May was a
busy month for both birds and visitors as migration finally got in
to full swing and the weather started to cooperate.
Our first rare bird for the season was a Dusky Flycatcher (DUFL
below left) in addition to a number of Hammond's Flycatchers (HAFL
below right). Silent Empidonax flycatchers are of course 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.
Both these species have greyish throats, yellowy bellies, narrow
bills, grey heads usually contrasting with greener backs and both
have almond shaped eyerings.
Looking at the two birds below the first thing to notice is head
shape being fairly rounded on the DUFL whereas the HAFL has a short,
steep forehead and long, flat crown. DUFL is the slimmest Empid with
a very narrow base to the tail and the outer edge of the outermost
retrices (R6) is contrastingly white. The bill is long and narrow
with straight sides, the lower mandible variable in colour from
yellow to dusky whereas in HAFL the bill is small and short with
straight sides, the lower mandible again varying in colour. The
lores are often contrastingly paler in DUFL as can be seen on the
bird below left.
Next comes wing
shape or morphology which differs markedly in the two species. Both
have an emarginated primary 6 (P6) an important feather for banders
as indentations on the outer web of the feather (called
emarginations) can help separate similar species in the hand. Unlike
many passerines all Tyrant Flycatchers have 10 primaries, the outer
10th primary full in length.
HAFL has the longest primary projection (the projection of the
primary tips beyond the tertial tips) of all the Empids (13-20mm)
and a long gap between the tips of P5 and P6 as can be seen in the
photo below left. HAFL also has a long wing and short tail with a
wing minus tail measurement of 11-19mm and tail minus primary
projection measurement of 35-42mm.
DUFL has a long tail and short wing
with a short primary projection (9-15mm) and the primary tips are
evenly spaced with P10 SHORTER than P4 unlike HAFL in the photo
above right where P10 is noticeably longer than P4.
Our DUFL below had a wing chord of 70mm, a tail length of 60mm with
a primary projection fractionally under 10mm (photo below left) with
P10 shorter than P4 (photo below right) allowing us to definitively
identify this silent Empid as a Dusky!
We welcomed the May Bird Monitoring
and Banding Workshop for the weekend of May 6th - 8th and were
rewarded with a great group of people and LOTS of birds with nearly
200 birds of 32 species for the Sunday field session including the
first Black-headed Grosbeaks and Western Tanager of the season.
The red pigment in the face of the Western Tanager is rhodoxanthin,
a rare pigment in birds. It is not manufactured by the bird
itself, which is the case with pigments used by the other red
tanagers. Instead, it is likely acquired from insects that
themselves acquire the pigment from the plants they feed on.
Everyone really did have an amazing
time and agreed they had taken their bird handling and molt and
ageing skills to a whole new level. After an intensive weekend
studying molt limits we were sorry to part company and thank them
all for their participation and for their very kind and generous
comments which can be seen by clicking on the link below:
Zonotrichia sparrows moved
through in good numbers with both White-crowned and Golden-crowned
Sparrows banded. Ageing WCSPs at this time of the year can be
challenging as both second years (SYs) and after second years (ASYs)
can show contrasting greater coverts, tertials and retrices and both
show the pseudolimits mentioned in previous blogs but SYs often
retain a few brown juvenal feathers in the hindcrown as in the photo
(below top right) and can reliably be aged SY.
5 subspecies of WCSP are generally recognized with both Gambelii
and Pugentis found in southwestern BC. Separating the two
subspecies is not always easy and intergrades occur complicating
Gambelii breeds in northwestern Canada & Alaska and the white
supercilium extends to the bill, lores are pale gray and the bill
orange-yellow or orange-pink. Pugentis (top two photos
below) breeds from coastal southwestern BC south to northwestern
California is generally smaller and browner than Gambelii with
pale lores and a yellow bill although differences with intergrades
(photo below bottom right) are subtle at best.
Second Year (SY) female Cooper's Hawk was an early morning treat as
we did a first net round at the beginning of the month. We discussed
ageing the smaller
Accipiter, Sharp-shinned Hawk last month and this bird was
similar with buffy fringing to the upperparts and very dull,
yellowish eye colour. She constantly raised the feathers of her
crown doing her best imitation of a Harpy Eagle! (photo below
The first Warbling
Vireo was banded and the first wave of Wilson's Warblers arrived,
all adult (After Second Year) males with extensive glossy, black
crown patches. Hermit Thrushes continued to be caught up until the
middle of the month which is much later than in previous years
likely due to the continuing cold, wet and unsettled weather we have
experienced this spring.
Hermit Thrushes are
short distance migrants and are in fact the only member of their
genus to overwinter in North America, other species such as
Swainson's Thrush overwintering as far south as Argentina.
Molt limits in members of the Catharus thrush family are
often easy to see as many hatch year / second year birds have buffy
tips on the retained juvenal greater coverts as can be seen in the
photo on the right the arrow pointing to the molt limit between the
replaced inner GC's without buffy tips and the 7 outer retained GC's
showing prominent buffy tips or tear drops, a common pattern in
members of this genus.
Primary 10 was mentioned in Tyrant Flycatchers above and
Catharus thrushes also have 10 primaries but here the 10th
primary is a vestigial (meaning characters which have lost their
original function through evolution) feather. This 10th primary is a
tiny feather not extending far beyond the primary coverts. The
variation in shape and size of this feather is also helpful in
After last months
wave of adult male Ruby-crowned Kinglets all of the RCKIs banded
this month were females. At this time of the year only males show
red or orange crown feathers.
Saturday May 14th
was a day to remember! A planned visit from the Washington Audubon
Society led by Neil Zimmerman was cancelled mid-week due to rain
forecasted for the entire weekend but at the last minute the rain
stopped and banding went ahead as scheduled.
The wet weather overnight kept migrants grounded and we suspected we
were in for a busy day as we listened to the chip calls of warblers
sounding everywhere as nets were opened before dawn. We weren’t
disappointed and the result was a record day with 315 birds
banded of 23 species!
The catch was dominated by Yellow-rumped Warblers with 215 banded
(147 Audubon’s, 23 Myrtle and 45 Intergrades) and the highlights
were a female Nashville Warbler, a MacGillivray’s Warbler, a
Pacific-slope Flycatcher and a SECOND Dusky Flycatcher.
We only had 5 experienced banders available and everyone worked
nonstop to process the line of birds brought in to the Pagoda only
to be replaced by another line as each net round was completed! You
know you’ve pushed volunteer help to the maximum when by the end of
the morning someone says “I never want to see another Yellow-rumped
With a number of volunteers away this weekend we were only able to
open 22 of our 30 nets and we all wondered just how many birds would
have been banded had we been able to operate all nets all day – we
estimated at least 500!
Sorry Neil and the Washington Audubon Society - Hopefully we can
schedule another visit later this year!
Our record day
included both MacGillivray's Warbler (ASY male below left) and this
worn ASY female NASHVILLE Warbler (below
right) both good 'gets' for us at Colony Farm. MacGillivray's
Warblers prefer coniferous forest edge habitat and Nashville
Warblers are annual but uncommon on the coast proving yet again the
importance of the old field habitat at Colony Farm for migrants
crossing the increasingly fragmented landscape of the Lower Mainland
And speaking of
good 'gets' for us at Colony Farm this Red-breasted Nuthatch banded
was a first for us!
Although a common bird throughout the Vancouver area Red-breasted
Nuthatches prefer coniferous forests and wouldn't normally be
associated with the open old field habitat where we band at Colony
(below left) began to arrive by the middle of the month with adult
males showing impossibly bright yellow plumages with broad, red
streaking on the breast and our first hatch year birds arrived. This
hatching year House Finch (below right) shows all the
characteristics of a bird in juvenile plumage with very
streaked/spotted plumage, very loosely textured body feathers and
swollen gape. Baby HOFIs like this one always show natal plumes on
their heads often giving the appearance of little horns and always
scoring a 10 on the cuteness scale!
continued to hamper the banding effort throughout the month and the
notoriously inaccurate weather forecasting in Vancouver often left
us frustrated as we either turned up for banding only to find it
raining and having to cancel or cancelling only to find clear
conditions by morning!
Wet weather during May can of course produce good fallouts of
migrants as was the case with our record day and also good numbers
or rare and/or uncommon species. This After Hatch Year (AHY) female
Western Meadowlark was another first species banded for us. This
Icterid prefers the drier grasslands of the BC Interior which
certainly hasn't been the case with the very wet conditions on the
coast this spring. Interestingly this bird had a partially developed
brood patch and we wondered if that could be evidence of breeding at
Colony Farm as the range of Western Meadowlark has been spreading in
A busy month for
visitors culminated on the last weekend with an arranged field trip
for 40 University of the Fraser Valley (UFV) biology students who
enjoyed lots of species diversity and watching the banding operation
including our Hummingbird monitoring. We always say that if you put
a live Hummingbird (or any bird for that matter!) in to a person's
hand you have a convert for life and hopefully that was the case for
many of the UFV students.
A large part of our work is education and raising awareness of
environmental issues including habitat loss and degradation and
using birds in the hand as teaching tools really is a way to make
these issues real for many people particularly for children and
students who will need to take conservation seriously in the coming
decades if we are to arrest the precipitous declines of many of our
Many thanks to Mark
Habdas, Kerry Kenwood, Carol Matthews, Dev Manky, Jason Jones,
Marianne Dawson, Saskia Wischnewski, Marg Anderson, Jerry Rolls,
Kate Fremlin, Ian Thomas, Greg Schultz, Debbie Wheeler, Celia Chui
and visiting bander Ben Schonewille the station Manager at Teslin
Lake Bird Observatory for their help with banding this month.