Empidonax flycatchers, who thought they were a good idea? The curse of the jobbing birder is the silent empid in autumn. Normally you would just lump (dirty word) our default Alder with the less than common Willow as a Trail’s, just like the old days before people realised that they sounded significantly different. Nowadays people also go at great lengths to come up with ways to decipher the ID of a silent empid, but it is something of a tortuous task. Why you would bother is another thing, why not just click ‘Trail’s’ and go back to your Cocoa? Well, sometimes it just doesn’t look right for Trail’s either and you have to bite the empid ID bullet.
In amongst the birding hullabaloo of Dorian, the west sneaked in some birds here under the wire. Say’s Phoebe, Hammond’s Flycatcher, a couple of western warblers and even the Western Kingbirds might actually have come from the west instead of the middle. So subtle was this little incursion that it was almost unnoticeable, almost. When it happened is open to debate, also has it happened twice or has it been a gradual dispersion thing? Our first clue in Nova Scotia was the trapping and banding of a Hammond’s Flycatcher on Bon Portage, so close to Cape Sable Island that I could chuck a hoop over it, well metaphorically anyway.
For Hammond’s Flycatcher to end up at Bon Portage required a delivery system. Such systems, when looked for within the mass that is the continent of Northern North America, are not too easy to detect, often it is the birds themselves that tell us it happened and not our revered Meteorologists whose accurate and insightful forecasts we so rely on. The Hammond’s was the first verified clue but was there one the day before?
September-11, 2019 was notable in our region because Dorian’s Purple Martins, previously thinly scattered up north, chose to converge on Chebogue Point, a data confirmed hirundine hotspot in Nova Scotia. Naturally there was local interest, given that our Purple Martin diet in the south is usually limited to a couple of birds a year and thus far, in 2019, none. When Sandra and I got there we counted a nominal 42 but knew there were more, Alix had 79 later, Kathleen 64. Our focus was on the martins but, when we found an empid sallying for insects in the yard attached to the farm, and not the farm yard which is a wholly different thing, we paid it the respect of taking its photo.
The field impression was that this was an odd looking bird. Why was subjective, but a summer of breeding Alder in the yard, our yard and not the yard attached to the farm, and watching them work daily built up a form of familiarity with their shape and size. The Chebogue empid didn’t fit the profile but, as our focus was something more purple, it got relegated to the ‘look at it later’ folder and on the blog I postulated the ID as perhaps Willow Flycatcher as it was emphatically not an Alder. That ID was based purely on the only other option that was not a rarity and not earnest or forensic examination of the evidence.
Posting it on the blog was done as routine and part of the martin post. More birds happened and the empid subsequently found itself relegated to the ‘round-tuit’ category, much like most of the domestic chores I’ve ignored during the Nova Scotia birding extravaganza, so roughly since May-2015. It was only when a western birder, Karen O’Neil, left me a message on the blog saying that it looked like a Dusky Flycatcher that I went back to the file and plucked out a reasonable selection of photos for further processing. Then I went to my pdf., library to read ‘The Ratio Approach’ by Forrest Rowland from the ABA magazine Birding, March 2009. I’ve mentioned this article before here. My only beef with it is it doesn’t define where you measure the tail length from. Base of the upper covers, tips of the upper coverts, end of the undertail coverts, stuff that you really need to know. I assume that you are to use the Pyle method, measuring the longest retrix (tail feather) from the tip to the point of insertion but you can’t see the point of insertion in photographs, or maybe I’m just misunderstanding the ratio methodology.
The idea of the ratio approach is to determine the specific ratio of the wing to tail length and the primary extension, the length of the 9th primary minus the length of the 5th. The concept being that the primary projection and tail-wing length ratio define the species. He helpfully provides a chart showing the differences, all you have to do is photograph your empid, make your measurement and do the math, simple! Well not really as I explained earlier. My best method for showing a short primary projection seemed to be the simple math of percentage, viz, wing length from the tip to the bend against primary projection. My percentage was 20.1% of primary projection for Alder (from a known ID photograph) and 11.7% from the Chebogue bird. This is not exact as a couple of mil will change the results, but not that much, the Chebogue bird has a short primary projection, indisputable.
Now the question is, which empids have the shortest primary projection based on the data from the ratio article? Of the ten empids measured, Alder came in third longest, Dusky eighth. 6-7 were Hammond’s and Grey, 9-10 were Pacific-slope and Cordilleran, none of those four were in contention based on range, vagrancy potential and plumage, yes Hammond’s actually looks different from other empids!
I suspect that many of my regular readers have, by now, slipped into a coma or have their brains dribbling out of their ears – it was bound to happen one day if you read this drivel for long enough. If the gulls don’t get you the empids will!
As you have yet to see any images of the empid in question, and at the risk of further cerebral discharge, her we are:
I am sure that you, like me, see that this bird looks disproportionate for an Alder Flycatcher and I’m using Alder as the default reference point because it is the default NS empid. To help with context, here is a known Alder Flycatcher in as similar pose as I have and from as similar time of the year.
Here are a few notes regarding the individual as observed in the field: It looked wrong for Alder straight away , long tailed and less smooth. It tail-pumped a bit, but only a bit and not the lusty tail pump of a Least, more subdued. It sallied out in the open, returning to the same limited area it flew from given the paucity of shrubs. It was less furtive than Alder often is and seemed happy to snatch prey off the floor, even landing there. Overall it lacked the rounded head look of Alder and there didn’t appear to be much throat contrast on dull underparts. It had an overall dullness, it looked dusky!
I mentioned the Least Flycatcher and it seems prudent to remind you of what they look like. This bird is from a few days after the putative Dusky Flycatcher. The look small, their bill is generally fairly petite and they look pale, well to me they do. They also habitually tail pump, they probably do it in their sleep.
Another source of information when trying to unravel the ID of the not Trail’s flycatcher was Alix d’Entremont’s blog because Alix had been through the same process when deciphering an empid in Kings County in 2012. You can read all about that here: http://alixdentremont.blogspot.com/2014/12/nova-scotias-4th-dusky-flycatcher.html
Obviously Ronnie and I have discussed this bird. Had it been in isolation, not diluted by Purple Martins, we would probably have spent more time on it, taking more photos and trying for a better angle, my shots were backlit but Ronnie got these from a slightly different angle. Published with permission.
So the silent empid (see I don’t just throw this together, well I do but…) is the fifth Dusky Flycatcher for Nova Scotia. Following the process by elimination, there really was only Dusky Flycatcher to choose from and unless someone tells me I am totally wrong and they can prove it; that is what I will go with. Whether eBird will go with that train of logic remains to be seen.