As a dane, this is the very first time I have heard the story about Scottish and Irish mercenaries settling in Denmark.
How many are we talking about and in what period. It would also be nice with some sort of documentation of your claim.
Haplogroups_In_Europe , Also anything on Wikipedia.org on Y Haplogroups concerning R1b (Alpine/Celtic). Most Norse, Balts, and Slavs are haplogroup R1a, which split from R1b an estimated 8,000 to 9,000 years ago. So called Scots, often Irish, were commonly used as mercenaries in the 16th and 17th centuries.
The supposed Danish massacre of the male population of Stockholm in 1520 (ordered by Christian II) was actually a mutiny by many Celtic mercenaries, who had not been paid in months. It is thought Christian only wanted certain hostile members of the nobility beheaded, but it grew into an orgy of murder and robbery that lasted for three days and eliminated most of the city's male population..
Gustavus Vasa forgave those of the Scots who didn't return to Denmark or Poland, used them in his army, and resettled them in the Vasternorrland area, from Virdso inland to the Norwegian border. Look for maps showing either R1b haplogroup or blood type O (Norse are heavily type A, alpines O)on the Swedish map and you will see that area of north central Sweden is quite different from the rest of the country.
In Denmark by comparison, the R1b gene seems to be evenly spread across the country. How much of the gene is from retired soldiers and how much from the many Scottish merchants and peddlars in the Baltic area is an open point of contention, but it should be noted that this is a Y chromosome, from male ancestors only. Also, if Sweden is any guide, much of the male population was eliminated in the 1600's, from the constant wars. Much of Sweden's Finnish population moved to that country during that time, to fill large areas of empty space, but there seems to be almost no Finnish movement to Denmark.
I haven't yet gotten any information on mtaDNA in Denmark, the female line of decent. If the amount of Celtic blood is noticably less among ancestral women, I imagine that would imply soldiers marrying local women. If the number approaches the male amount, I think that might signify merchants bringing their families to settle in areas that had lost large amounts of population.
In studying Scottish history, the high point of emigration to the Baltic seems to be immediately after 1655, when large numbers of disaffected Scottish soldiers took off for the region rather than live under the rule of Oliver Cromwell. How many took their wives? Again, finding out the numbers for female DNA would give some rough figures.
I find it interesting that the Catholics and many of the Episcopalians among the Scots predominantly settled in coastal Poland, with the Calvinist Scots heading for Scandinavia.
After the treaty of Altranstadt, the Poles were required to release all their foriegn mercenaries, mostly Irish and Scot, with some German artillerymen from the Hanseatic cities. By the time the returning soldiers had marched across the lowlands and southern Scandinavia to France, they were almost all Irish, who were recruited by the French into the Brigade Irlandais, which later morphed into the Foriegn Legion. What happened to the Scots?
We can only suppose, but I would think that, sharing a common religion and more than a century's familiarity and political loyalty with the people of the area, most of them would have settled into the Flanders, Holland, Denmark, Northern Germany area. Northern Germany is too mixed to assign any real genetic markers, but the haplogroup map puts Holland at almost 50% R1b, similar to Denmarks 50%, so obviously the Dutch got their share too.
The Swedes average about 25%, with signifcantly more in the south than the north. Which would make sense, since the empty land in the north was being competed for by newly arrived Finns, probably with families in tow.
You've peaked my curiosity, and I will do some research on the female side of the equation. Soldiers,merchants, political refugees from Cromwell, land hungry settlers moving to newly emptied areas, or some combination of all?
For a quick reference, try File:R1A map.jpg - Wikimedia Commons for a good breakdown of the R1a (Norse) variation in different parts of Scandinavia. The northern part of Denmark resembles eastern England or coastal Scotland more than most of Norway or inland Sweden.
Also, go to Ask.com and punch in Modern Human Variation: Distribution of Blood Types It's part of a lesson from Palomar College School of Anthropology. You will notice that unusual blob of type O in east central Sweden, and on the type A map, the striking resemblence between northern Denmark and southern England/Wales/Cornwall. Very different from southern Norway and Sweden just across the water.