Demography and Populations

Age At First Breeding; Intervals Between Breeding

No information.

Clutch

See Breeding: eggs, above.

Annual And Lifetime Reproductive Success

No information on lifetime reproductive success. For Fox Sparrows from Sheep Creek Valley near Juneau, se. Alaska, apparent nest success = 0.632 and Mayfield nest success = 0.573 (n = 19; Rogers 1994). At same location, fledglings/nest = 1.96 and fledglings/successful (hatching ≥1 young) nest = 3.38 (Rogers 1994). Of these nests, 36.8% (n = 9) failed to hatch eggs, with 31.6% failing from predation and 5.2% failing from other causes (Rogers 1994).

Number Of Broods Normally Reared Per Season

Few data; generally 1/yr.

Proportion Of Total Females That Rear At Least One Brood To Nest-Leaving Or Independence

From Sheep Creek Valley near Juneau, 63.2% (n = 19) of Fox Sparrow nests fledge ≥1 young (Rogers 1994).

Estimated longevity of Fox Sparrows wintering at Coyote Creek, CA, is 6 yr 7 mo (Sandercock and Jaramillo 2002). At same location, annual probability of local survival is 10.8% ± 1.2 SE for immatures after first capture, 27.4% ± 8.1 SE for adults after first capture, and 35.2% ± 0.0 SE for adults in later years. Recapture probabilities, which provide an index of survival, were 0.603% ± 0.065 SE for immatures and 0.496% ± 0.086 SE for adults at this same location (Sandercock and Jaramillo 2002). Longevity record for a Fox Sparrow is 9 yr 9 mo (Kennard 1975).

Diseases

No information.

Body Parasites

From Jewer and Threlfall (1978), who found that all Fox Sparrows they examined (n = 20) from Newfoundland had parasites. Known to host 20 genera of parasites, including 10 helminths, 8 arthropod ectoparasites, and 2 haematozoans. Most lightly infected bird was an AHY female that carried a moderate infection of Haemoproteus fringillae and Haemoproteus orizivora; 18 of 20 (90%) Fox Sparrows sampled were parasitized by helminths (5 genera of Trematoda [Conspicuum, Brachylecithum, Zonorchis, Tanaisia, shistasomid sp.], 2 genera of Cestoda [Paricterotaenia, Aploparaksis], 3 genera of Nematoda [Syngamus, Capillaria, Porrocaecum]) and 19 of 20 (95%) Fox Sparrows sampled carried ectoparasites (4 genera of Pthiraptera [Philopterus, Myrsidea, Ricinus, Brueelia], 1 genus of Siphonaptera [Ceratophyllus], 3 genera of Acarina [Haemaphysalis, Proctophyllodes, Analges]). Six out of 19 (32%) birds from which blood smears were taken bore Haematozoa of 2 genera (Leucocytozoon, Haemoproteus). See Jewer and Threlfall 1978 for details; see also Table 1 .

Inclement weather, especially freezing rain and deep snow, during spring migration and on wintering grounds, can cause high mortality (Terrill 1968). A population of Fox Sparrows wintering on Mandarte I., British Columbia, declined 63% during a period of severe winter weather; mortality (vs. dispersal) probably played a role here (Rogers et al. 1991).

Five out of 16 P. i. megarhyncha nests found by A. M. Ingersoll had pipped eggs or nestlings killed by Steller’s Jays (Austin 1968). In Hume, Fresno Co., CA, 50% of nests revisited by Burns (1988) were depredated. Fox Sparrows respond to such depredation, however, by quickly renesting (Blacquiere 1979, Threlfall and Blacquiere 1982, Burns 1988).

Initial Dispersal From Natal Site

No information.

Fidelity To Breeding Site And Winter Home Range

Twelve (23%) of 51 birds banded in 1970 on Gull I., Newfoundland, were recaptured on the island in 1971 (Threlfall and Blacquiere 1982). Nine (75%) of these were recaptured in nets set in same place each year, and remaining 3 (25%) were recaptured within 50 m of their banding location (Threlfall and Blacquiere 1982).

Dispersal From Breeding Site Or Colony

No information.

Home Range

No information.

Numbers

On Breeding Bird Survey (BBS) routes in w. U.S., anywhere from <5 to 50 individuals detected/route/yr (Price et al. 1995). In e. U.S., numbers detected/route/yr lower, <5–20 (Price et al. 1995). Density of breeding pairs varies among localities; most likely depends on habitat productivity (Blacquiere 1979). In n. Ontario, 15 of 32 10-km squares had >10 pairs/square (Rising 1987). In Jackson Hole, WY, density estimated at 2 individuals/4.5 ha. In Mineral, CA, 6 breeding pairs/2.63 ha (Linsdale 1928a). In some places in Alberta, densities as high as 12 pairs/1.61 km²(Linsdale 1928a). In Sierra Nevada, peak densities of about 1 pair/ha (Zink 1986).

Winter abundance highest along rivers; e.g., near Red River along border between Texas and Oklahoma (Root 1988). Winter abundance peaks also along Pacific and Atlantic coasts and along Mississippi and Tennessee Rivers, with lower relative abundance along Colorado and Missouri Rivers (Root 1988). In 1971, at Monte Vista National Wildlife Refuge, Alamosa, CO, 80 Fox Sparrows were recorded on Christmas Bird Counts, leading to an ephemeral peak in abundance for that location (Root 1988).

Trends

From 1966 to 1979, BBS data show a significant (p < 0.01) positive rate of annual change (30.8%) of Fox Sparrows in Newfoundland. No other location shows statistically significant trends for this time period and this trend not found in BBS data from Newfoundland for other time periods. Between 1925 and 1940 at Fox Bay, Magdalen Is., Quebec, abundance went from “common every-where” (Philipp 1925) to only 6 found (Braund and McCullagh 1940).

No information.