Pisa's urban pigeon population (Columba livia) has decreased by about 60% in the last two decades. This information comes from a University of Pisa study published in the journal Urban Ecosystems, which examined the pigeon population trend from 2004 to 2024. During this period, the number of birds fell from around 13,000 to fewer than 5,000. The decline was most noticeable in the historic center, where the population fell by more than 65%, from over 6,000 to less than 1,000. "Having data covering such a long time span is quite exceptional and has allowed us to observe changes that are normally missed by short-term studies", says Dimitri Giunchi, professor of Ethology at the Department of Biology at the University of Pisa. According to the study, the decrease cannot be traced to a single reason, but rather to a mix of multiple contemporaneous causes that have transformed the urban environment and limited the resources accessible to pigeons. In particular, the new waste management system, which included the implementation of underground bins and door-to-door collection, appears to have played a substantial role in restricting access to readily available food sources. Other circumstances, such as the pandemic's impacts and the lockdown on people's presence in the historic center, are likely to have had a role. "This study," Giunchi writes, "demonstrates how continuous monitoring of urban populations and careful management of the urban environment can become an effective model for coexistence with wildlife in cities. In the case of pigeons, the most important solution is decreasing access to food supplies associated with human activity, addressing the causes that promote their presence rather than the animals themselves".