European starlings often gather in large, noisy flocks, especially in fall and winter, and can quickly overwhelm a roosting site such as a row of trees, a sign, or a building ledge. They also nest in cavities, vents, and gaps in building exteriors, sometimes displacing native cavity-nesting birds.
Beyond the noise and mess associated with large roosts, accumulated droppings beneath a favoured perch can become a sanitation and odour problem. Bird control specialists can recommend deterrents suited to the site, from netting to sound and visual deterrents, to encourage flocks to relocate.