Yellow-legged Weaver

Description 

12 cm  

Males have the following characteristics:  

They are completely black except for a blackish-brown belly and undertail-coverts  

Some greenish sheen or gloss on the crown, nape, and mantle (Birds of the World) 

Brown vent 

Direct sunlight shows greenish edges to head and mantle that show a scaling effect 

Whitish iris  

Black bill  

Dull yellow legs  

Females are like the males except that they are less glossy, lack the green sheen, have duller undertail-coverts, and a yellow iris  

Juveniles are either blackish-green above and greenish-grey below or brownish overall. They have a shadow of a yellow collar and olive on the belly and vent as well as pale flesh legs. One specimen had chocolate brown upperparts and a brown throat and belly. Some speculate that this variation in plumage could potentially be non-breeding plumage.  

This species is very similar in appearance to Viellot’s Black Weaver (Ploceus nigerrimus) and Maxwell’s Black Weaver (Ploceus albinucha) 

The similarities are so striking that some have proposed that the Yellow-Legged Weaver may be a hybrid of these two species 

Both Viellot’s Black Weaver and Maxwell’s Black Weaver are all black with the former having a long hindclaw and the latter a shorter hindclaw with the Yellow-Legged Weaver having one of intermediate size (Craig, 2005) 

While proponents of the hybrid theory point to this as evidence that the Yellow-Legged Weaver is not a distinct species, no one can explain the species’ peculiar yellow legs (that are duller brown in the supposed parent species), greenish sheen (that is absent on the other two), and why the two species would hybridize only in that specific area of the Ituri Forest that lies at the easternmost fringes of both their ranges in the Democratic Republic of the Congo (DR Congo). Furthermore, skeptics point to the fact that Viellot’s Black Weaver is not a weaver of intact forest like the Yellow-Legged Weaver is supposed to be. 

Many suspect that the Yellow-Legged Weaver is a rare but distinct species that has a small population in a poorly studied region of the world 

Habitat 

This species is known only from the Ituri Forest in northeast DR Congo 

Within the Ituri Forest, this bird’s range extends from Avakubi, east to Siombo, Campi y Wanbuti south to Ukaika and east to Lima, Tungudu and Makayobe 

This species range overlaps with those of the Viellot’s Black Weaver and Maxwell’s Black Weaver 

Viellot’s Black Weaver can be found in southern Nigeria, Uganda, west Kenya, Angola, and DR Congo  

Maxwell's Black Weaver has a more fragmented range but is found in the Albertine Rift in DR Congo, the Central African Republic, the Congo, Gabon, Cameroon, Equatorial Guinea, Nigeria, Ghana, Ivory Coast, Liberia, Guinea, and Sierra Leone  

The few specimens of the Yellow-Legged Weaver that were collected were found in lowland rainforests in the canopy of tall and medium-sized trees (IUCN Red List) 

Diet 

The Yellow-Legged Weaver is assumed to be an insectivore that eats caterpillars since these insects were found in the first specimen of the species that was described by James Chapin in 1916 

Other Information 

Vocal behavior unknown  

Breeding behavior unknown (Birds of the World) 

Life span- 4 years (IUCN Red List) 

The Yellow-Legged Weaver has been classified as Vulnerable by the IUCN that made its last assessment in 2020. The population of this species is thought to be small and declining as a result of habitat loss due to agriculture, displacement, and armed conflict. From 2000-2019, this species’ range suffered a 13% loss in forest cover with a rate of decline between 1-15% over the next three generations. The Yellow-Legged Weaver’s extent of occurrence is 19,400 km² (IUCN Red List). 

To see a distribution map of the Yellow-Legged Weaver’s known range, click here. 

The Yellow-Legged Weaver was first described by James Chapin in 1916. From 1909-1915, Chapin was part of an expedition to explore the biodiversity of the DR Congo (known as the Belgian Congo at the time) with Herbert Lang. While he was based at Avakubi in the Ituri District, one of his assistants (Nekuma) brought him the first female specimen of the Yellow-Legged Weaver on September 20, 1913 (Chapin, 1954). 

From January to August 1921, Count Nils Gyldenstolpe led an expedition to Central Africa. During this expedition, he and his team investigated Lake Victoria, the Birunga volcanoes, the north shore of Lake Kivu, Lake Edward, the Congo forest north of Beni, Irumu, and Lake Albert. It was during this time that his team collected three specimens (two juvenile males and a female) of the Yellow-Legged Weaver in Kampi-na-Mambuti, Simbo within the same area that Chapin’s assistant collected the first specimen five years prior: the Ituri Forest (Gyldenstolpe, 1924). Since the Gyldenstolpe expedition, only six more specimens were collected of this species for a total of nine specimens. The last one (a male) was collected in 1959. What is interesting is that every specimen was found only in the Ituri Forest in the DR Congo. 

There have been only three recorded sightings of the Yellow-Legged Weaver since 1959. They both occurred in the Okapi Faunal Reserve in the DR Congo in 1990 and 1994. This is a reserve within the Ituri Forest; the only place where this species is known to reside (Birds of the World). 

The greatest challenge for the Yellow-Legged Weaver is the high rate of habitat loss that is happening across her narrow range. This habitat loss is caused not only by agricultural expansion but also by the indirect and direct impacts continuous armed conflict has had on diverse ecosystems in the DR Congo. During a wartime situation, there are several ways an armed conflict can negatively affect wildlife. Animals can be accidentally killed by mines or shells. They can be hunted and overexploited to feed troops. If they are an endangered species, they can even be used by hostages or pawns to hamper government troops or gain international support. War can affect park institutions in a reserve where endangered and vulnerable species are protected. Rebels can occupy an area and chase park officials away. With park institutions absent, this not only opens the door for rebels and poachers but also refugees from neighboring regions affected by the conflict to come in and overexploit park resources (Gaynor et al., 2016). All of these factors either have happened or continue to happen on some level in the DR Congo ever since the country ceased to be a Belgian colony in the 1960s. The armed conflict that has ravaged the country does not show any sign of ending anytime soon. While large mammals tend to be the center of attention, birds can be the target of poaching and habitat loss as war forces many in the country to overexploit resources in order to survive. 

The DR Congo has among the richest and diverse ecosystems in the world. Ironically, these areas are also among the most poorly studied and ravaged by habitat loss as a result of the incessant warfare that has plagued the country since independence. The Yellow-Legged Weaver is one of 13 rare species that are either only known from the DR Congo or are mainly known from this region. Other than the Yellow-Legged Weaver, the list includes the Itombwe Nightjar, Itombwe Owl, Chestnut Owlet, Grauer’s Cuckooshrike, Lendu Crombec, Kabobo Apalis, Prigogine’s Greenbul, Sassi’s Greenbul, Chapin’s Mountain Babbler, Prigogine’s Sunbird, the Upemba Masked Weaver, and the Black-Lored Waxbill. As more and more of their habitat is destroyed by agriculture and overexploitation, more and more of their members are captured or killed due to poaching and hunting with every passing year. As of now, the Yellow-Legged Weaver seems to be nominally protected within the Okapi Faunal Reserve that is located within the Ituri Forest but it is unclear how much of this forest is protected by park officials. If the armed conflict in the DR Congo does not cease, it is unsure how much longer these rare species can continue to cope with the direct and indirect impacts war has had on their survival. 

Conduct a DNA analysis of one or more of the nine known specimens of the Yellow-Legged Weaver to see if this bird is a distinct species, a hybrid, or a subspecies.

Order: Passeriformes 

Family: Ploceidae 

Genus: Ploceus/Malimbus 

Species: Ploceus/Malimbus flavipes* 

*Since only nine specimens of the Yellow-Legged Weaver have been found and next to nothing is known about this bird’s habits, there has been considerable debate among ornithologists regarding her taxonomic status. When Chapin first described this species in 1916, he placed her in the genus Malimbus due to the bird’s black plumage, bill shape, and square tail (Chapin, 1916).  

Others disagreed with Chapin. When Count Gyldenstolpe and his team conducted their expedition in the DR Congo in the 1920s, Gyldenstolpe described the specimens of the Yellow-Legged Weaver he saw as belonging to the Rhinoploceus genus. A year later after the end of his expedition in 1924, Gyldenstolpe was challenged by Erwin Stresemann who placed the bird in the Ploceus genus in 1925. He based his classification on a juvenile specimen of the species he himself was given by Rudolf Grauer who found the specimen at Ukaika. After Stresemann’s classification, Chapin later changed his mind and agreed with Gyldenstolpe in the assertion that the Yellow-Legged Weaver should be placed in the Rhinoploceus genus due to her open nostrils (Chapin, 1954). Over the years, checklists and ornithologists were split over the Yellow-Legged Weaver’s classification with some putting her in Ploceus and the other in Malimbus. 

The debate took a surprising turn in 2017 when Thilina N. de Silva et al. (2017) published a study that created a phylogenetic framework for the Ploceidae family. This study covered 2/3 of all recognized weaver species (77/116). Viellot’s Black Weaver and Maxwell’s Black Weaver (what many suspect are the Yellow-Legged Weaver’s closest relatives) were analyzed. De silva et al. argued that these species should be placed in the Malimbus genus instead of Ploceus. Even though the Yellow-Legged Weaver was not included in their study, they recommended that this bird be placed in the Malimbus genus along with her supposed relatives. Since they did not include the Yellow-Legged Weaver in their study, it is not surprising that several checklists have been reticent in adopting this change.

The debate surrounding the origins of the Yellow-Legged Weaver will likely continue until either a DNA analysis of the known specimens is done or more members of this species are found.