Members of the Artamidae, especially the woodswallows, have been known to cluster together during the night and day.
Accounts have appeared in literature from the earliest days of ornithological documentation in Australia.
The habit of clustering is believed to serve two purposes: retaining body heat during cooler weather and as a social form of camouflage.

Another unusual behaviour exhibited by an Artamid is the swooping on humans by magpies.
While there is not much information on this behaviour, previous studies have suggested that magpie attacks on humans may be strongly influenced by hormone levels.
For example, recent investigations indicate that the stress hormone corticosterone may cause magpie aggression and swooping.
Members of the Artamidae, especially the woodswallows, have been known to cluster together during the night and day. Accounts have appeared in literature from the earliest days of ornithological documentation in Australia. The habit of clustering is believed to serve two purposes: retaining body heat during cooler weather and as a social form of camouflage.
Another unusual behaviour exhibited by an Artamid is the swooping on humans by magpies. While there is not much information on this behaviour, previous studies have suggested that magpie attacks on humans may be strongly influenced by hormone levels. For example, recent investigations indicate that the stress hormone corticosterone may cause magpie aggression and swooping.
Artamidae