How did the range contraction in the UK affect the Sea Eagle's gene pool?

Genes suited for heavy pesticide use were lost

The massive reduction in the occupied territory experienced by the White-Tailed Eagle across continental Europe and the United Kingdom acted as a profound evolutionary filter. When the species faced severe declines due to persecution and habitat loss, particularly leading to extinction in the UK in the early 20th century, the genes carried by the surviving remnant populations were drastically altered. This contraction meant that any genes providing adaptations necessary for survival under intense modern pressures—such as surviving heavy pesticide exposure, direct human hostility, and scarcity of prey—were eliminated from the gene pool of the remaining birds. Therefore, the genes best suited for resilience against these specific contemporary threats were unfortunately lost during the bottleneck event.