Environmental Determinants Influencing Seasonal Variations of Bird Diversity and Abundance in Wetlands, Northern Region (Ghana)

Hindawi Publishing Corporation International Journal of Zoology Volume 2014, Article ID 548401, 10 pages http://dx.doi.org/10.1155/2014/548401 Research Article Environmental Determinants Influencing Seasonal Variations of Bird Diversity and Abundance in Wetlands, Northern Region (Ghana) Collins Ayine Nsor1 and Edward Adzesiwor Obodai2 1 2 Center for Savannah Ecosystem Research (CESER), P.O. Box TL 861, Tamale, Ghana Department of Fisheries and Aquatic Sciences, University of Cape Coast, University Post Office, Cape Coast, Ghana Correspondence should be addressed to Collins Ayine Nsor; Received 28 May 2014; Revised 10 August 2014; Accepted 14 September 2014; Published 29 October 2014 Academic Editor: Greg Demas Copyright © 2014 C. A. Nsor and E. A. Obodai. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The study assessed major environmental determinants influencing bird community in six wetlands over a 2-year period. A combination of visual and bird sounding techniques was used to determine the seasonal variations in bird abundance, while ordination techniques were performed to determine the influence of environmental factors on bird assemblage. A total of 1,169 birds from 25 species and 885 individuals from 23 species were identified in the wet and dry season, respectively. The shallow close marshes supported the greatest number of birds (𝑃 < 0.05) compared to the riparian wetlands. Bird diversity was significantly higher in the wet season than in the dry season (𝐹 = 4.101, 𝑃 < 0.05). Cattle egret (Bubulcus ibis) and marsh warbler (Acrocephalus palustris) were the most abundant. Using the IUCN “Red List” database guide, we noted that 96.2% of birds identified were least concern (LC). The yellow weaver bird (Ploceous megarhrynchus) was the only vulnerable species (VU) and represented 3.8%. From the three variables tested, bushfire and farming practices were the major threats and cumulatively explained 15.93% (wet season) and 14.06% (dry season) variations in bird diversity and abundance. These findings will help wetland managers design conservation measures to check current threats on birds from becoming vulnerable in the future. 1. Introduction Birds play a vital role in enriching the biodiversity of wetlands. This explains why wetlands are foremost recognized as a haven for waterfowl by Ramsar International in 1971 [1]. Their sensitivity to habitat perturbation makes them suitable as bioindicators to wetland health, through their population size and composition. Globally, over 150 bird species are reportedly lost since the year 1500 AD [2]. Recent reports have shown that birds have gone extinct at an exceptionally high rate, estimated to be 1,000 to 10,000 times the natural background rate [2]. Today, one in eight bird species is threatened with global extinction, with 190 species critically endangered and particularly alarming are sharp declines in a number of formerly common and widespread species, such as cranes and some waders. The International Union for the Conservation of Nature (IUCN) “Red List” have shown documented evidence that rate of extinction is getting worse among species confined to small islands to continental scale [2]. This loss is largely due to their increasingly intolerance to the slightest ecosystem disturbance [3] which is linked to pollution [4], habitat type and bird distribution [5, 6], wetland patch size [7], cutting of mangrove vegetation [8], farming practice and urban development within the wetland catchment [9–11], and habitat fragmentation [12]. These human disturbances at the landscape scale have structured the population and assemblages of birds because of their highly specific habitat requirements [13, 14]. Scientific studies on bird ecology, diversity, abundance, and spatial distribution are simply absent or poorly investigated in the Northern Savannah wetlands of Ghana. However, unlike the Northern Region, research on birds in the Southern forest belt [15–17] and coastal wetlands has been considerably extensive [18–22]. The only notable work 2 previously conducted in one of the wetlands under the current study (Kukobila wetland) was to establish a baseline of the types of birds found in the wetland [23]. Understanding overall bird responses to disturbances will as well require the assessment of the various disturbance scenarios on a seasonal basis, since the impacts of environmental determinants are many and vary along seasonal trends. Ecological changes and land use activities within wetlands catchment in Northern Region of Ghana are seasonally driven and can potentially affect bird assemblage, composition, and habitat preference. Of the 728 bird species recorded in Ghana [18–20] six of them are considered threatened and 12 near threatened [24]. For example the National Biodiversity Strategy for Ghana Report mentioned hornbill, parrots, and birds of prey, as the few keystone species under threat [25]. Though these findings were largely from the southern sector of Ghana (i.e., forest belt and coastal zones), the phenomenon suggests that some birds in the Northern Savannah zone might be under threat or at risk of extinction, giving recent undocumented, but observed, environmental disturbances on the wetlands. Therefore, the absence of a scientific investigation makes it impossible to determine the current state of bird population, composition, and habitat preference (using their proximate cues), on a seasonal basis among wetlands in the Northern Savannah zone. In this study, we apply multivariate ordination techniques to determine the influence of three environmental factors on the seasonal variation of bird population, diversity, and habitat preference among the wetlands. The outcome of this investigation will help equip wetland managers with first-hand information on the types of seasonal disturbance scenarios and how these disturbances could potentially modify bird assemblage in the future and the selection of appropriate conservation approach towards enhancing the sustainability of their population. 2. Methods The study was carried out in six wetlands located in the Northern Region of Ghana, with their coordinates as follows: (i) Wuntori (N09∘ 08.335󸀠 W00∘ 1 09∘ .685󸀠 ); (ii) Kukobila (N10∘ 08.723󸀠 W000∘ 48.179󸀠 ); (iii) Tugu (N09∘ 22.550󸀠 W000∘ 35.004󸀠 ); (iv) Bunglung (N09∘ 35.576󸀠 W000∘ 47.443󸀠 ); (v) Adayili (N09∘ 41.391󸀠 W000∘ 41.480󸀠 ); and (vi) Nabogo (N09∘ 49.941󸀠 W000∘ .51.942󸀠 ) (Figure 1). The six sites lie on the extensive floodplain along the course of the White Volta River, which has over time become incised and modified through meandering and aligning along various topographic features. This has led to the development of streams that have diverted from the main White Volta [26]. All six wetlands were classified as close shallow marshes ( (...truncated)