Researchers at Groningen University are using hundreds of wild starlings and jackdaws in an experiment about the impact of insomnia, RTL news said on Thursday.

Campaign group Animal Rights says the university is breaking the law by using wild birds and that animal experimentation rules state only animals bred in captivity can be used, unless there is no alternative.

The group claims the birds – up to 250 starlings and 50 jackdaws – are captured in nest boxes while young and have measuring equipment attached to their brains, after which they are are kept awake by being forced to fly in their cages. Once the relevant information has been collected, the birds are killed.

‘We do not understand why animals should suffer because of curiosity about what a shortage of sleep does to them,’ director Robert Molenaar said in a statement. The experiment, he said, is a ‘classic example of unethical animal experiments.’

The university said no laws have been broken because the experiment has been authorised by the animal testing commission.

‘The aim of the UG is to hold as few animal experiments as possible, and where possible not to use laboratory or other animals at all,’ the university said in a statement. ‘The research is being conducted within the framework of scientific sleep research and makes an important contribution.’