Comfort Behaviour

“Comfort behaviour includes movements of shaking, stretching, cleaning, preening and washing.” (MCKINNEY 1965, as quoted in AINLEY 1974)

Figure 3-10: Various Comfort Movements. a) Rapid-wing-flap, b) Ruffle-shake, a ruffling of the feathers with extension of the neck and slight back and forth wing movement, followed by a body-shake, c) Yawn, upright, d) Yawn, prone, e) Both-wings-stretch, segment 1, f) Both-wings-stretch, segment 2, g) Shoulder-rub – a Cleaning or a Preening Movement.

From AINLEY (1974)

In his paper ‘The comfort behaviour of Adélie and other penguins’, AINLEY (1974) gives both a comprehensive overview and exact descriptions of the behaviours concerned. Rather than trying to rephrase AINLEY (1974), THISTHESIS quotes his descriptions verbatim, unless indicated otherwise (e.g., parentheses, comments pertaining to THIS STUDY). Only behaviours relevant to incubating penguins, however, are listed in the following section.

a b c d e f g

3.1.4.3.1 Rapid-Wing-Flap

The rapid-wing-flap is a shaking movement predominantly involving the wings: “The wings move as far ventrally then dorsally as anatomically possible and with such force and rapidity that a ‘whirr’

is audible³⁴. During the least vigorous bouts the wing movement is 6.6 cycles per second. However, at the normal rate it is too rapid to be counted visually. The body and neck are stretched upward, and the feet shuffle about to help maintain balance” (AINLEY 1974, p. 25; also see fig. 3-10 a). “The feathers are sleeked. The behaviour often merges into or out of the both-wings-stretch” (ibid., p. 25, also see below). “Rapid-wing-flap is performed after long periods of inactivity and [ – less important with respect to incubating birds – ] after vigorous activity (e.g., swimming)” (ibid., p. 25).

3.1.4.3.2 Ruffle-Shake

The ruffle-shake is a shaking movement which involves the whole body³⁵. “While the neck stretches fully upward, the feathers of the entire body, neck and head are ‘ruffled’ […] beginning with the nasal, ocular, and occipital crests of the head” (AINLEY 1974, p. 25; also see fig. 3-10 b). “When the neck begins to pull back down, there occurs a slight headshake [(see below)] and an intermediate wing-flap. Both grade into the rotary movement of a body-shake. The wing movement is performed with 1/3 of the potential excursion of the wings at 4.5 cycles per second, and hence is a reduced version of the rapid-wing-flap. After the body-shake [sic], the feathers are relaxed […]. Tail-wags[³⁶], and/ or head-bobs[³⁷] sometimes follow. Ruffle-shakes are performed during and following long bouts of preening” (AINLEY 1974, p. 25f.).

PERSONAL OBSERVATION: Apart from the situations described in AINLEY (1974), ruffle-shakes were found to frequently occur after an incubating bird changed their posture from prone to upright.

3.1.4.3.3 Yawn

The yawn is a stretching movement. “The bill opens to the fullest extent for about a second while the head, sunk on the shoulders, tilts back. As the bill closes, the head returns to normal positions.

Yawns may occur in prone […] [(fig. 3-10 c)] or upright […] [(fig. 3-10 d)] birds. Frequently several yawns occur in succession. They also occur as part of the both-wings-stretch (see […] [there]), but in that association the neck stretches fully and usually upwards. The bill remains open longer when the movement is part of the both-wings-stretch than when it is performed alone” (AINLEY

1974, p. 26).

3.1.4.3.4 Both-Wings-Stretch

Apart from the head-scratch (see below), the both-wings-stretch is the most often described avian comfort movement (AINLEY 1974). The both-wings-stretch is a stretching movement consisting of “two segments which sometimes occur independently of each other. In the first segment […]

[(fig. 3-10 e)] legs and body are stretched so that the body is almost vertical and the feathers are sleeked […]. The tail is stretched downward, the neck is stretched upward and sometimes slightly forward, and the bill is often opened in a yawn. The wings are thrust backward until the tips almost touch behind the back. Segment one is held for a few seconds and then merges into segment two.

34 as long as the observer is close enough to the penguin to hear it…

35 It is not called a shake, for “[b]ody-shakes are performed to remove water from the body. After a few body-shakes and headbody-shakes, the birds perform ruffle-body-shakes.” (AINLEY 1974)

36 side-to-side movements of the tail, not separately evaluated in THISTHESIS

37 head movement caused by swallowing

In segment two […] [(fig. 3-10 f)] the bill usually closes although it still points upward. The head is withdrawn to the shoulders and the wings are brought against the flanks and lower abdomen. The legs and body remain stretched upward and the tail remains stretched downward. Segment two is held for a few seconds and often ends with a sneeze³⁸ or headshake. The feathers are then relaxed” (ibid., p. 27f.).

According to AINLEY (1974), the both-wings-stretch is sometimes performed by prone birds, but more usually observed after a penguin rises from a long period of inactivity, such as incubation.

“Rapid-wing-flap and this behaviour often merge into one another so that a rapid-wing-flap occurs between the two segments of the both-wings-stretch” (ibid. p. 28).

3.1.4.3.5 Headshake³⁹

The headshake is a shaking movement that does not extend below the neck. During the performance of a headshake, “[t]he head flicks from side-to-side perpendicular to the body axis”

(AINLEY 1974, p. 19; also see fig. 3-11). “These lateral movements vary in number, speed and amplitude. Headshakes remove [salt gland fluid⁴⁰], water, food, dirt, snow, […] and other foreign matter from the head and bill. They are characteristic of birds which have just emerged wet from the sea; of parents which have just regurgitated food to chicks; of birds hit in the head by feces squirted from a neighbouring bird; and of birds which have sneezed […]” (ibid., p. 19). “One of the most common usages of the headshake by a penguin is to flick drops of salt gland fluid from the bill tip where they normally form” (ibid., p. 20).

38 As this behaviour is identified by sound, it is not included in THISSTUDY. 39 spelt head-shake in AINLEY (1974)

40 order rearranged, as salt gland fluid (original position indicated by […]) was deemed to be not a foreign matter Figure 3-11: Headshake – a Side-to-Side Movement. From AINLEY (1974)

PERSONAL OBSERVATION: In addition to the headshake described in AINLEY (1974), recordings for THIS THESIS identified a head-shoulder-shake, during which the shaking movement extended beyond the neck, but did not include the whole body (see ruffle-shake). As the gradation between headshake and head-shoulder-shake was frequently fluent, however, these two were regarded as sub-categories and were not evaluated separately.

3.1.4.3.6 Cleaning and Preening

While cleaning movements serve to remove ‘foreign matter’ and allow various parts of the body to be employed as ‘cleansing agents’ (e.g., the foot in ‘head-scratch’, see below), preening serves to keep in order and maintain the plumage using head and/ or bill; it is defined as involving “contact of the bird’s bill and head with the feathers” (MCKINNEY 1965 as quoted in AINLEY 1974) – except in the wing- and shoulder-rubs (which despite of lacking bill-contact are also considered preening movements in the context of oil-preening; see below). According to AINLEY (1974), MCKINNEY (1965 as quoted in AINLEY 1974) differentiated three types of preening for Anatidae, a classification that AINLEY adopted for penguins: oiling, nibbling and washing. “Oil-preening [(see below)] includes transfer of oil to the feathers from the uropygial gland at the base of the tail. Nibble-preening [(see below)] includes any treatment of the feathers without use of oil or water, while washing includes

feather nibbling in the water during bathing[⁴¹]” (ibid., p. 30). AINLEY (1974) stated that oil-preening was almost always performed after the birds emerged from the sea (i.e., on wet plumage). In their study on the ontogeny and organisation of comfort behaviour in Adélie penguins, BEKOFF & al.

(1979) examined both oil-preening⁴² and nibble-preening⁴³ in dry⁴⁴ birds.

The main difference between oil- and nibble-preening is that the former serves to spread oil over the bird’s plumage, while the latter behaviour does not involve any distribution of oil but serves to keep the ‘lay-out’ of the plumage in order (thereby improving insulation). The motor pattern and sequences, however, are the same (AINLEY 1974). “When oil-preening begins, oil is distributed to the feathers by several movements, including a strict three movement sequence that transfers oil from the uropygial gland to the head and bill” (ibid., p. 31f.). Using the oil-covered head and bill, the bird then continues to spread oil across their plumage, preening with the bill wherever the plumage can be accessed that way, and rubbing their head on shoulders and wings to cover the remaining surface.

With the exception of the wings, which are usually taken care of once the bird is back in the colony;

oil preening is mainly observed after Adélie penguins have left the water and before they enter the colony. At the nest site, however, “Adélies commonly preen by nibbling; sometimes for 5-10 minutes during which the bird preens one or several spots, or even for most of an hour during which many parts of the body are preened. Nibble-preening is performed during periods of little other activity.

In fact, Adélies often doze for short periods during a bout and often the bout ends when the bird falls asleep” (ibid., p. 38).

Depending on context, the shoulder-rub is a cleaning or a preening movement. “The bird rubs the back or side of the head against the shoulder (AINLEY 1974, p. 28; also see fig. 3-10 g). “It is often performed after a bird emerges from the sea to remove water from the shoulder, upper back and head” (ibid., p. 28). “In other [(dryer)] contexts it removes foreign material from the head or shoulder”

(ibid., p. 28). “It is also performed during oil-preening to distribute oil to the shoulder” (ibid., p. 28).

Similar to the shoulder-rub, the wing-rub may also be a cleaning or a preening movement. “The wing is raised from the side to project straight out or slightly upwards and backwards. The back, side, or top of the head, or throat is then rubbed on the wing’s leading edge which is held uppermost (ibid., p. 29; also see fig. 3-12). “During oil-preening it functions to distribute oil on the feathers of the head after oil has been transferred from the uropygial gland to the wing edge” (ibid., p. 29).

41 and consequently does not apply to the penguins studies for THISTHESIS

42 which they termed “dry-oiling” to emphasise that bill contact with the uropygial gland was made and oil was distributed over the dry plumage

43 which they termed “non-oiling” indicating that no bill contact was made with the uropygial gland 44 i.e., birds which had been out of the water for at least two hours before observations started Figure 3-12: Wing-Rub – a Cleaning or a Preening Movement. From AINLEY (1974)

N.b.: To date, no allopreening has been reported for Adélie (or indeed any other Pygoscelid) penguins⁴⁵. JOUVENTIN (1982, p. 27), however, states that the ‘mutual display’ (see above) “has the same function⁴⁶ as mutual preening in other species.”

METHODOLOGICAL CONSIDERATION: THISTHESIS did not wish to re-examine the fine detail, nor analyse the individual components of preening, but regarded preening as a behaviour during which the bird focused their attention upon their own body rather than on their environment. With the exception of head-scratch (unequivocally a cleaning movement), the behaviours were subsumed in the category ‘preening’, as preening was considered the ‘basic action’ while shoulder- and wing-rubs (cleaning or preening movements) were frequently observed in conjunction with it.

3.1.4.3.7 Head-Scratch

The head-scratch is a cleaning movement. “Before scratching, the bird changes its centre of gravity so that it is supporting itself on one foot and its tail. It then arches its body toward the free foot and extends the neck downward. Finally it brings the free foot over the depressed flipper and scratches the head with a quick up-down motion” (AINLEY 1974, p. 29; also see fig. 3-13). “The free foot is always brought to the same level and thus the part of the head to be scratched depends on the position to which the head is lowered” (ibid., p. 29). Head-scratching is performed “independently of other behaviours but often occurs during bouts of intensive preening” (ibid., p. 29).

45 In the genera Spheniscus, Eudyptes, Megadyptes and Eudyptula, in contrast, it certainly helps reduce ectoparasites, and may constitute an important element in aggression-reduction, pair-formation and pair-maintenance.

46 i.e., serves a double function, as other penguins likewise perform ‘mutual displays’.

47 alert: keenly watchful, on the look-out, ready for sudden action (WEBSTER’S Comprehensive Dictionary 2003) Figure 3-13: Head-Scratch. From AINLEY (1974)