I didn’t know this sort of thing happened. Perhaps why one sometimes sees certain birds in places one never expects to see them.
(See quots.) Hence abmigrate v. intr.
1923 A. L. THOMSON in Brit. Birds XVI. 276 Some such term as ‘abmigration’ might perhaps be used to describe the northward departure in spring, for a new summer area, on the part of birds which had made no corresponding southward journey in the previous autumn. 1929 E. M. NICHOLSON Study of Birds v. 54 Birds which are native to one country, may ‘abmigrate’, and be found breeding in another, up to thousands of miles away. 1953 New Biol. XV. 54 Abmigration occurs when a bird (usually a young one), bred in this country and wintering here, accompanies foreigners which have also wintered here to their home countries in the Spring, instead of returning to its own British nesting grounds.