Effect of saltmarsh loss on the dispersal and fitness parameters of Dark-bellied Brent Geese

Abstract

1. The effect of loss of a spring staging site on dispersal and on the fitness parameters fecundity and survival of Dark-bellied Brent Geese Branta bernicla bernicla was investigated. A group of marked birds from an embanked saltmarsh area was compared with a control group of birds from nearby, non-embanked saltmarshes for a period of 13 years after the embankment. 2. Both displaced and control birds were seen at numerous sites other than their ringing site; long-distance movements were detected more frequently in displaced birds during the first years after the habitat loss. 3. Displaced birds appeared to move more often to less preferred sites that were not filled to capacity than did control birds. 4. Significant differences in subsequent fecundity and survival of displaced and control birds could not be detected; it appears that the majority of displaced birds succeeded in finding good alternative sites. There was, however, a tendency for the displaced birds to have lower breeding success and to survive less well, which suggests that subtle effects of displacement may occur. 5. Even if habitat loss has no significant effects on displaced individuals, loss of a spring staging site increases population pressure on the remaining sites and may reduce fitness parameters of the population as a whole. In addition, invasion of previously unused sites leads to increasing conflict between Brent Geese and agricultural interests. 6. In order to predict impacts of future habitat changes on bird populations, many more empirical data on long-term effects of habitat loss, such as provided in this study, are needed. © 1997 John Wiley & Sons, Ltd.