Return of displaced adults to breeding sites

Further evidence for bi-coordinate navigation in birds, and an associated map sense, comes from experiments in which breeding adults were taken from their nests, marked and released elsewhere. A watch at the nests could then reveal whether and when the marked owners returned. Experiments on more than 50 species, from songbirds to seabirds, have shown some remarkably high rates of return over distances varying from a few kilometres to more than 5000 km, depending on the species (Matthews 1968, Wiltschko 1992, Akesson 2003). Some non-migratory species, such as Eurasian Tree Sparrow Passer montanus, returned only in small numbers and only from short distances of up to a few kilometres, so they could have got back using their local knowledge (Creutz 1949). Other species returned after transportation over hundreds or thousands of kilometres, sometimes from areas they could never have visited, so they must have used other means (Matthews 1968). Among landbirds, high return rates over fairly long distances were recorded in various hirundines. Of 16 adult Purple Martins Progne subis released at distances of 2.5-350 km, all returned to their nests, but at greatly varying speeds, the most rapid involving an overnight flight of 350 km in 8.6 hours (Southern 1959). One Barn Swallow Hirundo rustica returned after release at 1725 km away (Southern 1959).

Among seabirds, some of the longest displacements involved Laysan Albatrosses Diomedia immutabilis (Kenyon & Rice 1958). Fourteen of 18 adults returned to the breeding island in mid-Pacific within 30 days, after having been transported between 2116 and 6629 km to six locations lying in different directions from the breeding place (Figure 9.3). These birds showed an extraordinary ability to return quickly over long distances, suggesting that they did not spend much time searching but knew from their release site in what direction to head in order to get home. The fastest bird covered 5148 km in 10 days after release off the Washington coast, giving a mean speed of 515 km per day. Similarly, Manx

Figure 9.3 Homing of Laysan Albatrosses Diomedia immutabilis breeding at Midway Atoll and displaced to different sites around the Pacific Ocean. Eighteen albatrosses were transported to six different sites between 2116 and 6629 km away, and 14 of them returned to the breeding island within 30 days. Grey shading indicates regular range. From Kenyon & Rice (1958).

Figure 9.3 Homing of Laysan Albatrosses Diomedia immutabilis breeding at Midway Atoll and displaced to different sites around the Pacific Ocean. Eighteen albatrosses were transported to six different sites between 2116 and 6629 km away, and 14 of them returned to the breeding island within 30 days. Grey shading indicates regular range. From Kenyon & Rice (1958).

Shearwaters Puffinus puffinus displaced from Wales to eastern North America managed the return distance of more than 4800 km in only 12 days, an average of 400 km per day (Matthews 1968).

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