Date: 9/24/19 11:30 am
From: larspernorgren <larspernorgren...>
Subject: [obol] Nancy Stotz' s Foxes . Escrow species alert for listers on this list
There are four subspecies groups of Fox Sparrows in North America and I fully expect each to be elevated to full species status in my lifetime, if not next year. All four occur in Oregon annually, two of them breed here: Thick-billed and Slate-colored; the Sooty makes Oregon its primary wintering ground, and the Red is a very rare but annual winter visitor.The eBird link Nancy posted leads to a Green Lakes checklist, rather than the Ochoco list. Post the checklist from the Ochocos Nancy and l promise to give the foxyfotos my full attention. I claim no expertise on Oregon's breeding Fox Sparrows, but my interest has increased substantially in the past week . Migration of Fox Sparrows from the north is now in full swing, so ID is more complicated than a week or two ago. The first bird in the Flickr file is a juvenile. The pale edges to the tertials are intriguing as they are associated with the Red Fox Sparrow. But buffy edges are also a common feature of juvenal feathers in a broad range of passerine species. According to Pyle the tertials are not shed in the first prebasic molt. So while many of the juvenal body feathers were already shed and replaced with adult colored ones, those three feathers that create a smooth transition from wing to body will be retained all winter. The second photo on the Flickr file is an adult and l would  call it Slate-colored:"crown and back uniformly, medium  brownish gray". The juvenile has different colored, much browner feathers emerging on the head and upper back. "...crown and back dark, dull grayish chestnut with indistinct, brown streaks". Such a bird is illustrated in my Sibley app, 2nd ed. as "Red x Slate-colored intergrade" and in Pyle bears the trinomial Passerella iliaca altivagans, the first entrant in the "Northern Red Group", the "true" Fox Sparrows,  nominate race P.i.iliaca. A common breeder in southern interior British Columbia, Pyle states"An intermediate form, this subspecies may belong with the Western Slate-colored Group."      Thickbills and Slatecolors have faint white/pale gray wingbars , much like the well defined white wingbars on the Red. But the Red and Sooty, both boreal breeders, have a common feature that their austral cousins lack: Short tails. Their tail measurement is consistently 14 mm shorter than their wing measurement. That's about 20%; while the tails on the southern two groups are essentially the same length as the wings, consistently 2mm longer. Nancy's juvenile bird is photographed in near profile so l made pen marks on blank paper to compare wing chord with retrices, and behold! The first is about 20% longer than the second.       The Thick-billed Fox Sparrow breeds in the extensive thickets of evergreen brush--Manzanita, Ceanothus("buckbrush"), and so forth--that cloak much of the landscape in the Sierra Nevada, southern Oregon, and the east slope of the Cascades. The northern and eastern limits of its range are poorly understood. The prevailing assumption has been that the breeding Fox Sparrows in the southern Washington Cascades are Slate-colored. But l believe Dave Irons' initial sorties have revealed Thick-billed. He also told me that the Oregon subspecies of Thickbill has a normal sized bill, not the eponymous tool of its California cousins.       Nancy's hike in the Ochocos straddles a biological divide. Remember the Blue Grouse? It got split, and the birds in the Cascades are now Sooty while ones in the Ochocos can be presumed Dusky. A similar assumption might apply to Fox Sparrows.        Sent from my Verizon, Samsung Galaxy smartphone
 
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