Specimens of Owls to be met with in North American collections are very generally in winter plumage; and the procuring of several of the species in the spring or during the summer, is comparatively of unusual occurrence. The fully ascertaining of the seasonal changes in any species is yet desirable, even if only confirming previously known facts, or the statements of authors. It is possible that _Nyctale albifrons_ is the adult of _Nyctale acadica_. This we give as an example illustrative of the importance of further observations, and may be allowed to add that, of several American species nearly related to others of Europe and Asia, the comparison of specimens of similar ages and in similar seasonal plumage, is only satisfactory and reliable. In Western North America, it is exceedingly probable that species of this family exist which are yet unknown to naturalists. In Texas, species known as inhabitants of Mexico may yet be detected. All the Owls found in the northern portion of the United States, are in some measure migratory, and some species appear to travel in large bands, scattered over a considerable extent of country. The Snowy Owl is sometimes abundant for a few days, and then will suddenly disappear from a district, perhaps soon to appear again. The Marsh Owl appears along the river Delaware occasionally in considerable numbers, and staying but a short time, or leaving apparently only a few stragglers. We once saw what was very nearly a flock of this species, on a shooting excursion in “the Neck,” as it is called, or the point of land below Philadelphia, formed by the junction of the Delaware and Schuylkill rivers, the larger portion of which is wholly devoted to the cultivation of culinary vegetables for the market of the city. On getting over the fence into a small field, in which a crop of cabbages had been raised, the smaller _heads_ of many of which remained, we were surprised to see a large number of stalks ornamentally surmounted by Owls. They soon, however, dispersed in all directions. The Barn Owl (_Strix pratincola_), as well as the Marsh Owl (_Otus brachyotus_), we have known to occur in open fields, where but little concealment was possible. The Red or Mottled Owl is very persistent in its locality, and the same pair probably returns to the woods that it has previously occupied in preceding seasons, in some measure disregarding encroachments on its extent. In a small tract of timbered land at Powelton, the hospitable residence of John Hare Powel, Esq., surrounded by villages constituting a portion of the suburbs of Philadelphia, a pair of this species continued to appear and to raise broods of young until within a period of only two or three years past, notwithstanding constantly occurring chances of molestation.