26 THE SCOTTISH NATURALIST 



departure of birds on migration form an exception, and 

 occasionally Buzzards and other such wandering species visit 

 the island. Also special circumstances, such as the severe 

 winter of 1916-17, when practically all the Lapwings and 

 certain other species left the island completely, may from 

 time to time affect the bird-life of the island, but I was led 

 to the conviction that for many species of birds even a mile 

 or two of sea must constitute a very real barrier. For 

 instance, in sailing through the Kyles I have often been 

 struck by the fact that one does not see any birds crossing, 

 though bees, on the other hand, are continually seen. 



The one really remarkable exception to this rule lies in 

 the daily passage of Rooks and Jackdaws from the Craigmore 

 shore to Toward, in Argyllshire, a distance of about two 

 miles. About nine o'clock in the winter mornings the Rooks 

 gather in little parties on the shore, and, usually after a little 

 delay, set out for the other side. For about an hour little 

 parties are crossing constantly, but between 10 A.M. and 

 3 P.M. hardly a bird can be seen making the passage. At 

 about three or four o'clock, according to the time of 

 year, the return journey takes place. The birds usually 

 arrive in one or two large flocks, at times up to four 

 hundred in number. Sometimes, curiously enough, they 

 return from the Ayrshire coast, about five miles distant, but 

 usually from the Argyllshire side. It is to be noted that the 

 order of crossing is never reversed. I have never seen 

 Rooks arrive in the morning in winter, or leave in the 

 afternoon, from which it would appear that though the Bute 

 Rooks cross to the mainland, the mainland Rooks do not 

 commonly cross to Bute. In spring and summer Rooks are 

 to be seen coming and going more or less at all hours of the 

 day, but never in large flocks. I have no doubt that these 

 birds are in fact always Bute Rooks. They always make for 

 their rookeries on their arrival, some stopping at the Craig- 

 more rookery, and some even going on towards the Kingarth 

 rookery at the other side of the island. I may say in 

 passing that I had these birds under regular observation for 

 about a year, I kept a kind of "crow-diary," with the 

 arrivals and departures carefully noted till I had many scores 



