European starlings are aggressive, flocking birds that are known for nesting in cavities and openings in structures. They actively seek out small gaps in vents, eaves, and siding, where they build nests using grass, debris, and other materials. 

Homeowners may first notice increased bird activity around specific entry points, followed by frequent movement in and out of openings. As nesting develops, sounds such as chirping, scratching, or fluttering may be heard within walls, ceilings, or vents. Starlings often travel in large flocks, and once a suitable nesting area is found, activity can escalate quickly. This can lead to heavy buildup of droppings, increased noise, and disruption in both residential and commercial settings. 

Nesting materials can block vents and restrict airflow, creating potential safety concerns, especially in dryer vents or exhaust systems. Over time, repeated nesting can lead to persistent issues as birds return to the same protected spaces. Because starlings are highly adaptable and persistent, infestations typically worsen without intervention, particularly if access points remain open.