Abstract:

The size of the Sand Martin population along the 556 km long Hungarian reaches of the River Tisza was 33300 pairs in 1990 and 30% of this population bred in the studied 73 km river stretch (9438 pairs). The characteristics of this population allow for an accurate annual estimate of size and survival rates. A computerized data bank has been developed to store and select surveying and ringing data which have been collected since 1986. The highest survival rate for adults was 0.503 ±0.0483 between the 1987-1988 breeding periods but since then this value has decreased to 0.294 ±0.0399 (1989- 1990) which is the same level as found in the 1986-1987 breeding period. The population size increased continuously from 1986 (6392 pairs) and reached its highest level (I 2071 pairs) in 1989. There were 9438 pairs in 1990. The Sand Martin's survival rate is also connected to weather conditions in African migratory and overwintering areas and monitoring work there would provide quantitative data not only for the population studied but also for the analysis of other species as well.