June - The
transition from spring to the summer season was heralded at the end
of May with the capture of our first hatch year birds of 2011 when
we banded a number of fledgling House Finches. They were aged as
hatch year (HY) birds as although they were in full juvenal plumage
they were capable of sustained flight and could well have fledged
anywhere in the surrounding area.
Conversely this fledgling House Finch was one of five aged local (L)
because their juvenal plumage was not yet fully developed, they were
incapable of sustained flight, and they were still being cared for
We always give
banding priority to dependent young like this and/or to adults
(especially females) that may be caring for young or incubating
eggs. Not only do we band and process these birds first upon
returning to the banding Pagoda from making our net rounds, but we
return them to the site of capture as soon as possible after
This is especially the case with retrapped females with edematous
brood patches (see below) where we will often record the band number
at the net and release them on the spot after extraction.
The breeding season
is a particularly advantageous time for banders because sex-specific
physiological changes in many species can allow otherwise unknown
sex birds to be designated as either male or female.
As most birders and banders know, many species are sexually
dimorphic meaning we can sex the bird based on characteristics such
as plumage coloration and/or size. However many species are sexually
monomorphic meaning both females and males look exactly alike and
these species can only be sexed in the hand in spring and summer
when they show breeding characteristics i.e. a cloacal protuberance
(CP) or a brood patch (BP).
In many monomorphic
species, the male's cloaca becomes enlarged and bulbous during the
breeding season, the base narrow and tip swollen (as in the photo
below left), the purpose being to store sperm and aid with
copulation. This is called a cloacal protuberance, or CP. The
swelling of a male's cloaca develops gradually and is not always as
obvious as this fully developed CP on a male Song Sparrow but can be
identified with experience.
on the other hand conduct most if not all of the incubation and
develop brood patches (BP). At this time they will lose the feathers
on the breast and belly to facilitate direct skin contact and
maximum heat transfer to the eggs for incubation.
The photo below right shows a fully developed brood patch with
wrinkled and highly vascularized skin. The development of the brood
patch progresses in stages similar to the development of the cloacal
protuberance of the male, the feathers of the breast and belly are
first shed and the blood vessels under the skin increase in size and
number until the brood patch is edematous (i.e. highly vascularized
and swollen) such as in the photo below right of a female Purple
Finch with a fully developed brood patch.
The result of all
this breeding activity is of course baby birds and we couldn't
resist the opportunity to show a couple more photos of birds
in juvenal plumage (Dark-eyed Junco below left and American Robin
below right) both scoring 10s on the cuteness scale!
Last month we
looked at two similar Empids in the hand, Dusky and Hammond's
Flycatchers - this month we were tested with another one! Our common
Empid is Willow Flycatcher (photo below right) which breed in
large numbers in the park, their distinctive "fitz-bew" songs
resonating seemingly from every bush - the bird below left had us
puzzled and our immediate thought was Alder Flycatcher!
Willow (WIFL) and Alder (ALFL) Flycatchers together form 'Traill's'
Flycatcher, our largest Empid, are virtually identical and
were actually considered the same species until the 1970's. ALFL
breeds across northern BC and WIFL across southern BC without
significant hybridization, both species breeding in wet thickets and
shrubby areas such as we have at Colony Farm.
Looking at the two birds below there were a number of subtle
differences which had us leaning towards ALFL. The first was the
much lighter lores of the possible ALFL compared to the WIFL without
conspicuous light-coloured lores. The second was the dorsal plumage
being somewhat greenish above compared to WIFL which is greyer
above. The third was the wing bars and tertial edgings of the
presumed ALFL which were slightly broader and brighter than the WIFL
and there was definitely a sense of more of an eyering which is
lacking on WIFL. One thing that didn't agree was crown spotting
which in the ALFL should be larger and more distinct although adult
crowns are more spotted than first year birds and males more than
Finally notice the size of the bill on the possible ALFL - although
this is not a factor to separate ALFL from WIFL the bill was
absolutely huge and reminded us more of the bill proportions on a
Tropical Kingbird rather than an Empid!
We looked at wing
morphology and determined that primary 6 (P6 below left) was not
emarginated (i.e. there was no indentation on the outer web) which
at least ruled out it being any other Empid as Traill's
(WIFL/ALFL) are the only Empids where P6 is not emarginated!
The bird was aged as an after hatch year (AHY) of unknown sex.
The wing (below
right) showed the classic 'eccentric' pattern of incomplete molt in
Tyrant Flycatchers with replaced and retained remiges (primaries
and secondaries) this bird clearly showing the difference in rachis
(shaft) colour between the retained two innermost primaries (PP1&2)
and the replaced outer primaries and inner secondaries. But as much
is not known of the molting patterns of this species this
replacement pattern could be from the preformative, prebasic or
We took our other biometric measurements, banded the bird with a
size '0' band which is the size for both ALFL and WIFL and recorded
species as 'Traill's' Flycatcher with notes as to the likelihood of
this silent Empid being an Alder Flycatcher!
banded this month was this Pacific-slope Flycatcher (photo below
left). Although the Latin name for PSFL is Empidonax difficilis
they are probably the least difficult Empid to identify
in the hand as the gray leg colour (photo below right) is unique,
other Empids having black or blackish legs.
We band a number of
Brown-headed Cowbirds each year and are always surprised when
visitors give them such a bad rap sometimes saying things like
“Don’t you euthanize them?”
We don’t! And actually we think they’re pretty neat birds and try to
educate people that the problem with Cowbirds is humans!
Originally birds of the open grasslands following cattle herds in
search of seeds and disturbed insects Cowbirds evolved to become
brood parasites, laying their eggs in the nests of other birds and
abandoning their young to foster parents as they continued their
In the course of a single nesting season, a female cowbird like this
one (photo below left) may produce as many as 40 eggs over as many
or more days. The challenge for her is she has to find as many nests
of potential host species at just the right stage of laying in order
for just a few of her offspring to have the chance to survive to
independence. This is actually about the same number of young that
many cowbird host species themselves will raise in a single season
by tending just one or two nests containing four or five eggs each!
The challenge is when cowbird nesting success almost completely
eclipses the nesting success of its host species particularly in
small forest fragments surrounded by agricultural landscapes. Some
of these fragments are large enough to attract forest nesting host
species such as Thrushes and in these areas the hosts experience
exceptionally heavy cowbird parasitism pressure due to the fact that
a very large population of cowbirds is supported by the ever
expanding surrounding agricultural landscape. This can cause what is
known as a "population sink" meaning the host species may
effectively raise only cowbird young but again, the irrefutable
negative impact of cowbirds on some host species in such areas is
symptomatic of the continuing conversion of forest to agricultural
and other land uses by human beings!
sexually dimorphic, females having pale grey body plumage and brown
heads and males having bright glossy black body plumage and rich
brown heads. Males do develop cloacal protuberances (CP) but females
do not of course develop brood patches.
Females are also considerably smaller than males with shorter wing
chords (the length of the unflattened wing) and in fact take a
smaller band size.
Cowbirds are members of the Icteridae family and can have complete
first and adult prebasic molts although the first prebasic molt is
rarely complete with a number of underwing coverts normally
retained. The photo on the right shows the left underwing coverts of
a second year (SY) male, the red arrow pointing to the darkly
pigmented and glossy black replaced coverts.
Although replaced underwing coverts are easy to see on males as in
this photo, the contrast between retained and replaced feathers on
females is much more difficult to detect and due to this some are
impossible to age.
banded species for us was this stunning after hatch year (AHY) male
Northern Harrier made all the more unusual as it showed up in one of
our woodland nets. We often see NOHAs hunting over the open fields
of Colony Farm where there is a large Townsend's vole population but
their slow, flapping flight near the ground and keen eyesight makes
it easy for them to avoid our nets in these more open areas.
Unlike other raptors Northern Harriers rely on hearing as well as
vision to capture prey. The facial disk is much like that of owls,
the stiff feathers helping to transmit sound to the ear openings to
flooded back in to the park this month filling the air with their
electric, high-pitched trills as they fly around devouring the
ripening Elderberry fruit.
CEDWs are one of our favourite birds and definitely one of the best
The name 'waxwing' comes from the waxy red secretions found on the
tips of the flight feathers (primaries, secondaries and retrices).
These red waxy appendages are usually restricted to the secondaries,
giving a usual maximum of nine wax tips per wing (seven wax tips is
by far the commonest number). Rarely, some retrices (tail feathers)
will also have the tips of their shafts red. More rarely
still, small red wax tips can be seen on one to a few inner primary
wing feathers. Our record was one bird with an impressive grand
total of 36 waxy appendages!
The exact function of these tips is not known, but they are age
related as is the extent of yellow on the tips of the retrices.
The number and length of waxy tips together with the extent and
glossiness of the black patch at the base of the chin allows us to
determine sex, the black being brownish black and much less
extensive on females and extensive glossy black on males.
This is not only
helpful to banders but is also helpful to birders particularly those
participating in citizen science projects like the Breeding Bird
Atlas as CEDWs can be identified not only to species but also to age
and sex using this information. We'll leave it to you to try this
out by ageing AND sexing the bird above left (answer is at the end
of the blog!)
Cedar Waxwings are
true frugivores which specialize in eating fruit and they can
survive on fruit alone for several months. We've noticed that when
CEDWs first arrive back and the Elderberry fruit isn't ripe they
develop hardened, sticky resign at the base of their bills and on
their foreheads (photo above right) which the birds are unable to
clean off their bills and feathers. Sometimes this hardens to such
an extent that feathers are shed, probably due to scratching as the
birds try to dislodge the irritating substance and creating
extensive bare patches at the base of their bills.
monitoring continued in June both at Colony Farm and on Vancouver's
north shore. We band both Rufous (RUHU) and Anna's (ANHU)
Hummingbirds here in Vancouver and we never cease to be amazed by
these tiny birds.
ANHUs are year round and overwinter in Vancouver whereas RUHUs breed
as far north as Alaska and overwinter in Mexico. ANHUs are larger
than RUHUs, this after hatch year (AHY) female (photos below right)
weighing in at 4.3 grams and the after hatch year (AHY) male RUHU
(photos below left) weighing in at a mighty 3.3 grams - that's not
much more than a Canadian penny which makes their long migrations
seem even more impossible with those tiny wings beating at 80 beats
per second and hearts beating at something like 1,200 beats per
minute in flight!
Apodiformes which comes from the Greek meaning 'no feet'. They
do of course have feet but they are too far back on their bodies to
enable them to walk which makes for great photo opportunities with
visitors who can marvel at a Hummingbird sitting on their open palm
before taking to the air again.
We make the bands
for Hummingbirds ourselves from thin sheets of stamped aluminum
provided by the federal Bird Banding Laboratory, carefully cutting,
filing and forming the bands to the correct size. The finished band
is not much larger than the tip of a retractable pencil (photo
right) and special pliers are used to attach them to the birds
Ageing Hummingbirds is relatively easy as all species can be aged
for the first 5 to 9 months after fledging by the extent of grooves
called corrugations along the lateral portions of the upper
When Hummingbirds are born the bill is soft and these deep grooves
are easily seen under magnification (photo below left) whereas adult
bills are smooth, hard and shiny along the entire length of the
upper mandible (photo below right).
after second year (ASY) female Evening Grosbeak turned up at our
feeders during the month. Although Evening Grosbeaks breed in BC
they are uncommon in the lower mainland and our previous
captures have all been in the very early spring. With no evidence of
a brood patch and a fat score of 3 (out of a possible maximum of 5)
she was almost certainly a transient and after a few days gorging on
our sunflower seeds left the banding area and wasn't seen again.
(PUFI) breed in large numbers in the park and can be separated from
House Finches (HOFI) by looking closely at the culmen (the ridge of
the bill from the base of the feathers to the tip) which is
straighter in PUFIs and more decurved in HOFIs.
PUFIs have delayed plumage maturation meaning males do not attain
their full purple plumage and become what Peterson described as the
"sparrow dipped in raspberry juice" until their definitive adult
prebasic molt following the breeding season in their second year.
Visitors often say they only have females at their feeders but
because of this these birds could actually be either females or
Ageing of this bird was therefore very easy! (answer at the end of
PUFIs are also facultative (as opposed to obligate) migrants meaning
they may or may not migrate depending not on ambient temperatures
but on whether enough food is available on their breeding grounds in
a given winter. We know this to be true as we band them during the
winter at our nearby Burnaby Lake winter banding station where we
operate feeders throughout the winter months.
Flycatcher showed up this month and had one of our volunteers
confused who called it a Willow when he brought it back to the
Like Willow Flycatcher P6 is not emarginated and there is no eyering
on this flycatcher but the dark vest is very different from any
Empid as are the smudged undertail coverts. This flycatcher has
a very long primary projection and the bill is much longer, the
underside being 1/2 to 3/4 dark versus pale on
Willow as illustrated in the photo
at the beginning of this month's blog.
Finally the wing tips of this flycatcher reach to the tips of the
undertail coverts (photo below right), on Traill's they are much
shorter making this bird a definitive Western Wood-Pewee.
We had another
first for the season and couldn't leave this month's blog without a
photo of Colony Farm's iconic bird, this absolutely stunning after
second year (ASY) male Lazuli Bunting which was a particular treat
for John Hague a visiting birder from Yorkshire, England who spent
the morning with us and got to see some of Vancouver's birds up
close and personal before leaving on his travels around the
province. As a Londoner I took a bit of an exception to him calling
all English southerners 'softies' and to the fact he supports
Sheffield Wednesday football team but apart from that he was really
quite a decent bloke! Happy travels and birding John!
Many thanks to Mark
Habdas, Kerry Kenwood, Carol Matthews, Dev Manky, Jason Jones,
Saskia Wischnewski, Ian Thomas, Greg Schultz, Debbie Wheeler, Celia
Chui, Sarah Gray, Eric Demers, Chris and Marguerite Sans, Marianne
Dawson and Gabriel Jamie visiting bander from Cambridge University
England for their help with banding this month.
The CEDW above is an adult (After
Second Year) male based on the number of waxy appendages, extensive
yellow on the retrices and extensive, glossy black base to the chin!
2. The PUFI above is an adult
(After Second Year) male