Vancouver Avian Research Centre

.....Research - Conservation - Education

October: It had to happen and after 3 months of picture perfect weather in Vancouver the rain came and came intensely severely hampering the banding effort for much of the month!

The highlight of the month was the addition of our new J-Trap - a 2.5 meter square walk in ground trap. The main function of this trap is for our 2013 special species study on Band-tailed Pigeons.

Little is known about the demographics of band-tailed pigeon populations because their habits and habitat make it impractical to locate and observe or trap an adequate sample of birds and monitoring information about population status is presently limited to annual estimates of relative abundance through the harvesting of birds primarily in the US. However, in the early 1970s the total population size was approximately at 2.9-7.1 million birds in the Pacific Coast region (estimated primarily from harvest reports) and has shown a consistent decline in the species occurrence.

The single greatest challenge in the monitoring and management of band-tailed pigeon populations is the lack of reliable information on population abundance. Existing surveys for this species provide only trends in abundance and no information about absolute population size.

Band-tailed pigeons inhabit coniferous forests primarily and are highly mobile habitat generalists often traveling long distances (up to 50 kilometers) to feed and drink. Their diet includes buds, flowers and fruits of deciduous trees and shrubs especially oak, madrone, elder, dogwood, cherry, cascara and huckleberry and large numbers (flocks of 100 individuals or more) regularly frequent the Park to feed on the elderberry fruit. This abundance within the Park suggests that habitats within the Park are of high relative value to this species in the Greater Vancouver area.

VARC's long term monitoring research will attempt to provide data to assess demographic and population size of Band-tailed Pigeons in the Park using geo-locator studies and by fully documenting biometric measurements, molt sequences and feather color and pattern related to age and gender of each bird trapped for banding.

Needless to say the trap was an enormous amount of work in both the design and construction and special thanks goes to Steve Howard (carpenter extraordinaire), Kyle Norris, Mike Nutter, Todd Heakes, Ivand Pulido and Debbie Wheeler who was the only one who was small and light enough to crawl along the funnel to attach the hinged door to the trapping box!

The trap will also be used during normal banding operations and has already been highly productive for many species of emberizids which make up the bulk of captures during fall and winter banding.
Most neotropical migrants had already sensibly left us for warmer, drier climes but some short distance migrants were still moving through the park like this hatch year (HY) female Yellow-rumped (Audubon's) Warbler (AUWA).

The 1st prebasic molt in AUWA is partial and usually includes all median and greater coverts and often the greater alula. This bird however had replaced all median coverts, the carpal covert and greater alula covert A1 (all marked with red arrows in the photo below right) but had retained all of the greater coverts and main lower alula feathers.

The contrast between the the replaced greater alula covert (A1) and lower main alula feather (A2) can clearly be seen on the closed wing of the bird (photo below left).
This likely late hatching Marsh Wren (MAWR) was still in the midst of its 1st prebasic molt replacing all of it's greater coverts and carpal covert.

MAWRs are uncommon for us in the old field habitat where we band as these small, secretive wrens are most often found in tall reed beds or marshes.

Interestingly we have only ever caught hatch year birds as they disperse away from the reed bed at the pond adjacent to the banding station where they breed. It may be that adult birds will only use the preferred habitats of reed beds and marshes as they begin southbound migration.

The 1st prebasic molt in House Finches is extremely variable and can be complete in some instances meaning hatch year birds replace all body and flight feathers so at this time of the year many birds are aged simply as unknown.

In others like this hatch year bird below the 1st PB is incomplete this bird having replaced all of its lesser, median and greater coverts, the carpal covert, all three alula feathers and the outer primaries and inner secondaries forming the 'eccentric' pattern seen in the photo left with the only retained feathers being the primary coverts and remiges between the red arrows.

 
Molt is particularly useful for aging NA landbirds in the hand in the winter and spring after birds have completed skull pneumatization (ossification) but there are other helpful indicators to age such as eye colour being duller and browner/grayer in first year birds and brighter/richer in adults.

One species where both eye colour and molt are very obvious is Spotted Towhee (SPTO) and males of this species provide very useful examples of eye colour and molt limits for trainee banders learning ageing techniques.

The eye colour of the adult male (below left) shows the characteristic bright red iris of an adult bird compared to the much duller, browner iris of the hatch year male on the right. Also notice the hatch year bird is showing a soft, flesh coloured gape flange (the area at the base of the beak where the two mandible meet) which will disappear and no longer be visible when the bird becomes an adult.

Male SPTOs also provide 'smack you in the face' molt limits for banders learning ageing techniques using molt and plumage criteria. The adult male wing (below left) showing what a quintessential adult wing looks like in the fall with jet black remiges and no discernible molt limits. Also notice the glossy, black rachises on the remiges of the adult bird with little or no wear to these feathers.
Contrast that to the hatch year male (below right) with a very obvious molt limit between the replaced lesser, median, great coverts and carpal covert and retained primary coverts and replaced tertials and retained primaries and secondaries. Notice here that the rachises of the retained primaries and secondaries are matt not glossy and dark brown not jet black and these poorly structured juvenile feathers are already showing signs of extreme wear to the tips.
And finally the retrices of the adult bird (below left) are broad, truncate with little wear compared to the thinner more tapered retrices of the hatch year bird right which again are showing lots of wear to the tips.
Notice also the amount of white on R4 of the hatch year bird (indicated with the red arrow) being much less extensive than on the adult bird.
So there you have it ageing SPTO 101 in the fall with (hopefully!) smack you in the face examples of ageing techniques!
Not anywhere near as obvious and far more subtle are the molt limits in the wing of this hatch year (HY) Fox Sparrow (FOSP)

As FOSP are one of our most abundant birds in the fall they are one of our special study species where we are examining molt more closely to better understand the extent of the 1st prebasic molt in the coastal northwest Sooty Group.

According to the Identification Guide to North American Birds (Part 1) by Peter Pyle the 1st prebasic molt in FOSP usually includes all median and greater coverts (rarely 1-2 outer GCs can be retained) and no tertials or retrices.

Our research on FOSP caught for banding at Colony Farm shows that the 1st prebasic molt on most birds of the Sooty Group is far less extensive as the wing below shows.
This bird had molted GCs 8 and 9 only (the smallest innermost CG10 only partially visible is likely not molted) and oddly given the unextensive extent of molt in the GCs, likely had replaced the innermost tertial (S9). The median and lesser coverts appear to be mixed molted and unmolted feathers.

We consulted with our friend and molt expert Bob Mulvihill who agreed with our age determination and looked at his notes for a dozen eastern FOSP from Powdermill, and most had molted all of their greater coverts and the carpal covert; a few also molted the greater alula covert (A1), and just one single bird had retained 5 juvenile outer greater coverts so it would appear from our research so far that the 1st PB of FOSP in the Sooty Group is less extensive than previously thought.

This same bird had a very conspicuous light-colored feather growth bar near the tip of its tail suggesting that it was probably not well fed for one day after it fledged from its nest.
Because the "fault" bar is near the tip of all the bird's rectrices, it formed when the tail was just a short stub, which is the usual length for most open cup nesting passerines when they leave the nest at about 10 days of age.
Wing feathers develop more rapidly in nestlings, with recently fledged birds typically having at least half grown wings. Although incapable of sustained flight this enables them to leave the nest where they are most vulnerable to predators.
The period of interrupted nutrition this bird suffered, evident as the fault bar near the tip of the tail feathers, would, therefore, show up much farther from the tips of the same bird's wing feathers.
Cold, wet weather in the spring may have played a role in making it difficult for the parents of this FOSP to adequately provide for all of their recently fledged young.
Extreme cases of unquestionably even fault barring like this can be useful as an ageing criterion - juvenal wing and tail feathers are grown concurrently, while adult wing and tail feathers ordinarily are grown in a staggered pattern.
In the example of the FOSP above we mentioned that the innermost greater covert (GC10) was likely an unmolted feather. When the 1st prebasic molt is partial and songbirds replace less than all of their greater coverts, the innermost (GC 10) is often a skipped (unmolted) feather!
This is often the case with Dark-eyed Juncos, our Oregon Junco (ORJU) below showing a clear molt limit between the retained juvenile outer greater covert (GC1) and the molted inner greater coverts (GCs 2-9) and the very obvious retained innermost greater covert (GC10).
In species with partial 1st PBs where less than all GCs are replaced it is always worth banders checking that innermost feather!
A few Hermit Thrushes (HETH) were caught for banding this month. HETH are short distance migrants and the only catharus Thrush to overwinter in Vancouver and to be regularly recorded on the Christmas Bird Count (CBC).

Like all catharus thrushes aging HETH is relatively easy with hatch birds (HY) often showing the buffy tear drops on retained juvenile greater coverts mentioned in previous blogs. The HY HETH wing (below left) showing a clear molt limit between the retained outer and replaced inner greater coverts (indicted with the red arrow).
The shape of the tiny vestigial outer primary (P10) is also helpful in determining age of catharus thrushes being narrower, tapered and shorter than the primary coverts in adult birds and broader, more rounded and longer in first year birds, often extending beyond the primary coverts as in the photo below right.

The VARC blog is not a soapbox but some of the things we still see happening to migratory birds in spite of migratory bird acts in most countries leave you shaking your head in disbelief.
In the Northeast Indian state of Nagaland, tens of thousands of Amur falcons are being trapped and slaughtered everyday during their migration from Siberia to South Africa. In October this year, a small group of conservationists were able to document this shocking massacre and initiate specific action steps to try and stop the killing. You can read their report and watch a video at this link:

Amur Falcon Slaughter

We received this on the same day that a report was released by a scientist at the University of California, Berkeley which estimated that 75% of all mammal species will have disappeared from this planet in less than 300 years!

On a lighter notes the 2013 VARC calendar is now available with stunning images of some of the birds banded during the 2012 season at Colony Farm.

The full calendar can be viewed and ordered online by clicking the image right with all proceeds going towards VARC's public outreach and and education programs for 2013.
2012 really was an amazing year for VARC and we achieved a number of significant milestones. With record numbers of visitors to the banding station and extended public and community outeach which included the addition of our schools and youth programs we were able to considerably extend our educational reach.
We implemented a number of special projects and species studies in addition to sustaining 4 days a week banding effort at the station during spring and fall migration and during the breeding season. This would not of course be possible without the help, dedication and commitment of our growing band of volunteers who give freely of their spare time during busy working lives, who instead of rewarding themselves with long lie ins on their weekends off, set their alarm clocks sometimes as early as 3.30 am during the summer months to join as at the station for dawn. We can never express our gratitude enough!

And finally, we would like to thank all of our sponsors and friends of VARC for their amazing financial support which allowed us to reach our fund raising goals for 2012 and to continue our work to provide data and research support that will allow for the safeguarding of bird habitats in the Vancouver area. Thank you all!

The Vancouver Avian Research Centre Society is a Registered Canadian Charity (# 82118 2656 RR0001)

Donations to a registered charity are of course tax deductible and we hope that people concerned about avian environmental issues in Vancouver will consider making a donation to further VARC's work. This can be done by simply clicking on the link below to make an immediate donation. Thank you for your generous support – it really is very much appreciated!

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