Wetlands underpin the survival of many organisms and human development in all regions of the world [1] . They host different types of vegetation distributed along water depth gradients creating a complex mosaic of microhabitats that can range from nearly terrestrial to open water [2] . Each of these microhabitats or some combination of them can provide water, food, and shelter for certain groups of birds and other species [3] [4] . The global evolution of avifauna shows that many groups of birds have adapted anatomically, morphologically, and physiologically to different wetland microhabitats. They performed the ecology according to the prevalent environment. Collectively, they are referred to as wetland birds [5] . There are many species of birds but the most commonly associated with freshwater wetlands are ducks and waders [2] but little studied in the swamps. A certain number of studies revealed that birds are excellent bio-indicators of the quality and functioning of aquatic ecosystems as well as flooded forests [6] [7] [8] [9] . Some are migratory and very useful in the ecological balance [10] , while others are useful in agriculture acting on the populations of insects and rodents which are harmful to crops [11] . For example, some granivores and frugivores also participate intensively in the regeneration of certain plants [12] [13] . All these aspects are services that birds provide in wetland ecosystems, including swamps, as demonstrated by [14] in the Debo and Walado lakes area of the lower Niger River delta.

The exploitation of wetlands for diverse activities, in particular, the cultivation of vegetables is increasing in developing countries, as in the case of the Democratic Republic of the Congo (DRC) in Sud-Kivu province (East of the Country). This is one of the causes of the reduction of their extent by nearly 35% since 1970 at the global level as highlighted in the report on the state of the world’s wetlands in 2018 by the Ramsar Convention [15] . Yet, African wetlands are disappearing despite a rich avian diversity [16] [17] .

In Sud-Kivu, the Nyamubanda swamp is vulnerable and its ecological and biological potentialities are not known. Despite their enormous ecosystem services beyond those of land including essential food, fiber and fuelwood, the Nyamubanda swamp does not escape intense destruction leading to a decrease in fauna and flora diversity [18] (unpublished data). Observations showed that the riparian population uses this swamp for commercial gardening and foraging for livestock throughout the year. These aspects remain of considerable concern as they indicate trends in avian diversity disturbance that would generally indicate an increase or loss of appropriate biodiversity at national and regional scales [8] . While any presence or absence, increase or decline in bird diversity has been used as an indicator of ecosystem quality in regional swamps [6] [19] .

This study aims to understand the avian diversity of the Nyamubanda swamp in the Nyangezi sector in an attempt to assess the effects of agriculture on the biodiversity component, avifauna in this case. Most of this swamp is used for shifting agriculture and another part for artisanal brickworks. [20] showed that agricultural activities such as the culture of rice had been influenced by some bird species in Ngozi (Burundi) and in the Ruzizi plain (DRC). Some bird species may cause damage to cereal crops [21] , which often leads farmers to hunt them and it therefore contributes to the decrease in the bird species population. In the same way, human activities could significantly reduce bird diversity in the Nyamubanda swamp. The purpose of this study is to determine bird diversity based on four types of habitats including rice and sorghum fields, papyrus and woody (Eucalyptus) landscapes in order to understand the distribution of the avifauna of the Nyamubanda swamp and contribute to the knowledge of the biodiversity of the wetlands of Nyangezi Territory in particular and DRC’s in general. Frequency analysis and species classification (Clustering) is an approach to understanding the effect of rice and sorghum cultivation on avian diversity in the Nyamubanda swamp.

Previous studies conducted in some marshes in the Sud-Kivu region and close to Nyamubanda marsh, identified 22 species, 9 families and 4 orders, in Mweze marsh according to the stage of rice cultivation [40] , unpublished data); and 36 species, 19 families and 8 orders in the Dundazi and Gombo marshes in the papyrus habitat [18] (unpublished data). These results are similar to those found in this current study. The timing of crops is thought to be the basis for fluctuating bird diversity in marshes. These results are different from those of [30] who worked on rice cultivation and its surroundings in the Ivory Coast and found 11 orders, including the 8 orders of Nyamubanda. This variability would be explained by microhabitat and geographic distance. Our results are very similar to those of [41] in the Kagogo-Gisumo swamp in Burundi which shows that non-random depredation in granivorous birds underlies high diversity in the swamp with cereal crops. This explains why rice and sorghum cultivation contributes to the abundance of birds in this swamp. The Passeriformes order was the most diverse in terms of species, families and individuals. It is the most diverse order worldwide [42] [43] [44] , as also encountered in West Africa [45] . The works of [28] [46] and [30] also point out that this order contains most of the crop-depredator species. This suggests that rice and sorghum cultivation would be the basis for the highest species diversity of the order Passeriformes in Nyamubanda swamp. This order is more distributed in marshes in the Sud-Kivu region following former research [18] [40] .

The rice and papyrus habitats are almost similar in abundance because it is easy to leave the rice field to rest in the papyrus, generally when the rice farmers are in the fields. The sorghum and woody plants are also close because the sorghum fields are near the woody landscape. When farmers are working in their fields, birds fly to the woody landscape. Regarding the families recorded in Nyamubanda swamp, the most present are Ploceideae, Estrildideae, Fringillideae, Coliidae, Nectarinidae, Pycnonotideae and Viduidae which are the top families based on their frequencies. These families were already recognized as frequent in cultivated fields in West Africa [28] and in Ivory Coast [30] in wetlands. Some of these birds are granivorous, frugivorous and insectivorous and are very abundant in Africa [47] . This explains why agriculture in the marsh has an impact on the abundance of local wetland birds. These results are close to those found in Burundi by [48] who found that Ploceideae is the most represented family, followed by Estrildideae, and Fringillideae. On the other hand, among the three families identified (Ploceideae, Estrildideae and Passerideae) by [20] in the Ruzizi plain, only the Passerideae family was identified in the Nyamubanda swamp but we identified more families than those found by [20] in Burundi. These results fall in the same observations as [49] [50] [43] who found that the Pycnonotidae family is more diverse at lower altitudes and in Sud-Kivu [51] with 12 species between 1200 m and 3000 m. Besides this family, 3 other families were found in the Nyamubanda swamp at 1500 m including Fringilidae, Estrildidae and Nectarinidae. Habitat type and elevation gradient [20] are thought to be among the factors influencing the distribution of families in the swamps. In this swamp, each habitat has its morphological approaches, especially the type of vegetation and feeding, which could be the cause of this inequity of families in the Nyamubanda marsh. The families of Estrildidae, Fringillidae, Nectarinidae, Ploceidae, Pycnonotidae and Viduidae are more present in the Nyamubanda marsh according to their high frequency (+50%). It is also observed that families such as Anatidae, Cuculidae and Columbidae are rare in this swamp.

The species Spermetes cucullata is the only ubiquitous species in all habitats explored. According to [34] , this species prefers grassy vegetation and gardens surrounded by trees, but also the genus Lonchura has been recognized as a pest of rice, sorghum or small millet [28] , and even maize [46] . These characteristics are supported by our findings and observations in the Nyamubanda swamp, which has extensive papyrus vegetation and trees. The cultivation of rice and sorghum is a major human activity in the Nyamubanda swamp, thus promoting the frequency of birds. [34] showed that the species Vidua macroura preferred areas with vegetation belonging to the Cyperaceae family, especially Papyrus, and in fields where cereals were grown. In West Africa, this species was also considered as a pest of rice and sorghum seeds [28] . In Burundi in the Kagogo-Gisumo swamp, [41] confirmed that this species was a predator of rice culture. We observed it feeding on rice and sorghum seeds during our sampling. Four species are present in both sorghum and rice habitats, including: Estrild astrilda, Vidua macroura, Crithagra monzambica and Spermetes fringilloides. These species are all granivorous [30] but also insectivorous. They are THEN classified as common wetland birds in view of their frequencies reaching more than 50% in wetlands. These species are widely distributed in Central Africa. They inhabit swamps, brushwood, lush grasslands, grasslands and forest margins [47] . The Nyamubanda swamp is full of all these characteristics making it a swamp to be integrated into the local development plan and landscape management plan.

The Nyamubanda swamp would be an important site for the conservation of wetland birds. Illegal hunting activities should be discouraged and forbidden. According to [2] , the habitats of this marsh are a direct source of food for these birds, playing a role in the protection and availability of nesting sites. The correspondence analysis (CA) showed that Rice and Papyrus habitats were very similar (Figure 2) and had a large number of species. The diversity of birds in the Nyamubanda swamp is linked to the food requirement approach [9] . As the sampling took place during the cultivation of rice at different stages and the harvesting of sorghum, these birds were preferentially encountered in these two habitats. In addition, Papyrus and woody plants are recognized among the preferred ecological environments for bird species. The lack of high species richness does not explain the decline in these habitats but rather the timing of capture would influence this trend. Many upland birds exploit wetlands seasonally or occasionally for food and water [52] . The Nyamubanda Swamp can be considered as a heterogeneous environment that can be linked to a mosaic of habitats with various environmental conditions, and bird population can also respond to this environmental variability [2] . The hunting of birds even in papyrus and woodland is an act that should be stopped in view of the ecological consideration of these habitats with respect to the birds inhabiting the local marshes.

The Nyangezi swamps are considered as a cradle of biological diversity, by the presence of favorable habitats for reproduction, refuge and feeding for different species. In the Nyamubanda marsh, a diversity of 27 species, 16 families and 8 orders has been inventoried for bird species. The order of Passeriformes was the most represented in the 4 habitats including rice and sorghum fields and papyrus grassland and woodland. The rice and papyrus habitats had almost the same abundance of families, while the woody and sorghum habitats were also close. The species Crithagra mozambica, Vidua macroura, Estrild astrild, Euplectes orix, Euplectes axillaris, Ploceus cuculatus, Ploceus xathops, Ploceus tricolor, Spermetes bicolor, Spermetes fringilloides and Spermetes cucullatus are more frequent in Nyamubanda swamp. Spermetes cucullata is the only species found in all four habitats. Cereal cultivation (sorghum and rice in this case) activity is one of the main causes of the abundance of bird species we found. Farmers should consider the timing of cultivation in this swamp to allow for proper monitoring of bird diversity. Papyrus and woodland habitats should remain a refuge area for birds. Forbidding hunting activities and planned exploitation of non-cereal lands in this area would be an important asset for the conservation of this biodiversity. This preliminary study in Nyamubanda swamp did not take into account monthly sampling for a good understanding of bird diversity. This is a very important aspect to develop in future work in relation to ecological factors to better understand the status of avian diversity of wetland birds in the Nyangezi swamps.

We thank Jean Nacishali for drawing up the map of this swamp and sampling stations. To the members of the Laboratoire d’Hydrobiologie, d’Aquaculture et de Gestion des Ressources Naturelles at the Université Officielle de Bukavu for their support in the field.

Gabriel Baguma collected the data and wrote the article. Cirhalwirwa Oliva Mugoli collected most of the field data. Mirindi Pascal Murhula and Ngabo Vianney Mulema participated in the field activities. Legrand Cirimwami supervised the team and reviewed the manuscript draft many times.

The authors declare that there is no conflict of interest

Baguma, G., Mugoli, C.O., Murhula, M.P., Mulema, N.V. and Cirimwami, L. (2023) Avian Diversity in Nyangezi Wetlands: The Case of Nyamubanda Swamp in the Territory of Walungu, Sud-Kivu, Eastern Democratic Republic of the Congo. Open Access Library Journal, 10: e9677. https://doi.org/10.4236/oalib.1109677