MYSTI.R11, or BIRD MIGRATION.
To most of us the mystery of migration is chiefly associated with swifts and the swallow tribe. We have been given both this year and last some astonishing examples, by good observers, of the punctuality of the date when the swifts leave particular places. They quit one parish on August 14th and another on August 17th ; and it is rare for even a single bird to be seen in the last week of August. This precision and literal obedience rather to the almanac than the weather have never been explained ; but it is difficult to avoid the inference that the hours of light are directly responsible. We know that many small birds only feed when it is light and die if the abstinence of food is prolonged. This was proved years ago at the Zoo, where electric light, prolonging the feeding hours, saved the lives of many species which had previously died incontinent—of starvation. As soon as the hours of darkness extend the fasting interval beyond a certain point, the internal economy of the bird compels departure. It is perhaps worth asking aviculturists the question whether migrant birds may not be reconciled to captivity by the use of electric light. The aviculturist, after all, has the key to some secrets denied to the field observer.
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