ISSN: 2639-216X
Authors: Ryttman H*
The three species White-tailed Sea Eagle, Golden Eagle och Caspian Tern have different developments in Sweden. The population of the White-tailed Sea Eagle is increasing with at least 10% per year, the Golden Eagle has a doubtful small increasing population and the number of Caspian Tern breeding in the Baltic Sea is decreasing. The analysis of the survival were calculated by North, et al. maximum likelihood method. All birds in the analysis were "found dead" and found between 1988 - 2017. The number of White-tailed Sea Eagles in the analysis were 548. The calculation of the survival show that the survival to breeding age 6+ for the White-tailed Sea Eagle was 44,5% ±2,3% (s.e.), next year 82,6% ± 2,4% (s.e.) and constant survival all other years was 84,2 ± 1,2% (s.e.). Calculating the number of young to maintain a stable populationen for the White-tailed Sea Eagle with the estimated survival gives 0,66 young per pair and year. In the beginning decades of the 2000 the White-tailed Sea Eagle have a production of about 1,6 young per pair and year. With a production of 0,8 young per year and per female, the White-tail Sea Eagle would increase with 20% per year if breeding begin at 6+ and 12% if the breeding begin at 7+. In the calculation of the survival of the Golden Eagle there were 135 individuals. The survival to the age of 5+ was 30,8%±4,5% (s.e.), next year 79,4% ± 6,5% (s.e.) and the years thereafter 86,0% ± 2,8% (s.e.). If the Golden Eagle begin to breed at the age of 6+ the survival correspond to 22,7% ± 4,2% (s.e.), 90,3% ± 5,5% (s.e.) and 84,1% ± 3,4% (s.e.). If these calculations of survival for the Golden Eagle the Golden Eagle must produce 1,14 young per pair if breeding at the age of 5+ and 1,56 young if the beginning of breeding is at age 6+ . The number of young per pair between 2010 - 2019 was 1,19 young per pair and year. With a production of 0,6 young per year and female the population of the Golden Eagle increase with 4,7% if the breeding age is 5+ but decrease with 2% if breeding begin at 6+ of age.Depending of a small number of ring och found Caspian Terns (115 individuals) and with only 80 individuals in my calculations the results are very uncertain. The survival was estimated to the age of 3+ to 40,8% ± 5,7%, the fourth year 85,5% ± 6,1% and all other years 78,0% ± 4,0%. It is not likely that the birds have a higher survival the fourth year than later. If the calculation is made from the first year and later the constant survival is 81% witch is the mean of the other calculation. Using these proportions of survivals each pair must produce 1,15 young per year to maintain a stable population. The Sweden and Finland populations produced 0,8 young per pair. With a production of 0,4 young per female the population would decrease with 3% per year.
Keywords: White-Tailed Sea Eagle; Population; Haliacetus albicilla
