wild at the time. After the disappearance of the passenger pigeon, the population of another acorn feeding species, the white-footed mouse, grew exponentially because of the increased availability of the seeds of the oak, beech and chestnut trees. It has been speculated that the extinction of passenger pigeons may have increased the prevalence of tick-borne lyme disease in modern times as white-footed mice are the reservoir hosts of Borrelia burgdorferi. Diet Beeches and oaks produced the mast needed to support nesting and roosting flocks. The passenger pigeon changed its diet depending on the season. In the fall, winter, and spring, it mainly ate beechnuts, acorns, and chestnuts. During the summer, berries and softer fruits, such as blueberries, grapes, cherries, mulberries, pokeberries, and bunchberry, became the main objects of its consumption. It also ate worms, caterpillars, snails, and other invertebrates, particularly while breeding. It took advantage of cultivated grains, particularly buckwheat, when it found them. It was especially fond of salt, which it ingested either from brackish springs or salty soil. Mast occurs in large quantities in different places at different times, and rarely in consecutive years, which is one of the reasons why the large flocks were constantly on the move. As mast is produced during autumn, there would have to be a large amount of it left by the summer, when the young were reared. It is unknown how they located this fluctuating food source, but their eyesight and flight powers helped them survey large areas for places that could provide food enough for a temporary stay. The passenger pigeon foraged in flocks of tens or hundreds of thousands of individuals that overturned leaves, dirt, and snow with their bills in search of food. One observer described the motion of such a flock in search of mast as having a rolling appearance, as birds in the back of the flock flew overhead to the front of the flock, dropping leaves and grass in flight. The flocks had wide leading edges to better scan the landscape for food sources. When nuts on a tree loosened from their caps, a pigeon would land on a branch and, while flapping vigorously to stay balanced, grab the nut, pull it loose from its cap, and swallow it whole. Collectively, a foraging flock was capable of removing nearly all fruits and nuts from their path. Birds in the back of the flock flew to