Reef heron

Egretta sacra (Gmelin, 1789)

Order: Ciconiiformes

Family: Ardeidae

New Zealand status: Native

Conservation status: Nationally Endangered

Other names: matuku moana, eastern reef egret

Geographical variation: Two subspecies, with E. s. albolineata in New Caledonia and the Loyalty Islands only

Reef heron. Adult stalking. Port Charles, Coromandel Peninsula, May 2009. Image © Neil Fitzgerald by Neil Fitzgerald Neil Fitzgerald: www.neilfitzgeraldphoto.co.nz

Reef heron. Adult stalking. Port Charles, Coromandel Peninsula, May 2009. Image © Neil Fitzgerald by Neil Fitzgerald Neil Fitzgerald: www.neilfitzgeraldphoto.co.nz

The reef heron is a dark grey wading bird most often seen in coastal areas in the north of the North Island. One or two birds may be found patrolling a rocky shoreline or nearby estuary. Although similar to the common white-faced heron it is not seen as frequently and has slightly different feeding habits. Reef herons occur throughout Polynesia, and their prevalence in northern New Zealand may reflect their preference for warmer climates.

The dark grey colour provides the bird with excellent camouflage when it is patrolling the shoreline rocks that are its main habitat. The reef heron is wary, and flies away when approached too closely. It will, however, use man-made structures for nesting.

Identification                                                                                                          

The reef heron is a medium-sized dark grey heron with a long, greyish-yellow, heavy bill and greenish-yellow legs. During the breeding season it develops long plumes, mainly on its back but with some also on its chest. It has no white face but a small streak of white may sometimes be seen on the throat. In flight it tucks its head back into its shoulders so that the length of its neck is hidden, giving it a hunched appearance. It stays fairly low unless travelling a significant distance when it may fly higher. Immature birds are brownish.

Voice: a harsh croak.

Similar species: the white-faced heron is paler and two-toned grey, with an obvious white face when adult. It has a more upright stance, and uses a much wider range of habitats than the reef heron, which is never seen away from the coast. In flight, the reef heron is uniformly dark, whereas the white-faced heron's dark flight feathers contrast with the paler grey wing coverts and body.

Distribution and habitat

Reef herons are widely distributed through eastern Asia, the tropical Pacific islands, Australia and New Zealand. Elsewhere there are two colour morphs, white and grey, with birds in intermediate plumage occurring also. Only the grey morph breeds in New Zealand, but there has been a single record of a white bird, at the Avon-Heathcote Estuary, Christchurch in June 1987. Typical grey birds may be seen in the North, South, Stewart and some offshore islands, with more birds found in northern areas.

The reef heron is a bird of the rocky shore, where it stalks around rock pools and small rivulets of water that may carry fish. It can also be seen on estuary mudflats feeding at low tide and may occasionally be seen wading in the shallow waves on sandy beaches. It is rarely seen inland.

Population      

The New Zealand reef heron population is estimated at only 300-500 birds, but they are regularly seen at the sites where they occur, and those populations surveyed appear to have been stable over the past 40 years. They are widespread and abundant elsewhere in their range.

Threats and conservation

The shoreline habitat occupied by the reef heron has ongoing threats from encroachment by development, and the birds are vulnerable to disturbance by people and dogs. The conservation status of this species was changed from nationally vulnerable to nationally endangered in 2013.

Breeding         

Reef herons are usually solitary birds, and they occur at low densities, with territories of adjacent pairs often many kilometres apart. They nest in dark places that are fairly low to the ground, e.g. in rocky caverns and under old bridges, etc. Nesting is usually September to December with the 2-3 eggs incubated by both parents. Hatchlings have dark grey down and are fed partially-regurgitated food from both parents. They start wandering near the nest after about three weeks, and continue to be cared for by the parents for a further two to three weeks. The family group may either break up at this time, or stay together through to at least February.

Behaviour and ecology

Daily feeding routines are influenced by tide cycles, with birds feed on the falling or low tide, including at night. Reef herons are usually seen individually but may sometimes be found in small groups, especially when roosting at high tide.

Food

Reef herons catch and eat small fish, crustaceans and worms. They move stealthily to catch their prey by surprise, and sometimes crouch with outstretched wings to create a shaded area underneath to entice prey within reach, which is then rapidly stabbed or grabbed. Other foraging techniques include moving carefully along the water's edge looking for prey, or using a foot to stir up the substrate in order to catch any prey so disturbed. Foraging reef herons generally ignore nearby birds of other species.

Websites

http://en.wikipedia.org/wiki/Pacific_Reef_Heron

http://www.teara.govt.nz/en/photograph/6433/reef-heron

http://www.nzbirds.com/birds/reefheron.html

References

Bell, M. 2010. A census of reef herons (Ardea sacra) in the Marlborough Sounds. Notornis 57: 152-155.

Crossland, A.C. 1992. First record of white phase reef heron (Egretta sacra) in New Zealand. Notornis 39: 233-234.

Edgar, A.T. 1978. The reef heron (Egretta sacra) in New Zealand. Notornis, 25: 25-58. Available from http://notornis.osnz.org.nz/system/files/Notornis_25_1.pdf#page=28 (sighted 22 July 2012).

Heather, B.D.; Robertson, H.A. 2005 The field guide to the birds of New Zealand. Auckland, Viking.

International Union for Conservation of Nature. IUCN red list of threatened species. http://www.iucnredlist.org (sighted 21 July 2012).

Marchant, S.; Higgins, P.J. (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1, ratites to ducks. Oxford University Press, Melbourne.

Robertson, C.J.R. (ed.) 1985. Reader's Digest complete book of New Zealand birds.  Reed Methuen, Sydney.

Robertson, H. A; Dowding, J. E; Elliott, G. P; Hitchmough, R. A; Miskelly, C. M; O’Donnell, C. F. J; Powlesland, R. G; Sagar, P. M; Scofield, R. P; Taylor, G. A. 2013. Conservation status of New Zealand birds, 2012. NZ Threat Classification Series 4. Department of Conservation. Wellington.

Recommended citation

Adams, R. 2013. Reef heron. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz

Reef heron

Breeding season
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun
Maximum number of successful broods
Unknown
Egg laying dates
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun

Reef heron

Social structure
monogamous
Breeding season
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun
Nest type
rock crevice
Nest description
Pile of sticks and other vegetable matter in a rock crevice or cave, among tree roots or under man-made structures.
Nest height (mean)
0.00 m
Maximum number of successful broods
Unknown
Clutch size (mean)
2-5
Clutch size (min)
2
Clutch size (max)
5
Mean egg dimensions (length)
46.00 mm
Mean egg dimensions (width)
35.00 mm
Egg colour
Pale blue-green
Egg laying dates
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun
Incubation behaviour
shared
Incubation length (mean)
25-28 days
Incubation length (min)
25days
Incubation length (max)
28days
Nestling type
altricial
Nestling period (mean)
35-42 days
Nestling period (min)
35 days
Nestling period (max)
42days
Age at fledging (mean)
35-42 days
Age at fledging (min)
35days
Age at fledging (max)
42days
Age at independence (mean)
Unknown
Age at first breeding (typical)
Unknown
Maximum longevity
14 years
Maximum dispersal
Unknown