits. The length and shape of the
outermost primary (P10) tends to be longer and more rounded in HY
birds than adults and the upper mandible lining (roof of the mouth)
pinkish to grayish white (photo below right).
Another bird in
juvenile plumage which caused a momentary double take was this hatch
year (HY) European Starling which was in the midst of its complete
1st prebasic molt when all body and flight feathers are replaced
(photo below right). In full juvenal plumage these birds are
entirely gray-brown although this bird was already replacing dull
juvenile feathers with iridescent feathers on the flanks (photo
Juvenile EUST can
be sexed based on the colour of the iris which is dark brown in
males and pale grayish with a yellowish tinge in females.
And finally a whole
family of Bushtits (BUSH) paid us a visit and normally when one
member of the family gets caught so do many of the other individuals
of these active, social birds traveling together in busy flocks!
BUSH are an ageing nightmare as the prebasic molt is complete in
both hatch year (HY) and after hatch year (AHY) birds and towards
the end of the year often have to be recorded as 'age unknown'.
However at this time of the year juveniles (photo below right) can
be separated from adults by very loosely textured feathers
particularly of the undertail coverts and by the shape and length of
the outermost primary (P10) being longer and more rounded in
juveniles than adults.
Sexing BUSH is possible by iris colour which is pale grayish white
in females like this after hatch year (AHY) bird (below left) and
entirely dark brown in males although the iris colour is only
reliable for sexing hatch year males after the 1st prebasic molt as
the iris is initially dark in both juvenile males and females. Our
hatch year (HY) bird below right was therefore recorded as 'sex
Thanks to all the
VARC volunteers who made the summer and particularly the NAOC such a
success. Between all the early mornings hosting field trips and
guests at the banding station and long days and evenings attending
the VARC booth at the NAOC we are constantly reminded that we have
the best volunteers anywhere freely donating their time to VARC in
the cause of avian research, conservation and education.
Thanks again 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,
Todd Heakes, Dev Manky, Marianne Dawson, Vinci Au, Sara Legros, Olga
Lansdorp, Christine Bishop, Kathy Elwood, Rufus Macintyre, Erin
O'Connor Marg Anderson and Hummer volunteers Marguerite Sans, Chris
Hart, Merie Lister and Alida Faurie for all their help.
Avian Research Centre Society is a Registered Canadian Charity (#
82118 2656 RR0001)
Donations to a registered charity are of course tax deductible and
we hope that people concerned about avian environmental issues in
Vancouver will consider making a donation to further VARC’s work.
This can be done by simply clicking on the link below to make an
immediate donation. Thank you for your generous support – it really
is very much appreciated!