Summary.
Small passerine species regularly migrate across at least 600 miles of sea, and some take longer journeys, notably the Greenland Wheatear. Disputes concerning the crossing of the Gulf of Mexico, Mediterranean and North Sea are summarized.
Pre‐migratory fat seems enough for a continuous Bight of 24–36 hours and perhaps more. Most of it is lost after drift.3. Diurnal migrants tend to coast into the wind before setting out to sea, especially in weather rather unfavourable for migration. Their following of coasts has no “guiding” significance. Sometimes they coast after crossing the sea. Night‐migrants do not normally follow coastlines.
The track of migrants over the sea by day and night is normally the resultant between their heading and the wind. This type of drift is not usually responsible for big “falls”, which are often associated with overcast weather. In overcast weather at sea migrants can sometimes maintain their heading, while at other times they are disoriented (so drift with the wind). That they turn to fly down‐wind is extremely doubtful, but there are still various puzzling features about drift.
Redetermined movements occur after drifted migrants have landed.
Some other problems are discussed, and problems for future work are suggested.