The lengthened bill should produce no difficulties in protraction of the upper mandible and depression of the lower for the reason that in the dove there is no known resistance offered to these movements. The genus _Icterus_ furnishes an example wherein resistance is met in the process of opening the mandibles; individuals of this genus thrust their closed bill into certain fruits and forcibly open their mandibles against the resistance of the pulp by strong protraction and depression, thus permitting the juices of the fruit to lake and ultimately to be consumed (Beecher, 1950:53). Beecher refers to the technique used in fruit-eating as "gaping." The result of gaping in _Icterus_ should be the presence of a more massive set of muscles concerned with protraction and depression than is found in non-gaping groups. Beecher found the situation to be exactly as expected in that genus and in other genera which also gape. Meadowlarks (_Sturnella_) and caciques (_Archiplanus_) gape and pry in soil and wood respectively (Beecher, 1951a:422 and 426). The lengthened beak would be a problem when the White-winged Dove attempted to pick up objects such as seeds, which do in fact constitute the largest percentage of its diet in spite of its nectar-feeding habit. A similar situation exists in the genus _Icterus_, which is primarily adapted for gaping even though it shows a preference for insects when they are abundant (Beecher, 1950:53). The lengthened beak could be compensated for by (A) migration of the anterior end of the jugal bar toward the rostral tip of the bill and away from the fronto-nasal hinge with a simultaneous enlargement of the adductor muscles of the lower mandible, or (B) enlargement of the one muscle that functions simultaneously as an efficient retractor of the upper mandible and adductor of the lower mandible, namely _M. pseudotemporalis profundus_. _Mm. pterygoideus dorsalis et lateralis_ perform the same function, but because of their position on the lower mandible they, apparently, are stronger retractors of the upper mandible than they are adductors of the lower. It will be recalled that the jugal bar bears the same, or nearly the same, relationship to the cranium in the white-wing as it does in the Mourning Dove and that the heads, excluding the beaks of both species, are of nearly the same proportions. Also, _Mm. adductor mandibulae externus_ and _pseudotemporalis superficialis_, the chief adductor muscles of the lower mandible, were not noticeably enlarged in the white-wing. It is also important to note that other combinations of migration of bone and/or enlargement of muscles could successfully solve the problem of providing sufficient leverage for the proper functioning of the lengthened mandibles, but it is my thesis that the second alternative sufficed for seed-eating habits and that that is the adaptation that was established; it is, in fact, the only one present in the White-winged Dove.