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Social Grooming in the Brown-headed Nuthatch may have
James A. Cox*
Abstract - Allopreening is a form of social grooming that has not been extensively studied in most
birds. Observations of allopreening in Sitta pusilla (Brown-headed Nuthatch) are described where
sex, age, and kin relationships were known for the individuals performing the behavior. Young of
the year allopreened adults and nest mates, adult male helpers allopreened breeding females and
unrelated adults, and breeding adults allopreened one another as well as young of the year. Previous
observations suggested allopreening served to maintain pair bonds in the Brown-headed, but
these observations suggest the behavior may have expanded functions. Although most allopreening
focused on neck and head regions where the behavior may primarily serve hygienic functions,
wings and backs also were allopreened frequently in a manner consistent with the social functions
suggested for other birds.
Allopreening, a form of social grooming performed by birds, has been documented
for scores of avian taxa, but the functions of the behavior are not well understood
(Radford and Du Plessis 2006). Allopreening is assumed to have important hygienic
functions in many species, but allopreening may also include social functions such as
maintaining pair bonds and social hierarchies or reducing strife among group members
and neighbors (Lewis et al. 2007, Radford and DuPlessis 2006). The paucity of information
on social grooming in birds contrasts sharply with the situation for mammals,
where social grooming has been documented as a major feature of social living (Radford
and Du Plessis 2006).
Allopreening has been documented frequently in Sitta pusilla Latham (Brown-headed
Nuthatch), but, because most observations involved unmarked individuals, the sex and
relationships of individuals engaged in the behavior were largely unknown (Withgott and
Smith 1998). For example, Barbour and DeGange (1982) described allopreening between
two nuthatches and suggested the behavior might assist in maintaining pair bonds. Barbour
and DeGange (1982) did not describe how sex was ascertained for the individuals
they observed, but sex cannot be determined accurately in this species based exclusively
on plumage (Withgott and Smith 1998). The Brown-headed Nuthatch also frequently
lives in family groups that contain ≤5 members and include breeders and non-breeding
helpers (Cox and Slater 2007). Nuthatches observed allopreening cannot be assumed to
be a breeding pair or even a male-female combination.
In this note, I provide new details on allopreening in the Brown-headed Nuthatch
based largely on observations of marked individuals recorded during the post-breeding
period. Since 2003, a large, individually marked population of Brown-headed Nuthatches
has been maintained on Tall Timbers Research Station (30.66°N, 84.22°W; Leon County,
FL) by placing unique color-band combinations on an average of 39.3 adults and 72.1
nestlings annually. Methods used to mark adults and nestlings are described in Cox and
Slater (2007). In 2011, I monitored post-fledgling activities by re-sighting the adults and
marked fledglings associated with 17 territories. The territories were visited for 20 min
on 2–4 occasions each month from May through November, and territorial responses
were elicited by playing recorded nuthatch vocalizations that included aggressive calls
*Tall Timbers Research Station, 13093 Henry Beadel Drive, Tallahassee, FL 32312. Corresponding
author - email@example.com.
Notes of the Southeastern Naturalist, Issue 11/4, 2012
772 Southeastern Naturalist Vol. 11, No. 4
and contact and foraging notes (Norris 1958). Individuals were identified by reading
color band combinations using a spotting scope (30–60x zoom), and all surveys were
conducted between 06:30 and 11:00 DST.
Allopreening was defined as a behavior where the bill of one nuthatch made contact
with the feathers of another individual in a preening motion. Ten instances of allopreening
were observed, and the behavior was classified as reciprocal when individuals preened
one another simultaneously or in succession (Barbour and DeGange 1982). Kin relationships
and social status (i.e., breeder versus helper) for adults were based on pedigree
data and behavioral observations made during the breeding season and followed Cox
and Slater (2007). Although most territories with ≥3 adults appeared to have a dominant
breeding pair and non-breeding helpers (Cox and Slater 2007), extra-pair copulations
have been documented infrequently in territories with ≥3 adults (K. Han, University of
Florida, Gainesville, FL, unpubl. data) and indicate that some helpers may also be breeders.
I use the term helper to refer to individuals that appeared to differ in social status
based on observations of copulation and other behaviors. Juveniles represented nestlings
marked prior to fledging, and sex for all individuals was based on DNA samples collected
and processed following Haas et al. (2010).
All observations of allopreening took place in settings identical to those described by
Withgott and Smith (1998), where individuals perched side-by-side on horizontal limbs.
Allopreening may take place throughout the year (Withgott and Smith 1998), but my
earliest observation occurred on 1 July (approximately 8 weeks after nestlings fledged),
while my latest observation occurred on 17 November. The observations typically lasted
≤2 min before individuals resumed other activities. Three observations involved ≥1
unbanded adults where relationships could not be assessed (including one instance of
reciprocal allopreening). The remaining observations were recorded in 7 independent territories
and involved color-marked birds where sex, age, and status could be assigned.
1 July: a helper male allopreened the breeding female for approximately 40 sec
while the breeding male sat on a nearby limb. The dominant male was observed
sitting near the female later during the survey, and there were no hostile
interactions between the helper male and breeding male.
7 July: a breeding male allopreened the breeding female for approximately 35 sec
15 August: a breeding male allopreened a juvenile male for approximately 1 min
6 September: a breeding male and juvenile male engaged in reciprocal allopreening
for approximately 1 min.
14 October: a breeding male from a neighboring territory allopreened a juvenile
male without reciprocation for approximately 30 sec. The breeding male was
the grandfather of the juvenile male.
21 October: a helper male allopreened the breeding male without reciprocation
for 20 sec.
17 November: a breeding female and 2 juvenile males engaged in reciprocal allopreening
for approximately 1.5 min. The female and a juvenile simultaneously
preened the second juvenile perched between them. Approximately 20 sec before
interactions ceased, the female moved to the middle and was allopreened
by both juvenile males.
Social grooming in mammals is thought to serve both hygienic and social functions,
but allopreening in birds has been viewed largely in terms of hygienic benefits because
2012 Southeastern Naturalist Notes 773
the behavior appears to concentrate on body areas that are difficult or impossible for individuals
to reach (Brooke 1985, Harrison 1965). Recent work on Phoeniculus purpureus
Miller (Green Woodhoopoe) provides a new framework for evaluating social versus hygienic
functions by considering the area on a recipient’s body where a donor allopreens
(Radford and Du Plessis 2006). When allopreening is focused around the neck, head, and
other areas difficult to reach with the bill (hereafter head preening), the behavior may
serve a hygienic function. Alternatively, when allopreening is directed toward wings,
backs, and other areas that can easily be reached with the bill (hereafter body preening),
the behavior may serve a social function. In the Green Woodhoopoe, the frequency of
head versus body allopreening varies in relation to season, social dominance, and social
setting and suggests the behavior has multiple functions (Radford 2008, Radford and Du
Although I did not quantify the specific time spent allopreening head versus body
areas, most donors directed their efforts toward head and neck areas in agreement with
a hygienic function. Donors were observed touching the back, wing, and belly less
frequently, but allopreening body areas occurred regularly and was consistent with the
social function described for the Green Woodhoopoe. Body allopreening was particularly
common in the 17 November observation where two donors allopreened a recipient. In
addition, the Brown-headed Nuthatch has a shorter bill than the Green Woodhoopoe that
enables individuals to reach portions of the neck that individual woodhoopoes can not.
Donor nuthatches that allopreened around the neck would be difficult to classify using
the head/body criterion established by Radford and Du Plessis (2006).
Allopreening in the Brown-headed Nuthatch appears to serve functions other than
maintenance of the pair bond emphasized by Barbour and Degange (1982). I observed
male and female breeders grooming juveniles, adult helpers grooming adult breeders,
and juveniles grooming juveniles. Norris (1958) also described reciprocal allopreening
between an adult male and helper male from a neighboring territory. Allopreening in the
Brown-headed Nuthatch may serve multiple functions, but additional data are needed to
assess the relative importance of allopreening for hygienic versus social functions. It may
seem daunting to collect behavioral data for a small songbird (11 g) that forages in the
canopy, but I observed approximately 0.15 allopreening events per hour of observation
(while also attempting to collect other data). This rate is similar to the ≈ 0.30 allopreening
events recorded per hour by Radford and Du Plessis (2006). Future studies also should
attempt to monitor the behavior both with and without the use of playback vocalizations.
The playback vocalizations elicit territorial responses that could influence the frequency
of allopreening as well as the body areas where allopreening is focused (Radford 2008).
Acknowledgments. This study was supported by the Wildlife Research Endowment at
Tall Timbers Research Station. I also thank an anonymous reviewer for helpful comments
on an earlier draft.
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Haas, S., J. Cox, R. Kimball, and J. Smith. 2010. Fine-scale spatial genetic structure in the cooperatively
breeding Brown-headed Nuthatch (Sitta pusilla). Southeastern Naturalist 9:743–756.
Harrison, C.J. 1965. Allopreening as agonistic behaviour. Behaviour 24:161–209.
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