Fox Sparrow
Passerella iliaca
Introduction
The Fox Sparrow is a bird of dense thickets and one of the most variable species with four main groups ranging from foxy red to gray to dark brown. It breeds across northern North America and south along the western mountains. It winters across southeastern North America west to Texas, New Mexico, Arizona and small numbers farther west along the Pacific coast.
Identification
Adult Male / Female (spring/summer)
Regionally highly variable. Generally the Pacific Northwestern Sooty Group Fox Sparrow has brightish, medium brown upperparts, with a reddish tinge; breast and belly spots moderately heavy and brown. Tail is rusty brown. Bill is large and usually yellow.
Juvenile
Similar to adults.
General Information
General:
Large rounded body sparrow. Length: 17-18cm. Wing: 26-27cm. Weight: 32grams.
Behaviour:
The Fox Sparrow is a shy, skulking bird of the ground and understory. It rarely ventures from cover and associates with sparrows. They use their strong legs to kick away leaf litter searching for its diet of insects, seeds and fruits.
Habitat:
The shy Fox Sparrow is an inhabitant of streamside thickets and chaparral across the northern boreal and western montaine regions of North America. They can also be seen kicking around under backyard feeders.
Information:
The Fox Sparrow is one of North America’s most geographically variable birds. With 18 subspecies divided into 3 or 4 distinct groups, this species shows extensive variation in range and plumage. The nest varies is size. It is built on the ground or in low crotches of bushes or trees. Clutch size is 2-5 pale bluish-green, with bold reddish brown-splotched eggs.
Similar species:
Song Sparrow, Savannah Sparrow.
Conservation Status:
Listed as Least Concern. Populations are stable.
Maps & Statistics
Capture Rates
Fox Sparrows can migrate short or long distances. As a winter resident of coastal British Columbia, it is thought that these individuals move from higher altitude summer breeding territories to lower elevations. This is reflected in capture rates that peak substantially during the fall months, especially during October.
Ageing and Sexing (Band Size: 1A, 1B)
Molt Summary:
PF: HY partial; PB: AHY complete; PA absent – limited
Preformative molt usually includes all med and gr covs (rarely 1 – 2 outer gr covs can be retained), but no terts or rects – PA limited to a few head feathers.
Note: A number of outer gr covs can be retained in the Pacific Northwestern Sooty Group Fox Sparrow (see photos below)
Warning: Fox sparrows are difficult to age and care should be taken assigning age codes other than after hatch year (AHY) to adult birds.
Plumages
With 18 subspecies divided into 3 or 4 distinct groups, Fox Sparrows show extensive variation, birds caught at Colony Farm, are generally in the Sooty (unalaschcensis) group, dark-brown or sooty-plumaged birds with comparatively shorter tails and medium-sized bills. Occasionally Slate-colored Fox Sparrow (schistacea group) from central interior British Columbia, show up at Colony Farm which are generally longer-tailed birds with grayish backs, and reddish wings and tails; and a number of intergrades have also been recorded.
Fox sparrows vary extensively in plumage and bill color, as shown here. Colour variation in the lower mandible, and in head plumage, do not appear to be correlated, or related to geographic variation but may be factors in age and sex.
4 groups of Fox Sparrows
Sooty Fox Sparrow (unalaschcensis group)
Juvenile
Birds in juvenal plumage are similar to adults but average duller upperparts with buffy edging to the wing coverts and streaks to the underparts. Juv M=F
HY / SY
This HY bird in September has not replaced all greater coverts and is showing a molt limit within the GCs (red arrow). Notice the rich brown edging to the replaced inner GCs and small buffy tips to the ends of the retained outer GCs. Notice also the darker replaced alula covert (A1) contrasting with the more lightly pigmented lower alula feathers (see macro photo immediately below). Finally notice the somewhat narrow, tapered primary coverts with no brown edging contrasting with the fresher, replaced inner greater coverts.
Fox Sparrows are among the Emberizid family which often show an alula covert (A1) molt limit. This can often be very subtle but in the bird below the contrast between the molted alula covert (A1) and the alula feathers (A2, A3) can be clearly seen. Note how the rachis or shaft of the molted alula covert indicated with the red arrow is darker than on the adjacent retained juvenal alula feathers.
Although the preformative molt in FOSP usually includes all greater coverts, this is not the case with birds of the Coastal Northwest Sooty Group (P.i. fuliginosa) which regularly retain outer GCs. This HY bird in October is again showing a clear molt limit (red arrow) between retained and replaced GCs. Notice again the buffy tips to the retained outer GCs (and median coverts) and narrow, tapered primary coverts with no brown edging contrasting with the fresher, replaced inner greater coverts.
The tail of the HY bird in October above shows very tapered and already quite abraded outer rectrices.
The following photos are all of typical HY birds in the fall showing molt limits within the gr. covs. and thin, tapered rectrices.
This SY bird in April also shows a molt limit within the GCs. Note the richly brown edged replaced inner GCs contrasting with the more washed out and lightly pigmented retained outer GCs. Note also that this bird has also replaced the two innermost tertials (S8 & S9) contrary to the usual preformative molt in FOSP which usually does not include tertials. Again notice the narrow, tapered primary coverts with no brown edging contrasting with the fresher, replaced inner greater coverts.
The tail of the SY bird in April above shows relatively tapered and already very abraded outer rectrices.
AHY / ASY
The wing and tail immediately below are of an after second year (ASY) bird of unknown sex in April. There appears to be an inner molt limit within the greater coverts which is likely a pseudolimit, or possibly a prealternate or adventitious molt limit. The primary coverts and remiges are too dark and lustrous to be a first year bird.
The tail of the bird immediately above is showing relatively fresh and truncate feathers diagnostic of adult birds.
The photo of the wing below is an example of the difficulty in accurately ageing Fox Sparrows in the spring. This bird is likely an after second year (ASY) but in examining the inner greater coverts and tertials there appears to be a molt limit which could either be a pseudolimit or prealternate molt limit. For this reason, the correct age assignment should be after hatch year (AHY).
The photo of the wing below is another similar example of the difficulty in accurately ageing Fox Sparrows in the spring. This bird is also likely an after second year (ASY) but in examining the inner greater coverts there appears to be a molt limit which again could either be a pseudolimit or prealternate molt limit. For this reason, the correct age assignment should be after hatch year (AHY).
The tail of the bird above also send conflicting messages being the somewhat truncate shape of an adult but also being extremely worn. The central rectrices also look browner and slightly more tapered than the other rectrices which adds to the puzzle of applying a definite age class except for that of after hatch year (AHY).
Gallery
