CAMDEN Council fears pigeons defecating on windows of Swiss Cottage Library could be a threat to public health. Officials are planning to put new netting on the roof of the 1960s Avenue Road building – designed by Sir Basil Spence – to prevent them nesting “The birds are presenting a risk to the health of employees and members of the public due to the fouling of louvre windows, which provide ventilation to the library,” a report said.