PURPLE HERONS – ADVERTISEMENT DISPLAYS – Bird Ecology Study Group

“In early December 2012, a small colony of 25–30 Purple Herons (Ardea purpurea) was observed as they roosted up amongst the contiguous crowns of mature raintrees (Albizia saman) in Perak, Peninsular Malaysia (above).

“This heronry was a hive of activity, as birds regularly flew in and out of the treetops, leaving for and returning from their feeding sojourns. There was also constant communication between the members of this colony, as multiple cues were being sent to each other in the form of various displays. The intentions of such advertisement displays may be to:

(a) pronounce its claim over a particular nest-site,
(b) ensure the neighbours maintain a respectful distance,
(c) advertise its attractiveness/fitness to the respective breeding partner.

“In this heronry, a vast majority of the birds (80–90%) were adults adorned with breeding plumage in all their splendour. The base of the bills also took on a reddish hue.

“One of the most common gestures was the erection of its head and neck feathers (above). This may be accompanied by the inflation of the throat region.

“The next display may be referred to as the ‘Snap’, as defined by Kushlan (2011). With head and neck feathers upright, the neck is extended forwards and downwards smoothly. With legs bent, an abrupt snapping of the bill accompanies the expanded throat (above). This display is mostly directed at immediate neighbours.

“The most conspicuous display may be referred to as the ‘Stretch’, which is a typical courtship behaviour among herons (Kushlan, 2011). In the purple heron, the entire body slowly adopts an almost vertical posture, with the bill pointing and rising skywards (image 4). We wish to introduce an alternative term of ‘Spearing the Sky’ to describe this yoga-like pose. Often accompanying this display is the erection of the elongated plumes of its lower neck and scapulars. When it reaches the apex of its extension, the throat is usually puffed up and there may be brief clappering of the bill.”