Vancouver Avian Research Centre

.....Research - Conservation - Education
Fall (September - October 2013)

September is always an exciting month at Colony Farm as dispersing hatch year birds flood the park bringing with them the potential of a vagrant bird well outside of its normal geographical range.

Such was the case this September when we met one morning at 6.30 am which seemed ridiculously late given we were getting up at 3.30 am to get to the banding station pre-dawn in June! By now the main push of migrants was over and after a clear night we weren't expecting a busy morning but this one turned out to be all about quality rather than quantity!

On the way in to the station we were talking about confusing fall warblers as we had just finished doing a book review for The Warbler Guide by Tom Stephenson and Scott Whittle and it sometimes seems like karma when something like this happens.

It was chilly first thing with frosty nets and the early net rounds were not very productive with Neotropical migrants

few and far between, the first Ruby-crowned Kinglets and Golden-crowned Sparrows definitely heralding that fall was just around the corner. But in banding as in life you never know what's around the corner and the 8 am net round produced the bird of the year for us!

With the bird in hand and only looking at the face you could easily be forgiven for calling it a first fall female Yellow-rumped (Myrtle) Warbler with the pale throat wrapping around behind the auriculars and dull plumage with faint, diffuse streaking and brown back. But on closer inspection the face pattern is different with the prominent supercilium although quite narrow and buffy in this individual. And then there are some of the 'eastern' warblers like Blackpoll, Bay-breasted or Cape May (or even a mega-rarity like Pine!) which can all look quite similar, especially first fall birds in dull, basic plumage.

But as can be seen from this side view the undertail coverts are yellow, the tail long and the black tail base and white pattern diagnostic for Palm Warbler, a new species for the station and our 92nd banded during our banding and monitoring studies.

The 1st prebasic molt in Palm Warbler is partial and includes all lesser, median and greater coverts but no flight feathers (primaries, secondaries or rectrices) - the molt limit indicated between the outer greater covert and inner primary covert with the red arrow in the photo below. Notice also the very narrow and tapered retained juvenal primary coverts.

The amount and extent of white on the outer rectrices (R5 & R6 in the photo above right) is also age (and sex) related in Setophaga warblers and is less extensive in HY/SY birds not extending to the inner rectrices.

Vagrant birds are exciting for birders and banders alike but they also have scientific value. Long term data sets may provide evidence for historic changes in population sizes and understanding the patterns of such occurrences is important in increasing our knowledge of dispersal of species. These long range dispersal events may also be critical for the survival of many species in the face of the anthropogenic climate changes we are seeing.

Another example of this could be the regular occurrences of Northern Waterthrush (NOWA) each fall in the park. This rare transient in the Vancouver area is becoming an expected capture for us at this time of the year. All of the NOWAs we have caught including this one have been hatch year birds based on the narrow rusty tips to the tertials and narrow, more tapered rectrices.

Long term monitoring helps establish abundance patterns for more common species as well. This fresh plumaged hatch year (HY) Dusky Flycatcher (DUFL) was another surprise during September. Although DUFL appear in small numbers in the spring, fall records are less common for us.

We've talked before about confusing Empidonax flycatchers in previous blogs and how we use wing morphology on birds in the hand to identify them to species. The primary tip spacing on this particular DUFL was somewhat unusual in that normally it is quite evenly spaced but on this bird there was quite a gap between primaries 5 and 6 (photo below right).

The head shape was also less rounded than on other DUFL we have banded although everything else fitted - the gray head contrasting with the greenish back, the overall slim shape and narrow tail base, the contrasting white outer edge of the outer rectrix (photo above), the contrastingly pale lores and almond shaped eyering and very short primary projection (photo below). Finally, the outer primary (P10) is shorter than primary 4 (P4) in this species (insert photo below) allowing us to make a definitive identification of this particular Empid.

The last of the locally hatched birds appeared in September including this recently fledged Ring-necked Pheasant. Ring-necked Pheasants are common in the park and we often flush them on early morning net rounds when they explode under your feet and fly away making their loud, harsh alarm calls. Adults are too heavy to be caught in our passerine nets but occasionally baby birds like this one are caught in the bottom shelves and although as introduced game birds we are not able to band them they do make for great photo opportunities!

2013 has been an extraordinary year for Anna's Hummingbirds which have firmly established themselves in the Vancouver area in recent years. This hatch year male was molting in the iridescent magenta-pink feathers of the head and throat diagnostic of adult males.

We maintain hummingbird feeders throughout the winter but still marvel how these tiny birds are capable of toughing out Vancouver winters when we often find the nectar frozen when we arrive at the station in the mornings.

September also sees the final stages of molt for many species which complete their prebasic molt on their breeding grounds.

Birds in active molt are very helpful to banders learning ageing strategies using molt and plumage criteria. These 'molt limits in the making' allow us to see the sequence of events unfold as birds go through the molting process and to memorize the differences between retained and replaced feathers to help us when looking at these same species later in the fall and winter.

The wing of this after hatch year (AHY) male Common Yellowthroat (photo below left) shows the very end of this bird's definitive adult prebasic molt when all body and flight feathers are replaced. Primaries molt distally (away from the birds body) with the outermost (P9 or P10) normally the last replaced. Secondaries molt proximally (towards the birds body) with the innermost (S6) normally the last flight feather replaced. In this photo P9 is still in sheath and S6 not quite fully grown (both indicated with reds arrows).

Banders must be careful however with species like Common Yellowthroat which can often have very extensive 1st prebasic molts including some outer primaries and inner secondaries, and look closely at the rachis colour which is typically darker/blacker on molted feathers and lighter/browner on retained juvenal feathers. In this wing all of the remiges have been replaced and the rachises are all black and of the same diameter in each feather group.

The rectrices of the same bird (photo below right) show the rounded, more truncate shape typical of adult birds although we have noticed that when these feathers are very fresh they can tiny sharp tips on the very ends.

This hatch year (HY) Song Sparrow (SOSP) was in the final stages of its 1st prebasic molt having replaced lesser, median and greater coverts and with all 3 alula feathers and all 3 tertials still in sheath (indicated with red arrows).

Notice the very washed out and brown appearance of the primary coverts (blue arrow) which lack the sheen and have browner rachises than the molted greater coverts.

When is a Purple Finch not a  'purple' finch? Well, normally if it's a female or young male as male PUFIs don't get their purple plumage until their definitive adult prebasic molt in their second year. This answers many peoples' question "Why are all the Purple Finches at my feeder females?" The answer is they're probably not but either females or young males.

The two wings below show examples of adult male and female PUFIs in flight feather molt. The wing below left shows an after hatch year (AHY) female in the early stages of replacing all of its wing feathers. The definitive adult prebasic molt in passerines starts with the lesser and median coverts, then tertials and innermost primaries, primary replacement proceeds distally towards the outermost primary, primary coverts molt with the corresponding primary as can be seen here and greater coverts molt shortly after the start of the primaries which is the stage at which this photo was taken.

Although aged as an after hatch year (AHY) this bird was almost certainly a second year bird (e.g. born in 2012) based on the very worn, tapered as yet to be replaced primaries, secondaries and alula. Compare the shape of the very broad, truncate replaced inner primaries and the very thin, tapered and worn adjacent outer primaries.

The wing below right shows a male in flight feather molt - this time there is no doubt as to the age of this bird - a second year male replacing brownish contour and flight feathers with purple washed feathers diagnostic of adult males.

VARC's inaugural Family Day was a huge success with parents and kids alike having a great time. It was a busy day with lots of birds and species diversity and a fantastic opportunity to talk to kids about birds and the environment and what they can do to help make a difference.

It was as much fun for all of us at the station and we plan to host a Family Day each month from May to October next season!

The photo below is of three Banders-in-the-making helping ferry birds back to the station for processing!

Less of a success was our Northern Saw-whet Owl (NSWO) monitoring which was in fact a complete disaster!

We spent four nights during the period out in the park from dusk until midnight with the audio lure going full blast at our 'playback nets' which occupy an area of the park which represents perfect habitat for Saw-whets.

Unfortunately, we did not hear, see or catch a single NSWO but did have a visit from this spectacular Barred Owl which sat a few inches above our nets one night allowing us to get within a few feet and spotlight it for photographs. Barred Owls are very aggressive predators of smaller owls so we were not sorry that it moved off and didn't appear again. 

We did however catch this gorgeous Long-eared Owl (LEOW) during our normal diurnal banding activities!

Ageing and sexing LEOWs like other raptors can be tricky and this bird was no exception.

Hatch year (HY) LEOWs retain all juvenal flight feathers resulting in primaries and secondaries appearing tapered and uniform in wear. The numbers of dark bars on the flight feathers are relatively large and the distance between them relatively small versus adults where the primaries and secondaries are fresh and more truncate and the number of bars relatively small and the distance between them relatively large. But this is all quite subjective and wasn't helped by very poor light and early morning fog which didn't make for good photographs of flight feathers which we could examine later. Our thoughts were that this individual was likely a hatch year year bird based on the flight feather criteria mentioned above but adding to the confusion was the very yellow iris which is more indicative of an adult which left us ageing this LEOW as simply unknown.

Either way there is something very special about all owls and they are among everyone's favourites as can be seen from the photos below of the two Sarahs! (All owl photos courtesy of Debbie Wheeler)

Ageing other non-passerines is certainly less tricky and with woodpeckers we can age beyond the maximum after second year designation of most passerines.

We've talked in previous blogs about molt in non-passerines and how following their first prebasic molt, hatching year (HY) woodpeckers like the male Downy Woodpecker below retain all of their juvenal primary coverts. Second year (SY) birds have all juvenal primary coverts until their second prebasic molt, when they replace up to several outer juvenal primary coverts.

The Northern Flicker below was a 3rd year bird based on the presence of three different generations (one being juvenal) among the feathers of the wing. The wing below shows the typical mixture of retained (more brown and worn) juvenal middle primary coverts and fresher (blacker and less worn) second basic outer primary coverts (i.e., molted in the birds' second fall after hatching) and third basic inner primary coverts (i.e. molted this year in the bird's third fall after hatching).

With the turn of the calendar year this bird will become an after third year (ATY) in 2014, specifically a bird alive in its fourth calendar year!

The first signs of fall were the arrival of winter visitors which included two uncommon species for us, two American Tree Sparrows and this White-throated Sparrow showing the distinct streaking to the central breast indicative of hatch year birds.

Molt limits in Zonotrichia sparrows can be tricky given the strong colour contrasts in the greater coverts. These so called pseudolimits (blue arrow - photo below left) simulate a molt limit but close examination of feather wear to the tips shows that these feathers are in fact the same generation and the molt limit is between the outer greater covert and inner primary covert and alula covert and lower alula feather as indicated by the red arrows.

The 1st prebasic molt does not include any flight feathers, the retained outer juvenal rectrices relatively narrow and tapered (photo below right).

And shrieks of pain at the nets announced the arrival of the first Northern Shrikes which although such stunning birds are probably our most aggressive species in the hand with that lethally hooked bill easily drawing blood and everyone at the station quickly bore the scars of extracting and processing these predatory songbirds.

Northern Shrikes breed much further north in the taiga and tundra and some overwinter in the park. Hatch year (HY) birds like this one are more brownish overall than adults with prominent molt limits in the wing and have distinct barring on the chest and less distinct face masks. In adults the strongly hooked bill becomes darker and develops a sharp ridge to grip prey and is an even more fearsome weapon to be avoided by banders!

So, that's it for another season at Colony Farm in which we again achieved a number of significant milestones.

As always none of it would be possible without the help of so many people which now seemingly includes a cast of thousands between all of the Friends of VARC, our sponsors and donors, visitors, workshop participants and of course all of the VARC volunteers who sacrifice their weekends and set alarms for unearthly hours during the summer months mostly on their weekends off to help with banding operations - again thank you all!

See you all in spring 2014 - Happy winter banding, ringing and birding wherever you are in the world!

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