44 PHILOSOPHY OF ZOOLOGY. 



stinence, since, as Gates by remarked, every day affords 

 an increase of warmth, and a supply of food. Hence we 

 need not perplex ourselves in accounting for the continu- 

 ance of their flight, or their sustenance in the course of it. 

 Such journeys would be long indeed for any quadruped, 

 while they are soon performed by the feathered tribes. 



It is often stated as a matter of surprise, how these birds 

 know the precise time of the year at which to execute their 

 movements, or the direction in which to migrate. But this 

 is merely expressing a surprise, that a kind and watchful 

 Providence should bestow on the feathered creation powers 

 and instincts suited to their wants, and calculated to sup- 

 ply them. How, we ask, does the curlew, when perched 

 upon a neighbouring muir during the flowing of the tide, 

 know to return at the first of the ebb, to pick up the acci- 

 dental bounty of the waves ? How are the sea-fowl, in hazy 

 weather, guided to the sea-girt isles they inhabit, with food 

 to their young, which they have procured at the distance 

 of many miles ? " The inhabitants of St Kilda,*" says Mar- 

 tin, " take their measures from the flight of these fowls, 

 when the heavens are not clear, as from a sure compass ; 

 experience shewing, that every tribe of fowls bend their 

 course to their respective quarters, though out of sight of 

 the isle. This appeared clearly in our gradual advances ; 

 and their motion being compared, did exactly quadrate 

 Avith our compass.*" 



In the course of these annual migrations, birds are some- 

 times overtaken by storms of contrary wind, and carried 

 far from their usual course. In such cases, they stray to 

 unknown countries, or sometimes are found at sea in a very 

 exhausted state, clinging to the rigging of ships. Such ac- 

 cidents, however, seldom happen, as these birds, year after 

 year, arrive in the same country, and even return to the 

 same spot. The summer birds of passage return not, it is 



