Answer by Thomas Zerbarini:
That depends on how large and how fast the aircraft is traveling. Also, how many birds the aircrafts strikes as well.
Small birds are typically a non event.
Medium birds can cause some skin dents and internal dents or popped rivets.
Large birds are the most dangerous. Large birds can cause significant damage and up to catastrophic failure of an engine, windshield or Radome nose cone.
Manufacturers go to great lengths to test engines for bird ingestion. Check out this test by GE,
As a pilot, anytime we encounter or suspect a bird strike we report that suspicion to the airport or Air Traffic Controller (ATC) to advise other pilots and airport personnel to inspect the runways for a circus or more birds that could be hazardous to other aircraft. Secondly, we'll run any appropriate checklists and determine if the flight can continue or be terminated. Upon landing, the crew will make a written maintenance entry and advice maintenance control of the bird strike Maintenance will conduct a thorough inspection on the aircraft to determine if any damage was encountered. Finally, the crew will file a written report to the company which will document the event for the company and FAA to research and/or track the bird strike event.
Bird strikes are usually not a serious event; but, they can be if the bird is large enough to cause severe damage.