Starlings are birds that were brought into the united states from europe for breeding purposes. their numbers have increased to such an extent that they have dislodged native birds, caused crop damage. they also carry swine diseases. what role do they play in the ecosystems of the united states?
a. dominant species
b. keystone species
c. invasive species

The correct answer is invasive species.

Explanation:

A species when introduced to a new region, in the presence of favorable environmental conditions they eventually grow in numbers through reproduction. In some cases the increase in the population size interferes with the existing flora(plants) and fauna(animals) and cause irreversible damage to the environment and human inhabitants too. In the current case, Starling birds are not native to United States however, they grew in numbers creating a tough competition for the native birds for the food sources and also posed a threat to humans as they are swine-disease agent carriers and hence they are termed as invasive species.

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the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.