Numerous other loop migrations have been documented throughout the world. In the fall, the short-tailed shearwater, is observed off the west coast of North America as far south as California. At this time the species is on the eastern leg of a tremendous figure-eight circuit around the Pacific Ocean (Fig. 26). The subalpine warbler and red-backed shrikes perform loop migrations between Europe and Africa. Both pass much farther to the east in the spring than in the fall (Moreau 1961). The Arctic loon travels south across inland Russia to southern Europe but returns to its Arctic breeding grounds via the Gulf Stream on the sea because this water is open much earlier in the spring than the inland waterways (Welty 1962). [Illustration: _Figure 26. Migration route of the short-tailed shearwater. An example of an incredibly large loop migration pattern in a pelagic species. Breeding adults return to two islands in Bass Strait during the last part of October after completing a figure-eight circuit of the northern Pacific Ocean (From Serventy 1953)._] Dog-legs Dog-leg migration patterns are characterized by a prominent bend or twist in the route. Studies have shown some of these illogical, out-of-the-way means for connecting wintering and breeding areas have no biological function, but instead, are the result of tradition much like the lineage of crooked streets in Boston can be traced back to old cowpaths (Welty 1962). Many species have extended their range in recent years, but the pioneers continue to retrace the old route from the point of origin even if the new areas are not on the same axis as the earlier route. The old pathways have apparently become implanted as part of the migratory instinct in all members of particular populations even after extending their ranges considerable distances from the original.