The bay-capped wren-spinetail (''Spartonoica maluroides'') is a species of

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

in the Furnariinae subfamily of the ovenbird

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Furnariidae. It is found in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...

, and

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

.Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt, G. Del-Rio, A. Jaramillo, D. F. Lane, M. B. Robbins, F. G. Stiles, and K. J. Zimmer. Version 28 September 2023. Species Lists of Birds for South American Countries and Territories. https://www.museum.lsu.edu/~Remsen/SACCCountryLists.htm retrieved October 20, 2023

Taxonomy and systematics

The bay-capped wren-spinetail is the only member of genus ''Spartonoica'' and has no subspecies. The bay-capped wren-spinetail was originally described as ''

Synallaxis ''Synallaxis'' is a genus of birds in the Ovenbird (family), ovenbird family, Furnariidae. It is one of the most diverse genera in the family and is composed of small birds that inhabit dense undergrowth across tropical and subtropical habitats ...

maluroides''. It was later placed in genus ''

Asthenes Canasteros and thistletails are small passerine birds of South America belonging to the genus ''Asthenes''. The name "canastero" comes from Spanish language, Spanish and means "basket-maker", referring to the large, domed nests these species mak ...

'' but has been recognized in ''Spartonoica'' starting in 1950. Genetic data show that it is not closely related to genus ''Asthenes'' but instead is

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to the cachalotes of genus ''

Pseudoseisura The cacholotes are four species of relatively large, heavy-billed furnariids in the genus ''Pseudoseisura''. They are found in shrubby habitats in the South American countries of Brazil, Bolivia, Argentina, Paraguay and Uruguay. They are essenti ...

''.

Description

The bay-capped wren-spinetail is long and weighs about . The sexes have the same plumage. Adults have a whitish

supercilium The supercilium is a plumage feature found on the heads of some bird species. It is a stripe which runs from the base of the bird's beak above its eye, finishing somewhere towards the rear of the bird's head.Dunn and Alderfer (2006), p. 10 Also k ...

on an otherwise sandy brown face. Their crown is rufous. Their upperparts are sandy brown to olive-brown with bold black streaks on the nape and upper back. Their wings are brown with cinnamon at the base of the flight feathers. Their tail is mostly brown and graduated with pointed feathers; the central pair have some black. Their underparts are whitish with a buff or cinnamon tinge on the breast, sides, and flanks. Their iris is dull white, whitish, or pale bluish, their

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

blackish, their

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

whitish to pinkish with a dark tip, and their legs and feet light tan. There are some minor differences in size and darkness of plumage, but little genetic divergence, between coastal and inland populations.Llambías, P. E. (2020). Bay-capped Wren-Spinetail (''Spartonoica maluroides''), version 1.0. In Birds of the World (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bcwspi1.01 retrieved November 18, 2023

Distribution and habitat

The bay-capped wren-spinetail is found from extreme southern Brazil south through Uruguay into northern Argentina as far south as

Río Negro Province Río Negro (, ''Black River'') is a province of Argentina, located in northern Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean. Its cap ...

. It also has occurred as a non-breeder in Paraguay. It inhabits reedbeds and sedges in freshwater, brackish, and saltwater marshes. In elevation it ranges from sea level to about .

Behavior

Movement

The bay-capped wren-spinetail's movements have not been fully defined. It appears to be mostly resident but the species has been noted as far north as Paraguay in the non-breeding season.

Feeding

The bay-capped wren-spinetail feeds on invertebrates, mostly insects and spiders. It usually forages alone, gleaning from marsh grasses and sedges. There is some evidence that pairs that nest in salt marshes preferentially feed in freshwater marshes.

Breeding

In Argentina the bay-capped wren-spinetail breeds between September and February. The species is monogamous, and both sexes build the nest, incubate the eggs, and brood and feed nestlings. The nest is an open cup (uniquely among

furnariid Ovenbirds or furnariids are a large family of small suboscine passerine birds found from Mexico and Central to southern South America. They form the family Furnariidae. This is a large family containing around 321 species and 71 genera. The ove ...

s) built of twigs and grass and placed low to the ground deep inside marsh vegetation. The clutch size is two to four eggs. The incubation period is about 13 days and fledging occurs 11 to 14 days after hatch.Llambías, P.E., Ferretti, V., Cardoni, D.A. and Maldonado, J.E. (2009). Breeding success and social mating system of the Bay-capped Wren-Spinetail (''Spartonoica maluroides''). Wilson J. Orn.. 121(4): 803–807. https://doi.org/10.1676/09-011.1

Vocalization

The bay-capped wren-spinetail's primary song is "a grasshopper-like buzz, long and tuneless, rising and falling away". It has other vocalizations whose purposes have not been defined.

Status

The

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

originally assessed the bay-capped wren-spinetail as Near Threatened but in 2022 revised the assessment to be of Least Concern. It has a large range and an unknown population size that is believed to be decreasing. "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 rgentina A further threat is overgrazing of grasslands by cattle and the establishment of wind farms."

References

{{Taxonbar, from=Q589026 bay-capped wren-spinetail Birds of Argentina Birds of the Pampas Birds of Uruguay bay-capped wren-spinetail Taxonomy articles created by Polbot