Hackle
The hackle is a clipped plume or short spray of coloured feathers that is attached to a military headdress, with different colours being associated with particular regiments. In the British Army and the armies of some Commonwealth countries, the hackle is worn by some infantry regiments, especially those designated as fusilier regiments and those with Scottish and Northern Irish origins. The modern hackle has its origins in a much longer plume, originally referred to by its Scots name, "heckle," which was commonly attached to the feather bonnet worn by Highland regiments (now usually only worn by drummers, pipers and  bandsmen). The smaller version originated in a regimental emblem adopted by the 42nd Royal Highland Regiment, to be worn in the sun helmet issued in hot-weather postings from the 1870s. British Army. Hackle colours in British fusilier regiments. Modern fusiliers. In the modern British Army, there is a single regiment of fusiliers, plus a battalion of a large regiment. Hackle colours are: Other ranks of the Royal Welsh, the regiment that was formed by the amalgamation of the Royal Welch Fusiliers and Royal Regiment of Wales, continue to wear the white hackle of the Royal Welch Fusiliers. Historic fusilier  regiments. There were several other fusilier regiments which have been amalgamated and no longer exist. The hackle colours worn were as follows: Non-fusilier regiments. Non-fusilier regiments which wear the hackle are: Royal Regiment of Scotland. Following the amalgamation of the regiments of the Scottish Division to form The Royal Regiment of Scotland on 28 March 2006, the following hackles are being worn by the regiment's constituent battalions: Whilst the white hackle of 2 SCOTS, red hackle of 3 SCOTS and blue hackle of 4 SCOTS have a known ancestry, the origin of 1 SCOTS black hackle and  5 SCOTS green hackle are not clear and have no apparent precedent. It may be that the black hackle of 1 SCOTS simulates the black-cock tail feathers originally worn in the 1904 pattern Kilmarnock Bonnet and latterly in the regimental Glengarry Cap by the Royal Scots and King's Own Scottish Borderers, who merged in August 2006 to form 1 SCOTS. Alternatively, it may be a sympathetic gesture to a former Lowland regiment, the Cameronians (Scottish Rifles), who went into 'suspended animation' in 1968 (and later disbanded), who wore a black hackle in their rifle green dress Balmoral. The  adoption of the green hackle now being worn by the Argylls battalion (5 SCOTS) is no doubt a continuation of that regiment's association with the colour green, most prominent in the hue of their regimental kilts and stripes on their regimental association ties. (It is, however, worthy of note that in the 19th Century, all line regiments of the British Army used to designate their "light company" with a green hackle.) The Regimental Band of the Royal Regiment of Scotland does not wear the hackle. However, the Highland Band of the Royal Regiment of Scotland (Territorial Army) continues to  wear the red hackle with the Tam o' Shanter. Tradition holds that the black hackle originated as a Scottish tradition of wearing a black feather in your hat to signify you have an ongoing quarrel with someone. Other regiments. Former non-fusilier regiments, now amalgamated, which also wore the hackle were: Other armies. Australian Army. There are five Army Reserve Regiments with Highland Companies in the Australian Army which wear the hackle: Canadian Army. There are several fusilier regiments in the Canadian Army which wear the hackle (the French-speaking fusilier regiments do not appear to do so): Scottish-influenced  non-fusilier regiments which wear the hackle include: Irish-influenced non-fusilier regiments which wear the hackle (on the caubeen): Dutch Army. A few infantry regiments in the Dutch Army wear the hackle: Indian Army. In the Indian Army, a few selected infantry regiments wear the hackle: South African Army. Scottish- and Irish-influenced regiments which wear the hackle include: