Peregrine falcons feed almost exclusively on birds they catch in full flight. Very exceptionally, they’ll catch a bat or a prey on the ground. Thanks to the cameras by the nest, the ornithologists can study the feeding habits of the Peregrines on the cathedral. All images are automatically stored when any type of movement occurs in the nest. This way, ornithologists can count the number of prey the parents bring to their young, they can compare the male’s behavior with that of the female, note at what times the chicks are fed and see from what age the young can feed themselves.

The identification of the prey also happens by means of the cameras. But this isn’t easy. Since the parents usually pluck the prey before bringing it to the nest, it is often difficult to see what species they have caught. The prey are therefore usually identified through direct observation with telescopes and through the remains that the falcons drop from the nest. You can see this collection of feathers from prey at our observation post. A final method to identify prey, is by going through the falcons’ supplies. The falcons regularly hide prey in the bell tower. These form a spare supply in case the weather is too bad to go hunting.

The prey are enormously diverse. Since the couple took up residence in the cathedral in 2004, they have feasted on at least 44 different bird species. The smallest, the Eurasian Reed Warbler weighed about 10 grams, whereas the largest, the Wood pigeon, weighed over 500 grams. The prey that is most often caught, is the City pigeon. It’s therefore not surprising that he is found in Brussels in large numbers.  Some prey are non-migratory birds, such as the Great spotted woodpecker. In other cases, they’re migratory birds such as the Curlew sandpiper. He was caught over Brussels, while he was on his way from Africa to the coasts of the Arctic Ocean in Siberia. Mostly, their prey consists of birds that we encounter frequently, such as Merles and Thrushes. But sometimes, the falcons catch species that are very rare and that were not known to occur in Brussels, like, for instance, the Corn crake. Thanks to the falcons, the ornithologists gain a lot of knowledge about the bird collection of Brussels.

Thanks to the project, another discovery was made. The Peregrine falcons on the cathedral hunt both day and night. A surprising discovery for a species that usually is only active by day! This behavior is an adaptation to city life, because the halo of the street lights provides enough light for the falcons to also catch their airborne prey by night.  And this explains how some migratory birds that only fly at night, such as the Quail or the Grey plover, have found themselves on the Peregrines’ menu.

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Rests of a pigeon