Roosting is when birds perch in one place to rest, sleep, or avoid bad weather. The locations of roost sites are such that they protect the roosting bird from the weather and from potential predation, especially by ground predators. Thus, roosts are often in larger trees, under sheltered overhangs on cliffs or in dense vegetation.
Roosting can occur during the day or the night. Birds that are more active during the day (diurnal birds like Greater spotted eagles), are more often awake when roosting during the day than when roosting during the night. The reverse is true for nocturnal birds, like owls.
Most birds roost individually, but some species roost communally in groups, which can be large. For example, roosts of Amur falcon (Falco amurensis) can hold thousands of birds (see this site). The composition of the groups can vary in relation to age, breeding status and season. A variety of raptor species roost communally, including eagles. Indeed, scientists have used feathers shed by eagles at roost sites as sources of DNA, and used that information to estimate population sizes (see this paper)
Greater spotted eagles at Al Jahra also roost, and they can be seen doing so during the daytime. However, it seems that they also might form loose groups to roost at night. Photos taken using a drone late in the day, show Greater spotted eagles roosting together in a Prosopis juliflora tree. The tree is surrounded by wet areas and reeds, so probably quite secure from ground predators, and well away from roads and lights. (A side note is that Prosopis juliflora is an invasive species that has spread across many areas of Arabia. Its greenness is appealing, but it is a pest species that should be removed when possible. The problem is that it is very hard to remove.
Apart from providing a secure place to rest, roosts can sometimes be a location where information can be exchanged. This has been shown in vultures from the Americas (see this paper). What happens there is that birds at the roost watch other birds as they come into the roost to see if they show signs of feeding (having a large crop), then they follow those birds the next day when they leave the roost, hoping they will lead them to food.
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