Answer:
Females that were coupled to British males produced more eggs and chicks than those who were matched to southern birds. Every year, blackcaps with Britain-oriented genes pass on their genes to new chicks. As a result, the number of blackcaps willing to fly to Britain is constantly increasing.
Step-by-step explanation:
Females that were paired with males from the United Kingdom produced more eggs and chicks than those who were paired with males from the United States. Every year, British-oriented blackcaps pass on their genes to new chicks. As a result, the number of blackcaps eager to fly to the United Kingdom is growing all the time.