Habitat‐dependent occupancy and movement in a migrant songbird highlights the importance of mangroves and forested lagoons in Panama and Colombia

Climate change is predicted to impact tropical mangrove forests due to decreased rainfall, sea‐level rise, and increased seasonality of flooding. Such changes are likely to influence habitat quality for migratory songbirds occupying mangrove wetlands during the tropical dry season. Overwintering habitat quality is known to be associated with fitness in migratory songbirds, yet studies have focused primarily on territorial species. Little is known about the ecology of nonterritorial species that may display more complex movement patterns within and among habitats of differing quality. In this study, we assess within‐season survival and movement at two spatio‐temporal scales of a nonterritorial overwintering bird, the prothonotary warbler (Protonotaria citrea), that depends on mangroves and tropical lowland forests. Specifically, we (a) estimated within‐patch survival and persistence over a six‐week period using radio‐tagged birds in central Panama and (b) modeled abundance and occupancy dynamics at survey points throughout eastern Panama and northern Colombia as the dry season progressed. We found that site persistence was highest in mangroves; however, the probability of survival did not differ among habitats. The probability of warbler occupancy increased with canopy cover, and wet habitats were least likely to experience local extinction as the dry season progressed. We also found that warbler abundance is highest in forests with the tallest canopies. This study is one of the first to demonstrate habitat‐dependent occupancy and movement in a nonterritorial overwintering migrant songbird, and our findings highlight the need to conserve intact, mature mangrove, and lowland forests

Wastewater disposal at safari lodges in the Okavango Delta, Botswana

Many safari lodges in the Okavango Delta obtain their water supply from boreholes in near-surface aquifers while disposing of their wastewater via soak-aways, creating a potential risk of contamination of their water supply. Most islands in the Delta contain sites where the groundwater has become salinised as a result of transpiration by island vegetation. This study of wastewater disposal at such a site on Chitabe Island, which involved surveying of the water table, measurement of groundwater salinity, field bacteriological screening and groundwater flow modelling has revealed that although water disposal has created a recharge mound, the depression in the water table induced by transpiration by island vegetation is such that pollutants will remain confined to the region of maximum groundwater depression. Although the soils are sandy, they exhibit significant filtration effects on bacteria. The field assay used in this study was unable to detect coliform and E. coli bacteria in groundwater within a distance of 20 m from the disposal point. Modelling of groundwater flows indicates that boreholes located on the outer fringes of the island are secure from contamination. The study suggests that disposal of wastewater into areas where the groundwater is salinised provides a sustainable solution to the problem of wastewater disposal in the Okavango Delta. Water SA Vol.30(1): 121-12