Estuaries are important for migratory bird populations because they serve as crucial stopover points where birds can rest, feed, and refuel during their long journeys. The rich biodiversity found in estuaries provides a variety of food sources for migratory birds, helping them regain their energy reserves before continuing on their migration routes. Additionally, estuaries offer shelter from predators and harsh weather conditions, making them essential habitats for migratory birds to successfully complete their journeys.