Vancouver Avian Research Centre

.....Research - Conservation - Education

September - is our busiest month of the year as the park fills with returning migrants and dispersing juveniles beginning their southbound migration.

Bird banding data provides a very important category of evidence for assessing and confirming the value of areas and habitats for migratory birds. By recording a measure of visible fat on migrants caught for banding and documenting changes in body mass and fat deposits through subsequent recaptures allows us to assess the quality of sites and/or habitats directly.

Many of the birds we band have large fat loads either initially or on their stopovers here which typically last from as little as a few days to as much as a week or more. The ability of migrants to deposit fat sufficient to fuel at least one whole night's migration is critical to their survival and to their long migrations to and from the Neotropics.

Fat is accumulated on a bird in three areas; the furculum (the area between the fused clavicles – the so-called wishbone), the wingpits and abdomen (see graphic below left). Each bird caught for banding is assessed for fat by blowing the feathers of the throat to reveal the furculum and scoring fat deposits on a scale of 0 - 5 (graphic showing cross-section of furculum below right).

The photo below (A) shows the hollow furculum of a Black-headed Grosbeak (BHGR) with no fat deposits - The lean body mass of a bird like this is 38-40 grams. Photo (B) shows a maximally fattened BHGR with fat overflowing the furculum and weighing 59 grams. Photo (C) shows the fat laden wingpit and photo (D) the fat laden abdomen of the same bird. Our record was one BHGR weighing in at a mighty 72.2 grams!

Migrants like these can double their lean body mass and the caloric density of this amount of fat is easily sufficient to sustain the energy demands of birds making non-stop nocturnal flights of maybe 700 kms or more and this of course is just one of several such flights these birds need to make to take them from their North American breeding grounds to their central and south American winter grounds.

The high insect and fruit production in late summer at Colony Farm provides an ideal environment for these birds to deposit fat sufficient to sustain the energy demands for southward migration and the VARC study has provided compelling evidence of the value of the old field habitat in the park where a fat depleted migrant can rapidly meet its nutritional needs.



2011 has certainly been a fantastic year for visitors and we've received lots of media attention too with SHAW TV the latest station to come out to film the banding and talk to us about avian and ecosystem conservation. The show was aired on 'The Express' their human interest magazine program and can be viewed by clicking here:

Shaw TV Video

This was the third film crew out this year and we're getting used to the media spotlight - this year Global and Shaw TV stations, next year 'Hello Magazine'!!

Speaking of visitors we welcomed Tim Ball a British 'A' Ringer and Trainer from the Reading and Basingstoke Ringing Group.

It's always great to have experienced visiting ringers and banders especially when they bring Cadbury's Boost Bars!

For some inexplicable reason we didn't get a photo of Tim but did get this photo of his life MacGillivray's Warbler and 'ringing tick'

Thanks for your help Tim - it’s always great to have another Brit around with a decent sense of humour!!!

The two warblers below show how similar some warblers look in basic plumage especially when they are females. The bird on the left with the split eye ring formerly of the genus Oporornis now of the genus Geothlypis and the bird on the right with the full eye ring formerly of the genus Vermivora and now of the genus Oreothlypis.

Getting used to the new scientific names is a challenge for many birders and banders and for some of us Dendroica Warblers will always be just that even though we've started the long process of trying to say goodbye! Still it's fascinating to see how our knowledge of these birds continues to develop and who would've guessed that American Redstart was related to Hooded Warbler?!

Both of these birds were hatching year (HY) females showing molt limits between the replaced outer greater coverts and retained inner primary coverts (illustrated on the corresponding photo below each bird with a red arrow)

If you don't know your Geothlypis from your Oreothlypis the answers to these birds identities are at the end of the blog!

Our final Bird Monitoring and Banding Workshop of the year was held the weekend of the 9th - 11th and a great group of people enjoyed not only fabulous weather but lots of birds and good species diversity. Everyone had a great time and all agreed they had become banding and molt converts!

It really is amazing to see people progress from little or no knowledge when we meet at lunchtime on the Friday afternoon to having extensive knowledge by the end of the weekend. Thank you to all of our workshop participants and especially for their extremely kind and generous course evaluations which can be seen on our workshop testimonials page:

Our workshops could never be the success they are without the help of all of our volunteers like Jerry here pointing out (I think!!) that there were still two more birds for processing!!! Nice outfit Jerry - you'll make someone a wonderful wife!!

Western Tanagers came through in good numbers this month and although noisy and aggressive in the hand are one of our favourite late summer species.

The 1st prebasic molt in this species usually includes all lesser and median coverts and none or as with this bird below just a single inner greater covert (indicated with red arrows in the photo below right). Very bright hatch year males like this can be separated from females by the extensive yellowish tips to the blackish median coverts and by their bright yellow rumps and throats.

Many of the birds we band in early September are still in juvenal plumage showing all the characteristics of recently fledged birds like this hatching year (HY) Black-headed Grosbeak (photo left) with prominent gape and the hatching year (HY) Eastern Kingbird (photo below left) with very bright mouth lining.

We discussed the shape of the outermost primary (P10) in EAKIs in the July Blog being helpful in separating males from females and juveniles from adults. The indentation or notch on the inner web of this feather is shorter in adult females than adult males and lacking on juveniles as can be seen in the photo below right.

In most Empidonax flycatchers like this hatch year (HY) Willow Flycatcher the prebasic molt occurs on the winter grounds so HY wing feathers are fresh looking having just grown in this summer.
An adult bird now carrying 6-8 month old feathers that have been used for one long distance migration, and which have been worn for an entire breeding season show extensive wear.
Fresh wing bars (edged or tipped median and greater coverts) of HY Empidonax flycatchers are buffy/yellow in appearance like this bird, not whitish as in adults.
The exception to this rule is Hammond's Flycatcher which is the only Empid molting flight feathers on its breeding grounds.

Continuing with the theme of Tyrant flycatchers in juvenile plumage this one could easily be confused in the field lacking the obvious smudged undertail coverts of its adult counterpart. Answer at the end of the blog.

Two more confusing hatch year (HY) Empids with brownish washed upperparts and buffy wing bars - Willow Flycatcher in the background and Pacific-slope Flycatcher in the foreground.

And a final confusing Empid this time one of the two species with grey heads, grey throats, yellowish bellies and almond shaped eyerings but this one with the long tail, short wing and where P10 is shorter than P4 - a hatch year (HY) Dusky Flycatcher.

Interestingly this is the first late summer/fall DUFL we have caught at Colony Farm all the other birds being spring captures.

Contrary to all these hatch year birds in fresh juvenile or first basic plumages, many adult birds coming to the end of the breeding season are now showing very worn feathers indeed like this after hatch year (AHY) female Common Yellowthroat. This bird with a receding brood patch (photo below left) was showing very worn flight feathers (remiges and retrices).

Feathers are dead structures like human hair or nails and damaged or worn feathers cannot be replaced until the annual molt cycle. Very worn feathers like these show just how important the annual prebasic molt is especially for birds undertaking long Neotropical migrations.

The 1st prebasic molt in Savannah Sparrows (SAVS) is partial and usually includes all lesser, median and greater coverts, usually 1-3 tertials but according to Pyle no retrices.

These photos show the wing of a hatch year (HY) SAVS which had replaced all lesser, median and greater coverts (the molt limit shown above right between the outer GC and inner PC), the two innermost tertials (S8 & S9) but we find that with our Pacific coastal subspecies that central retrices are indeed often replaced as can be seen in the photo right.

Warbling Vireos (WAVI) also appeared in good numbers this month like this handsome hatch year bird of unknown sex.

We always look closely at WAVIs hoping for the possibility of a Philadelphia Vireo (PHVI) which only breed much farther north in north-eastern BC and are rare in the Vancouver area.

Although PHVIs have a buttery yellow wash to the breast and a more distinct facial pattern some of our bright WAVIs have us hoping.

Unfortunately (or maybe fortunately!) there is no mistaking the two species in the hand as WAVI has a vestigial primary 10 (P10) shown with a red arrow in the photo left. In PHVIs this feather is so reduced as to be almost absent.

Still we'll keep trying!!

And finally this hatch year (HY) Winter Wren - OK then Pacific Wren (in England it's just called 'The Wren' Troglodytes troglodytes even though we've changed the name of our one to Troglodytes pacificus!) was another good 'get' for us this month being very uncommon in the old field habitat where we band preferring coniferous forests with fallen logs which provide ideal nesting sites for these tiny cavity nesters.

So that's about it for our penultimate blog of the year - I'm off on a short birding trip to Mallorca, Spain to catch up on migration in Europe and to brush up on my European bird ID skills and to hopefully see Eleonora's Falcon (Falco eleonorae) which delays its breeding season in late summer to time it with the arrival of migrating birds which pass through the Mediterranean islands at this time of year.

Thanks to Mark Habdas, Kerry Kenwood, Carol Matthews, Jason Jones, Marg Anderson, Jerry Rolls, Debbie Wheeler, Sarah Gray, Olga Lansdorp, Kyle Norris, Celia Chui, Mike Nutter, and Tim Ball for their help with banding this month.


1. The Geothlypis warbler on the left is MacGillivray's Warbler and the Oreothlypis warbler on the right is Nashville Warbler.

2. The Tyrant Flycatcher above is a Western Wood-Pewee.

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