GOMMENSALISM I5 



goose, arc known to seek the proximity of birds of prey at nesting time. 

 In Siberia the former species places its nest under cHffs occupied by a 

 pair of buzzards or falcons, which, it has been thought, assures the 

 geese some protection from marauding foxes. Another British species, 

 the red-necked phalarope, often seeks protection in its breeding haunts 

 in Iceland by nesting in close proximity to a sitting ptarmigan. The 

 ptarmigan is endowed with great courage and tenacity and drives off 

 the arctic skuas which otherwise persistently rob the phalaropes of both 

 their eggs and young. The wood-pigeon has also been observed on 

 several occasions nesting in the proximity of a breeding kestrel, sparrow- 

 hawk, merlin or hobby. 



The last four examples are incipient but true commensalism, as the 

 benefits are clearly confined to the side of the defenceless bird. How- 

 ever, with colonial nesters such as the weavers it is rash to assume, as 

 most observers have done hitherto, that no advantage accrues to the 

 more powerful partner. It is possible that the weavers act as sentinels 

 for the raptorial birds with which they associate during the breeding 

 season. The rather curious biblical warning given to idle gossips may 

 have been based on some acute ornithological observation in the 

 field: " For a bird of the air shall carry the voice, and that which hath 

 wings shall tell the matter." 



When the white wagtail breeds in the eyries of ospreys and eagles, 

 the association may also entail mutual benefit, for the wagtails have 

 been frequently observed and photographed hunting the insects in the 

 nests of their hosts. 



Durango has collected numerous examples of birds which 

 apparently seek protection by breeding in the middle of colonies of 

 more aggresive species. In Sweden and Finland tufted duck and turn- 

 stone nest in gull and tern colonies — in fact there it is unusual to find a 

 nest of these two birds in any other situation. They even follow the 

 colonies if for some reason the gulls and terns change their breeding sites. 

 In Britain tufted ducks nest alone in concealed situations on the edge of 

 lakes and ponds. Long-tailed tits also frequently build in colonies of 

 fieldfares. On Faro in the Baltic, although typical and suitable nesting 

 sites in the form of sandy beaches are available, the little tern chooses to 

 nest in colonies of arctic terns on stony ground. In Sweden, France and 

 America the black-necked grebe breeds in colonies of black-headed 

 gulls, whiskered terns and Frankhn's gull [Larus pipixcan). The white 

 wagtail is a regular inhabitant of gull colonies on the coast of Finland. 



