The surname Tulloch is one of the most common surname on the Island of North Ronaldshay, the northernmost of the Orkney Islands, off the north coast of Scotland. In 1851, people with the surname Tulloch comprised over a third of the population of the island - 184 out of the 526 people there.
The Tulloch family were first recorded near Montrose, in Northeast Scotland, in 1363. The family were minor lairds and clergyman, known as the "Tullochs of Bonnington". One of this family, Thomas Tulloch, was appointed Bishop of Orkney in 1418, which at that time was part of Norway. Bishop Thomas was one of the Scottish nobles who negotiated the transfer of Orkney to Scotland in 1468 as part of the marriage of Margaret of Norway to the Scottish king.
Under Bishop Thomas there was an influx of Scottish clergy into Orkney so that "in Orkney not only was there not a single Norse ecclesiastic after 1450, but not even a native of the Orkneys or Shetlands". Several of these clergymen appear to have come from his extended family. This was so widespread and successful that the 1851 census, four hundred years later, recorded more Tullochs in the Orkneys than any other county in Scotland, and Tullochs in Orkney and Shetland comprised more than half the Tullochs in the entire country. The parish of North Ronaldshay recorded the highest number of Tullochs in the country. Tullochs of Ness, and also continued in the clergy for several generations. For example, Jerome Tulloch was subchantor of Orkney in 1560, covering the Islands of Rousay and Egilsay. Jerome's nephew James Tulloch was then vicar of Rousay and Egilsay in 1600.
Presence on the island
The first record of Tullochs in North Ronaldshay are through four wills registered with the Orkney & Shetland Commissory Court, whose records go from 1611 to 1825. The earliest instances are:
In 1682 there is a record of a complaint from the Reader of North Ronaldshay, John Tulloch, to the Bishop of Orkney that the parish minister, James Strachan, hadn't paid him for the last three years. The Bishop ordered Strachan to pay his "at Hallowmass next £28 Scots". The next year Strachan was transferred to the nearby parish of Hoy and Graemsay. 
The Poll Tax returns for 1693 have been published in complete form for North Ronaldsay. The returns name 136 inhabitants, excluding minor children and paupers who may have totalled around 85 additional people. 35 of the named people were Tullochs - the most popular surname on the Island at the time and just over a quarter of the population. Of the 41 households, 10 were headed by a Tulloch: the six most northern holdings (Burray, Nether Linnay, Little & Middle Senis, Wastnesse and Shaltisquoy) and four other farms on the south (Nouster, Kirbister, Ness and Hooking).
Little Senis was headed by Thomas Tullach, probably the second son of Janet of Stennis named in the earlier will, and Wastnesse was headed by William Tullach, probably her third son. Shaltisquoy was headed by Steaven Tullach, presumably the eldest son of Andrew of Shallkiscow named in his will. Middle Senis - shown on the map as just next to Shaltisquoy - was headed by another Thomas Tullach, who may have been Andrew's second son. Nether Leine was headed by Alexander Tullach, presumably the eldest son of Magnus Tulloch named in his will. Finally William Tullach was the head of Bura, with unclear connections to the earlier wills.
In 1722, James Fea, the laird of Stronsay introduced 'kelping' to Orkney, where the abundant seaweed was collected and burnt to produce soda ash, a raw material for the manufacture of glass.  Fea was soon followed by the Traill lairds, who had bought North Ronaldshay in 1727.  The kelp boom supported an increase in the population and at its height saw 3,000 tons per year of kelp ash exported from Orkney.  The industry lasted until the 1820s, when the price crashed due to the popularisation of the alternative "Leblanc process" which produced soda ash from brine. The price falls provoked a wave of emigration across northern Scotland. 
In 1733, the Rental records for the island reveal 46 households in total, of whom 18 (39%) were headed by Tullochs. 
Parish records on North Ronaldshay date from 1759 for Births and 1819 for marriages.  The FreeREG website has indexed the birth records from 1800 and all the marriage records.  Cemetary inscriptions of Tullochs recorded by the Orkney FHS date back to 1823.
In 1755, the total population of North Ronaldshay and Sanday was recorded by the Statistical Accounts of Scotland as 1250, of which it is estimated 300 lived on North Ronaldsay. This was an increase of 35% in just over 60 years. 
The first man to be press-ganged in North Ronaldsay may have been a John Tulloch from Senness, in the 1770s. He seems to have taken to soldiering and served through the American War of Independence (1775-83) before returning to the island. It appears that the Laird's representative, who controlled the allocation of crofts, took this war service into consideration and placed John Tullochs' three sons in substantial holdings. John got Ancum, Tom went to Hooking and William had the tenancy of Senness, which was then one-seventh of the Easting." 
In 1787 there were 384 people on the island, living in 61 households, of whom 43 were farmers. 
The earliest parish records reveal that there were at least 22 Tulloch families who had children baptised in the period 1758 to 1780. Based on the average above, this would indicate around 140 Tullochs on the island at the time - just over a third of the population:
This ratio is consistent with the later census returns that showed a third of the population were "Tullochs".
By the 1830s, the decline in the the value of Kelp had made the large population of the island unsustainable. The laird of North Ronaldshay can to an agreement with the laird of Eday for a group to leave the island and settle on the undeveloped side. Twenty two families, eighty people in total, migrated to Eday in 1836.  The 1851 census shows 32 people living in Eday who were born in North Ronaldshay, including 11 Tullochs:
The first nationwide censuses from 1801 to 1831 only recorded the number of people in a household. The 1841 census was the first that recorded names. The 1851 census also recorded age, relationship to the head of household and parish of birth, which makes this census a primary candidate for analysis.
In 1851, from the 526 people recorded living on the Island there were 184 with the surname Tulloch. This was the most common surname on the island, followed by Swanney with 103, Thomson with 67 and Muir with 55.
Most of the Tullochs listed were crofters (tenant farmers) with, on average, around 5 acres of farmland and a similar amount of pasturage. Of the sixty five crofts listed in the census, 23 were farmed by Tullochs. These crofts totalled 268 acres of the 865 acres in total. The number of farms on the island had increased by 22 - over 50% - since 1787. This was due to the Norse practice of inheritance where farms were divided equally between children rather than going completely to the eldest son. These small farms managed to continue being sustainable only with the added income from kelp production. 
This increase was despite the creation in about 1840 of a large, 60 acre farm in Hollandstoun near the residence of the Island's proprietor, Holland House. Five crofting families near Holland House were "warned off" their land, including one Tulloch family, in order to create the new farm. A second farm, 18 acres, was also created in Howar, the residence of the laird's "Bailie", Charles Thomson.  Other large farming families were the Keldays, with 228 acres (including all the 142 acres of farmland in Holland), the Thomsons with 133 acres and the Swanneys with 118 acres.
The population of the island declined rapidly from its peak of 547 in 1881, following the decline of the Kelp industry. Fifty years later there were less than 300 people remaining, finally plateauing at 70 people in the early 2000s. Most of the ancient crofts are now abandoned, the island making most of its living from a thriving tourism industry based around bird watching. Roughly half of the remaining population are descended from the crofting families - including a number of Tullochs - with the other half being recent arrivals.