Aggressive Communication By Larus Glaucescens Part V: Orientation and Sequences of Behavior

[Analysis of aggressive communication between intruding and territory defending Glaucous-winged Gulls (Larus glaucescens) were made, based on aggressive encounters recorded on 4000 m of motion picture film. A description of communication by these birds was made based on the results of the film analysis. Special attention was given to the orientations of the intruding and territory defending gulls with respect to one another and to sequences of calls and displays of both birds during the encounters. Most behaviors were distributed non-randomly with respect to orientation. Radio controlled, automated gull models were constructed that consisted of a taxidermy-mounted head of a real gull mounted on a wooden body of approximately the normal body shape and size. Movement of the head and neck in a vertical direction and body rotation were controlled by the experimenter in the blind. Models were placed in gull territories to test the effect of model gull orientation upon Attack responses of defending birds. Time was recorded from the return of the territory defender to the moment Attack on the model occurred. It was shown that the model directly facing the interacting gull inhibited Attack and that the model oriented at right angles or facing away 180 degrees accelerated Attack. The effect of turning towards the responding gull and turning away during aggressive interactions was also studied by observing the response to the model when it was turned towards and away. Reponses showed that Attack was more frequent when the model was turned away (o degrees → 90 degrees) from the interacting gull and that Attack was less frequent when the model was turned towards (90 degrees → o degrees). Both film analysis and experimental work supported the hypothesis that orientation is an important feature of agressive communication by Larids. The analysis of sequences of behavior supported the hypotheses that sequences of behavior are important elements of communication by these birds. The distribution of behaviors relative to other behaviors was non-random. Additional experiments with moving models gave added suport to the assertion that sequences of behavior are important aspects of the communicative scheme of Larids. Two groups of defender behaviors were described on the basis of the orientation and sequence analyses.Onegroup, said to function within the "Attack Mode", included Defender Uuright Towards and Defender Attack. The other group, said to function within the "Display Mode", included Defender Mew and Defender Choke. The Attack Mode was the most frequently occurring mode of defender response. Evidence was presented which showed that elements of the Display Mode are used in response to the more threatening intruders, whereas the Attack Mode was used in response to submissive intruders. A functional model was proposed in an attempt to describe the communicative processes used by these birds., Analysis of aggressive communication between intruding and territory defending Glaucous-winged Gulls (Larus glaucescens) were made, based on aggressive encounters recorded on 4000 m of motion picture film. A description of communication by these birds was made based on the results of the film analysis. Special attention was given to the orientations of the intruding and territory defending gulls with respect to one another and to sequences of calls and displays of both birds during the encounters. Most behaviors were distributed non-randomly with respect to orientation. Radio controlled, automated gull models were constructed that consisted of a taxidermy-mounted head of a real gull mounted on a wooden body of approximately the normal body shape and size. Movement of the head and neck in a vertical direction and body rotation were controlled by the experimenter in the blind. Models were placed in gull territories to test the effect of model gull orientation upon Attack responses of defending birds. Time was recorded from the return of the territory defender to the moment Attack on the model occurred. It was shown that the model directly facing the interacting gull inhibited Attack and that the model oriented at right angles or facing away 180 degrees accelerated Attack. The effect of turning towards the responding gull and turning away during aggressive interactions was also studied by observing the response to the model when it was turned towards and away. Reponses showed that Attack was more frequent when the model was turned away (o degrees → 90 degrees) from the interacting gull and that Attack was less frequent when the model was turned towards (90 degrees → o degrees). Both film analysis and experimental work supported the hypothesis that orientation is an important feature of agressive communication by Larids. The analysis of sequences of behavior supported the hypotheses that sequences of behavior are important elements of communication by these birds. The distribution of behaviors relative to other behaviors was non-random. Additional experiments with moving models gave added suport to the assertion that sequences of behavior are important aspects of the communicative scheme of Larids. Two groups of defender behaviors were described on the basis of the orientation and sequence analyses.Onegroup, said to function within the "Attack Mode", included Defender Uuright Towards and Defender Attack. The other group, said to function within the "Display Mode", included Defender Mew and Defender Choke. The Attack Mode was the most frequently occurring mode of defender response. Evidence was presented which showed that elements of the Display Mode are used in response to the more threatening intruders, whereas the Attack Mode was used in response to submissive intruders. A functional model was proposed in an attempt to describe the communicative processes used by these birds.]