Le Conte's Thrashers and Carrizo Plains update


Kevin Zimmer
 

I spent Saturday birding Carrizo Plains, almost entirely along Elkhorn Road.  My primary objective was looking for Le Conte’s Thrashers, which had been curiously MIA on virtually all of my January–mid-March visits (and which were missed on the CBC).  Happily, thrashers were spontaneously and persistently vocal throughout the morning, and I located 5 different territories between 10–24 miles out Elkhorn Road (from its intersection with Seven Mile Road).  All territories were in classic habitat – located along alluvial fans vegetated by saltbush (Atriplex sp), including at least some taller/larger saltbush shrubs, which are seemingly critical for nest concealment from predators.  All thrashers encountered were lone (presumed) males, singing persistently from favored perches — I did not see any birds carrying food,, so it seems likely that females in these territories are probably incubating right now.  I had checked many of these same sites on 3-4 different visits between January and mid-March, without hearing or seeing a single thrasher, in what should have been within their nesting season window.  This species commences nesting season very early in the year (as do Crissal Thrashers in the Chihuahuan Desert in west Texas and southern New Mexico), and typically re-nests two or three times in rapid succession if conditions are favorable.  I’m guessing that the absence of song and apparent absence of thrashers from locations along Elkhorn Road where I have found them nesting for years may have been a response to the abnormally dry winter, and that the birds may have delayed onset of breeding until temperatures warmed sufficiently to support some insect emergence.  During my hiking on Saturday, I flushed small numbers of Band-winged Grasshoppers (Trimerotropis sp?) which overwinter as nymphs in desert soils and only emerge in spring once surface soil temperatures reach and remain above a critical threshold.  Once these ground mimic grasshoppers emerge, they are typically an important prey base for all desert-inhabiting insectivorous birds.  There was also a major emergence of some species of scarab beetle (black head contrasting with bright, rusty-orange elytra), individuals of which were constantly flushing from underfoot.

Interestingly, I also encountered 2 Sage Thrashers along one of the same washes, and they acted as if paired, with one of the birds periodically perching atop saltbushes to sing.  The species does not breed here, but I used to see similar behavior from migrating Sage Thrashers in southern New Mexico, which would pause for a few days in April during their northbound passage, and would sing as if territorial.

Other birds of interest included a Rough-legged Hawk (smallish pale head; broad dark, blotchy band across the middle of the abdomen; mostly whitish tail with black subterminal band; long, broad wings very pale below, narrowly outlined and tipped black, but with bold, black, carpal patches) about 20 miles out Elkhorn Road, which seems to be getting very late in the spring for that bird to still be around.  I also saw Loggerhead Shrikes carrying food at two different spots, and at one of these spots, I actually flushed a stub-tailed, fledged juvenile shrike from underfoot as I was following a Le Conte’s Thrasher.

Otherwise, masses of White-crowned Sparrows and scattered pairs of Bell’s Sparrows (canescens) — the latter singing and territorial – as well as 1 Golden Eagle, 1 Prairie Falcon, 1 Northern Harrier and 5-6 Red-tailed Hawks.  No sign of any lingering Ferruginous Hawks, Mountain Plovers, or Mountain Bluebirds.  One of the most unusual things that I saw was a pair of European Starlings perched atop saltbush shrubs off Panorama Road — they appeared oddly out-of-place!

On the way back home, I saw 3 Purple Martins (2 males and a female) perched on the wires along Hwy 58 in the usual nesting spot just east of the intersection with the road to Santa Margarita Lake.

Kevin Zimmer
Atascadero

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