Northwestern Crows (Corvus Caurinus) Search Along the Waterline During Low

Multiple Choice

Northwestern crows (Corvus caurinus) search along the waterline during low tide for whelks, or large snails. Which of the following statements about crows and/or the whelks they prey upon is TRUE?

A) Crows pick up a whelk and then carry it to a collection of whelks located in a safer feeding area away from the waterline.
B) Crows pick up a whelk, carry it over rocks, fly almost vertically upwards, then drop the whelk.
C) Large whelks are so heavy that carrying them costs more energy than the whelk supplies in calories.
D) Whelks are preyed upon only until clams are available, at which point the preference shifts entirely to clams.