# Fox sparrow

The fox sparrow (Passerella iliaca) is a large New World sparrow. It is the only member of the genus Passerella, although some authors split the species into four (see below).

## Taxonomy

More specific information regarding plumage is available in the accounts for the various taxa.
* Red fox sparrow, P. i. iliaca (Merrem, 1786) – this taxon breeds in the taiga of Canada and Alaska and winters in central and eastern North America. This is the brightest colored group.
* Sooty fox sparrow, P. i. unalaschcensis (Gmelin, JF, 1789) – this taxon breeds along the Pacific coast of North America from the Aleutian Islands south to northwestern Washington, and winters from southeastern Alaska south to northern Baja California. It is browner and darker than the red fox sparrow.
* Slate-colored fox sparrow, P. i. schistacea Baird, SF, 1858 – this taxon breeds in interior western North America and winters to the south and west. It has a gray head and mantle, brown wings, brown breast streaks, and a russet tail.
* Thick-billed fox sparrow, P. i. megarhyncha Baird, SF, 1858 – this taxon is mostly restricted to California and Oregon. This group is similar in coloration to the slate-colored fox sparrow, but features a particularly thick bill, as its name suggests.

## Description

Adults are among the largest sparrows, heavily spotted and streaked underneath. All feature a messy central breast spot though it is less noticeable on the thick billed and slate-colored varieties. Plumage varies markedly from one group to another.
Measurements:
* Length: 5.9–7.5 in (15–19 cm)
* Weight: 0.9–1.6 oz (26–44 g)
* Wingspan: 10.5–11.4 in (26.7–29 cm)

## Behavior

Fox sparrows are a generally common bird within their range. They forage by scratching the ground which makes them vulnerable to cats and other predators. Most populations of Fox sparrows migrate north for breeding, however some stable populations exist along the west coast of North America.

### Diet

They mainly eat seeds and insects, as well as some berries. Coastal fox sparrows may also eat crustaceans.

### Reproduction

Fox sparrows nest in wooded areas across northern Canada and western North America from Alaska to California. They nest either in a sheltered location on the ground or low in trees or shrubs. A nest typically contains two to five pale green to greenish white eggs speckled with reddish brown.

## Systematics

The review by Zink & Weckstein (2003), which added mtDNA cytochrome b, NADH dehydrogenase subunit 2 and 3, and D-loop sequence, confirmed the four "subspecies groups" of the fox sparrow that were outlined by the initial limited mtDNA haplotype comparison (Zink 1994). These should probably be recognized as separate species, but this was deferred for further analysis of hybridization. Particularly the contact zones between the slate-colored and thick-billed fox sparrows which are only weakly distinct morphologically were of interest; the other groups were found to be distinct far earlier. A further study of the nuclear genome, using microsatellites, showed similar separation between the four groups.
The combined molecular data is unable to resolve the interrelationship of the subspecies groups and of the subspecies in these, but aids in confirming the distinctness of the thick-billed group. Biogeography indicates that the coastal populations were probably isolated during an epoch of glaciation of the Rocky Mountains range, but this is also not very helpful in resolving the remaining problems of within-group diversity, and inter-group relationships.
Major taxonomic authorities currently differ in their treatment of the fox sparrow complex. The IOC World Bird List/Birds of the World: Recommended English Names and the HBW and BirdLife International Illustrated Checklist of the Birds of the World treat each of the four subspecies groups as a separate species, while eBird/The Clements Checklist of Birds of the World and The Howard and Moore Complete Checklist of the Birds of the World currently treat the complex as a single species.