Many deeds, sasine (land registry) records, and annual rentals of Orkney lands survive. As these often include the names of both owners (heritors) and tenants, they can be of considerable genealogical interest. Two forms of land tenure co-existed in Orkney for many centuries. These were odal or udal tenure which was of Norse origin, and feudal tenure of Scottish origin.
In practice most of the culivated land (townland) was held in the run-rig system where small plots worked by different tenants were intermixed in a bewildering mosaic without formal boundaries. The sowing and the harvest were shared by the tenants in proportion to their holdings. In addition each tenant had rights to grazings and turf on the commonty (the common land) which was usually poorer quality hill land separated from the townland by an earthen dyke.
The decline of udal holdings and the consequent ascendancy of larger feudal estates was accelerated by the Stewart earls (1564-1614), the episcopalian bishops of the 17th century, and the merchant lairds of the 18th century. In the mid-19th century the run- rig system gave way to the present field layout, the bishopric lands were sold and much of the common land was enclosed. Early in the 20th century the Earldom estate and many of the large feudal estates were broken up and sold to their tenants, and most of Orkney's rural land reverted to small owner-occupied farms.
Annual rental records were kept for all the large estates. In 1614 the earldom and bishopric lands were rationalised so that henceforth the Bishopric Rentals include all rents and skat liabilities in the "Bishopric" parishes (Holm, Hoy, Orphir, Sandwick, Stromness, St. Ola, Shapinsay, and Walls) and the Earldom Rentals likewise in the remaining parishes.
The earliest surviving Earldom and Bishopric Rentals have been published - see "Lord Henry Sinclair's 1492 Rental of Orkney" (W.P.L. Thomson 1996. ISBN 0907618 42 1), " Rentals of Ancient Earldom and Bishoprick of Orkney" (A. Peterkin 1820), and "The Church in Orkney" (A.W. Johnston 1940). Some of the later rentals also survive in the archives in Edinburgh and Kirkwall: these may include both rents payable and paid by the occupier, and sometimes name the heritor, occupier, and/or sub-tenant.But they are not indexed or catalogued as a single series, so searching can be laborious.The complex units of land valuation and associated terms in these rentals are explained by Thomson in his 1996 book.