Vancouver Avian Research Centre

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March is shoulder month at VARC as we finish winter banding ay Burnaby Lake and turn our attention to spring migration banding at Colony Farm.

Our big clean-up / set-up weekend was March 19th / 20th when everything was prepared in readiness for spring banding. Saturday was overcast but Sunday was a gorgeous day with blue skies and sunshine which definitely felt as though spring had finally arrived.

Lots of early migrants were seen in the banding area as we cleared net lane trails and set up nets and the first Tree Swallows kept us company checking out our nest boxes. It's a common misconception that all female TRES are brownish or have some brown on the head and/or back but After Second Year (ASY) females are entirely green-blue and cannot be separated from males. The photo on the right shows what is almost certainly a pair of TRES checking out box number 3!

We conducted our first full spring banding session on March 23rd which in addition to the normal suspects at this time of year produced both an After Hatch Year (AHY) Bewick's Wren and an adult After Second Year (ASY) Chestnut-backed Chickadee. Both of these species are uncommon for us preferring the more open woodland and forest habitats to the old field habitat where we band at Colony Farm.

Song Sparrows are our most abundant bird and we have now banded close to a thousand of them in the two seasons we have been banding at Colony Farm. Even though they are common birds SOSPs present a study opportunity as like other Spizella and Melospiza sparrows they can have very extensive 1st prebasic molts including not just contour feathers but flight feathers (primaries, secondaries and retrices) as well.
Primary coverts are always retained juvenile feathers and are the first feathers we look at when making our age determination. The Second Year (SY) bird below shows an obvious molt limit between the molted greater coverts (GCs) and primary coverts (PCs). Notice the appearance of the PCs - the very washed out, brown appearance - the shafts or rachis being browner than the molted GCs with no sheen to the feathers - overall they are simply much duller feathers.
Song Sparrows are among the Emberizid family which often show an alula covert (A1) molt limit. This can often be very subtle but in the bird below the contrast between the molted alula covert (A1) and the alula feathers (A2, A3) can be clearly seen both in the photo on the left and quite obviously in the close-up photo on the right. Note how the shaft of the molted alula covert indicated with the red arrow is darker than on the adjacent retained juvenile alula feathers.

Another key to ageing Song Sparrows in the winter and early spring is eye colour. Eye colour of juvenile SOSPs is duller (browner/grayer) than in adults which are brighter with chestnut coloured irises. The photo below left of the SY SOSP associated with the wing above shows this dull, brownish iris.
This characteristic is not only helpful in ageing Song Sparrows but is helpful in ageing other species as well as can be seen in the photo below right of a Second Year (SY) male Spotted Towhee - again the very pale and dull iris of this bird immediately identifies it as a bird born last year and which will turn bright red as the bird ages.

Two more signs of spring arrived on March 23rd with our first American Goldfinch and Savannah Sparrows banded. American Goldfinches are the only finches that molt their body feathers twice a year - once in their prebasic molt following the breeding season and again in their prealternate molt in late winter / early spring when they assume their very bright body plumage and soft part (e.g. bill) coloration. The transition from basic (non-breeding) plumage to alternate (breeding) plumage can leave AMGOs looking bizarrely patchy as was the case with the After Second Year (ASY) male in the photo below left.

Savannah Sparrows are another of the most abundant birds we band at Colony Farm and are a grassland species which show enormous site fidelity to nesting areas returning not just to the park or even the general fields from previous years but to specific locations within those fields. Our retrap data shows the importance of maintaining habitat for returning birds many of which are caught either in the same net as previous years or a net adjacent or close to the original one!

The SAVS we banded in the photo below right was interestingly a Second Year (SY) bird of unknown sex. Generally the first returning birds are the more experienced After Second Year birds having returned at least once previously and we wondered if this bird was a late hatching bird which spent the winter locally or only a short distance further south.

We are all excited that spring is finally here and our main migration monitoring and banding program can begin in earnest. Spring is our favourite time to band as Neotropical migrants return in their bright alternate plumage and each net round brings its own surprises as we wonder what will turn up at Colony Farm this year!

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