Vancouver Avian Research Centre

.....Research - Conservation - Education

Vancouver winters are long, dark, cold and wet and hard not only for birds but for people too especially birders and banders waiting for spring which at times seems like it's never going to arrive!

Our winter banding program was rained out on countless occasions which pleased some VARC team members who were able to turn alarm clocks off on the weekends and sleep-in. We promised we'd make up for all that sleep as we began to gear up for spring migration banding!

Winter finally loosened its grip in March and birds began to move responding to increasing daylight and hormonal changes. The sound of skeins of geese flying over the banding station finally convinced us that spring really was just around the corner!

It's almost impossible to believe looking out across the old field habitat where we band which is virtually bird less at this time of the year that it can be transformed in to such a critical oasis for breeding and migratory birds come spring and summer.

And talking of tough environments for birds it doesn't get much tougher than being an overwintering Hummingbird in Vancouver!

This stunning adult male Anna's Hummingbird somehow managed to endure sub zero temperatures by visiting a single feeder we kept under the eaves of the banding pagoda.

Even though the nectar periodically froze, amazingly this tiny bird found enough food resources to survive and kept us all amused by its constant chipping tik as it buzzed backwards and forwards to the feeder.

 

At this time of year our species diversity is limited to resident birds like the Black-capped Chickadee (BCCH) below which choose to stay and tough out the winter rather than risk the high stress, energetic costs and risks of migration. 

Ageing BBCHs was discussed at length in a whole photo essay in our January 2011 blog which can be viewed here: http://birdvancouver.com/blog_january11.html

This second year (SY) bird of unknown sex shows a discernable molt limit in the greater coverts - the outer two greater coverts are identified as retained juvenal feathers due to their much more worn, washed out and lightly pigmented appearance versus the replaced inner greater coverts. As mentioned previously, in members of the tit family (Paridae) retained greater coverts will sometimes (but not always) show a step out (or down) being longer than replaced ones (indicated with the red arrow) as in the example below.
The blue arrow points to a
pseudo limit which is the result of a natural colour contrast within the inner greater coverts and can simulate a molt limit but is NOT the result of feather replacement. Feather wear is another important clue for banders when ageing birds - retained juvenile feathers which are of poor quality start to show signs of wear in spring having been worn throughout the entire fall and winter months.

The tail of the same bird (photo below right) also shows wear to the retained juvenile feathers. Tail shape
is another helpful clue to ageing birds in the hand but it is important not to use tail shape alone as it is generally not very reliable due both to individual variation and the possibility of accidental loss and replacement (called adventitious molt)
Chickadees often lose and replace tail feathers as was the case with this bird which at some stage over the winter had lost and replaced just the two central retrices (R1).
Had this bird lost and replaced all of its retrices the tail would appear uniformly adult and lead us to make a wrong age determination, again emphasizing the importance of ageing using molt limits on the wing.

A much more uncommon bird for us was this handsome Chestnut-backed Chickadee (CBCH). Unlike Black-capped Chickadees, Chestnut-backed Chickadees prefer the tall coniferous trees to the open old field habitat at Colony Farm.

CBCH exhibit similar molt patters to BCCH - this second year (SY) bird of unknown sex again showing a distinct molt limit in the outer greater coverts and the step out between retained and replaced feathers and tapered outer retrices with little or no white to the outer web.

Red-winged Blackbirds (RWBL) are partial migrants meaning that within a population not all birds migrate; some do and some don't. Last winter we didn't find a single RWBL in the park whereas this winter, being milder for the most part, lots of birds stayed and more arrived back earlier than last year.

 

 

 

Ageing male RWBLs is easy at this time of the year as second year (SY) males do not have the brilliant red epaulettes (lesser coverts) of adult birds (photos above).

Although the prebasic molt can be complete in RWBLs, underwing coverts are often retained in the first PB contrasting markedly with the adjacent blacker feathers (indicated by the red arrow pointing to replaced feathers in the photo right).

The first prebasic molt can include all flight feathers although some remiges (primaries and secondaries) can be retained as was the case with this bird showing a contrast in rachis colour between retained and replaced feathers.

 

 

 

 

 

 

 

Females are altogether more difficult to age not having the contrasting glossy black plumage of their male counterparts. Although underwing coverts can be retained in second year birds they are extremely difficult to see even under magnification often leading us to make a safer age determination at this time of year of after hatch year (AHY). The lesser coverts of adult females normally show mixed bright orange and blackish feathers forming an indistinct shoulder patch or epaulette. This bird was therefore aged as an AHY female but noted as 'leaning towards ASY' or after second year in our notes.

Dark-eyed Juncos are primarily altitudinal migrants moving from colder, higher ground  to lower, warmer elevations in the winter. The flashy white outer retrices of Juncos are a welcome sign of early spring as large numbers of birds move back through the park.

There are six subspecies groups in North America of which ours is Oregon Junco (Junco hyemalis simillimus) hence the alpha code of ORJU.

The first prebasic molt in ORJU is partial and includes 3-10 inner greater coverts, sometimes 1-2 tertials and very occasionally central retrices. This second year (SY) male had replaced 8 inner greater coverts and retained the two outermost (indicated with the red arrow) the molt limit between GC's 2 and 3 and the two innermost tertial (S8 & 9) indicated with the green arrow. Primary coverts (blue arrow) are always retained feathers in all these examples of partial first prebasic molts and show the thin, tapered and somewhat worn appearance of retained juvenal feathers.

This bird had not replaced any retrices all of which were showing wear typical of retained juvenal feathers.

The odd tiny pin feather visible on the head of this bird is the result of its prealternate molt discussed later in the blog.

Ageing and sexing some birds is very easy with 'smack you in the face' molt limits. The very dull eye of the male Spotted Towhee below almost doesn't require a molt limit to determine its age but a quick look at the wing reveals a very obvious limit (red arrow) between the glossy black replaced lesser, median and greater coverts and the retained juvenile primary coverts, primaries and secondaries (this bird had also replaced all 3 tertials), the retained juvenile feathers again showing a high degree of wear (blue arrow). 

The first of a long list of scheduled visitors this year was a group of Fish, Wildlife and Recreation students from the British Columbia Institute of Technology (BCIT) who came out in early March ahead of exam finals to get some practical, hands on experience at the station.

Spring finally arrived in April and as always we forgive Vancouver the long, cold, dark, wet winter months  as the rhododendrons and azaleas bloom in the community gardens in the park and Vancouver looks its stunning best on a sunny spring day with fresh snow still on the north shore mountains.

Warblers began arriving with two Nashville Warblers (NAWA) banded in addition to good numbers of Wilson's (WIWA) and Orange-crowned Warblers (OCWA).

The first wave of these returning neotropical migrants consists almost entirely of adult males - the OCWAs with extensive orange crowns which can easily be seen when the feathers of the crown are parted, the WIWAs with glossy black crowns extending far to the back of the crown (photo below right) and the well defined crown patch of the NAWA (photo right).

 

Ageing and sexing wood warblers in the spring requires a complete understanding of the molt cycle of the individual species being studied. All of these birds will have undertaken a prebasic molt following the breeding season last year when adults replace all body and flight feathers. In species where the annual prebasic molt is the only molt occurring annually breeding occurs in basic plumage and the result when looking at an adult bird, which has undertaken this complete definitive prebasic molt, in the spring is that there are no discernible molt limits on the wing between replaced and retained feathers.

However, in many species there is a SECOND molt that occurs prior to the next prebasic molt called the prealternate molt which occurs in the late winter / early spring. This molt occurs in both adults and first year birds so that in the spring first year birds will show three generations of feathers but adults will also show molt limits but only two generations of feathers between adult prebasic and adult prealternate feathers.

The after second year (ASY) male Myrtle Warbler below is showing such a molt limit (shown with red arrow) between the outer four greater coverts replaced as part of the birds definitive adult prebasic molt last year and the six inner greater coverts replaced as part of its adult prealternate molt this spring.

This prebasic molt occurs in many species of passerines but is often restricted to feathers of the head and throat as is the case with the WIWA, OCWA and ORJU mentioned earlier.

Although tail shape is not reliable for ageing Setophaga (formerly Dendroica) warblers as all age classes can show rounded retrices as mentioned in previous blogs the extent of white on retrices r2 to r6 of this adult male and the extensive black centers to the uppertail coverts are all reliable indicators to confirm our age determination. 

Hermit Thrushes are relatively short distance migrants wintering in the southern US and south to Central America but some remain further north along the pacific coast and they are always the first of the Catharus thrushes to return.

This second year (SY) bird of unknown sex is showing the typical buffy tear-drop pattern of retained juvenal greater coverts in this genus. Note the molt limit between the 7 retained outer greater coverts (red arrow) and 3 replaced inner greater coverts (black arrow) which have chocolate brown edging and lack these buffy tear drops. These buffy tips can easily be seen on the closed wing indicated by the green arrow (photo below left).

The blue arrow points to primary 10 (P10) which is a vestigial feather in Catharus thrushes, the characters having lost their original function through evolution. This tiny feather which has probably little use to the bird is of great use to banders in making their age determinations. In addition to the molt limits on the wing mentioned above the length and shape of this feather varies with age being longer and more rounded in first year birds and shorter and more sharply pointed in adults.

Although listed as 'common' birds of western forests we rarely see or even hear a CASSIN'S VIREO so we were delighted when one showed up in our nets and was a new bird banded for the station.

Formerly lumped together with Blue-headed and Plumbeous Vireos as the Solitary Vireo it is now split as a separate species.

This after second year (ASY) bird of unknown sex shows the pale lores and eyering which gives the bird the quintessential field mark of its bold white 'spectacles'.

A very late AMERICAN TREE SPARROW (ATSP) was banded on the 21st April. ATSPs are annual but uncommon winter visitors to Vancouver breeding in the tundra of the far north.

The rusty crown and eyeline, bi-coloured bill and dark spot in the centre of the pale breast distinguishing it from other Spizella sparrows.

This second year (SY) bird of unknown sex is showing a strong molt limit between the replaced outer greater covert and retained inner primary covert and thin, tapered and worn retrices.

 

This stunning adult female Sharp-shined Hawk (SSHA) had everyone racing back to the station when she was brought in from a net round.

She was one of 5 SSHAs banded this month!

We were very happy to receive notification from the Bird Banding Laboratory this month of a significant recovery of one of our banded birds.

A Cedar Waxwing banded at Colony Farm on June 12th, 2010 as a second year male was recovered in Santa Clara County, California at the southern end of the San Francisco Bay area on March 8th this year!

Unfortunately the recovery was as a result of a window strike and the bird was found dead.

We hosted our spring Bird Identification Workshop on the last weekend of April with lots of people and lots of birds! Our Sunday field session at the banding station enables participants to see birds up close and personal, to study field marks and to use the skills and practice the techniques they have learned at the course.

Everyone had a great time and we were really overwhelmed with the feedback we received from workshop participants and thank them all for their very kind and generous course evaluations which can be viewed here:

http://birdvancouver.com/testimonials_id.html
 

We banded our first DUSKY FLYCATCHER of the spring this month along with two Hammond's Flycatchers. We have spoken about the biometric measurements we use to separate these two very similar Empidonax Flycatchers in the hand in a previous blog (May 2011 Blog) but thought we'd take a moment to pass on some useful tips to birders which may help with identification in the field.

These two very similar Empids both have greyish throats, yellowy bellies, narrow bills and almond shaped eyerings but as can be seen from the photographs below Hammond's (photo left) has a short, steep forehead and long, flat crown and the longest primary projection (distance between the tips of the tertials and tips of the primaries).

Dusky has a fairly rounded head (photo right), short primary projection and the outer edge of the outer retrices (r6) is contrastingly white.

It's still much easier to be a bander than a birder when it comes to identifying these confusing Empids as we can look closely at primary tip spacing and wing morphology which is quite different between the two species and take wing, tail and primary projection measurements to make an accurate determination but hopefully this information will help!

This After Hatch Year (AHY) HOUSE WREN was a nice surprise this month and only our second record for the station.

House Wrens are larger than the more common Pacific Wren, lack the short, buffy supercilium, have longer bills and tails and barred undertail coverts.

 

And finally, we were delighted to receive notification from the North American Ornithological Conference (NAOC)  that the abstract “The importance of old-field habitats to birds in a suburban-urban landscape” submitted by VARC was evaluated by the scientific committee and accepted as a Poster Presentation from some 1230 abstracts.

VARC will be hosting field trips and workshops for the conference which will be help at UBC from the 15th - 18th August. The 4 day scientific program will include Plenary Speakers, presentations, symposia, contributed papers, poster sessions and scientific and ENGO workshops.

Thanks 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, Marg Anderson, Todd Heakes and Dev Manky for their help with banding this month.

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