Breeding

Phenology

Pair Formation

Few data. While the pair bond remains year-round, courtship behavior starts usually at the end of winter (Butts 1931, Kilham 1972). In Ohio, courtship recorded in late Jan, but most common in Mar (Peterjohn and Rice 1991).

Nest Building

In Pennsylvania, recorded as early as Apr 9; mean date May 13 (Brauning 1992). In the White Mountains of California, a pair using a bluebird box constructed a nest in late April, the earliest of any of the six nest-box-using species in the study (Hall and Morrison 2003).

First/Only Brood Per Season

In British Columbia (Campbell et al. 1997), dates for 28 clutches ranged from 24 Apr to 11 Jun, with 56% recorded 1-15 May. In Ontario (Peck and James 1987), 28 Apr-29 May, with most (10 of 19 nests) 5-13 May. In Quebec (Lanoue and Rail 1996), mid-April to mid-May.

Bent (1948) reported the following dates when nuthatch nests contained eggs: Arizona -- Apr 22 to May 28; California -- Mar 21 to Jun 29; Colorado -- May 13 to Jun 25; Florida -- Mar 15 to Jun 11; New York -- Apr 29 to May 30; Oregon -- Apr 19 to Jun 24; Pennsylvania -- Apr 21 to May 11; Wisconsin -- Apr 29 to May 11.

In Bethesda, MD, eggs hatched on May 23 (Kilham 1968). In Oregon, nests with young were recorded on May 16 and May 23 (Gabrielson and Jewett 1940). In British Columbia (Campbell et al. 1997), dates for 42 broods ranged from 4 May to 12 July, with 55% recorded between 20 May and 12 June.

In Ohio, first young fledge second half of May; most young leave nests during Jun (Peterjohn and Rice 1991). Hall and Morrison (2003) reported six young fledging from a nest-box in the White Mountains of California on 19 June.

Second Broods Per Season

Neither renesting after nest failure, nor more than one brood per season, reported. Eurasian Nuthatches attempt to breed only once a year (Enoksson 1988, Pravosudov 1993).

Nest Site

Selection

Not clear which sex selects the nest site.

Microhabitat/Site Characteristics

Generally uses natural cavities or old woodpecker holes (Bent 1948, McEllin 1979, Ritchison 1981). May enlarge existing holes but does not excavate cavity on its own; often reuses cavities year to year; also known to use nest boxes, but sparingly (Harrison 1978, Peck and James 1987, Campbell et al. 1997).

In Colorado (McEllin 1979a), height of nest trees 14.0–17.0 m (range), diameter 53.8 cm (49.5–59.4 cm, based on 7 nests). Cavity location varies from 5 to 20 m above ground (Bent 1948). Seven nests in ponderosa pine in Colorado averaged 9.0 m above ground (range = 7.5–12.3 m; McEllin 1979a). Five nests in deciduous trees in Minnesota ranged between 4 and 12 m high (Ritchison 1981).

Nest cavity entrance at least 3-4 cm in diameter; larger often preferred (Kilham 1971a). In Ontario (Peck and James 1987), entrance diameter 1.8-15 cm, with most in 3.8-5.7 cm range; at 2 Ontario nests, cavity depth 25.5 cm.

Nests reported in ponderosa pine (McEllin 1979a), silver maple (Acer saccharinum), American elm (Ulmus americana), hackberry (Celtis occidentalis), and black walnut (Juglans nigra; Ritchison 1981). In Colorado (McEllin 1979a), most of nest hole entrances faced south (70%); none north, northwest, or west.

The Eurasian Nuthatch also usually breeds in natural cavities and old woodpecker holes, rarely using nest boxes and never excavating its own hole (Nilsson 1984, 1987; Pravosudov 1993). Most Red-breasted Nuthatches also use natural cavities or old woodpecker holes, but some appear to excavate their own cavity (Harrison 1978). Brown-headed and Pygmy Nuthatches excavate their own nest hole in dead wood or they may enlarge a partial cavity (Harrison 1978).

Nest

Construction

Only the female builds (Bent 1948, Kilham 1968). Little known about nest construction or structure, but nuthatches observed to carry hairs and pieces of bark to the cavity site (Bent 1948, Kilham 1968).

In Oregon, one nest was “lined with wadding from an old mattress lying beside the trail” (Gabrielson and Jewett 1940). Harrison (1978) described a nest cavity as “floored with bark flakes and strips and lumps of earth; with a cup of finer bark shreds, grasses and rootlets, but mainly lined with fur, wool, hair and feathers.”

Nest Defense

Two forms of nest defense behavior noted: bill-sweeping and distraction display (Kilham 1968). A nuthatch usually performs bill-sweeping with an object, such as a crushed insect, in its bill. It may be performed both outside and inside the nest for many minutes at a time. The behavior may employ the chemical defense secretions of insects to help keep tree squirrels from entering the nest cavity (Kilham 1968). Kilham (1971b) described a case when a pair of nuthatches breeding in his aviary also used beetles to sweep the nest site. The beetles used were identified as Meloe angusticollus, a species that, when handled, exudes a copious, oily, vesicant fluid from coaxal joints (Kilham 1971b). Likewise, strong-smelling material is occasionally used in nest construction, e.g., nicotine-laden filters from cigarette butts made up the bulk of the lining of one active nest inspected by J. Zickefoose (pers. comm).

In the distraction display (see Fig. 6), a nuthatch of either sex spreads its wings and remains in a fixed position while swaying back and forth. This behavior may serve to startle a squirrel when it is very close to the nest (Kilham 1968; Long 1982).

Maintenance And Reuse Of Nests

No data but thought to reuse nests often. No information on maintenance.

Eggs

Shape

Subelliptical to short subelliptical (Harrison 1978).

Size

Length x breadth (mm): aculeata, 19.02 (18.20–20.22) x 14.01 (13.49–14.58); n = 20 clutches (128 eggs; L. Kiff, Western Foundation Vertebrate Zoology). 40 eggs averaged 18.8 x14.3 mm; extremes: 19.8 x15.0, 17.3 by 13.0, and 18.3 x15.2 mm (Bent 1948).

Mass

Not reported.

Color

Background color white, creamy white, or even pinkish-white (Bent 1948), speckled and spotted with light red, reddish-brown, brown and purplish-red, and sometimes paler gray and purple spots (Harrison 1978).

Surface Texture

Smooth with little gloss (Harrison 1978).

Eggshell Thickness

Not reported.

Clutch Size

Average for 20 nests was 6.4 (L. Kiff, Western Foundation Vertebrate Zoology; no measure of dispersion about the mean available).

Egg-Laying

No data. In Eurasian Nuthatches, female lays 1 egg/day, always at night (VVP).

Incubation

Incubation Period

Reported as 12 d (Allen 1929), 13-14 d (Ritchison 1981).

Parental Behavior

Roles And Attention To Eggs And Incubating Mate

Only the female incubates; male enters the nest only to feed her (Bent 1948; Ritchison 1981). Male fed female an average of 6.9 times/h.

Incubation Rhythm, Duration Of Attentive Periods

During 21 h of observation of 3 females, mean length of an incubation bout was 31.1 min ( range = 8-67 min), mean period off the nest was 4.3 min (1-12 min; Ritchison 1981).

Hatching

No information; needs study. Cavity nests limit access, although this species does use nestboxes; thus nest cams would allow hatching and other details at the nest to be recorded.

Young Birds

No data on growth or development. Cavity nests limit access, although this species does use nestboxes, which would allow access to nests for growth studies. Such studies needed.

In Eurasian Nuthatches, neither brood size nor habitat type affected growth rates of body mass and fifth primary; the length of the primary on the 18th day post-hatch varied significantly among years (VVP).

Parental Care

Brooding

Only the female broods.

Feeding

Mostly from Ritchison 1981; others as noted. Both parents feed young (Butts 1931, Bent 1948). During the first days after hatching, the male brings most of the food while the female spends much time in the nest. In first 4 d after hatching, feeding rate of male increases from 6.9 to 12.7 trips/h. Later, the female becomes more active in feeding young. In last 7 d before fledging, one female made 14.3 feeding trips/h and the male made 7.7 trips/h.

In Eurasian Nuthatches, male visits to the nest average 10.1/h (r = 4.2 times on the first day after hatching to 13.5 on the 19th day; VVP), female 6.8/h (r = 2.4–9.2). The male brings 60.0% of all feedings (VVP).

Nest sanitation. Fecal sacs removed from nest dropped 6-60 m away, 95% in the direction of the principal foraging site (Weitzel 2005).

Cooperative Breeding

Not reported.

Brood Parasitism

Rarely parasitized by Brown-headed Cowbird (Molothrus ater; Bent 1948), as is typical of hole-nesting species. Only 1 of 25 nests parasitized in Ontario (Peck and James 1987). No data on likelihood of intraspecific brood parasitism (egg-dumping).

Fledging Stage

Young leave nest on 26th day after hatching; stay with their parents for several weeks and then disperse (Butts 1931, Ritchison 1981).

Immature Stage

See Demography and Populations: range (natal dispersal).