N. b.: Phases bordering onto missing data were only included in counts for phase durations, if they exceeded 20 s
2. Signal death occurred when an egg temporarily succumbed to the unfavourable climatic conditions; resurrection was at times possible by switching the egg-powering battery off and on
4.3.4 Disturbance Data
188.8.131.52 Final Categorisation and Operationalisation of Disturbance
The final categorisation of disturbance, its transcription as well as the calculation of total disturbance performance indicator values (operationalisation) differed for focal groups and focal animals due to the different sampling methods employed,
N.b.: In THISTHESIS, the term ‘operationalisation’ is used for both a priori and a posteriori defined operators and thus includes human visitation (a priori) as well as conspecifics (a posteriori). For each operator, the term ‘categorisation’ is used to refer to distinct categories. Disturbance by predators/ aircraft did not receive any operationalisation, although for skuas, the qualitative distinction between overflights of different height and presence on the ground was made.
184.108.40.206.1 Human Disturbance
Disturbance types: In both years, the effects of two contrasting types of visitor conduct were recorded. Throughout visits of the type silent and slow, movements and noise were kept to a minimum, movement towards (approach) and away from (retreat) the penguin group visited occurred at a slow pace; at the given distances, the visitor(s) stood or knelt quietly, avoiding ‘sideways’
movement (movement which did not change the distance to the colony edge).
In contrast to that, the conduct type loud and fast had the visitor(s) approach and retreat at a brisk pace. During the entire visit, they did not keep their voice(s) down, continued to move around at the given distances (‘sideways’ movement), and also occasionally abruptly extended their arms (waving, pointing).
Number of ‘disturbers’: Visiting experiments limited the number of human visitors to either one (‘1 person’) or three (‘3 persons’).
Visiting regimes: A total of four ‘visiting regimes’ were examined. In 2000, the two different types of conduct described above were displayed by a single visitor, and the regimes were termed
‘1 person, silent and slow’ (1 P, S&S) and ‘1 person, loud and fast’ (1 P, L&F), respectively.
The same types of human conduct were repeated in 2001, but this time the number of visitors was augmented to three (see fig. 4-5) resulting in the regimes ‘3 persons, silent and slow’ (3 P, S&S) and ‘3 persons, loud and fast’ (3 P, L&F).
Distance from the source of disturbance: Distance was measured between visitors and the edge of the colony. For visiting experiments, three distances had been predetermined, viz., 15 m, 5 m, and 3 m (s.b.). Distances were ‘sign-posted’ by small piles of pebbles and rocks. Additionally, human visitors moved between these distances during approach and retreat.
Duration of exposure to the disturbance: Visits followed a standard time-space protocol.
The Human visitor(s) left the tent (through the back-’door’), walked round the tent, and approached group B (2000) or group X (2001) in a straight line. With respect to group C (2000) and group Y (2001), visitor(s) left the tent and walked along the foot of the hill opposite the study colony until they could approach the group in a straight line as well (see chapter 220.127.116.11, fig. 3-25).
At the three predetermined distances from the colony edge (15 m, 5 m, and 3 m, resp.), visitor(s) spent two minutes each. Retreat from the closest distance likewise occurred in a straight line but did not include any in-between stops. Time to the nearest second was noted separately for each of the distances, approach and retreat. Total time of visit depended on visitor speed as well as the distance between group and tent.
Duration of behaviour and heart rate recordings: To gauge the magnitude of the impact of human visitation (changes between pre- and during-visitation), the immediacy/ delay of waning of responses after stimulus withdrawal (changes between during- and post-visitation) and the speed of recovery (absence/ persistence of changes between pre- and post-visitation), penguin heart rate and behaviour were recorded for some time before58 and after the visits (2000: 10 min before, 10 min after; 2001: 20 min before, 15 min after). To facilitate comparisons, analyses presented here were performed on 30 min of behaviour and heart rate regardless of duration of original transcriptions. Details on visiting schedule and visiting regimes are presented in table 4-16.
58 The pre-visitation period also served to collect information on individual resting heart rate (BALDOCK & SIBLY 1990) and
‘baseline’ behaviour and helped to accommodate susceptibility of heart rate to climatic conditions (CULIK & al. 1989).
Recapitulation: In 2000, groups B and C were subjected to a switch in visiting regime after approximately two thirds of the fieldwork period, resulting in two datasets each for group B (B1: ‘1 person, loud and fast’, B2: ‘1 person, silent and slow’) and group C (C1: ‘1 person, silent and slow’, C2: ‘1 person, loud and fast’). The switch mainly affected focal group transcriptions, as post-switch recordings had to be discarded for most focal-animal transcriptions due to insufficient visibility of respective FAs. Because of logistical and climatic problems, fieldwork in 2001 (groups X and Y) started late in the Adélie penguins’ incubation period. Since the visiting schedule introduced during the previous season (visits once a day for two successive days, followed by ‘baseline’ recording) was to be adhered to for comparative purposes, it was impossible to repeat the switch (tab. 4-16).
Table 4-16: Human Visitation Schedule and Visiting Regimes. Recordings with (purple) and without (turquoise) human visitation per group. A, B, C, X, Y: study groups of penguins; B1, C1: datasets prior to switch in visiting regime, B2, C2: datasets after switch in visiting regime, unvis: no human visitation occurred; 2000, 2001: year of data collection; no:
no fieldwork possible; dc: discarded for various reasons; L&F: loud and fast, S&S: silent and slow; 1 P: one visitor, 3 P:
18.104.22.168.2 Conspecific59 Disturbance
Conspecifics were defined as being birds of the same species, currently not engaged in incubation.
No distinction was made between non-breeders/ failed breeders and breeding birds not on the nest (i.e., the partner was incubating). The empirical approach to recording conspecific actions was dealt with differently during focal-group and focal-animal analyses.
Disturbance type: Although conspecifics also differed in conduct, they could not be induced to collectively display these differences on cue. Conspecific conduct did not feature with respect to focal groups (i.e., conspecific presence only). As for focal animals, differences used to categorise conspecific conduct included speed of movement (stand/ lie, walk, run) and selected behaviours (e.g., stand up from previously prone position, fight, nest stone theft at the focal animal’s nest).
Number of ‘disturbers’: Movements of conspecifics were not channelled or otherwise manipulated, and the number of conspecifics present fluctuated naturally. ‘Boundaries’ for inclusion of conspecifics into transcriptions were devised for focal groups and focal animals, respectively:
For focal groups, the first and last nest within each row constituted the limits on the left and right.
To the front, some space was included in front of the first row; to the back, the fifth row of nests marked the exclusion line (fig. 4-12).
As for focal animals, all conspecifics present within the three concentric nest zones depicted in figure 4-13 were included.
Distance from the source of disturbance: The colony edge did not pose a limit to conspecifics, i.e., non-incubating conspecifics were found throughout the colony.
With respect to entire focal groups, distance measurements for individual conspecifics were therefore considered rather pointless: Examination of the behaviour of each of a number of conspecifics
59 The reader is kindly asked to keep in mind that during human visitation, conspecifics usually (per)formed the background disturbance on top of which the other type occurred.
Human visitation schedule and visiting regimes: recordings with (purple) and without (turquoise) human visitation per group
Day and Month Group
(Year) 12 Nov. 13 Nov. 14 Nov. 15 Nov. 16 Nov. 17 Nov. 18 Nov. 19 Nov. 20 Nov. 21 Nov. 22 Nov. 23 Nov. 24 Nov. 25 Nov. 26 Nov. 27 Nov. 28 Nov. 29 Nov. 30 Nov. 01 Dec. 02 Dec. 03 Dec. 04 Dec. total unvis total vis A (2000) unvis 1 1 1 no 1 1 no 1 1 1 no 1 1 1 1 1 1 1 no 1 1 no 1 18 0 B1 (2000) unvis/ 1P, L&F 1 1 1 no 1 1 no 1 1 1 no 1 1 1 1 4 8
B2 (2000) unvis/ 1P, S&S 1 1 1 no 1 1 no 1 2 4
C1 (2000) unvis/ 1P, S&S 1 1 1 no 1 1 no 1 1 1 no 1 1 1 1 4 8
C2 (2000) unvis/ 1P, L&F 1 1 1 no 1 1 no 1 2 4
X (2001) 3P, S&S 1 1 1 no no no 1 1 5
X (2001) unvis 2 1 2 1 no 0 no no 1 2 9
Y (2001) 3P, L&F 1 1 1 no no no 1 1 5
Y (2001) unvis
2001: delayed arrival in the field
1 1 2 1 no 1 no no 1 end of
7 total recordings with human visitation: 34 (2000: 12 L&F, 12 S&S; 2001: 5 L&F, 5 S&S)
total recordings without human visitation: 46 (2000: 30; 2001: 16)
towards each of a number of incubating birds and subsequent translation into a value representing the impact on the group as a whole was outside the scope of this investigation. Instead, the number of conspecifics present within focal-group ‘boundaries’ was noted separately for six areas (outside colony, colony edge-R1, R1-R2, R2-R3, R3-R4, R4-R5) delineated in accordance with the rows (fig. 4-12).
Figure 4-12: Areas Delineated for Focal-Group Primary Transcription of Conspecific Presence. Double-headed arrows indicate between-row areas used for transcription of sessions recorded at group X. The grey arrow depicts direction from which visitors approached. C: conspecifics currently not engaged in incubation; rows were differently coloured for better discrimination, and nest codes reflect colours used (r: red = R1, o: orange = R2, y: yellow = R3, b:
blue = R4).
As regards focal animals, three concentric zones of increasing area were designated round the focal penguin’s nest (concept ‘borrowed’ from NIMON 1997). Zone ‘a’ comprised the area immediately surrounding the focal penguin’s nest up to the nearest neighbouring nests, zone ‘b’ the area between one and two nests away, and zone ‘c’ the area between two and three nests away from the focal penguin (fig. 4-13). These zones continued beyond the colony edge.
Duration of exposure to the disturbance: Conspecifics moved and stood unrestrained. Due to sampling method (Instantaneous-Scan Sampling), time of exposure did not feature with respect to focal groups. As regards focal animals, time of presence of conspecifics was separately noted in the three nest zones of increasing distance from the focal animal (fig. 4-13).
22.214.171.124.3 Predator/ Aircraft Disturbance
Due to their rare occurrence, disturbances by predators as well as by aircraft noise were sampled ad libitum. This information was not systematically evaluated and did not receive any operationalisation. With respect to predators, however, species, approximate height of overflight (high, medium, and low) and occurrences of presence on ground were noted whenever possible.
The rare instances of aircraft ‘presence’ were noticed by noise, not visual appearance; a distinction between helicopter and plane was not feasible.
Figure 4-13: Nest Zones Delineated for Focal-Animal Primary Transcription of Conspecific Disturbance. The sketch depicts nest zones drawn around focal animal C1-1. FA: focal animal, N: neighbour; a, b, c: concentric nest zones of increasing distance from focal nest in centre.