Vancouver Avian Research Centre

.....Research - Conservation - Education

February

The mild weather has allowed us to move the banding operation back to the main Colony Farm station to start preparations for spring migration monitoring and banding.

We have maintained our seed and nectar feeders over the winter months and were greeted by a cacophony of sound from a flock of some 50 plus male Red-winged Blackbirds which had found the feeders and a gorgeous male Anna's Hummingbird visiting the nectar feeder.
Red-winged Blackbirds move out of the park during the winter months so the sight and classic sound of singing males is a happy indication that spring really isn't far away.

With
some 14 subspecies geographic variations are fairly well marked in RWBLs but with substantial variation in individuals likely the result of frequent mixing. Polygamy is well documented in RWBLs with research showing that males have as many as 15 female mates but that up to 50% of nestlings have been sired by another male and not the territorial male!
Our subspecies is Agelaius phoeniceus caurinus breeding in coastal south-western BC to north-western California and wintering as far south as southern California.

Ageing and sexing male RWBLs really doesn't present too much of a challenge even though the 1st prebasic molt is incomplete/complete meaning that hatch year birds can replace all body and flight feathers like their adult counterparts.

After second year (ASY) adult males like the bird on the right have velvety black body plumage with bright scarlet red epaulettes (lesser coverts) whereas second year (SY) males like the bird on the left are much duller with dull orangish or orangey red and yellow mixed with blackish feathers.

A close up of the epaulettes of a second year male are shown in close up on the photo below left.

The last juvenal feathers to be replaced of blackbirds and cowbirds are found among the underwing coverts. The contrasts between retained juvenal and basic underwing coverts of males are obvious as shown in the photo above right showing the glossy black replaced basic feathers in stark contrast to the paler, browner and more lightly pigmented retained juvenal feathers of this second year (SY) male.

Contrasts between juvenal and basic underwing coverts in females of these species however are much more difficult to discern; furthermore, depending on the species and/or populations being studied, the absence of any retained juvenal underwing coverts may or may not be confidently interpreted as evidence that the bird is an ASY individual.
 

Other early migrants on the move included Ruby-crowned Kinglets and White-crowned and Golden-crowned Sparrows.

Our very first RCKI of the season was this handsome After Second Year (ASY) male which surprisingly was a retrapped bird banded last year! He was aged as an after second year bird then so now must be in at least his fourth calendar year.  According to the Bird Banding Lab the longevity record for RCKI is 5 years and 7 months definitely making him a senior in Kinglet years!
When we caught him last year in net 16 he weighed in at a mighty 6.3 grams (not much more than a fattened Hummingbird) We caught him again this year in net 16 weighing exactly 6.3 grams!

Although the longevity record for Kinglets is 5 or 6 years, most small songbirds live for only a year or two which is really not surprising given that these tiny birds have to tough out cold often freezing, wet winters finding enough small insects to survive. When we hold a retrapped bird from a previous year we never cease to marvel at their endurance and ability to survive and always wonder where their travels have taken them since we last held them.

We banded the first Golden-crowned Sparrows of the season - all second year (SY) birds of unknown sex. These Zonotrichia sparrows have both a definitive prebasic molt following the breeding season each year and like many other songbird species an additional prealternate molt in the late winter / early spring.

The 1st prebasic molt is partial normally including all lesser, median and great coverts allowing us to make our age determination based on finding a molt limit between the outermost greater covert and innermost primary covert. The prealternate molt normally includes a number of inner greater coverts, tertials and central retrices.

Adults of these species also have a prealternate molt in the late winter / early spring and therefore also show molt limits but in adults there are only two generations of feathers, adult prebasic and adult prealternate versus three generations of feathers in SY birds, juvenal, first basic and first alternate. To complicate matters even more Zonotrichia sparrows also have pseudolimits - that natural colour contrast which simulates a molt limit mentioned in our January photo essay on Black-capped Chickadees!

We'll be talking more about prealternate molt in April when the Dendroica warblers return!

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