Slender-tailed Cisticola

Slender-tailed Cisticolas are found in northeastern Angola and adjacent southern Democratic Republic of Congo, a region that has been rarely visited by birdwatchers and ornithologists for much of the past 50 years. The species was photographed by Michael Mills in February 2024 after being lost for 14 years.

Also known as Black-tailed Cisticola, the species differs most notably from other cisticola species by their long, glossy-black tail. From the little that is known about its habitat and distribution, it appears to favor miombo woodland habitats.

The Slender-tailed Cisticola was first described in 1882 and a total of 14 specimens of the species were collected between 1882 and 1958 (Irwin, 1991). After that, there were several sight records of the cisticola between 1972 and 2009. In July-August 2010, a family group of Slender-tailed Cisticola were photographed and sound recorded near Cacolo, Angola, by Michael Mills, Martim Melo and Alexandre Vaz (Mills et al., 2011). After that there were apparently no documented records of the species until February 2024 when Mills found them again near the area.

Slender-tailed Cisticola is listed Data Deficient by the IUCN that made its last assessment in 2016.  This is because much is still unknown about this mysterious cisticola and its habitat across northeast Angola and southeast DR Congo. A recent survey in Cacolo in 2010 suggests that the Slender-Tailed Cisticola’s habitat remains undisturbed and untouched by decades of civil war. Further surveys are needed to ascertain whether the same can be said for other habitats within this bird’s range. The population of this species has not been quantified but is suspected to be stable. 

To see a distribution map of this species, click here. 

The most recent records of Slender-tailed Cisticola are photographs from February 2024 by Michael Mills near Cacolo, Angola. These photos are the first documented records of the species in 14 years. Prior to 2024, the most recent records of the species were in July-August 2010 (Mills et al., 2011).

The Slender-tailed Cisticola was first described by Jean Cabanis as Dryodromas melanura in 1882. A similar bird was described by S.A Neave in 1909 as Dryodromas pearsoni. It would be a few decades before James Chapin suggested that these two birds were one and the same with the name being changed to Cisticola melanurus. Before 1972, all ornithologists had were 14 specimens of the species: 6 specimens from Angola and 8 from the DR Congo. These specimens were collected between the years 1880-1960 from seven different locations in northeastern Angola and southern Democratic Republic of Congo (Irwin, 1991). 

In 1972, a Slender-Tailed Cisticola was spotted in northeast Angola. This would be one of a few sightings of the species due to the fact that ornithologists were barred from entering its range as a result of a civil war in Angola that lasted 27 years (1975-2002).  In 1988, W.R.J Dean and his team saw a pair of Slender-tailed Cisitcolas in Angola. This pair was spotted in a mixed flock in mature Brachystegia boehmii woodland. 

From January 26-February 2, 2005, Ian Sinclair and his team went to northern Angola. On February 2, they found a pair of Slender-Tailed Cisticolas 30 km north of Calandula in the Malanje province, Angola. They reported that the pair had an "unusual foraging behavior." They saw the pair creep amongst the leaves and edges of the foliage in the canopy in the company of hyliotas and eremomelas. They noticed the long black tail and the wing-flicking and snapping that only happened when the bird was disturbed. An important observation was that this bird did not have the dramatic or exaggerated wing-snapping, branch-hopping, and tail-swinging of the São Tomé Prinia (Prinia molleri). This suggests that the Slender-Tailed Cisticola is a distinct species (Sinclair et al., 2007). 

In March 2009, A. Hester saw a Slender-Tailed Cisticola near Kolwezi in the Lualaba province, DR Congo.  

From July-August 2010, M.S.L Mills and a team of researchers searched for the Slender-Tailed Cisticola in northeast Angola. They investigated known sites where the species was seen in the 20^th century. From July 26-August 3, they searched two areas along the main road from Luanda to Saurimo in Lunda Sul 40 km north of Calandula. They focused their search in miombo woodland and clearings at the edges of this habitat. They investigated areas 40 km north of Calandula but did not find any Slender-Tailed Cisticolas. Instead, they found plenty of Short-Winged (Cisticola brachypterus), Piping, and Whistling (Cisticola lateralis) cisticolas. Since there was a sight record from Calandula 210 km west of Cafunfo, they searched east in the provinces of Lunda Norte and Lunda Sul (especially in the Cacolo area 200 km to the southeast). Three out of the six specimens of this species that were collected in Angola were collected near Cacolo with the 4^th being collected from nearby Mona Quimbundo. On July 31, Mills and his team followed the road from Cacolo southwest towards Cacumbi and searched any habitats they thought were suitable for the Slender-tailed Cisticola. They camped at the edge of Saoyaze village 7.5 km southwest of Cacolo. They found a group of 6-8 Slender-tailed Cisticolas in a nearby woodland.  

For two days (July 31-August 1), they followed this group as they foraged in the crowns of low-lying trees within the dense miombo woodland near Saoyaze village. This group spent the entire day within an area of 2 hectares of miombo woodland. Since they moved loosely together, it was hard for Mills and his team to count the exact number of individuals as well as determine their sex and age. This group of Slender-Tailed Cisticolas spent most of their time in closed canopies but were also seen foraging at the edge of well-developed woodland with denser undergrowth and sparser canopy cover. What was interesting is that these birds flew over a cassava field.  

Mills and his team described their behavior as foraging in the leaves of the canopy of the largest trees in the biome. They were also described as hopping on the ground where they foraged in densely tangled vegetation and in the leaves of smaller trees 8 m above the ground. Most of their time was spent in dense undergrowth in the morning in the presence of Tawny-Flanked Prinias (Prinia subflava). When disturbed, the Slender-tailed Curlews flew into the canopy of nearby trees. Mills and his team noted the curious use of the tail. The tail was held below the horizontal where it moved horizontally and vertically in a random fashion. These cisticolas did not flick their tails or wings. Although they looked similar to Long-Tailed and Piping Cisticolas as others have noted in the past, they did not seem to be related to the Apalis family. The birds they observed were silent while foraging in the undergrowth, made a soft, seep call, and sometimes a sharper chip. They theorized that both were probably contact calls. As past observers noted, Mills and his team heard a clicking/wing-snapping sound made in flight that was done in short bursts with no accompanying vocalizations. This sound was usually made when the Slender-Tailed Cisticolas were disturbed and flying to a tree from the undergrowth. However, this sound was also heard randomly. This demonstrated to them that this behavior was not linked to the breeding season. It is interesting to note that Mills and his team heard some of the cisticolas do an "inconspicuous song" from the crown of a tall tree. This song consisted of various short burry phrases lasting 0.2 seconds each at intervals of 1-6 seconds and lasting at least 15 seconds but sometimes for several minutes. This song was unlike that of the Piping and Long-Tailed Cisticolas. 

Mills and his team managed to trap a Slender-tailed Cisticola in a mist net, take some photos, and record vocalizations. Based on their observations, Mills et al., concluded that the Slender-tailed Cisticola is indeed a distinct species. They point to the Slender-Tailed Cisticola's unique song, distinctive primary feathers, and wing-snapping behavior as proof. It was clear to them that this bird is not an Apalis nor a subspecies of the Piping or Long-tailed Cisticolas even though the latter two are perhaps this bird’s closest relatives. They do admit however that this bird is very unique among cisticolas. Slender-Tailed Cisticolas forage at all levels from the ground to the canopy and inhabit mature, closed-canopy miombo woodland. They do, however, favor clearings and open areas with denser undergrowth. During their survey, Mills et al., noticed that this habitat was widespread in Cacolo with little evidence of human disturbance. They surmise that the Slender-ailed Cisticolas’s range could easily go beyond Cacolo and that incomplete sampling might explain why this bird’s range appears scattered (Mills et al., 2011).  

The survey done by Mills et al. produced the first recordings of the Slender-tailed Cisitcola, made important observations regarding the bird’s behavior, and took important photos and samples.

Ever since the species was first described, there has been uncertainty surrounding this bird’s species status, behavior, and habitat preferences. Throughout the years, there have been conflicting reports regarding the Slender-Tailed Cisticola from researchers in the field and ornithologists. Some insisted the bird was an apalis even when the bill clearly showed an affinity to cisticolas. Others, such as Françoise Dowsett-Lemaire and R.J Dowsett, suggested that this species was conspecific with the Piping Cisticola. The fact that no photos or recordings were made of the bird only served to intensify the debate. 

The greatest controversy surrounded the species’ tail and wings. After a thorough examination of 12 specimens, M.P.S Irwin and other researchers argued that this species is not an apalis but an aberrant member of the Cisticola genus based on their examination of the tail and wings in comparison to specimens of Long-Tailed and Piping cisticolas. The species’ long, graduated black tail looks similar but lacks the black subterminal spot present in her relatives. According to Irwin et al., the Slender-Tailed Cisticola has very rounded wings with 5 distal primaries that are highly specialized with the rachis being twice the width of those of the Long-Tailed and Piping cisticolas. They are also glossy black and highly melanized whereas the rachis is light brown in Long-Tailed and Piping cisticolas. The outermost primary is needle-shaped in the Slender-Tailed Cisticola (it is blade-like in Piping and Long-Tailed Cisticolas). These wings separate this cisticola from her relatives.  

Another thing Irwin et al. noticed was the sexual dimorphism of this species. In the males, the outer web of the outermost rectrix is white while in females it is edged brown. Further differences include the Slender-Tailed Cisticola having colder, whiter underparts than the Long-Tailed and Piping cisticolas which have buffy underparts. The bill of this species has a flesh-colored lower mandible and a more arched and robust culmen in contrast to its relatives. There is also no evidence of seasonal plumage from breeding to non-breeding dress in contrast to this bird’s relatives. Irwin et al., conclude that the long tail, rounded wings, reddish crown and mantle, grey wing-coverts and outer webs of the primaries and secondaries are the key characteristics of the Slender-Tailed Cisticola that make this bird a cisticola (not an apalis) as well as a distinct species from the Long-Tailed and Piping Cisticolas that are her closest relatives. 

Over the years, there have been conflicting observations regarding the Slender-Tailed Cisticola’s behavior and habitat. Some have reported the bird in tall trees. Others in dry woods near grassy clearings. Others in climax woodland feeding on the branches and crowns of low-lying trees in the canopy with others claiming the bird fed low in the undergrowth. S.A Neave reported the bird as common on the Lufupa River at the end of October that could be found in pairs in tall trees and flew with a clicking sound. J. Vincent reported that the species made a small, continuous “squeak” similar to a Blue Waxbill (Uraeginthus angolensis). He further remarked that he heard no wing-snapping and that the bird acted like an apalis. Assuming the bird inhabits a miombo biome, ornithologists point out that both the Piping and Long-Tailed Cisticolas are known to live in the same biome with a narrow zone of hybridization recognized in the DR Congo. Due to the fact that so much is unknown relating to its range, some have postulated that the Slender-Tailed Cisticola could be sympatric with or replace either the Piping or Long-Tailed Cisticola in certain areas throughout Angola and the DR Congo. What makes calculating the bird’s range even more difficult is that researchers, such as M.P.S Irwin, have cast doubt on the precise location of the sites where the known specimens were collected. Many are of the opinion that while the Slender-Tailed and Long-Tailed cisticolas differ in behavior and have mutually exclusive ranges, the former is thought to be partially sympatric with the dispar subspecies of the Piping Cisticola in Angola and the DR Congo (Irwin, 1991) 

In 2010, M.S.L Mills and a group of researchers found a group of 6-8 Slender-Tailed Cisticolas in a woodland southwest of Cacolo in Angola. Their observations shed much needed light on the debate over the Slender-Tailed Cisticola’s identity. They concluded that the Slender-Tailed Cisticola is indeed a distinct species. They point to the Slender-Tailed Cisticola's unique song, distinctive primary feathers, and wing-snapping behavior as proof. It was clear to them that this bird is not an apalis nor a subspecies of the Piping or Long-Tailed Cisticolas even though the latter two are perhaps this bird’s closest relatives. They do admit however that this bird is very unique among cisticolas. Slender-Tailed Cisticolas forage at all levels from the ground to the canopy and inhabit mature, closed-canopy miombo woodland. They do, however, favor clearings and open areas with denser undergrowth. During their survey, Mills et al., noticed that this habitat was widespread in Cacolo with little evidence of human disturbance (Mills et al., 2011). 

Slender-tailed Cisticola is similar in appearance to both Tabora (Cisticola angusticauda) and Piping Cisticolas (Cisticola fulvicapilla) and has sometimes been considered conspecific with those species (Ryan et al. 2020). Field observations and sound recordings made in 2010, however, support the conclusion that Slender-tailed Cisticola is a distinct species (Mills et al., 2011).

The English name Slender-tailed Cisticola is used in the Clements/eBird taxonomy and Birds of the World, while the species is called Black-tailed Cisticola by the HBW/BirdLife taxonomy and IOC World Bird List.