It is a widespread belief that animals in captivity behave differently from animals in the wild. In this paper it is attempted to analyse in what aspects behaviour in captivity differs from that in the wild and in what aspects it is the sa/ne. Also advantages and disadvantages of behavioural research in captivity and in the wild are being discussed. The author studies a captive colony of Humboldt Penguins (in Emmen Zoo) since 1983 and performed a study on the same species in Peru in 1987. In 1990/91 she studied Magellanic Penguins on New Island (Falkland Islands). The studies in Emmen and Peru have shown that the form of behaviour was very similar in these different conditions. In some cases a difference in frequency was observed. To summarize: the quality of behaviour was similar, while the quantity was different. While natural conditions ensure the most natural frequency of behavioural displays, research in captivity has its own advantages. It offers additional information to research in the wild, because it is possible to obsersve certain behavioural aspects in more detail Captivity also offers very good opportunity for long-term studies on an individual basis, since individuals are recognizable in an easy, non-interfering way and since individuals usually live longer than in the wild. Since seabirds are long-lived, they are suitable subjects for such a study. A combination of research in the wild and in captivity will give the best information. The relatively simple and stable environment captivity provides, makes it easier to interpret observed phenomena than in the wild. It is pointed out that also in nature conditions may vary a lot. Therefore it is suggested to regard the captive environment as one of the many conditions animals are able to cope with, which they may do by altering the frequencies of their behavioural displays. Comparisons of the frequencies of behaviour in different environments, including captivity, will be very enlightening for understanding of the functions of these displays.