Vancouver Avian Research Centre

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April started with very wet weather which hampered our banding effort in the first half of the month and migrants were few and far between as the cold, wet weather kept birds from pushing northwards.
The coldest day was April 15th when torrential overnight rain was followed by freezing temperatures and by the time we arrived at the banding station at 6.00 AM our nets were quite literally frozen solid - Welcome to spring banding in Vancouver! As banding was not going to be possible until the sun came up and things started to thaw part of the banding team were dispatched in the VARC truck to Tim Horton's (Canadian coffee shops) for coffee and breakfast biscuits with sausage (very healthy!)

It actually took a full 3 hours until our nets (and fingers) were finally thawed enough to open and we were all cursing Mark Habdas who had left us for a week to go down to Mexico to band in tropical temperatures with Manuel Grosselet. The constant emails with photos of loaded nets full of Yellow-breasted Chats, Orchard Orioles, Blue-winged, Golden-winged and Chestnut-sided Warblers were starting to get to us as we tried to counter with photos of Juncos and Sparrows which is all we were catching! We still haven't forgiven either of them!

Tree Swallows had already been back braving the weather for several weeks. Unlike other aerial insectivores TRES have the ability to use plant foods to survive periods of food shortages which can only be the reason our birds survive at this early stage of the season. We have one of our swallow boxes mounted below our weather station outside our banding Pagoda and a pair of TRES kept us amused by landing on the wind vane and spinning around like some Disneyworld ride for swallows!

Spring finally arrived the following weekend and with it the first big push of Kinglets. Our catch was dominated by adult male Ruby-crowned Kinglets showing their bright red crown feathers (below left). In Kinglets molt limits are often not helpful for ageing as the 1st prebasic molt can be limited to lesser and median coverts which are extremely hard to see on such tiny birds but other characteristics are useful such as tail shape which is more reliable in Kinglets than other species with adult retrices broad and truncate compared to the narrower, tapered and more pointed retrices of  second year birds. Using tail shape with the overall appearance of primary coverts allows us to make accurate age determination in most instances.

Along with this wave of Kinglets a flock of some 25+ Mountain Bluebirds arrived. Although common in the open ranchland areas of the interior of BC MOBL are uncommon here on the coast. The old field habitat where we band at Colony Farm adjoins an open area where two of our 30 nets are deployed and we waited anxiously to see if we would be lucky enough to catch one of these stunning birds which would be a new species banded for the site. Suddenly all the cold, wet weather was forgotten as we caught not one but ELEVEN of them, five females and six impossibly bright blue males.

Interestingly all eleven birds banded were Second Year (SY) birds born last year and now in their second calendar year.

During their 1st prebasic molt MOBL replace a number of inner greater coverts and retain a number of outer greater coverts.

The boundary between a retained and replaced feather is the so called molt limit banders use to make their age determination. In birds like male MOBL which are such brightly coloured birds these molt limits are easy to see. The photo on the left clearly shows this molt limit (indicated with the red arrow) between the 5 retained outer juvenile GC's and the 5 replaced inner GC's. There is also a noticeable 'step-in' with the retained feathers being conspicuously shorter than the replaced feathers similar to the pattern in Catharus thrushes.

We wondered if the large numbers of MOBL appearing on the BC coast this spring likely caused by unusual weather patterns is also a result of inexperienced first year birds

without the navigational experience of their adult counterparts causing birds to stray from their normal breeding range.

Two Northern Shrikes were also banded this month being birds that overwinter in the park before heading off to the taiga and tundra to breed.

The Northern Shrike is a predatory songbird named 'Butcher Bird' by early ornithologists who referred to the shrike's habit of killing prey and impaling it on thorns or barbed wire fences. This behaviour was characterized as wanton killing, but is in fact an adaptation to store excess food to survive periods of food scarcity.

The strongly hooked bill and sharp ridge to grip prey is a fearsome weapon which also needs to be avoided by banders!

Both birds were second year (SY) birds of unknown sex showing clear molt limits between retained and replaced feathers and distinct barring on the chest.

On the subject of predatory birds we also banded this gorgeous second year (SY) female Sharp-shinned Hawk. As with other raptors and unlike passerines females are often significantly larger than males and in fact take a larger band size as was the case with this bird. The cheeks of females, adults in particular, are much more widely streaked with rufous.  In addition to a cleaner cheek adult males have a more clean, gray appearance of the head and back.

Hatch Year birds can have a complete first prebasic molt but this does not usually commence until their first spring. Juvenal feathers are more brown and those on the upperparts usually have buffy edges which can be seen in the photo below left. The light orangey/yellow eye color is also an immature trait and will turn deep orange or red as the bird ages. Some individuals however (especially females) may never attain deep orange or red irises but the presence of the light orange eye colour and retained juvenal feathers allowed us to accurately age her as a second year bird.

We were pleased to welcome the first group of BCIT Wildlife Ecology & Management students on their annual field trip to the banding station where we did our best to convince them that birds where better than fish or small mammals! Everyone had a great time and agreed that it had been worth getting up early on a Saturday morning to learn more about the birds and habitats of the Vancouver area.

Our first Violet-green Swallow banded was a real treat. As swallows can have complete first and adult prebasic molts the lack of a molt limit at this time of year does not mean a bird is necessarily in it's third calendar year (or older) so the only thing we can definitively say is the bird was not born this year and the After Hatch Year (AHY) ageing code is used.
This After Hatch Year (AHY) bird was sexed female based on wing chord and plumage the crown being brownish and the postocular area and cheek grayish. The dorsal view in the photograph below right shows the violet and green colours by which the species gets its name.

Savannah Sparrows flooded back in to the old field habitat, their buzzy songs a sure sign of spring. SAVS are one of our favourite sparrows with their intricate patterning and bright yellow lores.

The tertials on these birds are much longer than most other passerines, extending almost as long as the outer primaries, a characteristic unique to grassland sparrows and other ground dwelling finch species. The elongated claw on the hind toe, or hallux, which is unlike those seen on most "perching" birds is another characteristic of Savannah Sparrows and other grassland birds, like longspurs and pipits, that probably aids in stability and movement across the flat, open areas where they feed and nest.

Other early migrants included a good number of Fox Sparrows of both the Sooty and Slate-coloured forms. Pacific coast Sooty Fox Sparrows (below left) have little if any gray in the plumage, have browner backs and are darker overall compared to the interior Slate-colored Fox Sparrows (below right) which have brownish-gray heads with thickly spotted and streaked whitish underparts. Although hybridization is not fully understood we suspect that the two forms do hybridize where ranges overlap in BC as a number of birds banded appeared to be intergrades.

And speaking of elongated claws on hind toes (halluces) Fox Sparrows have evolved extremely long claws to uncover food by using them in the characteristic double-scratching backward kicking motion to reveal seeds and insects in leaf litter.

Other photo highlights of migrants banded this month in photographic order below included: Yellow-rumped (Audubon's) Warbler, Yellow-rumped (Myrtle) Warbler, Lincoln's Sparrow (showing a prealternate molt limit in the tertials), Hermit Thrush, Golden-crowned Sparrow.

As with all birders and banders we love spring migration - it's such an exciting time of the year and you just never know what will turn up and we all curse our 'real' jobs which stop us from banding 7 days a week!

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