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An introduction to the behaviour of the goldeneyes : Bucephala islandica and B.clangula (class aves, family anatidae) Myres, Miles Timothy

Abstract

In the summers of 1955 and 1956 a field study was undertaken on the behaviour (locomotory, comfort, agonistic, courting, coition and brood) of the Barrow's Goldeneye (Bucephala islandica) in the Cariboo District of British Columbia. This is the first stage of a five year study of the behaviour of Sea Ducks of the Tribe Mergini. An attempt has been made to summarise the behaviour of B.islandica and also of the closely-related species B.clangula, that is described in the literature. Generic similarities, and specific differences, in the courtship displays of these two species have been described. An attempt has been made to discover the likely sources of these displays from among the locomotory, comfort ar agonistic behaviour patterns. Illustrations of the postures and movements described in the text have been made from films by the author, and two other sources. An attempt has been made to link items of behaviour to the ecological, biological and systematic aspects of duck biology. Thus both the behaviour itself comes to have a biological setting and raison d'etre, and behavioural aspects of breeding and population biology, and population management and manipulation, may be better understood. Among Comfort Movements Drinking appears to have given rise to a courtship display found chiefly in the pre-coition sequence. Wing- and Leg-Stretching is also a comfort movement found in display (only in the pre-coition behaviour). Preening generally (especially Splash-Bathing) occurs frequently under conditions of stress e.g. after a territorial encounter and after coition. The Upwards-Stretch, Wing-Flap, Tail Wag complex of movements is also frequent under conditions of stress, and occurs especially as a "signing-off" (? appeasement) display at the end of an encounter. Agonistic behaviour is interesting, in that the diving ducks tend (goldeneye particularly) to use underwater diving as their major aggressive tactic. Threat may derive from intention diving. The "alarmed" position is hard to derive from other postures. Inter-specific aggression is frequent and indicates that the Aythyini are more of an irritant to goldeneye than are the Anatini. Case-histories of inter-specific aggression helped to throw light on the nature of territory in goldeneye, and on fatigue and refractory periods in the attack motivation. Goldeneye have a wide variety of courtship displays. The Head-Up and Head-Raised positions (with the Neck-Withdrawing movement) are rather alike in the two species. The Head-Throw of B.clangula is much more extreme in form than the equivalent movement in B.islandica. In B.islandica the Pseudo-Kick and Kick are much less differentiated, than the Head-Throw and Head-Throw-Kick of B. clangula. An analysis is made of the two forms of pumping motions, to show their basic similarity, but species differentiation. The Coition Sequence is very similar in the two species. There is a marked Post-Coition display. The downies leave the nest by scrambling up the inside of the nest cavity, and tumbling from the nest-hole all together. The female has a special call which is used to force all the downies off at one time. On the lake the same call gathers the young together around the female. The importance of this means of ensuring that the young fledge together is discussed. The actions of the female at fledging are described. Females are poor guardians of broods, but they show considerable hostility towards each other during the brood period. Downies greet each other and the female by a movement which at first resembles the Rotary Pumping of the adult drake, and the female. Rotary Pumping thus is a "greeting" movement.

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