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Sep 25 2011

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Zigzag Heron (Zebrilus undulatus)

Zigzag Heron

[order] CICONIIFORMES | [family] Ardeidae | [latin] Zebrilus undulatus | [authority] Gmelin, 1789 | [UK] Zigzag Heron | [FR] Onore zigzag | [DE] Zickzackreiher | [ES] Avetigre Enana | [NL] Zigzagreiger

Subspecies

Monotypic species

Genus

Zebrilus is a monotypic genus in the family Ardeidae. It consists of one species the Zigzag Heron.
Even though the Zigzag Heron resembles a tiger-heron in its barred plumage and forest habitat, it is most closely related to bitterns. The resemblance of Zebrilus to large tiger-herons in plumage and forest habitat, and the uniqueness of some of its osteological features( e.g. small size, shape of the bill, angle of the bill with the skull, and form of the sternal keel). Like bitterns, Zebrilus has 10 tail feathers, instead of the normal 12. In addition, Zebrilus and bitterns have pure white eggs. Large tiger-herons, in contrast, have eggs that are colored and blotched (e.g. beige-yellow with reddish brown or violet blotches in Tigriornis and bluish white with paleviolet blotches in Tigrisorna lineatum. The nest of Zebrilus also is remarkably similar in some respects to those of certain bittern species. Zebrilus constructs a shallow round platform in trees or bushes between 1 and 3 m above water. Tiger-herons construct nests in trees between 6 m and 15 m above ground or water.

Physical charateristics

A small dark striped heron with black upperparts with dark cross bars. front neck and brest lighter dark buff. Underparts are buff, densely mottled brown and black at chest and less dense at abdomen. Primaries and tail black.

Listen to the sound of Zigzag Heron

[audio:http://www.planetofbirds.com/MASTER/CICONIIFORMES/Ardeidae/sounds/Zigzag Heron.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 0 cm wingspan max.: 0 cm
size min.: 28 cm size max.: 33 cm
incubation min.: 0 days incubation max.: 0 days
fledging min.: 0 days fledging max.: 0 days
broods: 0   eggs min.: 0  
      eggs max.: 0  

Range

South America : North, Central.Inhabits the Amazon basin of Colombia, Venezuela, Guyana, Suriname, French Guiana, Ecuador, Peru, Bolivia and Brazil.

Habitat

This rare species is unevenly distributed in the regions where it appears. It lives on the ground along the banks of small rivers or swampy areas in the forest, where it searches for food under fallen leaves or in the mud surrounding shallow pools. It moves by hopping, zigzagging along the ground.

Reproduction

Unknown, the text here is from a study performed in Ecuador. Nest records from two years of observation in Ecuador suggest that the Zigzag Heron breeds from April through July and that the herons may nest more than one time in one season. The Zigzag Heron appears to lay only one egg, as often reported for the Rufescent Tiger-Heron (Tigrisoma lineatum). The Zigzag Heron egg was pure white, rather than the bluish-white, often blotched eggs of the Rufescent
Tiger-Heron. Downy young appear completely yellowish-cream or white and gradually mature into the rufous immature plumage, with the darker feathers of the head, wings, and back emerging last. The bill and legs of the juvenile Zigzag Heron are yellowish-green, whereas the adult has a blackish bill and greyish horn legs. The adults were not seen near the nest as the young grew, and it is assumed that this
was due to increased time expenditures on hunting. The five nests were all shallow, round platforms averaging 17 x 22 cm. They were similar to nests of the larger Rufescent Tiger-Heron nests discovered in the same area, but they were usually ringed by a thorny edge-barrier while the Tiger-Heron nests were not. The edge-barriers were made from various thorny plants, primarily Uncaria tomentosa (Rubiaceae) and Bactris palms. The nests were found on the edge of water, either an oxbow lake or a permanent stream. Nests were placed an average of 1.5 m above the water, although up to 3 m above the water when the level was low. When built on a stream edge, nests averaged 2 m from the bank. The one egg discovered was elongated and white.

Feeding habits

Hunts prey while appearing tense and with a flickering of its tail. If the prey moves away, the bird relaxes and ceases tail movements. If the prey doesn’t move away, the usual consequence is the adoption of a more horizontal stance on the branch. The neck gradually extends as the bird leans forward on its perch preparatory to a diving strike. If the prey is immediately below the bird and the bird is perched more than 0.5 m above the water, the elongated bird reaches a position of hanging head downwards. The tail is then depressed to ?clasp? the perch. Thereafter the bird dives at its prey, partially immersing itself in the water. When perched at water level or just above it, the vertical hanging is omitted and the tail is not used as a ?clasp.? Sometimes the heron stands in a tangle of branches in the bittern-posture and catches flying insects, probably dragonflies (Odonata). Once the bird strikes at prey while standing in water up to its abdomen. In addition, small prey items are seized by pecking into the water while wading slowly or standing still. During unsuccessful1 strikes at prey, the bill often impales dead leafs floating in the water. These are removed by vigorously beating the bill against branches.
Feeds mainly small fish, invertebrates and to a lesser extend insects.

Video Zigzag Heron

httpv://www.youtube.com/watch?v=5tWs7uEM2mo

copyright: D. Fisher


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Little is known about this secretive and small heron. In Suriname it is a rare species occuring in wet forests. The Zigzag Heron may prove to be more numerous than previously thought in areas that provide the proper requirements.Among these requirements may be a closely related series of oxbow lakes with substantial lakeside vegetation and undisturbed forest. The frequency of sightings suggests that the paucity of past sightings may be a result of the secretive habits, previously unknown voice, and the specific habitat requirements of the Zigzag Heron, rather than uniformly low population numbers throughout its range. Given the knowledge of these specific habitat requirements and its voice, Zigzag Herons may be found to range widely but thinly throughout Amazonia and the Guianas.
Zigzag Heron status Least Concern

Migration

Unknown, but probably sedentary throught its Amazonian and Guianan range.

Distribution map

Zigzag Heron distribution range map

Literature

Title The voice and first nesting records of the Zigzag Heron in Ecuador
Author(s): PETER ENGLISH
Abstract: Recent sightings of the little-known Zigzag Heron ..[more]..
Source: Wilson Bull., 103(4), 1991, pp. 664-668

download full text (pdf)

Title Phylogenetic relationships of the Zigzag Heron (Zebrilus undulatus) and white-crested Bittern (Tigriornis leucolophus) estimated by DNA-DNA hybridization
Author(s): Frederick H. Sheldon, Kevin G. Mccracken and Keeley D. Stuebing
Abstract: Recently we, acquired DNA of two rare species of h..[more]..
Source: The Auk 112(3):672-679

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Title Relative Patterns and Rates of Evolution in Heron Nuclear and Mitochondrial DNA
Author(s): Frederick H. Sheldon, Clare E. Jones, and Kevin G. McCracken
Abstract: Mitochondrial cytochrome b sequence data from 15 s..[more]..
Source: Mol. Biol. Evol. 17(3):437-450. 2000

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Title Notes on the foraging behavior of the Zigzag Heron.
Author(s): Nigel J. C. Mathews & K. Brooke
Abstract: The only recent field observations reported for th..[more]..
Source: Wilson Bull., 100(l), 1988, pp. 147-148

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Title OBSERVATIONS OF THE BEHAVIOR OF THE ZIGZAG HERON
Author(s): WILLIAM E. DAVIS, JR,. PAUL K. DONAHUE & ELEANOR G. PERKINS
Abstract: Reliable sight records of’the Zigzag Heron (Zebril..[more]..
Source: Condor, 82:460-461

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