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Aspekte Des Paarverhaltens Von Agapornis Personata Reichenow (Aves, Psittacidae, Loriini)
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Der ostafrikanische Papagei Agapornis personata Reichenow 1) lebt in Gruppen von 20-30 Individuen. Die vorliegende Arbeit schildert nach Gefangenschaftsbeobachtungen einige Komponenten des Paarverhaltens; sie soll später ergänzt werden durch eine Darstellung der Soziodynamik der Art. Die Paarbildung geschieht durch langsame Annäherung bis zur völligen Vertrautheit. Es treten dabei keine balzartigen Zeremonielle auf. Nur wenige Komponenten (Simultan-rufen, Imponierstellung) sind leicht formalisiert. Die Resultate der zur Abklärung der sozialen Regeln angestellten Begegnungsversuche sind erst teilweise verwertet, doch sind wenigstens die Regeln für die Partnerwahl gestreift. Hingewiesen wird auf das häufige Auftreten von Doppel-Paarbindungen und Umpaarungen. Nur zum Gatten zeigt ein erwachsener Vogel eine grössere, sich in positiven Kontaktformen äussernde soziale Nähe. Wir bezeichnen die nicht an die Fortpflanzungsperiode gebundenen Ausdrucksformen dieses Verhältnisses als neutrales Paarverhalten: es sind Kraulen, Schnabelberührung, Füttern. Kraulen: Die gegenseitige Gefiederpflege bleibt auf Kopf und Vorderkörper beschränkt, was sich als eine noch im Kontaktverhalten bestehende Distanzierung aus-deuten lässt (S. 17). Schnabelberührung : Kurzes Verzahnen der Schnäbel als Kontaktgebärde. Auftreten in vielseitig abgewandelter Situation, z.B. zur Begrüssung, als Besänftigungsgebärde, zur Bekräftigung der Paarbindung bei "Gefahr von aussen" (S. 22), als Kontroll-Schnabelberührung zur Synchronisierung der Gatten während des Fütterns. Die formalen Übergänge zur Verwendung des Schnabels zu Kampf, Kraulen und Füttern regen Überlegungen über die mögliche Genese aus einer dieser Verhaltensweisen an. Die Frage bleibt aber offen, solange keine Vergleiche mit verwandten Arten vorliegen (S. 26 ff.). Füttern: Während der Brutphase wird das Weibchen vom Männchen gefüttert und frisst nicht selbständig. Oft hält sich das Füttern über die Brutphase hinaus und wird also Teil des neutralen Paarverhaltens. In der Kette der Komponenten BettelnSchnabelberührung-Aufwürgen-Übergabe ist beachtenswert die zur Übergabe des Futters unerlässliche Synchronisation der Tiere (S. 19) und der Bereitschaftsruf (S. 20), der die Kontroll-Schnabelberührung ersetzen und den Ablauf wesentlich beschleunigen kann. Balz und Paarung: Der Balztanz des Männchens besteht vor allem aus mannigfachen Bewegungsinitien als Ausdruck der sexuellen Erregung. Jedes Männchen hat einen individuellen Balzstil, indem es nur eine Auswahl der artspezifischen Komponenten ausführt. Einige Beispiele versuchen dieser Tatbestand näher darzustellen (S. 35 ff.). Besondere Probleme der Stimulation stellt die aussergewöhnliche Länge des Coitus (S. 46). Bedeutsam ist auch das sowohl in Vorspiel wie Nachspiel eingeschaltete Füttern - es stellt schwierige Fragen der Motivation (S. 45). Die Motivation des Paarverhaltens ist erst teilweise geklärt. Auch generelle methodische Probleme sind noch offen. Von den Beobachtungen her drängt sich die Feststellung auf, dass der Zusammenhalt des Paares durch eine positiv-soziale Tendenz gewährleistet wird, die im Sinne von CRAIG-KORTLANDT zu der "quiescing situation" des Beisammenseins in einer bestimmten sozialen Distanz führt, und damit die Grundlage zu den für diese Stufe der sozialen Nähe typischen Kontaktbewegungen bildet. Sie wirkt dem Auseinanderfallen der Gemeinschaft entgegen und als kampfhemmendes Element auch formend auf Balz und Paarbildung.
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Quantitative Aspects of Mating Behavior in Drosophila
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Individual Samarkand wildtype D. melanogaster males were permitted the choice between either two white-eyed or two red-eyed females or between a red-eyed and a white-eyed female. Observations of the flies were made over a period of about two hours and premating periods, intermating periods and the durations of copulations were recorded. Approximately 82% of the males copulated first with white-eyed females and the premating and intermating periods before copulations with white-eyed females were significantly shorter than before the copulations with red-eyed females. The red-eyed females tended to resist the courtship of the males while the white-eyed females were more passive. The type of the second female present had little influence on whether or not the males would copulate a second time. However the red-eyed females were stimulated to mate sooner than the white-eyed females when a previous copulation had occurred in the vials. With each type of female, the average durations of the second copulations were longer than the first. The durations of the second copulations were positively correlated with the durations of the first. The correlations were low but very significant.
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Egg Shell Removal By the Black-Headed Gull, Larus Ridibundus L.; a Behaviour Component of Camouflage
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The Black-headed Gull removes the empty egg shell shortly after the chick has hatched. The present paper describes some experiments on the function of this response, and on the stimuli eliciting it. Carrion Crows and Herring Gulls find white eggs more readily than normal gulls' eggs; it is concluded that the natural colours of the eggs afford a certain degree of cryptic protection. When normal eggs are given an egg shell at 15 cm. distance their vulnerability is greatly increased; this "betrayal effect" decreases rapidly with increased distance between egg and shell. We therefore conclude that egg shell removal helps to protect the brood from predators. As reported by C. BEER (1960) the Black-headed Gull removes a surprisingly wide range of objects from the nest. Large scale tests with egg shell dummies in which colour, shape, size and distance from the nest were varied showed that objects of all colours are carried but that "khaki" (the normal ground colour of the egg) and white are particularly stimulating, while green elicits very few responses. Egg shells elicit more responses than cylindrical rings of the same colour, and these are responded to better than "angles". Size can be varied within wide limits; very large rings elicit fear which interferes with removal. Various other indications are mentioned which show that the score as obtained in the mass tests does not accurately reflect the responsiveness of the reaction itself but rather the result of its interaction with other behaviour tendencies. The eliciting effect decreases rapidly with increasing distance. On the whole, the gulls' response is very well adapted to its main function of selectively removing the empty shell, but the relatively high scores for objects which have very little resemblance to egg shells suggest that it is adapted to the removal of any object which might make the brood more conspicuous. A pilot test showed that gulls which have incubated black eggs respond better to black egg shell dummies than normal gulls. The lack of promptness of the response as compared with non-colonial waders (Ringed Plover and Oystercatcher) is adaptive, since it tends to reduce predation by other Black-headed Gulls, which are shown to prey selectively on wet chicks. A hitherto unrecognised function of territory is suggested. In a discussion of the entire anti-predator system of the Black-headed Gull its complexity and its compromise character are stressed: the safety demands of the individual clash with those of the brood; there are conflicts between the several safety devices which each benefit the brood; and there are clashes between the ideal safety measures required by each type of predator.
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Agonistic Behaviour Among Blue Tits At a Winter Feeding Station
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Agonistic behaviour in Blue Tits was observed at a feeding station from January 26 to March 15, 1959. The behaviour observed when two birds met at the feeding station was broken down into separate elements to relate behaviour with underlying tendencies to attack, escape, or stay. Encounters between birds were brief and considered instantaneous. The presence of an erect crest and fluffed body feathers was associated with an increased tendency to escape. Facing the rival, horizontal body, erect nape, raised wings, and fanned tail were indicators of an increased attack tendency. An open beak was given largely by an aggressive bird with a strong tendency to stay rather than attack. Maximum probabilities of correctly predicting the outcome of an encounter between two birds by using different combinations of behaviour elements were 0.48 for attack, 0.94 for escape, and 0.79 for staying. Hence much of a bird's motivation to attack or stay was not reflected in its external behaviour. Attack and escape both decreased in frequency from January through March. Birds also tolerated each other at closer distances. Likewise the behaviour elements associated with attack and escape tendencies diminished in frequency. This reduced the observer's ability to predict from a bird's behaviour if it would attack or escape. The reduced agonistic behaviour with season may have been the result of increased social organization of the birds using the feeding station, habituation to the strange stimuli associated with the feeder, or to increased hunger. The agonistic behaviour elements had strong signal value. If a bird showed behaviour elements indicative of an escape tendency, the rival escaped less and stayed more. Likewise aggressive behaviour in one bird elicited increased escape and reduced attack in the second. Finally, appeasement behaviour in one bird resulted in less attack and less escape in the second bird. The probabilities of attack, escape, and staying following a particular combination of behaviour elements changed with season. Therefore behaviour elements are not perfect reflectors of the underlying motivation of a bird.
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Territorial Behaviour of Juvenile Atlantic Salmon (Salmo Salar L.)
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1. The territorial behaviour of young Atlantic salmon is described from observations made in the field and the laboratory. Six agonistic activities occur during the defence of territories; these are charging, nipping, chasing, frontal display, lateral display and fleeing. Certain colour changes of the fish are associated with extremes of aggression and submission. 2. The causation of the six agonistic acts is discussed. Charging, nipping and chasing result from high attack tendencies; fleeing is a result of high escape tendencies. Frontal and lateral displays occur as a result of conflict between attack and escape and are most common during fights between two aggressive fish when conflict is presumed to be high. Frontal display indicates relatively high levels of the tendency to attack; lateral display of the tendency to escape. 3. Agonistic behaviour among aquarium-held fish fluctuates with several factors. Territories are not defended actively until after a period of adaptation to new surroundings, particularly if the fish have been kept in crowded holding tanks for some time. Agonistic encounters increase with more frequent feeding, due probably to better condition and greater activity of the fish, resulting in more frequent infringements of territories. Gradual increase in numbers of fish in an aquarium leads first to an increase, then to a falling off in agonistic activity, as the non-territory-holding fish, which are moderately active with small numbers of fish present, form a closely-knit, stabilized group as the aquarium becomes crowded. 4. The territories of young salmon appear to be primarily feeding territories. The behaviour associated with their maintenance is important for optimum growth and survival and for maintaining position for long periods in fast flowing streams. The fate of hatchery-reared fish planted in rivers may be related to their ability to secure and maintain territories in competition with wild fish.
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"Rodent-Run" Distraction Display By a Passerine, the Superb Blue Wren Malurus Cyaneus (L.)
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Distraction-display as performed by the Superb Blue Wren, Malurus cyaneus, takes the form of a true "rodent-run" and is stimulated by the alarm call of the young; this display is described and illustrated. Both male and female perform, although the colouring of only the latter resembles that of a small mammal. The display in other, related, spe:ies is discussed, and it is postulated that it may be a generic characteristic developed before sexual dimorphism and speciation were manifest.
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