Why Young Red Kites Flock Together at Night—New Study Reveals Surprising Patterns

A new study has uncovered why young red kites often gather in large groups at night. Researchers from the Swiss Ornithological Institute tracked 216 birds over six years, analysing nearly 34,000 overnight stays. Their findings, published in the Journal of Animal Ecology, reveal clear patterns linked to age, sex, and social behavior.

The study focused on red kites (Milvus milvus) across Europe, including Switzerland, Germany, Bulgaria, and Spain. Young, non-adult birds—especially males—were far more likely to use communal roosts than females. In fact, young males were twice as likely to join these gatherings compared to their female counterparts. As the birds matured, however, their behavior shifted: by age three, visits to communal roosts dropped significantly.

These roosts, sometimes hosting dozens of birds, appear to serve key social functions. Researchers suggest they act as hubs for sharing information about feeding spots. They may also help non-breeding birds find partners or scout potential territories. Breeding pairs, on the other hand, avoid communal roosts entirely, preferring to stay near their own territories.

The study also noted that roosting sites were concentrated in areas where red kites had been reintroduced and habitats improved. Brandenburg, Germany, for example, saw the species return by 2012 after being extinct there in the 1990s. While wind farms were sometimes nearby, no evidence suggested they directly affected roosting behavior or caused collisions.

The research provides the first detailed insights into why young red kites gather at night. It highlights the role of communal roosts in social learning and population connectivity. With German breeding pairs now numbering between 850 and 1,400, such behaviors could be vital for the species' ongoing recovery.