98 THE MIGRATION OF BIRDS. 



coast-line, by far the most broken and interrupted 

 of all, reaching from Cape Serdze in north-east Siberia 

 to Tasmania, wliich may be roughly estimated at 

 some 10,000 miles. Fifthly, we have the West 

 Indian Ocean coast-line, extending from Suez to 

 the Cape of Good Hope, a distance of some 6000 

 miles ; and sixthly, the East Indian Ocean coast- 

 line, reaching from the head of the Persian Gulf to 

 Tasmania, a distance of, say 10,000 miles. 



From these facts it may readily be seen that 

 birds which follow coast-lines have practically a 

 continuous road, easy to follow, stretching from one 

 hemisphere to the other, and long enough to in- 

 clude the limits of all but the few very widest 

 migratory flights. Birds do not, however, strictly 

 confine their flight to all the indentations of a coast- 

 line. Were they to do so, the length of their 

 journey would be enormously increased. It may 

 be laid down as a pretty general rule that during 

 actual migration flight along a coast, all the bays 

 are avoided in which the boundary headlands are 

 visible by the species of most powerful wing ; that 

 only the narrow inlets are crossed by the less 

 powerful winged ; and only the weakest fliers of 

 all follow the winding course of the land. Promon- 

 tories are also crossed to a very great extent. That 

 this is a fact is easily proved by the vast number 

 of birds that cross a headland, compared with the 

 small number that may be observed in deep in- 

 dentations of the coast ; always excepting, of course, 

 the normal migration into any area, which often 



