Bay-capped Wren-spinetail Spartonoica maluroides


Justification of Red List Category
This wetland habitat specialist is thought to have a moderately small and severely fragmented population, and is likely to be declining owing to the drainage and degradation of wetlands for agricultural developments. It is therefore considered Near Threatened.

Population justification
The global population size has not been quantified, but this species is described as 'fairly common' (Stotz et al. (1996).

Trend justification
A slow decline is suspected to be occurring, owing to on-going drainage and conversion of wetland habitats.

Distribution and population

Spartonoica maluroides occurs in extreme south Brazil (Rio Grande do Sul), Uruguay, and central Argentina (east Formosa, Chaco, Corrientes, Entre Ríos and Buenos Aires west locally to Córdoba, Santiago del Estero and Mendoza, and south to Río Negro) (Ridgely and Tudor 1994, Chebez et al. 1998, J. C. Chebez in litt. 1999). It is an uncommon, but regular winter visitor to Paraguay (R. Clay in litt. 2009). It is uncommon to locally fairly common, but probably overlooked.


This species occurs up to 900 m in brackish and freshwater marshes with extensive growths of Eryngium and Scirpus, and may associate with Spartina grass (Ridgely and Tudor 1994, Pearman and Abadie 1995, Parker et al. 1996, A. Jaramillo in litt. 1999). Breeding biology is described by Llambías et al. (2009).


This species is limited to wetland habitats, and is therefore highly threatened by marsh drainage and the drying effects of Eucalyptus and Pinus plantations, particularly in east Entre Ríos and north-east Corrientes (Pearman and Abadie 1995).

Conservation actions

Conservation Actions Underway
Conservation Actions Proposed
Carry out surveys to assess the species's population size. Monitor rates of habitat loss and degradation within its range. Campaign for the protection of suitable wetland habitats within the range, including the gazetting of protected areas at key sites.


Size: 14 cm. Summary: A small streaky, long tailed marsh furnarid. Id: Above, fawn with black streaking and contrasting rufous crown and indistinct white supercillium; wings dusky with cinnamon bases to flight feathers; long pointed tail brown. Underparts whitish becoming buffy on flanks. Similar: Three sympatric species (Hudson's Canastero Asthenes hudsoni, Sulphur-bearded Spinetail Cranioleuca pyrrophia and Grass Wren Cistothorus platensis) also found in marshes are basically similar, though all lack the distinctive rufous crown. Hints: Inconspicuous and hard to see; most often located by voice. Voice: A 2-3 second mechanical reeling trill.


Text account compilers
Butchart, S., Gilroy, J., Sharpe, C J

Jaramillo, A., Chebez, J.

Recommended citation
BirdLife International (2019) Species factsheet: Spartonoica maluroides. Downloaded from http://www.birdlife.org on 17/09/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/09/2019.