Return Migration 355 



ritory or breeding site is referred to as homing. The reaction is par- 

 ticularly familiar among birds, but other types of vertebrates, many 

 species of insects, certain Crustacea, and some other invertebrates are 

 known to home. Even the pulmonate snail OncJiidium, after leaving 

 its home crevice in the rocks to feed in the surrounding area, returns 

 to its own particular crevice and cannot be induced to enter any other 

 (Arey and Crozier, 1921). Bees fly unerringly back to the hive from 

 distances greater than 6 kilometers. 



Homing is especially well developed among birds. The distances 

 covered are often spectacular, and the precision with which the home 

 territory is located is little short of miraculous. Although small perch- 

 ing birds may travel only 100 m or so to procure food, hawks and 

 eagles forage for many kilometers, and sea birds often range widely 

 over the ocean before returning to the home site. When investigators 

 have carried parent birds great distances away from their nests and 

 released them in unfamiliar surroundings, the prompt return of the 

 birds to their breeding sites has demonstrated the extraordinary 

 strength of the homing reaction as well as the existence of some highly 

 successful method of orientation. The fact that the performance of 

 domesticated homing pigeons improves with training and familiarity 

 with the terrain indicates that these birds use landmarks to some 

 extent, but other methods of orientation must also be employed 

 (Matthews, 1950). 



In nature birds will home across unfamiliar country and over water 

 where no landmarks exist. Perhaps the most spectacular instance of 

 homing is that of a Manx shearwater that was taken from its nesting 

 burrow on the Island of Skokholm, Wales, banded for identification, 

 and transported across the Atlantic by airplane. This bird was re- 

 leased from the Logan International Airport, Boston, Mass., on June 

 3, 1952, and arrived back at its burrow in Wales 13 days later, having 

 traversed 3000 miles of ocean. We do not know whether birds and 

 other animals use the same methods of orientation for homing as they 

 do for seasonal migrations. The whole fascinating subject awaits 

 further study. A general discussion of orientation was presented in 

 Chapter 6. 



Return Migration. Many birds, mammals, fishes, and other animals 

 move seasonally from one habitat to another, sometimes traversing 

 great distances. Journeys of this sort in which at least some of the 

 population completes a round trip are known as return migrations. 

 The most spectacular movements of this sort are found among the 

 vertebrates, but return migrations also occur in the invertebrates, as 

 exemplified by certain crabs and by butterflies (Williams et al., 1942). 



