52 DESCRIPTION OF THE PHYSICAL FEATURES 
also observed. A corn-crake took off its young this year in one of 
the gardens, leaving four or five rotten eggs in the nest besides, 
which we saw : it has bred here regularly for some seasons. The 
stormy petrel bred last year on the island ; but we will speak 
further on, under the different species, of the bird-life of the Pent- 
land Skerries, having kept, as usual, a careful list and notes of all 
those we saw. We had a fine smooth return passage to Huna, 
and were very glad to have achieved our visit to the Skerries. 
The cultivated area of the county of Caithness encircles the 
whole north and east portions, extending round the coast, and 
averaging in width about 2|- miles on the north coast, going, 
however, much further inland in some parts, where it follows 
the courses of the rivers, such as those of Thurso and Wick, as 
well as of the smaller burns which run to the sea. The valley of 
Thurso is cultivated to a distance of several miles inland. On the 
east coast this strip of cultivated land is narrower, disappearing at 
Duncansbay Head, as indeed it does at all the points where the 
uplands abut upon the coast-line. Near Wick it widens again, and 
for many miles inland, cultivation has gained land from the flow, 
owing to the impulse given to agriculture by the rich supplies 
of manure obtainable at the fish-curing stations — the surplus her- 
rings in abundant seasons being sold to the farmers at about 2s. 
per barrel. The cultivated land reaches along the line of railway 
to Georgemas Junction — about the highest point of the line, — and, 
stretching along both sides of Loch Watten, joins with the cultivated 
lands of the Thurso valley. There seems to be little doubt that 
this depression, richly cultivated, and holding a few oases of plan- 
tation, forms the natural highway of spring migrants, when, owing 
to the prevailing wind at the spring migration season being more 
to the south of east than usual, birds hug the coast of the Pentland 
Firth, and seek shelter and rest before attempting the further pas- 
sage of the North Sea. Thus, as we shall show, spring migrants to 
Norway are not unfrequently met with on the north-east coast of 
Caithness. 
The cultivated areas of the Thurso and Wick rivers offer 
greater inducements to spring migrants flying east. In the ex- 
