Demography and Populations

Measures Of Breeding Activity

Age at first breeding; intervals between breeding

White-breasted Nuthatches apparently start breeding in the first year of their life (Bent 1948, Butts 1931); exact data not reported.

Clutch

Few data; needs study. In British Columbia (Campbell et al. 1997), 23 clutches ranged from 3 to 7 eggs (3 eggs-2 nests, 4E-4N, 5E-8N, 6E-4N, 7E-5N), with most nests (15) having 5-7 eggs. In Ontario (Peck and James 1987), 21 nests as follows: 3 eggs – 1 nest; 4E – 2 N; 5E – 1 N; 6E – 6N; 7E – 5N; 8E – 6N; thus most in range of 6-8.

Average clutch size recalculated from Bent (1948) is 7.3 ± 1.2 eggs (range = 5-9). Harrison (1978) stated that clutch size is usually 5-9, but sometimes 10. Fifty clutches of cookii averaged 7.3 + 1.1 (SD) eggs (r = 5-10; L. Kiff, Western Foundation Vertebrate Zoology). In the Eurasian Nuthatch, average clutch size is 6.8 in Europe (Nilsson 1987), 6.5 in Siberia (Pravosudov 1993).

Annual And Lifetime Reproductive Success

Surprisingly few data, needs study. In British Columbia (Campbell et al. 1997), of 17 nests found with eggs and followed to a known fate: 11 produced at least 1 fledgling, for a success rate of 65%. No data on lifetime success of individuals.

In the Eurasian Nuthatch, breeding success (percent of eggs that fledge) is 50% in Europe (Nilsson 1986) and 58% in Siberia (Pravosudov 1993).

Number Of Broods Normally Reared Per Season

Pairs breed only once a year; no second clutches observed.

Life Span And Surviorship

Data sparse. Of 21 individuals banded in Ohio woodlots, 10 disappeared in < 2 yr (Butts 1931). The longest life span reported for this species is 9 yr and 10 mo (Klimkiewicz et al. 1983; http://www.pwrc.usgs.gov/BBL/homepage/long6882.htm).

Estimated mean annual survivorship from 1980–87 at a Maryland feeding station was 35% (n = 32; Karr et al. 1990), records not corrected for probability of recapture. When corrected for probability of recapture, annual survivorship was 63% in the northeast region of North America (DeSante et al. 1998) and, in river corridors within the farmland of Ohio, 27% and 26% for adults in the presence and absence, respectively, of supplemental food in the form of bird feeders (Doherty and Grubb 2002). Juvenile survivorship (annual) in the same river corridors was 21% in both the presence and absence of bird feeders. At the Ohio site, apparent annual survivorship was also positively related to woodlot area (Doherty and Grubb 2002) and was higher for woodlot residents than for river-corridor birds. Greater opportunity for dispersal along river corridors was thought responsible for the lower apparent survivorship there.

In the Eurasian Nuthatch in Siberia, annual adult survivorship averages 64.4%, varying from 20% to 61.1% in different years (Pravosudov 1993). In Europe, winter survival of S. europaea varies between 42.9 % and 74.4% (Enokson 1988).

Disease And Body Parasites

Diseases

West Nile virus arrived in Ohio in 2001 and was detected in every county in 2002. During the winter of 2002-2003, 9.6% of 135 Ohio White-breasted Nuthatches tested positive for West Nile virus antibodies. However, there was no statistical difference in recapture-probability-corrected annual survivorship before and after arrival of the virus, both annual survivorships about 50% (D. A. Zuwerink et al. unpubl.).

Body Parasites

Known to forage on undigested seeds in raccoon feces, thereby potentially becoming vulnerable to the nematode parasite, Baylisascaris procyonis (Page et al. 1999).

Range

Initial Dispersal From Natal Site

From Butts 1931, and others as noted. Nothing is known about the behavioral mechanisms or extent of natal dispersal, but all young leave the territory where they were raised. After dispersal, most young nuthatches establish their own territories, usually in pairs, and breed in those territories the following year. Some young birds fail to establish a territory and remain as floaters until they can obtain one or, perhaps, migrate.

In the Eurasian Nuthatch, dispersal distances varied from 36 m to 11 km in Belgium, with a median of about 1 km (Matthysen and Schmidt 1987). In Germany, natal dispersal for males and females, respectively, averaged 700 m and 825 m (Winkel 1989). In this species, young establish their own territories in Europe (Matthysen 1987), but live inside the territories of adult birds in Siberia (Pravosudov 1993). Young birds that settle first in the fall have a greater chance to become breeders the next spring (Pravosudov 1993).

Fidelity To Breeding Site

Little information; needs study. Once breeding, individuals appear to spend their life on the same territory (Butts 1931, Bent 1948).

Home Range

In this species, the home range is the same as the territory. See Behavior: spacing.

Population Status

Numbers

In a Colorado ponderosa pine forest, average density 9.2 birds/100 ha (McEllin 1979b). In W. Virginia, average of 19 “singing” males/100 ha, with 49/100 ha in mature hardwood forest at 300 m elevation; in winter, 19 individuals/100 ha (Hall 1983). In Ontario, Canada, density 11 to 100 pairs/10 km² in the south; in the north, only 1 of 9 census areas exceeded 10 pairs/10 km² (Cadman et al. 1987). Elsewhere in s. Canada, 2.5 territorial males/10 ha in sugar maple/beech forest; 2.3 males/10 ha also in sugar maple; and 4.3 males/10 ha in white birch (Lanoue and Rail 1996). In Missouri, 5–7 pairs/100 ha in the Ozarks, 3–4 pairs/100 ha in the remainder of the state (Robbins and Easterla 1992).

In e. Kentucky, average winter density 11.6 birds/100 ha (McComb and Moriarity 1981).

In some parts of W. Virginia (and perhaps elsewhere), “this species seems to undergo periodic fluctuations in population. In the early 1950s and again in the mid–1970s, White-breasted Nuthatches became extremely scarce in Monongahela County [WV], and it was not unusual to fail to record them on field trips. Between these periods, the population built up to a more normal level” (Hall 1983).

Trends

BBS data (Sauer et al 2005; http://www.mbr-pwrc.usgs.gov/bbs/bbs.html) show stable populations 1980-2004; in no region with sufficient sample sizes was there a significant decline or increase during this period.

Population Regulation

Little known; needs study. Factors influencing breeding rates and adult survival seem particularly lacking (but see Doherty and Grubb 2002). Key influences to examine: 1) nest site limitation; hole-nesting species often have difficulty finding quality nest sites; nest box studies could provide an interesting window on this question. 2) Predation on eggs and young, and adults over winter – what rates and how does this vary with forest type, weather, predator regimes and food supply? 3) Dispersal – ability to colonize new areas. How sedentary is this species? Long-term banding studies needed.