Do birds of prey roost communally?
Though communal roosting is generally uncommon across diurnal birds of prey, it is well known within the harriers and seen in virtually all species worldwide. Communal winter roosts of 100 or more marsh harriers have been documented in the Netherlands, but congregations tend to be smaller here in the UK. Communal winter roosts of hen harriers have been studied in south-west Scotland, revealing that there is a degree of interaction between individuals when they arrive at the roost just before dusk. Communal roosting may allow birds to gauge feeding opportunities based on which individuals look well-fed, but may also reflect the availability of suitable roosting sites. Many of these winter roosts take place at traditional places, with the best known located in the south and east of England.
At mixed roosts, marsh harriers can be joined by hen harriers, merlins, peregrines and short-eared owls. Unusually for British raptors, the harriers are often seen roosting on the ground.
Though this bird flies alone, communal roosts are common among marsh harriers.