Demography and Populations

Age At First Breeding; Intervals Between Breeding

Age at first breeding approximately 1 yr and breeds annually thereafter. Of 41 James Bay, Ontario, nests studied 1983–1985, at which ages of both adults known, 19 pairings were of after-second-year (ASY, 2+ yr) birds, 12 of second year (SY, yearling), 6 of ASY male and SY female, and 4 of SY male and ASY female (CCR).

Clutch

Mean clutch size shows latitudinal increase in size from about 2.5 eggs in the West Indies to 4.5 eggs in Canada (see Briskie 1995, Prather and Cruz 1995; also Schrantz 1943, Graber et al. 1983, Wiley 1985, Kessel 1989, Sealy 1992, Rogers 1994). D. p. babad: St. Lucia, mean 2.3 ± 0.61 SD (n = 61); D. p. cruciana: Puerto Rico, 3 studies, mean 2.3 ± 0.78 SD (n = 61); D. p. gundlachi: s. Florida, mean 2.5 ± 0.73 SD (n = 16); and D. p. aestiva: Illinois, 4.0 (n = 33); Iowa, 4.5 (n = 41); s. Manitoba, 4.5 ± 0.02 SD (n = 1,005); cf. D. p. parkesi n. Manitoba, 4.6 ± 0.51 SD (n = 54); cf. D. p. rubiginosa se. Alaska, 5.11 ± 0.57 SD (n = 20); D. p. banksi w. Alaska, 4.9 ± 0.7 SD (range 36, n = 14), mode 5 (n =10). See also Table 1 .

Annual And Lifetime Reproductive Success

See also Life span and survivorship, below. In Manitoba study, for 974 eggs laid in 227 nests, 546 hatched and 340 young survived to leave the nest (Goossen and Sealy 1982). In central Alberta, of 676 eggs laid in 171 nests, 451 hatched and 364 young survived to leave the nest (CC). In British Columbia, 42% of nests with known outcomes (n = 74) fledged ≥1 young (Campbell et al. in press). On sw. coast of James Bay, 52 of 72 (72%) nests in 1982–1985 fledged ≥1 young. Of 19 nests that failed from known causes, 9 due to adverse weather (exposure of young), 7 from depredation, 3 abandoned (CCR).

Number Of Broods Normally Reared Per Season

One brood normally reared; second broods only rarely attempted (Goossen and Sealy 1982).

Daily survival of nests (which measures the probability a nest survives 1 d without predation or other loss) in n. Manitoba during incubation 0.969 ± 0.008 SD (n = 61 nests) and with young in the nest 0.974 ± 0.012 SD (n = 36 nests; Briskie 1995); daily survival of nests prior to initiation of incubation 0.9469 ± 0.180 SD (n = 208 nests, 320 d); during incu-bation 0.9870 ± 0.035 SD (n = 177 nests, 1,852 d); dur-ing nestling period 0.9765 ± 0.064 SD (n = 113 nests, 639 d); and from first to last fledge 0.9924 ± 0.062 SD (n = 92 nests, 266 d; Hébert and Sealy 1993b).

Annual adult survival rate, based on returns of banded birds to same breeding location, 0.526 ± 0.077 SE (Roberts 1971); this value underestimates actual survival since dispersal included as mortality. Maximum reported longevity 8 yr, 11 mo by male (323 recoveries of 86,348 banded birds; Klimkiewicz et al. 1983).

Diseases

No information.

Body Parasites

Limited information. Reported Mallophaga include Philopterus subflavescens (Peters 1936) and Myrsidea ridulosa (Malcomson 1960); also nematodes (NKK).

Exposure

Little information. Spider webs may pose hazard; warbler flushed and trapped in web of black and yellow argiope (Argiope aurantia; but released by observer; Coale 1912). Incubating females found dead on nest 2 times, possibly dead of starvation (Sealy et al. 1986). In 3 yr study in central Alberta, at least 4 nests found on ground or seriously damaged immediately after storm; once dead young found hanging from vegetation around nest (CC). Some nesting losses attributed to weather and manner of nest construction (Goossen and Sealy 1982, Briskie 1995).

Predation

See Behavior: predation, above.

Competition With Other Species

No information.

Initial Dispersal From Natal Site

No information.

Fidelity To Breeding Site And Winter Home Range

During 4 yr study, all 41 returning males resided in same location as previous year or within 2 territories (Yezerinac et al. 1996). At James Bay, Ontario in 1984 and 1985, 15 of 23 (65%) known-identity breeding males and 13 of 24 (54%) females were returning birds from a previous year; dispersal distances between 1984 and 1985 nests of returning males averaged 26.7 m (range 9.5–57.0, n = 7), of females 64.5 m (range 13.0–155.0, n = 4; CCR).

Individuals known to return to same wintering location in successive years, based on 3 banding returns from Guatemala (Nickell 1968) and 3 from El Salvador (Thurber and Villeda 1974, 1976).

Dispersal From Breeding Sites

No information.

Home Range

No information.

Numbers

One of the most widespread and abundant warblers in North America. Specific routes with highest counts were 70.1 birds/route (Siskiyou Co., CA), 66.6 (Harney Co., OR), and 63.9 (Ontario Co., NY; Price et al. 1995). Reported densities vary widely, from 0.7 pairs/ha in n. Manitoba (Briskie 1995), to 3.4 pairs/ha in Wisconsin (Young 1963), to 4.6 pairs/ha in s. Illinois (Brewer and Hardy 1950), to 7.2 pairs/ha in central Illinois (Karr 1968), to 14.4 pairs/ha in s. Manitoba (Goossen and Sealy 1982).

Trends

Breeding Bird Survey data for 1966–1996 give following trends (Sauer et al. 1997). All data, and for U.S. and Canada separately, no statistically significant, long-term trend identified; at more regional level, five strata (with n > 14 routes) showed statistically meaningful (p < 0.001) long term changes: decline for Northern Pacific Rain Forest strata (S94; Vancouver I.), –3.0%/yr; and increases for southern New England (S12; including Massachusetts, Connecticut, Rhode Island), +1.3%/yr; Great Lakes Plain (S16; including e. Wisconsin, s. Michigan, nw. New York), +2.5%/yr; St. Lawrence Plain (S18; including s. Ontario), +2.2%/yr; Till Plains (S31; including Illinois, central Indiana, central Ohio), +5.1%/yr; and Aspen Parklands (S30; including central Albeta, s. Saskatchewan, s. Manitoba), +1.3%/yr.

No information. Cowbird parasitism can have adverse affect on individual breeding attempts, but at population levels pressure is not severe; only at very low densities might cowbird parasitism threaten local warbler populations (see Conservation and management, below).