Vancouver Avian Research Centre

.....Research - Conservation - Education
Spring 2017

As everyone who lives in Vancouver knows winter 2016/17 was one of the longest, snowiest and wettest in memory (I also didn't mention darkest!). Preparing the station for spring migration banding was a maintenance nightmare as the heavy weight of compacted snow had brought down tree limbs and flattened elderberry and blackberry bushes across net lanes some of which had to be entirely re-cut.

Nevertheless, we got underway on schedule on April 1st although more sessions were cancelled than completed in the early part of the month due to the incessant rain. We delayed opening our far field nets which were completely underwater until the second weekend of April but the very first bird on the very first net round to these nets was this Hammond's Flycatcher.

Silent Empidonax flycatchers are the birder's nightmare but Empids in the hand although confusing, are less of a challenge as we have the opportunity to take biometric measurements and examine wing morphology which usually allows us to make the correct identification.

Least, Hammond's and Dusky Flycatchers are all very similar and all three species occasionally turn up in our nets. Least has a whitish throat and whitish belly whereas both Hammond's and Dusky have greyish throats, yellowy bellies, narrow bills and grey heads usually contrasting with greener backs and both have almond shaped eyerings (photos below).

Hammond's has a short, steep forehead and long, flat crown although this can be somewhat arbitrary when you have nothing to compare it with and when the bird like this one has a slightly raised crest!

But one of the diagnostic field marks for Hammond's is that they have a very long primary projection as can be seen in the top photo below.

Hammond's bill is small and short with straight sides, the lower mandible varying in colour (photo below right).

In addition to a very long primary projection, wing morphology shows a long gap between primaries 5 and 6 with a short gap on each side (photo below left).

In contrast Dusky Flycatcher has a long tail and short wing with a short primary projection and the primary tips are evenly spaced.

So, when you're out birding and see that silent Empid and think Least, Hammond's or Dusky you'll know what it is! Here's one to test your ID skills! (answer at the end of the blog!)

An early sign of spring for anyone interested in birds in North America is the transformation of American Goldfinches from drab winter (non-breeding) plumage to bright yellow summer (breeding) plumage.

This second year (SY) male is undertaking this dramatic change molting of all of its body feathers but no flight feathers.

And it's not just the body feathers on American Goldfinches that undergo a dramatic change - their bill colour does too!

In winter they have dark mandibles that change to bright pinkish/orange in the spring. Bird's bills are comprised of keratin, the same hard material which human hair and fingernails are made of. But if keratin is non-living, then how can a goldfinch's bill change to bright orange during the breeding season? The answer is that keratin makes up only the hard outer sheath of a bird's bill, beneath which lies living skin tissue with active blood vessels.

Birds really are brilliant!

Ageing  American Goldfinches in the hand is easy. First year (hatch year/second year) birds show a buffy tip or fringe to the carpal covert (photos below). Adults (after hatch year/after second year) lack this buffy tip and often have a bright yellow shoulder (this is not the shoulder often referred to in field guides but actually the bird's wrist).

Banders should be aware that adults can show a white tip to the carpal covert but it is usually off to one side and never buffy as in the examples below.

Sexing AMGOs is easy too as males have jet-black remiges (primaries and secondaries) whereas female's wings are never jet black and vary from brownish black to a subdued black that contrasts less obviously with the white tips of the greater coverts (photos below).

Another clue to ageing AMGOs in spring and summer is that they are the only birds where we can use the prealternate molt to age as only second year (SY) birds molt their inner greater coverts as part of their prealternate molt in late winter/spring.

So, we'll leave you to age and sex the wing below! (answer at the end of the blog!)

One of the reasons we all love spring as birders and banders is that many birds are in alternate plumage giving them their bright summer breeding plumages. That especially applies to Setophaga warblers like this stunning adult (after second year) male Audubon's Warbler.

Ageing and sexing wood warblers in the spring requires a complete understanding of the molt cycle of the individual species being studied. Adult birds like this one will have undertaken a definitive prebasic molt following the breeding season last year when all body and flight feathers are replaced.

In species where the 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 the SECOND molt referred to above that occurs in the late winter/early spring prior to the next prebasic molt. This prealternate 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. In adults however there are only two generations of feathers, definitive basic and definitive alternate feathers.

The wing of the above adult male Audubon's Warbler is showing such a molt limit (shown with red arrow) between the outer three greater coverts replaced as part of the birds definitive adult prebasic molt last year and the seven inner greater coverts replaced as part of its definitive (adult) prealternate molt this spring.

And speaking of Yellow-rumped Warblers it looks as though we are going to see a return to Myrtle and Audubon’s Warblers according to a new study which says Yellow-rumped Warbler may be at least three separate species.

Myrtle is the form that birders in the eastern U.S. and most of Canada see with with a white instead of yellow throat. It also has a longer migration, and a distribution that stretches farther north than the other forms.

Audubon’s is the form familiar to birders in the western U.S. and parts of BC and Alberta. Males have yellow throats and gray on the head, back, and breast and are shorter distance migrants.

So what about the hybrid zone that swayed scientists to lump the species back in 1973? According to the research, it’s relatively narrow, just 80 miles across and hasn't moved or widened in 50 years, but in SW BC we're not sold on that as during spring we see and band equally large numbers of Myrtle (photo below) and Audubon's warblers suggesting that the hybrid zone could be considerably wider.

Nashville Warblers are uncommon birds for us in the Vancouver area so they are always welcome additions to species diversity on our net rounds.

The wing (below) of the  after second year (ASY) male above is a good example of what definitive adult plumage, with no discernible molt limits among the coverts or alula, looks like in spring. Notice the uniformly adult wing coverts with prominent greenish edging and broad, truncate outer rectrices with a corner to the inner web diagnostic of adult birds.

Correctly sexing a bird depends on correctly ageing it first always remembering that young (HY/SY) males can look a lot like adult (AHY/ASY) females.

This second year (SY) male Wilson's Warbler had a fairly extensive, shiny black cap which showed only feint greenish, mottling towards the hindcrown.

The wing however confirmed our age determination with a clear molt limit between the outer greater covert and adjacent inner primary covert and between the alula covert (A1) and lower main alula feather (A2) show below with red arrows.

Notice also the extensive wear and fade to the visible remiges (primaries and secondaries) and extensive wear to the rectrices particularly the central rectrices - all of these feathers are retained juvenile feathers. The central rectrices are bilaterally symmetrical and are raised above the plane of attachment of the remaining rectrices ensuring that they cover the closed tail.

The feathers absorbing the brunt of the exposure to the elements are the tertials, the coverts, in particular the greater coverts, and central rectrices. Because of the protection they provide for the remaining flight feathers and because of their extreme exposure to wear, the tertials and central rectrices are the only flight feathers likely to be included in partial preformative molts.

We hosted the first of two Bird Monitoring and Banding Workshops in May and had a  full house with another great group of people. Participants came from  as far away as Alberta and Washington sacrificing their entire weekend to learn about molt and ageing of NA landbirds in the hand.

We then had 30 odd parents and kids for the first VARC Family Day of the season.

We see public outreach and education to raise awareness of environmental issues as they relate to birds as a very important part of the work we do at VARC. Parents and children are introduced to the research techniques required for monitoring migratory birds and the population ecology and ecosystem dynamics of wild bird populations, in an age specific way.  They learn about bird migration, the various habitats and communities birds depend on during migration and the breeding season, and the conservation actions required to protect these habitats to ensure the long term survival of bird species.

Special thanks to Jason Jones who was interpreter for the morning and to Martine Cutbill who continues to come up with the most amazing arts and crafts for the event - this time owls for the kids to make out of pine cones, googly eyes, felt and feathers!

 

It certainly made this little girl's sixth birthday! Thanks to everyone for their help in making these events at the station such a success.
And a YELLOW-BELLIED SAPSUCKER! ok, ok, not a Yellow-bellied Sapsucker but a second year Red-breasted Sapsucker but it DID have a yellow belly! (photo below right)

Note also the zygodactyl toe configuration of woodpeckers. Toes are numbered 1 to 4, 1 is the hind toe or hallux, toes 2 to 4 are the front toes numbered inner to outer. The usual arrangement of toes in passerines is 3 toes in the front and 1 in the back in a configuration termed anisodactyl.

In some species (Owls, Cuckoos and Woodpeckers) toe 4 has shifted to back with 2 toes forward and 2 toes backward - an adaptation for climbing.

By the end of May the station was looking fantastic and although 4 am seems awfully early when the alarm goes off, it's worth it when you get out there on a gorgeous morning with the mist rising over the old field habitat where we band.

The preformative molt in Orange-crowned Warbles normally includes all median and greater coverts but this second year (SY) male had replaced just a few lesser coverts and was showing extreme wear to all of the retained juvenal feathers - notice the wear to all of the visible remiges (primaries and secondaries) in the photo below as well as the coverts and contour feathers.

Possible a late hatching bird or second brood with insufficient resources to undergo the normal preformative molt following the breeding season last year and unlikely to be a successful breeder this year.

That wasn't the case with this gorgeous pair of second year (SY) Yellow Warblers, the male on the left showing extensive red streaking to the breast and the female right with no breast streaking. Caught side by side and almost certainly a breeding pair, she was however shy and refused to look at him for the photo!

The photo immediately below of the wing of the female is showing three generations of feathers. In the preformative molt following the breeding season last year, she replaced lesser, median, inner greater coverts and the carpal covert and stopped molting, preformative molt limits shown with red arrows between the greater alula covert (A1) and lower main alula feather (A2) and between the carpal covert and adjacent primary covert.

In the first prealternate molt during the late winter/early spring she replaced some median coverts, 7 inner greater coverts (some or all of which may have been replaced in the preformative molt) and all 3 tertials (blue arrows) which may also have been replaced in the preformative molt. Hence, the three generations of feathers are formative (carpal covert and greater alula covert), first alternate (some median coverts, inner 7 greater coverts and all 3 tertials) and retained juvenal (outer 3 greater coverts, primary coverts, lower 2 main alula feathers and primaries and secondaries).

The male had undertaken a similar molt sequence but had replaced all 10 greater coverts in his preformative molt, the preformative molt limit shown clearly between the outer greater covert and adjacent primary covert, between the carpal covert and adjacent primary covert and greater alula covert and lower alula feather (red arrows). He had similarly replaced the inner 7 greater coverts and all 3 tertials in his first prealternate molt (blue arrows).

In both examples notice the wear to the remiges (primaries and secondaries) which are retained juvenal feathers.

And a nice study of adult, after second year (left) and second year (right) male Black-headed Grosbeaks.

In members of the Cardinalis family (Grosbeaks and Buntings) where males have such contrasting and distinctive plumages, there is often an extensive molt including all greater coverts, carpal covert, alula, tertials, and in buntings especially, additional inner secondaries and outer primaries.

These can be very easily seen and are helpful in learning molt patterns in these species and can also be helpful in looking for molt limits in females of the same species.

The wing and tail of the SY male above is showing such molt - what we call 'smack you in the face' molt limits! :o)

The wing of the above ASY male is another good example of what definitive adult plumage, with no discernible molt limits among the coverts or alula, looks like in spring. Notice the uniformly adult wing coverts and extensive white wing patch and broad, truncate outer rectrices again with extensive white to the outer rectrices (R6) and compare to the SY male wing and tail photos above.

And finally another confusing looking Empid looking more like a Myiarchus with it's raised crest than an Empidonax - an adult Willow Flycatcher!

Thanks as always to all of our intrepid volunteers who sacrifice their weekends and set alarms for ridiculously early hours during the spring and summer, mostly on their weekends off, to help with banding operations - again thank you all!
Answers: The answer to our question ageing and sexing the American Goldfinch wing above is second year (SY) male - the right wing of the bird shown in the photo! Can you also see where the prealternate molt limit is within the greater coverts?

The Empid in the ID challenge photo is a Dusky Flycatcher (photo credit Mike Tabak - thanks Mike!) 

Please note: All images are copyrighted and are not to be used without permission.

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