Final answer:
A hunter aged 14 or older must register for HIP when they purchase their first hunting license, which helps in wildlife management through tracking of migratory bird harvests.
Step-by-step explanation:
A hunter 14 years of age or older is required to register for the HIP (Harvest Information Program) when they purchase their first hunting license. Therefore, the correct answer is A) When they purchase their first hunting license. HIP registration is a mandatory requirement for hunters who wish to hunt migratory bird species. It helps wildlife agencies to better understand harvest trends and manage populations effectively.