Vancouver Avian Research Centre

.....Research - Conservation - Education

May is one of our favourite months as the numbers of birds and diversity increase as neotropical migrants move back through the park many of them in bright alternate breeding plumages.

Many birds undertake this second prealternate molt in the late winter early spring and none more noticeable than American Goldfinches (AMGO) which are the only finches to change all of their body plumage twice a year.

In alternate plumage, both age classes (second year - SY and after second year - ASY) have very bright body plumage and soft part (e.g., bill) coloration, but SY birds typically have dull greenish brown epaulets (lesser coverts) at the bend of the wing as can be seen in the bird below left.

ASY birds usually have bright yellow 'shoulders' although this criterion alone is not altogether reliable for determining age of AMGO males, because ASY males sometimes have dull greenish lesser coverts, and SY birds sometimes will show precocious development of bright yellow lesser coverts.

Ageing American Goldfinches is easier than in many species as there are two ageing shortcuts banders can use. First we look for a buffy tip on the carpal covert. At this time of the year only SY birds have a buffy fringe to the terminal edge of this feather - adults lack this buffy tip to the carpal covert (although they can show a white tip) and in spring/summer AMGO’s are the ONLY birds where we can use the prealternate molt for ageing as only SY birds molt their inner GC’s as part of their prealternate molt.

The wing below right shows these two ageing shortcuts - the blue arrow pointing to the buffy tip on the carpal covert and the red arrow pointing to the replaced inner greater coverts of this second year male's prealternate molt this spring.

MacGillivray's Warblers moved through in higher numbers than usual - this gorgeous after second year (ASY) male showing the quintessential field mark of the split eyering or eye arcs of this species and the wing showing no discernible molt limits.

The first wave of Orange-crowned Warblers (OCWA) contained almost all adult males like the bird right showing extensive orange in the crowns and prime examples of what definitive adult plumage, with no discernible molt limits among the coverts or alula and truncate flight feathers (primaries, secondaries and retrices), looks like in the spring.

Correctly sexing a bird depends on correctly ageing it first always remembering that young (HY/SY) males can look a lot like adult (AHY/ASY) females.

Such was the case with this adult (ASY) female Wilson's Warbler showing a quite extensive black cap which could easily be confused with a second year (SY) male. The wing (below right) however again shows definitive adult plumage, with no discernible molt limits among the coverts or alula, nicely edged primary coverts and truncate brightly edged green remiges (primaries and secondaries).

Our Hummingbird monitoring program kicked off this month as returning Rufous Hummingbirds moved through the park. Our Hummingbird station consists of 3 Hall traps (photo below left) each operated by an electronic remote trap tripper (photo below right) which sits above the trap and is triggered by radio control form the banding station.

Special thanks to electronics genius and all round good guy Kyle Norris for building our state of the art trap trippers which really are quite something!

Our very first customer was the stunning adult male Anna's Hummingbird mentioned in the April blog which had overwintered in the park and which entered the trap quite literally as we were setting it up and proving the old adage that there's no such thing as a free lunch!









And this equally stunning adult male Rufous Hummingbird which always have visitors captivated when they hear of the amazing migratory journeys of these tiny birds breeding as far north as Alaska and overwintering in Mexico - wings beating at 60-80 beats per second, hearts beating at over 1,200 beats a minute in flight and weighing little more than a Canadian penny!

Our May Bird Monitoring and Banding Workshop was full with participants sacrificing their weekend to learn about molt and ageing of NA landbirds in the hand.

It always amazes us how people can progress from little or no knowledge when they arrive on Friday lunchtime to extensive knowledge by the end of the weekend. Before leaving the course we ask them all to complete workshop evaluations and rate the overall experience of the workshop from 1-10 and we were delighted to receive a total score for our May workshop of 99% which was a record and really pretty amazing!

Thanks to all our course attendees for their kind comments which as always can be viewed on our testimonials page by clicking here.

The workshop is a pretty intensive 3 day course which focuses on accurate ageing and sexing of NA landbirds using molt and plumage criteria. After working late in to the evening on the Friday followed by two early morning field sessions and more classroom work on Saturday and Sunday by Sunday afternoon everyone is feeling the effects and we called this photograph of one workshop participant "Molt Overload"!!

We had lots of visitors to the station again this month. A large part of our mandate is public outreach and education to raise awareness of environmental issues particularly as they relate to habitat conservation for birds.

Much is being talked about regarding 'Nature Deficit Disorder' in children these days, a term coined by Richard Louv in his 2005 book Last Child in the Woods, referring to the alleged trend that children are spending less time outdoors, resulting in a wide range of behavioural problems.

We always notice how happy kids are when they are outside visiting the banding station and interacting with wild birds and both these young ladies were totally absorbed - Savannah on the left (really should be holding a Sparrow!) helped ferry Hummingbirds back from the traps to the banding table and Amy on the right concentrating on the perfect shot of a nice male House Finch!

Speaking of kids May saw the start of the VARC 'Birds are Brilliant' schools program when we hosted a group of 70 Grade 7 students from Mulgrave private school in West Vancouver.

The children were split in to 3 groups and rotated between 3 stations - one where we talked to them about the miracle of migration and the need to safeguard habitat for breeding and migratory birds, one where they had to collect information matching birds to habitats, song and food sources and the banding station itself where they were able to interact with wild birds.

At the end of the morning we talked to them about birds and the environment and the things they can do to help make a difference by being conscientious consumers, keeping cats indoors and building bird friendly gardens and campuses. Their homework project was to each build a simple wooden mobile to prevent window strikes.

We've always said that if you put a wild bird in to a kids hand you have a convert for life and although these kids may go on to all sorts of career paths, they will never forget the unique experience of holding a migrant warbler which like the two photos of Wilson's Warblers below may have been in the tropical high plains of Costa Rica only a week or so before.

The visit was an outstanding success and seeing the look on kids faces as they held and released wild birds was really priceless!

Is it a it a it's Superwoman!

With all the visitors it's nice to have some superhuman help! Here is Lois Lane (aka Sarah Gray) using her kryptonian powers to band a Purple Finch during the Mulgrave School visit!

The first signs of the breeding season were obvious this month with many resident birds caught for banding already showing breeding characteristics.

This female Downy Woodpecker was showing a developed although not fully vascularized brood patch (photo below left). Unlike in passerines where the female does most if not all the incubation in the near passerines such as woodpeckers males also incubate and develop brood patches. In Downy Woodpeckers the female incubates during the day and the male incubates at night.

Molt in near passerines is also different than passerines allowing us to age birds in to their fourth year. Its not until its third fall, when it is a third year bird, that it replaces any inner primary coverts and, as with this bird (photo below right), a few middle  juvenal primary coverts (now extremely brown and worn in comparison to the recently molted primary coverts on either side) sometimes are not replaced
So, with the change of the calendar year the bird below becomes an after third year, specifically a bird alive in its fourth calendar year.

Brown-headed Cowbirds (BHCO) were back in the park their liquid sounding gurgling notes and thin, sliding whistles much in evidence this month.

Song learning in BHCOs must be innate, since as brood parasites the birds aren’t raised by members of their own species.

Males and females have several different mates within a single season but we thought this pair caught side by side made a very handsome couple at least for the moment!

This spring has been a record for us for Sharp-shinned Hawks banded with two more this month - a second year (SY) male (left).......

.....and this adult female right!

When is a Purple Finch not a  'purple' finch? Well, normally if it's a female or young male as male PUFIs don't get their purple plumage until their definitive adult prebasic molt in their second year. At this time of the year second year PUFIs are normally sexed as 'sex unknown' unless they have breeding characteristics such as cloacal protruberances or brood patches.

This precocious second year male was the exception to the rule and while not having the entire 'dipped in raspberry juice'  plumage of full adult males he was certainly unusually strongly washed with purple leaving us in no doubt as to his sex. His first prebasic molt after the breeding season last year included all lesser, median and greater coverts and the carpal covert - molt limits indicated with red arrows between the replaced outer greater covert and retained inner primary covert and between the alula covert and main lower alula feathers.

The photo below left shows why we call PUFIs 'purple pinches' - unlike the similar House Finch, Purple Finches always bite in the hand!

Following his definitive prebasic molt after the breeding season this year our SY male above will look like the 'sparrow dipped in raspberry juice' left!

The first of the season's confusing Empids arrived with this 'Traill's' Flycatcher. Showing all of the characteristics of an Alder Flycatcher with a narrow, white eyering, greenish dorsal plumage, pale lores and distinct crown spots this bird simply didn't have the 'feel' of a Willow Flycatcher and at the time WIFLs had not arrived in the park.

Much is not know on molting patterns in this species with more study needed. This after second year (ASY) bird of unknown sex was showing clear molt limits between replaced inner greater coverts and tertials presumably from its prealternate molt which should have included primaries and secondaries but didn't!

No such difficulties with this gorgeous second year (SY) male Western Tanager showing clear molt limits between retained juvenile feathers, first basic feathers (red arrow) and first alternate feathers (blue arrows).

Equally easy to age and sex was this adult (ASY) male Black-headed Grosbeak. Like Purple Finches males do not get their adult plumage until their definitive prebasic molt following the breeding season in their second year; SY males vary from looking a lot like females to looking nearly like adult males.

We now have 18 nest boxes for Tree Swallows (TRES) in the old field habitat creating lots of nesting opportunities for these cavity nesters.

As both the adult and first prebasic molt can be complete in TRES ageing this species requires close scrutiny of the body plumage.

If there is any brown on the head or back the bird is a female and varying amounts of brown indicate age as follows:

  • >50% brown indicates a second year (SY) female

  • 10-50% brown indicates an after hatch year (AHY) female

  • 1-10% brown indicates an after second year (ASY) female

If the head and back are entirely green-blue it may be a male of any age or an ASY female at which point we measure the flattened wing chord as a measurement below 114 mm bird indicates a female and one above 121 mm a male.

Our bird right was aged AHY and sexed female based on wing chord.

The first Swainson's Thrushes arrived 'home' this month with several significant retraps including this bird banded in 2009 as an after second year (ASY) then and now in at least its sixth calendar year!

Migration really is a miracle and it never ceases to amaze us that these long distance migrants which have possibly overwintered as far south as Argentina can navigate back so precisely to the same location year after year returning not just to the Lower Mainland or Vancouver but to the very same place within Colony Farm often meaning we retrap birds from previous years in the very same nets in which we caught them originally!

And finally this second year (SY) female Yellow-headed Blackbird (YHBL) was a nice surprise and new species banded for the station.

We have seen YHBL only once before at our station feeders and again it was a female. The marsh adjacent to the banding station has a large Red-winged Blackbird (RWBL) colony and as YHBL often nest in the same marsh habitat as RWBL it may be that this bird was scoping out a possible nesting site there.

It was interesting to note an unusually high number of YHBLs on a recent trip to the interior of BC this year.

There are exceptions to almost every rule in molt and ageing and YHBL is one of them. Unlike all of the other Blackbirds which can have complete first prebasic molts YHBLs don't!

In YHBL the 1st prebasic molt is partial meaning only body feathers and some wing coverts and possibly tertials and central retrices are replaced.

This 1st PB in YHBL is supposed to include ALL median and greater coverts but no tertials or retrices and little is know about the prealternate molt which is suspected to be absent or limited.

This bird had replaced only the 5 inner GCs and retained the outer 5 GCs, a clear molt limit and 'step-in' indicated by the red arrow in the photo above right,

In addition to the yellow of the head and breast being mottled with brown in SY females (photo above) the outer primary coverts are relatively tapered and often have white tipping indicated by the red arrow on photo right.


Thanks to Mark Habdas, Kerry Kenwood, Carol Matthews, Jason Jones, Jerry Rolls, Debbie Wheeler, Sarah Gray (aka Superwoman!), Mike Nutter, Kyle Norris, Eric Demers, Celia Chui, Louise Routledge, Monica Nugent, Todd Heakes, Dev Manky, Marianne Dawson, Vinci Au, Sara Legros and Hummer volunteers Marguerite Sans, Alida Faurie and Erin O'Connor  for their help with banding this month.

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