Zebrilus undulatus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Pelecaniformes Ardeidae

Scientific Name: Zebrilus undulatus (Gmelin, 1789)
Common Name(s):
English Zigzag Heron
Taxonomic Source(s): SACC. 2005 and updates. A classification of the bird species of South America. Available at: #
Identification information: 28-33 cm. Smallish, dark heron. Cryptic, brown and black vermiculated plumage. Variable leg colour.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Lees, A.
Facilitator/Compiler(s): Butchart, S., Ekstrom, J., Khwaja, N., Symes, A.
This species qualified for uplisting from Least Concern to Near Threatened (under criterion A3c) during 2008-2012 because it was projected to decline by a rate approaching 30% over the next three generations (20 years) owing to deforestation in the Amazon, based on analyses in Bird et al. (2011) using the deforestation scenarios in Soares-Filho et al. (2006). The latter projected the impacts of 27 planned road-building projects in the region: 14 of which were due to be completed in 2008, six in 2012, and three each in 2025 and 2018. Hence the majority of the deforestation was projected to result from roads built during 2008-2012, but is projected to continue because the roads will provide easier access for hunters.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Zebrilus undulatus is a poorly known species of the Orinoco, Negro and Amazon basins. It occurs in east Colombia, where it is considered rare and local (del Hoyo et al. 1992). In bordering Venezuela there have been an increasing number of records, and the species may be locally common (Hilty 2003). From here, its range extends eastwards through Guyana to Suriname, French Guiana and north-central Brazil, and south-west to east Peru and north-west Bolivia (del Hoyo et al. 1992). It appears generally very rare, but has probably been significantly under-recorded due to its elusive nature and is likely to have a wider distribution than is currently known (Restall et al. 2006, A. Lees in litt. 2011).
Countries occurrence:
Bolivia, Plurinational States of; Brazil; Colombia; Ecuador; French Guiana; Guyana; Peru; Suriname; Venezuela, Bolivarian Republic of
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:7100000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population numbers are not known.

Trend Justification:  This species is suspected to lose 14.6-18.4% of suitable habitat within its distribution over three generations (20 years) based on a model of Amazonian deforestation (Soares-Filho et al. 2006, Bird et al. 2011). Given the susceptibility of the species to hunting and/or trapping, it is therefore suspected to decline by a rate approaching 30% over three generations, although given it is elusive and under-recorded, the species is probably far more widely distributed than currently thought.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:This species occurs in the streams, pools, marshes and swamps of tropical evergreen forests, as well as in mangroves. Its diet is not well documented but is thought to mainly consist of small fish and flying insects (del Hoyo et al. 1992). It has also been observed foraging in "leaf muck" (Restall et al. 2006).
Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):6.7
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s):

The primary threat to this species is accelerating deforestation in the Amazon basin as land is cleared for cattle ranching and soy production, facilitated by expansion of the road network (Soares-Filho et al. 2006, Bird et al. 2011). It is also susceptible to hunting, for example in Venezuela (del Hoyo et al. 1992, A. Lees in litt. 2011). Proposed changes to the Brazilian Forest Code reduce the percentage of land a private landowner is legally required to maintain as forest (including, critically, a reduction in the width of forest buffers alongside perennial steams) and include an amnesty for landowners who deforested before July 2008 (who would subsequently be absolved of the need to reforest illegally cleared land) (Bird et al. 2011).

Conservation Actions [top]

Conservation Actions:

Conservation Actions Underway
None is known.

Conservation Actions Proposed

Expand the protected area network to effectively protect IBAs. Effectively resource and manage existing and new protected areas, utilising emerging opportunities to finance protected area management with the joint aims of reducing carbon emissions and maximizing biodiversity conservation. Conservation on private lands, through expanding market pressures for sound land management and preventing forest clearance on lands unsuitable for agriculture, is also essential (Soares-Filho et al. 2006). Campaign against proposed changes to the Brazilian Forest Code that would lead to a decrease in the width of the areas of riverine forest protected as Permanent Preservation Areas (APPs), which function as vital corridors in fragmented landscapes.

Citation: BirdLife International. 2016. Zebrilus undulatus. The IUCN Red List of Threatened Species 2016: e.T22697291A93606335. . Downloaded on 20 September 2018.
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