Archer-type units have the ability to strike at flying units.
WoodsyErf-b1-p057 and Shady Elves, as well as Men, all have archers. While men have other unit types, it is possible (though unclear) that Woodsy and/or Shady Elves only have archer units, or that all such elves are automatically archers, in addition to or instead of, any other classification. It is likely, though not supported directly via the comic, that Shady and especially Woodsy elves are superior archers to all others. (As this is a common feature of such units in other games).