There are 17 subspecies of Fox Sparrows recognized by Pyle (1997) divided into 4
categories.  Most wintering Fox Sparrows fall into the "Coastal Northwest Sooty"
form.  One of the projects being carried out at the Neawanna Wetland Preserve is
attempting to document Fox Sparrow forms.  Fox Sparrows captured during the
winter banding effort will be measured and (when possible) photographed with the
goal of determining which subspecies each belongs.
 

From banding data collected thus far, a trend of size (wing length) to bill  structure (nalospi/depth ratio) is emerging.  The diamonds represent  birds captured at the Neawanna.  The squares  connected by red lines are approximate  ranges of measurements for each subspecies according to Pyle (1997).  It appears that the continuum of Coastal Sooty Fox Sparrow forms winter at the Neawanna site.  Larger "thick-billed" individuals are probably sinuosaand smaller "narrow-billed" individuals are probably fuliginosa,but all forms would seem to be present.  A pattern of size  difference by sex is also emerging.  Birds  above the regression line are probably male and those below the line female. Very small individuals also average much  redder.  Gray and brown individuals are  evenly distributed at middle and larger sizes.

 

991-38560  WING = 80.0mm  TAIL = 73.0mm  EXCUL/CUL = 11.6/9.5  BILL DEPTH/WIDTH = 7.4/5.7  BILL RATIO = 1.28  MASS = 34.6g  FAT = 3  probable ridgwayi

991-38561  WING = 74.5mm  TAIL = 70.0mm  EXCUL/CUL = 12.3/9.4  BILL DEPTH/WIDTH = 6.9/6.4  BILL RATIO = 1.36  MASS = 33.6g  FAT              -  probable      chilcatensis/fuliginosa

991-38562  WING = 82.0mm  TAIL = 75.5mm  EXCUL/CUL = 11.4/8.7  BILL DEPTH/WIDTH = 7.2/6.1  BILL RATIO = 1.21  MASS = 36.0g  FAT = 2  probable sinuosa

991-38564  WING = 79.0mm  Tail = 72.0mm  EXCUL/CUL = 11.7/8.7  BILL DEPTH/WIDTH = 6.9/6.0  BILL RATIO = 1.26  MASS = 33.5g  FAT = 3   probable unalaschcensis

What do all these numbers mean?

And if your up to the challege check of White-crowned Sparrow subspecies and
the scariest of all: Song Sparrow subspecies.

If you have an opinion as to which subspecies are represented in the following
photographs, share it with us.  Useful comments will be posted here.
 

References

Gillson, G. 2002. Fox Sparrow Identification. http://thebirdguide.com/fox/fox.htm

Pyle, P. 1997. Identification Guide to North American Birds. Slate Creek Press, Slate Creek Press, Bolinas CA.

Zink,R.M. 1986. Patterns and evolutionary significance of geographic variation in the Schistacea  group of the Fox Sparrow (Passerella iliaca ).Ornithological Monographs. v40. AOU, Washington,DC. Birds. Slate Creek Press,

Zink,R.M. and A.E.Kessen. 1999. Species Limits in the Fox Sparrow. Birding, 31(6):508-517. Birds.