spectacular morning migrant flight on West Cuesta Ridge, including a very rare spring record of Virginia's Warbler!


Kevin Zimmer
 

This morning (Wednesday, 4/28), Bill Rucci and I went up to West Cuesta Ridge, in part, to look for Mountain Quail in places where I had excellent luck in finding them last year in April and May, but also, to see if the passage of this last cold front might finally produce a big push of migrants.  Will Knowlton had reported on a big morning flight of migrants from West Cuesta Ridge on 24 April of last year, and I was hoping to find something similar this morning.

We parked at the bottom, and started hiking up the Antenna Road (TV Tower Road) at 0740h.  Note that the Los Padres NF has a closure of this road to all vehicles in effect through at least November, which means you have to either hike or mountain bike up.  We hustled up the first 1/4-mile section of the road beyond the locked gate, but came to a screeching halt as soon as we noticed that passerines were funneling upslope from the south, and literally streaming across the road and through the crowns of the oaks.  At first, we had a hard time even identifying any of these birds, because they weren’t pausing anywhere in sight before blasting on upslope.  But we could also see birds streaming through the trees and across the road up ahead.  We soon found a spot just short of the first big gap where the freeway is clearly visible (if you come to a spot where the road bends sharply to the right, and the bank directly ahead is covered with flowering Ceanothus, you’ve gone too far), and where the crowns of many of the oaks on our left (downslope) were not far above eye-level.  This allowed good viewing of birds as they bubbled up from below, before they even got to the road.  Once in this spot, we basically did not move for the next 90 minutes.  Passerines continued to leap-frog their way through the oaks without slowing until about 0915h, which is when we continued up the road, hiking up to beyond the side road to the antennas and through the main cypress grove and botanic area, looking in vain for Mountain Quail, which we didn’t even hear.  We didn’t make it up to the best area for quail until around 1100h, at which point, it was warm and windy, and the only things that were vocal were Wrentits, Bewick’s Wrens, and Blue-gray Gnatcatchers.  We did see a single Olive-sided Flycatcher, a couple of Lawrence’s Goldfinches, and a group of 20+ Cliff Swallows with a few Vaux’s Swifts passing overhead.

On the way back down, we ran into a small pocket of migrants in the same spot where we had lingered for so long in the morning.  Pausing to check these 8-10 birds out, my eyes were immediately drawn to a proportionately long-tailed warbler pumping its tail up and down steadily as it clambered about in some oak branches hanging over the road.  Raising my binoculars to the bird, I was amazed to see that it was a male Virginia’s Warbler, a rare visitor to our county (and to all of Southern California) in any season, but particularly unexpected in spring.  The bird was not unlike a longer-tailed version of a Nashville Warbler (with a similar bold, white eyering), of which we had seen many (see below) in the morning, but was paler and distinctly gray above (including the wing-coverts and folded remiges) except for a greenish-yellow rump, and was mostly white below (including the throat and entire belly), with a large yellow patch in the center of the breast (not even extending completely to the sides), and bright yellow vent.  The tail-pumping motion was not only more constant than the analogous tail motions we had seen from some Nashville Warblers in the morning, but it also differed qualitatively, in a way that I couldn’t quite put my finger on – I think it was perhaps more up-and-down, without any real lateral movement.  Once I had confirmed to myself that the bird was a Virginia’s Warbler – a bird I know well from a decade of living in New Mexico and west Texas, not to mention another 30+ years of guiding in Arizona, NM, CO and TX – I tried to photograph it, but without luck.  It ducked back into the cover of the oak, then flew to the next tree, where we lost track of it after being distracted by a male Hermit Warbler, a female Hermit Warbler, and a male Black-throated Gray Warbler, all of which were flitting about in the same oak that the Virginia’s Warbler had flown to.  That was at ca. 1430h, and we remained in the area looking for the bird for another 30 minutes, without seeing any further sign of the bird.  I’ve seen only a few Virginia’s Warblers in SLO County, and all of these were in fall.  I’m not sure how many (if any?) spring county records there are, but I know the species is less expected in California in this season.  

Following are my counts of the various migrants that we encountered today.  I would estimate that we only identified perhaps 25% of the passerines that we saw – the birds were moving too fast, and in a 360º arc around us – so the numbers below for the more common species should be viewed as very conservative estimates of what was actually there.  I found it interesting that we did not record a single Yellow-rumped Warbler on the morning, given that I am still seeing the species daily through our yard in Atascadero.  I would also note that I personally have never seen a migratory movement of this sort in western North America before – the number of birds pouring past us, and the constancy and intensity of the action was much more reminiscent to me of the spring ‘fallouts’ that I’ve experienced on the Gulf Coast in Texas when weather conditions are favorable to such an event.  It really was something special!  For those looking to replicate our experience, I would suggest getting there a little earlier (maybe by 0700h) and getting into position and then ride it out (in retrospect, had I known how dead things would be higher up, I’d have spent the whole day down below in the migrant zone) for as long as it goes. I would charge back up there tomorrow morning myself, except that I’ll be happy to still be ambulatory after the death march from the highway up to way beyond the antenna towers and back!

Vaux’s Swift  -  2
Pacific-slope Flycatcher  -  4
Olive-sided Flycatcher  -  1
Cassin’s Vireo  -  1
Warbling Vireo  -  45
Hermit Thrush  -  3 (seems late to me)
Swainson’s Thrush  -  1
Nashville Warbler  -  65
Virginia’s Warbler  -  1
Yellow Warbler  -  4
Townsend’s Warbler  -  5
Hermit Warbler  -  4
Black-throated Gray Warbler -  40
Wilson’s Warbler  -  50
Western Tanager  -  5
Lincoln’s Sparrow  -  1 (also seems late)
Lazuli Bunting  - 2
Black-headed Grosbeak  -  10


Kevin Zimmer
Atascadero

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