An Analysis of the Display of the Goldeneye Duck (b uCephala Clang Ula (L.))

1. A quantitative analysis, based on 22,000 feet of motion picture film, was carried out on the sexual display of the Goldeneye duck (Bucephala clangula (L.)). 2. Each of the actions performed during display is described, and its duration is given as a convenient measure of rigidity or stereotypy. 3. Goldeneye display is divided into two main categories, flock display and precopulatory display. On the whole the actions performed in the two categories are separate and distinct. Birds going through flock display may start precopulatory display without a sharp break, so that flock display may be regarded as a preliminary to precopulatory display. 4. An analysis of the duration of the actions revealed that individuals are more stereotyped in the performance of their actions than the population, and that individuals can sometimes be classed as "fast" or "slow" in their performance. There is also a tendency for a bird who is, for example, "slow" in one action to be "slow" in another action. 5. An analysis of form showed that three of the actions are performed to the right or to the left. Two of these actions are alternated from side to side, one of them with extraordinary precision. The third action, occurring after copulation, is usually given to the right. 6. The analysis of precopulatory display shows that the male gives eight actions and the female three. During the main body of the display, the male swims around the female, while she remains motionless in a prone posture. The male then repeatedly performs five of the eight actions. These actions are given with different frequencies, so that each does not have an equal likelihood of occurrence. 7. The male actions are not given in a fixed sequence. However, some of the actions tend to follow one another at a higher than chance frequency. 8. The male's precopulatory behavior starts with a set action and ends with a set sequence of actions. The middle portion of the display is made up of actions which are not given in a set sequence. When the frequency of the actions in the middle portion changes, copulation is unsuccessful. The performance of the display actions at set frequencies may, therefore, be a necessary part of the male's performance. 9. The male always gives two, and sometimes four, postcopulatory actions, while the female gives two. These actions occur only after successful copulation, and therefore are part of a one-to-one stimulus-response interaction. 10. In flock display there are fourteen male and four female actions. The actions of both male and female occur with different frequencies, five of the male actions being very rare. Several of the actions are strongly associated with territorial defense and fighting, and therefore occur much more frequently on the breeding grounds than on the wintering grounds. 11. Both the males and females tend to order or link some of their flock display actions. When an ordering effect does exist, it is usually a "one-way" ordering, that is, two actions are likely to occur in one order, but not in the reverse order. Pairs of actions, repeatedly alternated, are also found, but they are rare. 12. An analysis was made to see whether an action by one bird was a stimulus eliciting a specific response by another. With the exception of the postcopulatory actions, which must be stimulated by copulation, no one-to-one interactions were found. Some of the actions used in territorial defense tend to be associated with specific stimuli by another made. However, the general conclusion is that specific stimulus-response interactions are rarely found. 13. Two other factors, the number of birds in a flock and the distance between birds, were analyzed. Both distance and number of birds influenced the actions performed, but did not determine them to any large extent. 14. The data is discussed in relation to the evolution and the functions of courtship behavior.