Many issues can arise from refusing to acknowledge the presence of active bird nests on your site. Firstly, it will be putting wild birds at risk of danger or disruption, increasing the chance of harm coming to them. Secondly, under certain legislation such as the Wildlife and Countryside Act 1981, bird species are subject to legal protection, and it is against the law to endanger them, their eggs and their active nests. Disregarding the rules will lead to criminal prosecution such as a fine or prison sentence.