Captivity and began a breeding population in chesapeake bay

In 1962, five mute swans escaped from captivity and began a breeding population in Chesapeake bay. Today, there are over 4,000 mute swans living in the bay. each hear they eat approximately 10.5 million pounds of aquatic grasses. These grasses provide habitat for waterfowl and crustaceans, improve water quality, decrease erosion, and increase dissolved oxygen concentration in the bay. The swan are also aggressively territorial, and have been drive native birds such as tundra swans and black ducks from feeding and roosting areas.
Analyze the situation described. Then explain which of the following ecological principles could be active in each particular situation. Ecological principles: coevolution, realized niche, fundamental niche, tolerance, competitive exclusion, resource partitioning, character displacement, top-down versus bottom-up controls, trophic structure or trophic levels, keystone species, competition, disturbance 

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