Towns have fought them with firecrackers, propane cannons, repellants and, sometimes, chain saws. The crow is probably the most intelligent bird on this continent and is well known for its ability to detect trouble. Crows quickly learn that a moving car is no danger, but will rapidly flee if the driver stops and gets out. In areas where they are constantly hunted, they learn the difference between a hunter with a gun and a farmer with farming implements. This degree of wariness is enhanced as the year progresses due to constant persecution by man.
Crows use a system of guards that observe and sound warnings to all other crows in the area.
These sentinels guard fields of feeding crows. They also send scouts in advance of feeding forays to check for danger. Migration Crows are called short distance migrants. Some may only move a few miles from the nesting territory to ones that move a few hundred miles. This seems to occur more in the northern climates where winters get fairly harsh.