Sparrows once thrived alongside people, but today their numbers are shrinking dramatically across Europe. Studies show that common urban species like the house sparrow have lost a large part of their population since the 1980s, with hundreds of millions fewer birds than decades ago. Unlike woodland birds that nest in trees, house sparrows depend on small wall cavities, roof gaps, and other features of human dwellings for nesting. These sites are becoming scarce as buildings are renovated, façade