About 3500 !!! Lesser Kestrels roost in the trees in a Greek village.
Original article in French:

[Google]Translation of the entire article:
[[The Lesser Kestrel ( Falco naummani ) is a small bird of prey with a length between 27 and 33 cm, strongly resembling Kestrel ( Falco tinnunculus ) (read Distinguish Falcons Kestrel and Lesser Kestrel ). It is a species primarily insectivorous but also eat small birds, reptiles and rodents.
The Lesser Kestrel is gregarious: they nest in colonies on cliffs and ancient buildings and winters in small groups. The species breeds in the Mediterranean region to China via Central Asia. It is migratory and winters in sub-Saharan Africa to West Asia. This raptor but did not migrate directly: for weeks, individuals perform pre-migration, during which they (especially the young of the year) are preparing for the upcoming trip.
They sometimes form enormous dormitories in wintering areas, usually in trees: a member of the League for the Protection of Birds was discovered in January 2007 in Senegal dormitory involving 28,600 birds. Large pre-migration gatherings are also noted in summer in southern Europe, for example in the French departments of Pyrénées-Orientales, Aude, Aveyron, Lozère and Bouches-du-Rhône (read dormitories of Lesser Kestrels in the south of France ), Spain and the Balkans (read A huge dorm Lesser Kestrels in Albania ). Before joining the site where they will spend the night, they gather in pre-dormitories (see Pre-dormitories,) Eg on pylons (read Influx of Lesser Kestrels in the south of France ).
In an article published in 2016 in the Journal of Raptor Research, Greek ornithologists presented the results of 15 years of follow-up of a pre-migration dormitory located in the city of Ioannina, in the northwest of Greece: to 3 500 falcons were counted together in August. They spend the night in Eastern plane trees ( Platanus orientalis ) growing on the shores of Lake Pamvotida and hunt grasshoppers in remote alpine meadows of 34 km. For the protection of the species, it is vital to identify and protect dormitories and hunting areas used during the pre-migration period.]]