A collision between an aircraft and one or more birds is termed a birdstrike. Birdstrikes may cause significant damage to an aircraft and/or, if the birds are ingested into a jet engine, a significant and sudden loss of power. If this happens during take-off or initial climb of a fully-loaded passenger aircraft, the result can be catastrophic.
Any bird is a potential hazard to aircraft, with the hazard increasing with the size of individual birds and the presence/ size of flocks of birds.