Bird Ringing for Science and Conservation

From Bird Ringing to Conservation Action

Information about connectivity of breeding, resting and wintering areas as well as survival data within and among populations is crucial information for any conservation action. These data can only be collected through marked individuals, and bird ringing still is the easiest and cheapest way to gather suitable sample sizes for sound analyses.

Migrating birds are global players and what – in a human sense – could be called their “home” is, of course, not restricted to the breeding ground. Not surprisingly, reasons for population declines or increases do not always lie in the area where a bird raises its young. Ringed and recovered birds show conservationists where their breeding grounds, stopover sites and wintering areas are situated. This enables investigation of what is happening there and if any conservation action is required.

		Analysis of ringing data revealed the first quantitative assessment in the hunting of migratory birds. Despite legal protection in many countries, shooting and trapping of migrant birds is still wide-spread in the Mediterranean area where they suffer from substantial losses.
		By mark-recapture studies the impact of hunting and the possibility and prerequisites of sustainable harvesting of wild birds can be estimated.

Complex analytical methods, so-called mark-recapture analyses of marked birds, make it possible to compare survival rates between years, between regions or before and after special conservation activities. Furthermore, the impact of a special reason for mortality can be estimated. For example it was possible to show that one out of four juvenile and one out of 17 adult White Storks die each year at electrical power lines. Since the reporting probability of different causes of mortality are different, these models based on ringed and recovered individuals provide much more reliable information than any simple count of cases. It is also possible to test if a distinct reason of mortality might be offset by other reasons, thus reducing the overall effect on a population. Such analyses provide conservationists with information about the crucial issues to address and enable them to evaluate conservation effort.

Recoveries of birds reported as shot during hunting activity are of the utmost importance for the proper management of the populations of game birds. Reports of shot ringed birds are used in mark-recapture analyses to answer the question of whether hunting mortality is additive or compensatory to natural mortality and what level of harvesting of wild birds of a distinct population is sustainable. Geographical variation in the average survival rates of Robin and Song Thrush was correlated with the hunting pressure experienced by those populations. This suggests that, for these two species, hunting causes mortality that is additional to natural mortality.

Monitoring of bird populations as required by several international conventions is a prerequisite for effective protective measurements for the many declining bird species. However, counting heads does not provide information about the reasons for population changes since it does not account for survival rates, age structure, longevity or productivity in the populations. EURING holds the only long-term data set covering most bird species which can be used to study a whole range of crucial population characteristics. The potential for further co-ordinated European-wide bird ringing research is immense. EURING and the National Ringing Schemes have the potential to co-ordinate large numbers of amateur ringers for such projects (see page 17).

Recently, the African winter quarter of the highly endangered Aquatic Warbler has been discovered in the Senegal delta area.