Eagles can be dangerous when provoked.  They steal food from other birds even when food is abundant.  Eagles have a strong impulse to grab things and take them back to its nest.  Sometimes this impulse results in odd things being brought to the nest.  When eagles of different ages perch in the same tree, the oldest birds usually occupy the highest perches.  The threat display of the bald eagle is the "spread eagle" of heraldy.  The feathers are erect, particularly on the head and neck;  the head is stretched up or forward;  the wings are held partly or wholly open;  and the body is held upright and slightly toward.  Physical contact is rare, but aggressive displays occasionally, lead to injury.  Eagles usually challenge birds that are likley to yeild.