Vancouver Avian Research Centre

.....Research - Conservation - Education
 

October - is always a bit of a sad month as it's our last month of banding and monitoring at Colony Farm for the season and banding normally calms down as most neotropical migrants have headed south leaving us with quieter fall days. That wasn't the case this month which saw huge numbers of sparrows moving through the park and proved to be one of our busiest months of the year with lots of species diversity!

With Lincoln's, Savannah, Song, Fox, White-crowned, Golden-crowned and White-throated it really was 'sparrow month' and provided a great opportunity to look at molt patterns in these species.

The two photographs of White-crowned Sparrows (WCSP) below show how difficult ageing by molt limits can sometimes be and how important it is to have experience with the species banders are working with.

The 1st prebasic molt is partial in WCSP and usually includes all lesser, median and greater coverts, sometimes 1-3 tertials and sometimes up to several central retrices.

The wing below left shows a hatching year (HY) White-crowned Sparrow (WCSP) which had completed its 1st PB and replaced all lesser, median, greater coverts and carpal covert but nothing else - no tertials or central retrices - the molt limit shown with the red arrow between the replaced outer greater covert and retained inner primary covert.

The  wing below right shows an after hatch year (AHY) WCSP in the final stages of its definitive adult prebasic molt with P9 still in sheath and final inner secondaries growing in (S6 indicated with a red arrow is usually the last flight feather replaced in complete adult prebasic molts in passerines).

Zonotrichia sparrows also have the strong colour contrasts or pseudolimits mentioned in previous blogs to further complicate matters. The blue arrows in both photos below point to pseudolimits in both the HY and AHY birds which can easily mislead banders in to thinking these nicely edged inner greater coverts represent molt limits when in fact they do not.

Tail shape is also helpful in ageing many species being tapered and more abraded on retained juvenal feathers in hatch year (HY) birds and broad and truncate with a corner to the inner web and relatively fresh feathers in after hatch year (AHY) birds. The outer retrices (R4-R6) show the greatest age specific differences as can be seen in the two photos below - the red arrow pointing to R5 on each bird.

The very fact that tail feathers are frequently lost and replaced between normal molts is one of the reasons why tail feather shape must be used with great caution by banders, and only with other supporting characters (e.g., molt limits), when determining the ages of birds in hand.

Of course at this time of the year the crown stripes of  hatch year (HY) White-crowned Sparrows are brown and after hatch year (AHY) birds black and white making age determinations easy which is hugely helpful to beginner banders studying molt limits in this species.

Continuing on the theme of Zonotrichia Sparrows Golden-crowned Sparrows arrived in good numbers this hatch year (HY) bird of unknown sex showing the typical head plumage of a first year bird with light brown crown stripes as opposed to the black crown stripes of its adult counterpart.

Again, the 1st PB is partial in this species usually including all lesser, median and greater coverts but no tertials or retrices, the molt limit shown with the red arrow between the replaced outer GC and inner PC and again the pseudolimit shown with the blue arrow pointing to the colour contrast between the richer brown inner greater coverts.

And two more Zonotrichia sparrows turned up making almost a complete set of North American Zonotrichs for October! This time two hatch year (HY) White-throated Sparrows an uncommon bird for us and only the second and third banding records for the station!

A few Orange-crowned Warblers (OCWA) were banded at the beginning of the month this series of photos showing a hatch year (HY) male OCWA (left) and an after hatch year (AHY) male OCWA right.

In many species of warblers, sparrows and vireos the first prebasic molt is partial with all lesser, median & greater coverts  replaced but no tertials or other flight feathers. In OCWA this partial first PB can include a number of tertials and occasionally central retrices.

The wing of the HY bird (below left) shows a clear molt limit between  the replaced outer greater covert and retained inner primary covert - primary coverts are retained feathers in all these examples of partial first prebasic molts. The wing of the AHY bird (below right) is a prime example of what definitive adult plumage, with no discernable molt limits among the coverts or alula, looks like in fall.   There was even a trace of a feather sheath remaining on the outermost primary, showing that this bird was near the very end of its complete definitive prebasic molt. Also note the very broad, truncate inner primaries and secondaries shown in this photo.

Tail shape mentioned in sparrows above is also helpful in ageing wood warblers - HY retrices are again retained juvenal feathers, are thinner, more tapered and less durable and become worn more quickly as can clearly be seen in the photo below left. The AHY tail (below right) are replaced adult feathers, are broader, more truncate with an obvious corner to the inner web and are simply better quality feathers with more structure showing little or no wear.

Ageing Yellow-rumped Warblers in the fall is relatively easy with clear molt limits showing between replaced greater coverts and retained juvenal primary coverts and obvious alula covert (A1) and carpal coverts (CC) molt limits shown with red arrows in the photo below right.

Sexing Yellow-rumped Warblers in the fall is all together more difficult and often a complicated assessment of multiple plumage characteristics and wing length.

Males tend to have broader and darker black side streaking than females and the yellow spot under the wings also tends to be much brighter and cleaner in males. In addition to side streaking, upper tail coverts are useful in sexing some birds, males having feathers with broad, dark black centers that are neatly and cleanly edged in gray and female upper tail coverts have a narrower dark center band and are broadly edged in gray with buffy/brown.

All of these characteristics were present with the bird below left which was aged as hatch year (HY) based on the obvious molt limits mentioned above and sexed as female. However, many Yellow-rumped Warblers in the fall cannot be confidently sexed and are simply recorded as 'sex unknown'.

Lincoln's Sparrow (LISP) arrived in huge numbers the catch completely dominated by hatch year (HY) birds showing clear molt limits between replaced greater coverts and retained primary coverts (photo below left - blue arrow) and strong alula covert molt limits (red arrow) between the replaced alula covert (A1) and retained lower alula feathers (A2 & A3).

Pyle indicates that LISP only occasionally replace tertials and sometimes central retrices but our experience with the gracilis subspecies is that they almost always replace the two inner tertials and central retrices as can be seen in the photos below - the inner replaced tertials indicated with the green arrow (photo left) and the central retrices (photo right) indicated with the blue arrow the bird's right hand innermost rectrix (R1) still growing in this example.

Although the first prebasic molt in Redwing Blackbirds can be complete including all flight feathers, the bright scarlet red epaulettes (lesser coverts) and velvety black body plumage of this bird left as in doubt as to its age as an after hatch year (AHY). Hatch year (HY) birds show much duller epaulettes and body plumage.

 

This wing and tail would have had us guessing if we hadn't seen the entire bird - It is in fact a leucistic Common Yellowthroat!
Leucism is a condition characterized by reduced pigmentation caused by a reduction in all types of skin pigment, not just melanin which causes albinism. Melanin pigments strengthen feathers and make them more resistant to abrasion.

Leucism is very rare in birds with only something like 0.0001% of birds affected. These birds with abnormally white feathers are more visible to predators so often do not survive long and those that do may not be successful breeders having more difficulty attracting mates.

This was the first case of leucism we have ever seen in COYE.



And speaking of weird plumage aberrations the two birds left had us momentarily doing double takes - The Bewick's Wren (photo left) was the brightest individual we have ever seen with a bold white supercilium, chestnut crown and auricular and a face pattern reminding us more of a Carolina Wren than Bewick's!

We catch very few Bewick's Wrens but the ones we have caught have not only been much grayer but also much smaller than this individual. Subspecies references point to Interior West (T.b.eremophilus) birds being larger and paler with whitish underparts which matched this bird.

We would welcome any comments from other banders with experience with this species and particularly with experience with the Interior West subspecies.

 

 

The very same day this bird showed up amidst the hundreds of Purple Finches (PUFI) we have banded this year. PUFIs are one of our most abundant species and this year will vie for top 3 most banded birds so when it comes to PUFIs we think we know when something looks different!

The things that struck us about this bird was it's very bright supercilium and how crisply streaked the underparts were. The other thing was the tiny bill being only 8mm from nares to tip much too short to be a Cassin's Finch but below the minimum length for PUFI too!

We came to the conclusion it was just a bright hatch year (HY) PUFI with an unusually short bill but even our most common birds can have us guessing sometimes!

The two male PUFI s below show more 'normal' bill sizes in this species and these photos show the delayed plumage maturation transition male PUFIs make from brownish birds in their first year to purple Purple Finches at their second or first definitive adult prebasic molt in their second year.

They really were an abundant species this year and invaded the park in huge numbers but adult males like the bird below right were always a real treat and reminded us of Roger Tory Peterson's famous description of the 'sparrow dipped in raspberry juice'!

Unlike Rufous Hummingbirds (RUHU) Anna's Hummingbirds (ANHU) are permanent residents in the Vancouver area and therefore molt here on their breeding grounds.

Both the first and adult prebasic molt is complete meaning  all feathers are replaced on both hatch year birds and adults.

Ageing Hummingbirds was discussed in the June blog and is done by examining the bill under magnification and looking at the extent of corrugations along the lateral portions of the upper mandible. The bills of adult birds like this after hatch year (AHY) female are smooth, hard and shiny along the entire length of the upper mandible.

 

 

 

 

 

 

ANHU are one of the eight species of small gorgeted Hummingbirds in NA and have 10 primaries, the 10th full in length, and unlike passerines only 6 secondaries and 10 retrices. This bird was in the midst of her complete prebasic molt replacing all body and flight feathers.

 

Bill deformities are not common occurrences among the thousands of birds we band each year but occasionally  appear and take many different forms from minor defects which do not appear to adversely affect the bird to major defects which almost certainly affect the bird's chance of survival.

The 'crossbilled' Audubon's Warbler (photo right) had a trace of fat and weighed a healthy 13.7 grams slightly above the average weight of 12.5 grams for both males and females and was obviously not adversely affected by the deformity.

The Spotted Towhee (photo below left) was a hatch year (HY) male completing it's first prebasic molt and with an enormous growth on the upper mandible. The bird was otherwise healthy weighing 38.7 grams grams but definitely not scoring on the cuteness scale!

The hatch year (HY) Black-headed Grosbeak (photo below right) was missing half of its upper mandible which one would think would almost certainly affect it's ability to feed and chances of survival. Amazingly enough this bird weighed a healthy 44 grams well within the average range for a hatch year bird in June.

It's a tough enough life for a healthy neotropical migrant let alone one with a major defect like this one and it would be fascinating to see if this bird is able to survive and return to us next year!

We've talked in previous blogs about molt in non-passerines and how following their first prebasic molt, hatching year (HY) woodpeckers 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.

This Downy Woodpecker 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) specifically a bird alive in its fourth calendar year!

On the theme of woodpeckers this very bright second year (SY) male Northern Flicker was banded - males of course show the bright red moustachial stripe which is lacking in females of this species.

And a new species banded for the site occurred this month when not one but two Wilson's Snipe (WISN) were captured. We regularly see and occasionally flush WISN in the wet, grassy fields at Colony Farm and were expecting one to show up in a net at some stage. We weren't expecting it to be our net 6 though which is in the middle of a thicket and probably the most unlikely of all of our nets to expect one let alone two snipes!

These superbly camouflaged birds have long, flexible bills and the tips can be opened and closed without movement at the base of the bill. Their bills have sensory pits at the tip which allow the snipe to feel prey when probing in deep mud.


 

October may be an odd month to be talking about swallows but we received the draft of the video from the Western Wilderness Committee which we helped to produce on the decline of Barn Swallows in Canada back in July. Isabelle Groc (photo credit above) and Mike McKinlay did an excellent job with the production of this project which will be used to promote the fact that BC has no endangered species legislation. Although BC has the greatest biodiversity in the country, it is one of only two provinces in Canada – the other being Alberta – that has no stand-alone law to protect endangered wildlife.

The final version of the video will be finished in December and we'll post a link for anyone interested in viewing it.

Our final group visit of the year occurred when we hosted students from British Columbia Institute of Technology's (BCIT) Fish, Wildlife and Recreation (FWR) program.

The FWR program prepares students for careers in the conservation and management of fish, wildlife, parks and outdoor recreation and we did a good job convincing them that their focus should be on on avian and ecosystem conservation.

Everyone had a great time on a particularly busy morning with lots of species diversity including the White-throated Sparrow and a stunning Cooper's Hawk and we were definitely successful in swaying some students to focus their studies on birds!

Kinglets came through the park in good numbers during the month comprising a number of adult males displaying prominent crown patches including the handsome after hatch year (AHY) male Ruby-crowned Kinglet (below right) which had the most extensive and vividly red crown patch we have ever seen.

Pine Siskins (PISI) are not common birds for us preferring coniferous forests to the old field habitat where we band.

Ageing PISIs is relatively easy with molt limits occurring within the greater coverts on hatch year (HY) birds; the innermost glossy black replaced GCs contrasting with the outermost retained juvenal GCs as in the photo below left the molt limit indicated with the red arrow.

The after hatch year (AHY) wing (photo below right) is uniformly adult with broad, truncate remiges (primaries and secondaries) with an extensive yellow wing patch which is lacking in hatch year birds.

The two tail photos below each wing again show the characteristics of first year versus adult birds; the hatch year tail left with tapered outer retrices with sharply pointed tips versus the adult tail right with very broad truncate outer retrices with a corner to the inner web and extensive yellow which is also likely sex related being brighter and more extensively yellow in males than females although care should be taken in assigning sex categories to birds based purely on the extent of yellow in the flight feathers as much overlap occurs.

This gorgeous hatch year (HY) Northern Shrike (NSHR) of unknown sex was one of two NSHRs banded and proof if we needed it that the fall banding season is almost over as overwintering birds return to the park - the feint mask, brownish plumage, heavy, dusky barring on the breast and underparts and very obvious molt limit among the greater coverts of the wing allowing for an easy age determination and this bird still showing the remnants of a gape.

 

It was a good year for us for Accipiters with 3 Cooper's Hawks and 7 Sharp-shinned Hawks banded, this tiny hatch year (HY) male showing the characteristics of hatch birds with very dull, yellow eyes and buffy fringing to the upperparts.

And this nice hatch year (HY) male Varied Thrush added to species diversity for the month another uncommon bird for us preferring mature coniferous forests  to the old field habitat where we band.

An enormous thank you to all the people who have made 2011 such an amazing year for VARC, to our sponsors and supporters MetroVancouver and Pacific Parklands Foundation, our generous donors and friends of VARC, to our patron Robert Bateman for his support but most of all to all of our amazing volunteers who give freely of their time and without whom we wouldn't have a banding program. These are the folk who set alarms for unearthly hours during the summer months to get to the banding station for pre-dawn on their weekends when everyone else is having a lie-in and who do it all with such good humour....well most of the time anyway!

It really is a privilege to have such a fantastic, fun group of people who really have become like family to us.

Our winter banding program will commence on December 1st when we scale back the operation to a limited number of nets adjacent to our feeder station at Colony Farm. Although not the most exciting time to be banding in the Pacific Northwest it is an opportunity for volunteers to work on their net extraction and ageing and sexing skills with our trainers and for everyone to keep their hands in ahead of spring migration banding again next year.

Finally, I wanted to find a fitting end to our last blog of the year and the 2011 banding season at Colony Farm and couldn't think of a better one than this extract from Miyoko Chu's great book "Songbird Journeys - Four Seasons in the lives of Migratory Birds"

"When migratory birds cross our paths, they compel us to stop and marvel at their beauty, their fluid lives in four seasons and distant places, and the ecological intricacies they require to survive. As the miracle of migration continues, the arrival of songbirds each spring is a cause for celebration, for summer would not be the same without them. In autumn, though, we cannot keep them; the songbirds grow restless and depart, leaving us with emptier winter days and a quiet reminder that we should not take them for granted."

Songbird Journeys – Miyoko Chu

 

See you all in spring 2012 - Happy winter banding, ringing and birding!

Home | About UsEducationResearch| Volunteer | About Birds | Gallery
 

Copyright 2008-2016 VARC - Designed by Derek Matthews. Administration by Mark Habdas