By definition a system is "a set of principles or procedures to which something is done; an organized scheme or method".
In the pigeon sport, there are many different systems which have been developed over time and fine-tuned by the sharing and passing down of information from one fancier to the next.
The main function of any racing system is motivation.
The widowhood system of racing pigeons, essentially involves motivating the cock bird through controlled contact with his hen.
A strict regime of training, feeding and resting are of paramount importance for success with this system and as such a lot of effort is required of the fancier. However, when properly put into practice, it is seemingly the most effective way to race cock birds.
Originally the natural system was the way all pigeons were raced until Belgium fanciers discovered and developed the widowhood system.
On the natural system hens and cocks are raced whilst they are mated, breeding and feeding youngsters. While this may be doable for shorter races, it is just not feasible to expect energy-sapped pigeons to perform to the same level at long distance racing as a well-rested and primed cock bird racing home to his mate.
The jealousy system works by using a single hen to play two cocks off against one another.
Essentially, it involves allowing each cock an hour or two with a single hen (in full view of the other cock bird) to make them "jealous" of each other before being basketed. The idea is that this jealousy will encourage the cocks to race harder to get home to the hen.
The celibacy system uses the denial of the sexual urges of both the cocks and hens as the primary motivator. Unlike with the widowhood, no specific mate is used to motivate any specific bird and the birds are not allowed to raise a round of youngsters.
Manipulation of light and dark have been used in veterinary fields and farming for many years. For example, with horses increased light encourages a mare to ovulate and with chickens it causes them to lay eggs.
In pigeon racing, the darkness system manipulates the length of the day to artificially bring on changes in the moult associated with winter, during which time pigeons only moult their small body feathers and not their primary flights.