European starlings and eastern bluebirds both nest in naturally occurring cavities. in areas where both species occur, starlings often evict bluebirds from their nesting holes and raise their own young there. this is an example of:

Competition

Explanation:

The organisms living in a particular ecosystem constantly interact with each other and these interactions are of different types:

1. Mutualism

2. commensalism

3. predation

4. competition

5. parasitism

In a situation where there are limited resources are available and the species present in the ecosystem want to utilize the similarly limited resources and thus, do not want to compromise this leads to competitive interaction.In the case of competition one of the species tries to eliminate the other species and the fittest wins.In the given case it can be seen that both the starling and the bluebird occupy cavities and hence, compete with each other, however, the bluebirds are evicted by the starlings and hence, this is an example of competition.