May was a busy month for both birds and visitors as migration finally got in to full swing and the weather started to cooperate.
Our first rare bird for the season was a Dusky Flycatcher (DUFL below left) in addition to a number of Hammond's Flycatchers (HAFL below right). Silent Empidonax flycatchers are of course 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.
Both these species have greyish throats, yellowy bellies, narrow bills, grey heads usually contrasting with greener backs and both have almond shaped eyerings.

Looking at the two birds below the first thing to notice is head shape being fairly rounded on the DUFL whereas the HAFL has a short, steep forehead and long, flat crown. DUFL is the slimmest Empid with a very narrow base to the tail and the outer edge of the outermost retrices (R6) is contrastingly white. The bill is long and narrow with straight sides, the lower mandible variable in colour from yellow to dusky whereas in HAFL the bill is small and short with straight sides, the lower mandible again varying in colour. The lores are often contrastingly paler in DUFL as can be seen on the bird below left.

Next comes wing shape or morphology which differs markedly in the two species. Both have an emarginated primary 6 (P6) an important feather for banders as indentations on the outer web of the feather (called emarginations) can help separate similar species in the hand. Unlike many passerines all Tyrant Flycatchers have 10 primaries, the outer 10th primary full in length.
HAFL has the longest primary projection (the projection of the primary tips beyond the tertial tips) of all the Empids (13-20mm) and a long gap between the tips of P5 and P6 as can be seen in the photo below left. HAFL also has a long wing and short tail with a wing minus tail measurement of 11-19mm and tail minus primary projection measurement of 35-42mm.

DUFL has a long tail and short wing with a short primary projection (9-15mm) and the primary tips are evenly spaced with P10 SHORTER than P4 unlike HAFL in the photo above right where P10 is noticeably longer than P4.
Our DUFL below had a wing chord of 70mm, a tail length of 60mm with a primary projection fractionally under 10mm (photo below left) with P10 shorter than P4 (photo below right) allowing us to definitively identify this silent Empid as a Dusky!

We welcomed the May Bird Monitoring and Banding Workshop for the weekend of May 6th - 8th and were rewarded with a great group of people and LOTS of birds with nearly 200 birds of 32 species for the Sunday field session including the first Black-headed Grosbeaks and Western Tanager of the season.
The red pigment in the face of the Western Tanager is rhodoxanthin, a rare  pigment in birds. It is not manufactured by the bird itself, which is the case with pigments used by the other red tanagers. Instead, it is likely acquired from insects that themselves acquire the pigment from the plants they feed on.

Everyone really did have an amazing time and agreed they had taken their bird handling and molt and ageing skills to a whole new level. After an intensive weekend studying molt limits we were sorry to part company and thank them all for their participation and for their very kind and generous comments which can be seen by clicking on the link below:
http://birdvancouver.com/testimonials.html

Zonotrichia sparrows moved through in good numbers with both White-crowned and Golden-crowned Sparrows banded. Ageing WCSPs at this time of the year can be challenging as both second years (SYs) and after second years (ASYs) can show contrasting greater coverts, tertials and retrices and both show the pseudolimits mentioned in previous blogs but SYs often retain a few brown juvenal feathers in the hindcrown as in the photo (below top right) and can reliably be aged SY.
5 subspecies of WCSP are generally recognized with both Gambelii and Pugentis found in southwestern BC. Separating the two subspecies is not always easy and intergrades occur complicating matters further.
Gambelii breeds in northwestern Canada & Alaska and the white supercilium extends to the bill, lores are pale gray and the bill orange-yellow or orange-pink. Pugentis (top two photos below) breeds from coastal southwestern BC south to northwestern California is generally smaller and browner than Gambelii with pale lores and a yellow bill although differences with intergrades (photo below bottom right) are subtle at best.

This gorgeous Second Year (SY) female Cooper's Hawk was an early morning treat as we did a first net round at the beginning of the month. We discussed ageing the smaller Accipiter, Sharp-shinned Hawk last month and this bird was similar with buffy fringing to the upperparts and very dull, yellowish eye colour. She constantly raised the feathers of her crown doing her best imitation of a Harpy Eagle! (photo below right).

The first Warbling Vireo was banded and the first wave of Wilson's Warblers arrived, all adult (After Second Year) males with extensive glossy, black crown patches. Hermit Thrushes continued to be caught up until the middle of the month which is much later than in previous years likely due to the continuing cold, wet and unsettled weather we have experienced this spring.

Hermit Thrushes are short distance migrants and are in fact the only member of their genus to overwinter in North America, other species such as Swainson's Thrush overwintering as far south as Argentina.

Molt limits in members of the Catharus thrush family are often easy to see as many hatch year / second year birds have buffy tips on the retained juvenal greater coverts as can be seen in the photo on the right the arrow pointing to the molt limit between the replaced inner GC's without buffy tips and the 7 outer retained GC's showing prominent buffy tips or tear drops, a common pattern in members of this genus.

Primary 10 was mentioned in Tyrant Flycatchers above and Catharus thrushes also have 10 primaries but here the 10th primary is a vestigial (meaning characters which have lost their original function through evolution) feather. This 10th primary is a tiny feather not extending far beyond the primary coverts. The variation in shape and size of this feather is also helpful in ageing Catharus thrushes.

After last months wave of adult male Ruby-crowned Kinglets all of the RCKIs banded this month were females. At this time of the year only males show red or orange crown feathers.

Saturday May 14th was a day to remember! A planned visit from the Washington Audubon Society led by Neil Zimmerman was cancelled mid-week due to rain forecasted for the entire weekend but at the last minute the rain stopped and banding went ahead as scheduled.

The wet weather overnight kept migrants grounded and we suspected we were in for a busy day as we listened to the chip calls of warblers sounding everywhere as nets were opened before dawn. We weren’t disappointed and the result was a record day with 315 birds banded of 23 species!

The catch was dominated by Yellow-rumped Warblers with 215 banded (147 Audubon’s, 23 Myrtle and 45 Intergrades) and the highlights were a female Nashville Warbler, a MacGillivray’s Warbler, a Pacific-slope Flycatcher and a SECOND Dusky Flycatcher.

We only had 5 experienced banders available and everyone worked nonstop to process the line of birds brought in to the Pagoda only to be replaced by another line as each net round was completed! You know you’ve pushed volunteer help to the maximum when by the end of the morning someone says “I never want to see another Yellow-rumped Warbler!”

With a number of volunteers away this weekend we were only able to open 22 of our 30 nets and we all wondered just how many birds would have been banded had we been able to operate all nets all day – we estimated at least 500!

Sorry Neil and the Washington Audubon Society - Hopefully we can schedule another visit later this year!

Our record day included both MacGillivray's Warbler (ASY male below left) and this worn ASY female NASHVILLE Warbler     (below right) both good 'gets' for us at Colony Farm. MacGillivray's Warblers prefer coniferous forest edge habitat and Nashville Warblers are annual but uncommon on the coast proving yet again the importance of the old field habitat at Colony Farm for migrants crossing the increasingly fragmented landscape of the Lower Mainland of Vancouver.

And speaking of good 'gets' for us at Colony Farm this Red-breasted Nuthatch banded was a first for us!

Although a common bird throughout the Vancouver area Red-breasted Nuthatches prefer coniferous forests and wouldn't normally be associated with the open old field habitat where we band at Colony Farm.

Yellow Warblers (below left) began to arrive by the middle of the month with adult males showing impossibly bright yellow plumages with broad, red streaking on the breast and our first hatch year birds arrived. This hatching year House Finch (below right) shows all the characteristics of a bird in juvenile plumage with very streaked/spotted plumage, very loosely textured body feathers and swollen gape. Baby HOFIs like this one always show natal plumes on their heads often giving the appearance of little horns and always scoring a 10 on the cuteness scale!

Wet weather continued to hamper the banding effort throughout the month and the notoriously inaccurate weather forecasting in Vancouver often left us frustrated as we either turned up for banding only to find it raining and having to cancel or cancelling only to find clear conditions by morning!
Wet weather during May can of course produce good fallouts of migrants as was the case with our record day and also good numbers or rare and/or uncommon species. This After Hatch Year (AHY) female Western Meadowlark was another first species banded for us. This Icterid prefers the drier grasslands of the BC Interior which certainly hasn't been the case with the very wet conditions on the coast this spring. Interestingly this bird had a partially developed brood patch and we wondered if that could be evidence of breeding at Colony Farm as the range of Western Meadowlark has been spreading in recent years.

A busy month for visitors culminated on the last weekend with an arranged field trip for 40 University of the Fraser Valley (UFV) biology students who enjoyed lots of species diversity and watching the banding operation including our Hummingbird monitoring. We always say that if you put a live Hummingbird (or any bird for that matter!) in to a person's hand you have a convert for life and hopefully that was the case for many of the UFV students.
A large part of our work is education and raising awareness of environmental issues including habitat loss and degradation and using birds in the hand as teaching tools really is a way to make these issues real for many people particularly for children and students who will need to take conservation seriously in the coming decades if we are to arrest the precipitous declines of many of our migratory songbirds.

Many thanks to Mark Habdas, Kerry Kenwood, Carol Matthews, Dev Manky, Jason Jones, Marianne Dawson, Saskia Wischnewski, Marg Anderson, Jerry Rolls, Kate Fremlin, Ian Thomas, Greg Schultz, Debbie Wheeler, Celia Chui and visiting bander Ben Schonewille the station Manager at Teslin Lake Bird Observatory for their help with banding this month.