Designed by scientists from Cordoba, it is a kind of metal harness that fits over the back of the birds and controls the passage between different pens or environments.

The scientists call their invention the "individual physical barrier". It is a small metal bar placed in the back of the bird that slightly exceeds the width of the body and is secured with a harness provided by two elastic bands of cloth around the base of the wings.

"It works in conjunction with a fence that divides the environments and contains an opening for a door that cannot be crossed by birds carrying the device on their backs, while those that do not have the device can cross freely," he explained inventor of the device and project leader, Dr Diego Guzman, a member of the group of Dr Raul Marin at the Institute of Biological and Technological Research (IIByT), from the National University of Cordoba (UNC) and CONICET.

In experimental studies with quail, the device proved to be effective to prevent the birds moving between different environments.

Dr Marin said the individual physical barrier overcomes many methodological difficulties in research. Studies of social interactions in animals, he explained, are often made in conditions in which all individuals interact, like it or not.

"In other cases, birds can be seen, smelled, and/or heard, but can not physically interact," said Dr Marin, who is also a researcher at the Institute of Science and Food Technology (ICTA) at the UNC.

However, the new system allows studies where some birds can "choose" to stay in the room with other birds carrying the device or move to a different area. In this way, some birds can choose whether to access different resources found in different rooms, or whether to physically interact with their peers, for example by mating or fighting.

But if the social encounter in that environment is negative, for example if they lost a fight or mating partners were not attractive, the birds can return to the starting room, except those carrying the harness device.

"The novelty of this system is that the bird can repeat these visits at will and thus effectively self-regulate their social contact," Dr Guzman said.

Their study, published in the scientific journal Poultry Science, provides evidence that use of the device does not affect the behaviour of birds. It did not alter their movement, or their fear responses or recognition, nor their reproductive behaviour, Dr Guzman explained.

The use of this resource opens a new workspace in studies of interaction, motivation and social preference of birds, the scientists say.

"A better understanding of these aspects lead to perfecting the management guidelines and selective breeding programmes. These processes have important consequences both economically and for the welfare of birds during their intensive farming for human consumption," the researchers said.

The device could also have a direct application in the poultry industry, for example, breeding chickens for meat. In such cases, birds should be in pairs, but males can not too much because they would be unable to mount the female, among other consequences. On the other hand, if food is rationed too much, this would lower the number of eggs that each female produces.

One solution would be to provide males with the device and put extra food in another room so that only females can access it, Dr Guzman said.

However, more testing of other prototypes is required according to the size of different birds to prove their efficiency, said Dr Marin.