SPECIES

Brown-headed Nuthatch Sitta pusilla Scientific name definitions

Gary L. Slater, John D. Lloyd, James H. Withgott, and Kimberly G. Smith
Version: 1.1 — Published August 18, 2021

Behavior

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Locomotion

Walking, Hopping, Climbing, Etc.

May climb upward or downward on trunks. Very occasionally seen on ground. Generally, when foraging spends most of its time hopping along substrates, occasionally flying short distances to new sites within a tree or in a nearby tree. After finding a seed or large insect, flies (occasionally hops) to a nearby limb and begins hammering.

Flight

Flight fairly weak and slow, with discrete series of wing beats, resulting in flight pattern of shallow dips. Most flights are short-distance, within trees or between nearby trees. However, continuous flights of several hundred meters have been observed (JHW). May capture dislodged insects in flight. Very short flights (1–3 m) from a branch to a lower one may be made as glides without flapping (JHW).

Swimming And Diving

Not known to occur.

Self-Maintenance

Preening, Head-Scratching, Stretching, Bathing, Anting, Etc.

Birds may preen at any time of day, most often while perching upright on branch in full sunlight. Head-scratching mode not known. Allopreening has been documented repeatedly and among a wide variety of participants (Cox in press). Allopreening performed by breeding adults on one another and young of the year, adult male helpers on breeding females and unrelated adults, and young of year on adults and nestmates. One observation of allopreening between adult male and helper male of a neighboring threesome (1). Most bouts < 1 minute. Individuals typically perch side-by-side on a horizontal limb. The majority of allopreening is focused on the head and neck, presumably for hygienic purposes, although wing and back allopreening is consistent with social functions suggested for other birds (e.g., maintain pair bonds, reinforce social hierarchies; Cox in press). Behavior is often reciprocal among participants (Barbour and DeGange1982, Cox in press). No information on stretching, bathing, or anting.

Sleeping, Roosting, Sunbathing

From 1, except where noted. Birds roost either in cavities or on pine branches, hidden in pine-crown foliage. Females or pairs generally roost in the nest cavity beginning before eggs are laid and through the nestling period. Norris did not observe helpers roosting in cavities with breeding pairs, but 3 birds were observed entering a roost hole in N. Carolina in Apr (JHW). While fledglings are gaining independence, parents seem to roost in the open, apart from fledglings. On 2 occasions, adults found leading fledglings to roost on upper branch of pine trees, then departing to roost elsewhere (GLS). During winter, pairs and groups appear to roost together, although communal roosting by individuals from adjacent territories has been observed under some environmental conditions. In S. Florida, average territory roost size was 3.4 individuals (range 2-10, n = 20 territories) during cool and wet El Nino winter of 1998-1999, whereas in 2000-2001 territory roost size averaged 2.2 individuals (range 1-3, n = 20 territories; GLS). In Georgia in Dec, Fleetwood (62) found together in a nest box a pair that had bred together in 1942 and 1943, an offspring of the male's 1944 mating with his own daughter by the 1942–1943 female, and an unbanded bird.

Foraging flocks may fall silent and motionless for periods of 5–15 min and sit inconspicuously in trees as if napping (P. Yaukey pers. comm.).

Sunbathing often accompanies preening.

Daily Time Budget

In spring and summer, nuthatches awaken before sunrise—but after many other species have begun singing—and go to roost before sunset (1, JHW). Mean awakening time of 14 min before sunrise (n = 11, Mar–Jul) and roosting time of 14 min before sunset (n = 4, Mar–May) recorded by Norris (1). On basis of limited data, females appear to enter roost cavities earlier and leave later than their mates (1). Quantified time budgets in winter in Georgia revealed 43% of time spent traversing bark surfaces, 22% hammering seeds, 20% foraging at cones, 7% resting, 5% carrying seeds, 2% excavating cavities, and 1% foraging in pine needles (n = 193 observations; 65). Cone-foraging and seed-hammering were more prevalent late in the day, perhaps reflecting a need to store energy for the night (P. Yaukey pers. comm.). Time budgets varied significantly between pine and mixed habitat, but not between flocked and unflocked birds (65).

Agonistic Behavior

Physical Interactions

Intraspecific interactions may include supplanting individuals from perches, attempting thefts of food, in-flight pursuits, and fighting with physical contact. In one instance, a fight between 2 birds (apparently males competing for a female) resulted in one bird hopping atop the other and pecking viciously at its back and tail until they both tumbled through the air. Aggressor gave Chortle-Chatter (see Sounds: vocalizations, above) during the 6–8 s of fighting and for many minutes before and after (JHW).

Communicative Interactions

Intraspecific threat and appeasement displays are not described.

Spacing

Territoriality

Territory sizes for 6 groups in longleaf pine forest in Georgia, Mar–May, were 2.8 ha for a breeding pair, 2.1 and 3.2 ha for 2 nonbreeding pairs, 2.8 and 3.2 ha for 2 breeding threesomes, and 4.2 ha for a nonbreeding threesome (Norris 1958). On an urban campus in Texas, mean territory size was 7.4 ha (range 4.4 – 16.2, n = 6, Herb and Burt 2000). Territories of nonbreeding groups overlapped considerably, but those of breeding groups were exclusive (1). Nests may be located inside or outside of foraging areas.

Territories appear to be established and defended by males, and individual birds vary in intensity of territory defense. Vocalizations and chases are used in defense (1).

Pairs have been shown to breed in the same general area year after year. In 2 Florida populations, breeding pairs frequently excavated nests <100 m from previous year's nest site, with 5 pairs excavating in the same snag for > 2 yr (Cox and Slater 2007). Nest sites have been recorded 32 and 360 m from previous nests, and in the same nest box in consecutive years (62). In winter, birds were found roosting 68 m from the spot where they had bred that year (62).

In winter, nuthatches following mixed-species flocks are nonterritorial (see Demography and populations: range, below).

Individual Distance

Mated pairs or sibling fledglings may perch next to each other, feathers touching. With Carolina Chickadees (Poecile carolinensis) and Tufted Titmice (Baeolophus bicolor) in winter flocks, Yaukey (72) tested for effects of food supplementation and predator simulation on interbird distances and flock cohesion. While food supplementation had little effect, he found that predator simulation elicited 2 responses: some nuthatches moved closer to chickadees, while others left the flock completely. Overall, nuthatches in mixed flocks averaged slightly >15 m distant from the nearest chickadee or titmouse.

Sexual Behavior

Mating System And Sex Ratio

Apparently monogamous, although paternity studies have not been carried out. Cooperative breeder.

Sex ratio is apparently strongly male-biased. Among collected specimens, Norris (1) documented male: female ratios of 1.52:1 for adults (n = 403) and 2.64:1 for juveniles (n = 65).

Pair Bond

Pair bonds commonly extend over several years (Cox and Slater 2007). In Florida, 50% of territories consisted of individuals paired the previous year (Cox and Slater 2007). Fleetwood (62) documented that 1 male mated with a female for 2 consecutive years, then with his own daughter in the third year, and then with the original female in the fourth year.

During the early part of the breeding season, the male brings food to the female, which responds with begging calls and wing-quivering displays. Male continues to feed his mate at the nest site during incubation. Both sexes may quiver wings and twitter (71) at the nest site, although usually only the female begs. Male appears to guard the female during the early breeding season, following her from tree to tree while foraging (JHW).

Copulation has been described twice. On 19 Jan in Georgia, male and female perched side by side on a branch, both quivering their wings. While the female remained in position, the male mounted her 4 times. Courtship-feeding took place the same day: The bird perched in the cavity entrance presented the bird outside the cavity with a pine seed, while both quivered their wings (P. Yaukey pers. comm.). In Georgia on 8 Apr, a pair flew to a tree following mate-feeding at the nest. The female quivered her wings, the male mounted her, then they both flew. While in flight, they “came together for a short time and then broke apart. These actions were repeated several times” (73: 331).

Observations of allopreening in the non-breeding season suggest maintenance of a year-round pair bond (74). Paired birds have been found roosting together through the winter of the year before nesting (62, GLS).

Extra-Pair Mating Behavior

No data. One attempt observed between a male of a pair and a female of a threesome, but neither bird bred successfully (1). No studies of paternity.

Social and Interspecific Behavior

Degree Of Sociality

During the breeding season, pairs remain together, and helpers remain in fairly close contact with pairs. Species is somewhat gregarious outside of the breeding season, foraging together in small groups (66). See Breeding: cooperative breeding, below.

Play

No information.

Nonpredatory Interspecific Interactions

Best-known interactions include those with other species in winter foraging flocks and those with cavity competitors near nest sites.

In winter, routinely joins mixed-species foraging flocks that may include Eastern Bluebird (Sialia sialis), Carolina Chickadees, Tufted Titmice, Pine Warblers, Yellow-rumped Warblers (Dendroica coronata), kinglets (Regulus spp.), Brown Creepers (Certhia americana), White-breasted Nuthatches, and various woodpecker species. In Louisiana, Morse (59, 60) found flocking Brown-headed Nuthatches and Pine Warblers to number typically 4–8 each; nuthatches averaged 5.0 ± 2.3 SD per flock (n = 57 flocks). In Arkansas and Florida, Pine Warblers are usually the most abundant flock member, and flocks often number >50–100 birds, of which 2–20 may be nuthatches (JHW). In fast-moving winter flocks, nuthatches sometimes are left behind, as they forage from productive cones and take time to hammer seeds (59). In Morse's (59) study, 98.2% of mixed flocks (n = 57) contained nuthatches, and 39.7% of nuthatch groups (n = 141) were participating in mixed flocks. In Georgia, 57% of nuthatches (n = 72) were in mixed flocks in pine forest, but significantly larger proportions were flocked in mixed and deciduous habitat (65).

Appears to compete with Pine Warbler for food in winter flocks; the 2 species displace each other from preferred microhabitats (59, 75). Although Brown-headed Nuthatches in winter flocks may shift their activity toward distal portions of branches to avoid encounters with Pine Warblers, agonistic interactions with warblers result from nuthatches' use of proximal limb sections as hammering sites (59). In Morse's (59) study, warblers attacked nuthatches 2.6 times/100 foraging observations, while nuthatches attacked warblers 2.2 times/100 foraging observations, and fight frequency was higher during heavy cone crops, when nuthatches frequently used proximal limb sections for seed-hammering. Most attacks by nuthatches were supplanting attacks, while warblers usually attacked nuthatches from the air. Warblers often attacked from a distance, but in close-range interactions nuthatches nearly always won. Morse speculated that the nature of the attack and defense in these species might drive displacement in substrate use.

Also noted were attacks on White-breasted Nuthatches (1.0/100 observations), attacks by White-breasted Nuthatches (1.9/100 observations), and attacks on Carolina Chickadees (1.3/100 observations; 59). Nuthatches attacked chickadees only when chickadees foraged at pinecones for seeds.

In Georgia, interactions most frequently involved Carolina Chickadees (43% of all interactions), followed by Downy Woodpeckers (Dryobates pubescens; 13%), Tufted Titmice (10%), and Pine Warblers (9%; P. Yaukey pers. comm.). Nuthatches won 66% of all interactions (n = 77 with 14 species), including 97% with chickadees, 0% with Downy Woodpeckers, 0% with titmice, and 100% with Pine Warblers.

Contrast between results of P. Yaukey (pers. comm.) and Morse (59) in relation to antagonism with chickadees and Pine Warblers may be because Yaukey's flocks contained fewer Pine Warblers than Morse's (P. Yaukey pers. comm.). In breeding season, interactions with Pine Warblers seem rare, and occur primarily near nests (1).

Interactions with chickadees and titmice in winter mixed flocks may be partly regulated by predation threat, but apparently not by food availability (72). In developed residential areas, flocking with chickadees—but not titmice—was decreased (58). Regarding foraging movements in winter mixed flocks, nuthatches led Yellow-rumped Warblers (n = 17 observations), Pine Warblers (n = 2), and Red-cockaded Woodpeckers (n = 1), but followed Tufted Titmice (n = 14), Carolina Chickadees (n = 10), and Ruby-crowned Kinglets (Regulus calendula; n = 5; 60).

May feed commensally near Red-cockaded Woodpeckers, gleaning prey that woodpeckers dislodge but are unable to capture (76).

In the breeding season, regularly and aggressively chased from nest sites by various cavity-nesting birds—including competitors for nest sites, usurpers of nests, and potential nest predators. These most commonly include Eastern Bluebirds (Cornell Nest Records Program [CNRP], 1, 77, 49, Stanback et al. 2011), Carolina Chickadees (CNRP, 78, 1, 30), European Starlings (Sturnus vulgaris; CNRP, 30), House Sparrows (Passer domesticus; CNRP, 79), and various woodpecker species (CNRP, 78, 1, 71, 49).

In s. Florida, for example, nuthatches aggressively chased Red-bellied Woodpeckers (Melanerpes carolinus) and bluebirds approaching within 25 m of a nest, and dive-bombed perched or foraging birds nearby, giving loud vocalizations, sometimes dive-bombing >200 times (49). Although such actions seldom had a major and immediate effect on larger birds like Red-bellied Woodpeckers, group size may be a factor in the ability to defend the nest site. G. Slater (pers. comm.) observed 1 group of 4 birds that was especially effective in chasing off Red-bellied Woodpeckers; on one occasion, the foursome knocked a woodpecker to the ground from a nearby snag. On the other hand, a single Brown-headed Nuthatch that harassed a White-breasted Nuthatch at a suet feeder was “seized by the head and soundly shaken” (78: 79).

Most interactions with cavity competitors seem to occur at atypical nest sites and in less-preferred habitat (77). On urban golf courses, numbers of nuthatches increased dramatically when bluebirds were excluded from nest boxes by reducing the size of the entrance hole; when bluebird-accessible entrance holes returned, bluebirds usurped nearly all the nuthatch nests (Stanback et al. 2011).

Predation

Kinds Of Predators; Manner Of Predation

The only predation event of an adult described in the literature involved a Swallow-tailed Kite (Elanoides forficatus, Cox 2012b). Other bird-eating raptors seem likely predators. During winter and hawk migration, Sharp-shinned (Accipiter striatus) and Cooper's (A. cooperii) hawks have been seen to attack mixed flocks that include nuthatches (JHW). American Kestrels (Falco sparverius) elicit alarm reactions from nuthatches (59) and have been observed chasing nuthatches (GLS).

Confirmed nest predators include various snakes (CNRP, 71, 80, Withgott 81, 82, 49), broad-headed skink (Eumeces laticeps; Cox and Slater 2007), flying squirrels (Glaucomys volans; 83), house cats (Felis domesticus; CNRP, 84), and Red-bellied Woodpeckers (1, 49). Suspected nest predators include House Wrens (Troglodytes aedon; CNRP), Blue Jays (Cyanocitta cristata; 1, 30), House Sparrows (CNRP), European Starlings (30), opossums (Didelphis virginiana; 85, and other mammalian predators (49).

Response To Predators

Response to predation attempts by raptors varies. May freeze, crouching against a limb and remaining motionless (JHW), or may decrease movement without freezing, give loud vocalizations, or even—inexplicably—fly long distances in the open (60). In experiments presenting a simulated accipiter threat to winter mixed flocks, Yaukey (72) documented 2 responses: Nuthatches either moved closer to chickadees and titmice or ceased flocking with them. Yaukey concluded that both strategies may be advantageous, but that remaining loosely flocked may be disadvantageous.

Potential predators on nests or fledglings, when detected, may be scolded loudly with Rubber Ducky Vocalizations (see Sounds: vocalizations, above) and harassed with dives (see Social and interspecific behavior, above). Norris (1) describes dive by female with wings outstretched and vibrating but not beating, which veered away within 1 m of him.

Recommended Citation

Slater, G. L., J. D. Lloyd, J. H. Withgott, and K. G. Smith (2021). Brown-headed Nuthatch (Sitta pusilla), version 1.1. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bnhnut.01.1