Abundance and prey capture success of Common Terns (Sterna hirundo) and Pied Kingfishers (Ceryle rudis) in relation to water clarity in south-east coastal Ghana

Abstract Background Water clarity may negatively influence rate of plunge diving and prey capture success of piscivorous plunge-diving birds, and therefore has implications for their conservation in polluted urban wetlands. We studied the relationship between water clarity and the abundance and prey capture success of Pied Kingfishers (Ceryle rudis) and Common Terns (Sterna hirundo) in two polluted coastal waters of south-east Ghana—the Weija Lake and Densu Delta Ramsar Site. Methods On each wetland, data on abundance and prey capture success of plunge-divers were collected in four spatio-temporal quadrats of 100 m × 100 m and analysed with concurrent measurements of water quality parameters using GLM regression with Pearson’s correlation coefficients. Results Mean prey capture success of Pied Kingfishers (34.7 ± 13.1%) and Common Terns (35.3 ± 11.0%) were similar but the two species responded differently to water clarity. The abundance of Common Terns was significantly higher in less transparent/more turbid water while that of Pied Kingfishers showed no significant relationship with turbidity and transparency. In contrast, the prey capture success of Common Terns was neither related to transparency nor turbidity, as opposed to that of Pied Kingfishers which was significantly higher in more turbid/less transparent waters. Correlations between capture success and bird abundance, as well as capture attempts were insignificant, suggesting that increased fish abundance associated with cloudy water may not necessarily promote higher abundance and capture success of foraging birds. Thus, when foraging in less transparent water, capture success may depend more on predator avoidance by fish prey than lower prey detectability of foraging birds. Conclusion Within a gradient of 15–51 cm transparency studied, lower water clarity did not constrain prey capture success of Common Terns and Pied Kingfishers. Further studies on the foraging ecology of plunge-divers in coastal Ghana are however required to make firm conclusions on the relationship between water clarity and foraging birds and fish prey abundances, as well as capture success

Patterns of green space change and fragmentation in a rapidly expanding city of northern Ghana, West Africa

Green spaces such as forests, grasslands, and croplands (including gardens) can be found in urban environments. Although they benefit human and animal well-being, they have become threatened due to rapid urban growth and unplanned development. Yet, little attention has been given to studying the dynamics of urban green spaces in sub-Saharan Africa. In this study, we examined the dynamics of land use and land cover (LULC) change and fragmentation (especially, green spaces) within the second fastest urbanising city in Ghana, Tamale. In particular, we focused our analyses on its urban core (∼5 km radius around the city centre) due to its relevance to urban economy and society. Landsat data was used to estimate fragmentation metrics of past and future LULC changes in the study area from 1990 to 2052. We found clear patterns of green space decline and fragmentation within the urban core: i.e., green spaces became patchy over time and the pattern was expected to continue in the future. Additionally, we found the built-up class benefited from the decline of green spaces with the latter being significantly negatively correlated with human population size. Our investigation reveals that protected forests and tree plantations contributed to a significant proportion of available green spaces in the urban core. However, these areas were becoming increasingly threatened by forest reserve downsizing, indiscriminate activities (e.g., logging and encroachment), and sale of public lands to private developers, practices commonly associated with population growth. Hence, the enforcement of relevant local legislations (e.g., the 2016 Land Use and Spatial Planning Act [Act 925]) coupled with the integration of urban initiatives and policies that encourage green spaces are needed to ensure the sustainability of urban ecosystems for the well-being of humans and the environment