Vancouver Avian Research Centre

.....Research - Conservation - Education

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 station!

July - 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 convert!!).

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.

Brown Creepers (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 Swallow boxes.

Although Mourning 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.


VARC participated 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 and participation.

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 viewed here: VARC Poster (please allow a few moments for it to load).

Throughout the 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 America.

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 alumni.

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 guys!

Lots of baby birds in juvenile plumage made for many gratuitous photographs and lots of oohs and aahs from banders and visitors alike.

Clockwise are 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 net #7!

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 Superwoman (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 counterparts.

Swainson's Thrushes 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 grounds.

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 or Alaska.

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 limits!

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 (HY/SY) birds.

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.

Western Tanagers (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 below right).

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 hardening process.

These corrugations 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.

Northern 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!

Northern Waterthrushes are not thrushes of course but one of the larger, terrestrial wood warblers which spend most of their time walking on the ground.

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.

Chipping Sparrows (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 sparrows.

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 below left)

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 unknown'.

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.

The Vancouver Avian Research Centre Society is a Registered Canadian Charity (# 82118 2656 RR0001)

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