Three acts of predation by Black-billed Magpies (Pica pica hudsonia) on small mammals indicate that magpies will not only attack prey opportunistically encountered at close range, as suggested by recent literature, but will also pursue prey detected at long distances.
Reese, Kerry P.
"Three additional cases of predation by magpies on small mammals,"
Great Basin Naturalist: Vol. 45
, Article 22.
Available at: http://scholarsarchive.byu.edu/gbn/vol45/iss1/22