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Tuesday, May 16, 2017

Hermit Warbler Hybrid Twitch


May 16 2017 Mount Douglas Park Victoria BC Canada

Note: Since the original posting the bird is now considered to be a hybrid.
Pleases the bottom of the page for a detailed discussion from
bcbirdalert


I hadn't planned on birding except that is except for an hour or two at Brydon Lagoon in Langley City. However events didn't quite work out as planned. One moment I was in Starbucks sipping coffee and the next I was driving to the Tsawwassen Ferry Terminal. Travelling companions Mel, Carlo and myself boarded the ferry in the knowledge that we were to be picked up by a fellow birder on the other side and would be driven to Mount Douglas Park in Victoria where we hoped to see a Hermit Warbler. The warbler had overshot its normal range, that being California, Oregon and Washington. I think I am right in saying this is the first BC record of a Hermit Warbler for twenty years.

Mount Douglas Park summit.
Nikon  P7100.
Mount Douglas Park with downtown Victoria in the distance.

The Hermit Warbler was found in the Garry Oaks and close to the evergreens lower down the slope.

This a snippet from the popular RBA Blog

"At 10:15 am on May 15-2017, Daniel Donnecke found and photographed an adult male Hermit Warbler at Mount Douglas Park. The bird was singing and was seen on Glendenning Trail. This is a steep trail that heads straight down into the oaks from the parking lot at the summit, which is located at the end of Churchill Dr.

Daniele saw the bird in the area of the trail where the oaks first hit the conifers. The bird was in an oak tree near the first large douglas fir tree, which is located halfway down the trail. It was in a mixed warbler flock consisting of Orange-crowned, Wilson's, Townsend's and Yellow-rumped Warblers"



Twitchers Twitching!
Taken with iPhone 5s

Hermit Warbler 

As you can see from the photos above, the visit was a total success, we only had to wait a mere two hours for the bird to make a sixty-second appearance before it disappeared into the acres of woodland. 
Finally the pressure of success or failure was off, there were beaming smiles all around, a few high fives and the dreaded return walk back to the summit suddenly seemed effortless. Ann Nightingale drove us back to the ferry. Thanks Ann. Tired but happy all the talk back home was about the hermit warbler, birds and birders. 
Yet another awesome days birding in Beautiful British Columbia!


UPON REVIEW

**Upon review of new photos (see HERE), the amount of green on the back of the bird concerned me, along with the dark streaks on the bib corner (the area on the side of the chest where the wing tucks in, which is often hidden by the wing) and lower flanks. I have sent all available photos of this bird along with my concerns to a few experts. They were made aware that the photos that concerned me initially were taken in evening light. All information will be sent to the Victoria and BC Bird Records Committee. I will also update the blog with any major developments.

I believe that it is important to be completely transparent and wanted the public to be aware that Silu Wang gave her opinion. She is a Ph.D. candidate in the D.Irwin Lab at UBC and studies Hermit Warblers in the hybrid zone, in the Cascades Region of Washington State. She explained that the bird has a predominantly Hermit Warbler plumage background, but with Townsend's Warbler plumage introgression.  She used the hybrid index based on the eight plumage landmarks as specified by Rohwer and Wood (1998). She was presented with all available photos of this bird and viewed them carefully. She estimated the hybrid index (ranging from 0 to 1, with 0 being pure Hermit Warbler and 1 being pure Townsend's Warbler) and for this bird she felt he should have a hybrid index of 0.12, which is smaller than 0.25 (the cutoff value for Rohwer & Wood 1998 classification). Therefore, based on Rohwer and Wood 1998 classification, it should be a Hermit Warbler.

However, the fact that it has a hybrid index of 0.12 instead of 0 means that it does not have a pure Hermit Warbler plumage, and that there are some traces of Townsend's Warbler introgression.

She noted that on another photo by Liam Singh, showed a greenish wash close to the tail covert see HERE She said that some hybrids only show a greenish upper back, and the fact that the green goes quite far down for this bird, further supported TOWA introgression.

She also looked at the video I linked to above by Geoffrey Newell. In that video she noted that when the bird was preening his crown was light grey, but the grey went quite forward, see screenshot HERE.

She explains that she views this bird as a Hybrid, despite Rohwer and Wood (1998), as stated below:

Rohwer and Wood 1998:  Hermit Warbler (because Hybrid index =0.12 <0.25).

Wang et al in prep:            hybrid (because Hybrid index =0.12, not 0).




"It's never too late to start Twitching"
John Gordon
Langley/Cloverdale 
BC Canada


1 comment:

  1. Great day with great people and a fantastic bird! Pure hermit warblers are so rare in BC! What a terrific find for Daniel. Your shot turned out good haven't looked at mine yet.

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