Starlings are small birds that will enter a house through any number of openings. One of their favorite spots to enter is the soffit vents, or little ventilation holes below the eave area on a house leading into the attic. These holes are typically screened off from the interior during the original construction process, but over time this screen can weaken, and starlings will push right through.
Most houses have several exhaust vents where bathroom ceiling vents exit the structure. The exit usually has little flaps or louvres. Unfortunately, starlings can easily perch on the bottom edge of that vent and use their beaks to open the flaps to enter the duct. Once they enter this space, they will quickly clog the exhaust vent with their nesting materials and, once hatched, the young chicks will wake up the household each morning at 5AM. Not fun!
Once they are inside, starlings can build a fairly large nest, and often return to the same location each spring to lay their eggs and raise their chicks. This nesting process is so ingrained in their DNA that if we seal up the hole they are using they will continue opening up new holes through similar entry points on the same house just to get back in. That is why we recommend sealing up all similar holes on a structure, even if they are not currently occupied.