Namibian Journal of Environment

Ecological niche modelling of tree and wood pipits in southern Africa and adjacent countries may help to delimit distributions based on citizen science data

2023-06-25T12:17:11+00:00

Distribution maps are generally based on documented records rather than true occurrence patterns. This may be problematic for cryptic, under-reported species that occur in areas poorly covered by observers. Species distribution models may help overcome this challenge. Here, all available records of the migratory Anthus trivialis (tree pipit) and resident Anthus nyassae (wood pipit) for southern Africa and adjacent areas were assembled to train generalised linear models, random forest and gradient boosting machine species distribution models. Sampling pseudo-absences from a common species’ similarly biased records helped to account for the spatial sampling bias present in the data. The model outputs suggest that A. trivialis and A. nyassae display a latitudinal habitat suitability gradient in the area of interest, opposing a latitudinal reporting gradient. The migratory behaviour of A. trivialis may blur its ecological niche. More and more reliable field observations are needed to confirm these findings. This study provides a clear framework to assist distribution delimitations from citizen science data by counteracting observer and sampling biases.

The importance of large pans and surrounding bushveld for black rhino (Diceros bicornis ssp. bicornis) habitat use in the Kalahari: implications for reintroduction and range expansion

2023-05-29T10:19:23+00:00

In the Kalahari region of southern Africa, recurrent droughts can affect local livestock production and even lead to the loss of traditional farmland. As a result, the wildlife economy has grown in importance as a profitable approach to the sustainable use of native game species adapted to these challenging climatic conditions. This has led to restoration efforts in the region that have brought back wildlife including the critically endangered black rhino (Diceros bicornis). To understand the interrelationship between a reintroduced black rhino population and a rural Kalahari wildlife reserve, this research project aimed to decode the key drivers of black rhino habitat use based on a multiscalar approach of combined aerial and ground information on ecogeographical variables (vegetation and artificial habitat components) together with spatial rhino location and individual movement data. On average, black rhino home ranges were found to be 67 ± 20 km2, with core areas of 24 ± 11 km2. These are predominantly covered by the landscape types of bushveld and calcareous pans. Analysis of the different landscape factors present in the reserve showed that vegetation heterogeneity, vegetation density, vegetation damage, browse availability and waterhole density were significantly higher in the pooled core areas of the total population compared to less frequented areas. Furthermore, a binary logistic regression model predicted that browse availability and vegetation heterogeneity of medium to large woody species to be the most significant effect on black rhino habitat use. The model also showed a negative correlation with Acacia spp. saplings, which can be explained by the decline or absence of saplings in the core areas due to the continuous feeding pressure of black rhinos and other herbivores. Evaluation of black rhino habitat use and spatial distribution indicates a strong preference for the mosaic of microhabitats around calcareous pans and surrounding lunette dunes covered by bushveld. Together with the year-round availability of water (rain-fed lakes and artificial waterholes), these focal points are of high ecological importance and provide suitable habitat conditions that may highlight the potential for further black rhino reintroduction and range expansion, as well as general rewilding efforts in the region.

An evaluation of the simultaneous utilisation of the northern Namib coastline by desert-adapted lions (Panthera leo) and recreational shore anglers, during the 2022/2023 Torra Bay Campsite season, in the Skeleton Coast National Park

2023-02-24T12:46:43+00:00

Since 2017 desert-adapted lions (Panthera leo) that occupy large sections of the Skeleton Coast National Park and the Northern Namib in Namibia have expanded their movements along the arid coastline and increased their use of marine food items in the inter-tidal zones. The annual opening of the Torra Bay Campsite during the December/January holiday period for offshore line fishing has raised increasing concerns of conflict between lions and anglers. During the 2022/2023 season the simultaneous use of the Torra Bay coastline by anglers and lions was evaluated. One lioness utilised the Torra Bay coastline for 34 days or 50% of the Torra Bay season. She adapted her activity patterns by hunting along the inter-tidal zones at night and retreated inland during the daytime and avoided interactions with anglers. Notwithstanding, the lioness continued to utilise the coastal habitat and prey on marine food items, particularly Cape fur seals (Arctocephalus pusillus) that contributed 78% of her biomass consumption. An awareness campaign with regular updates on five social media platforms in combination with the constant presence of conservation authorities may have contributed to public awareness, respectful behaviour from Torra Bay visitors and no incidents of conflict.

Status, distribution and numbers of birds in the Ogongo Game Park, north-central Namibia

2023-02-06T20:46:21+00:00

In 2012, a simplified territory mapping method was employed to study the distribution and numbers of all birds breeding in the Ogongo Game Park (OGP). OGP is situated approximately 50 km north-west of Oshakati, in the Outapi district, Omusati region, North-Central Namibia. The area of the park is approximately 1000 ha. The vegetation of OGP comprises mainly mopane savanna Colophospermum-Acacia nilotica. In total, 142 bird species were recorded: 101 breeding residents, 19 regular visitors, 10 irregular visitors, 3 vagrants, 10 Palaearctic migrants. Maps showing the distribution of identified territories are presented for all breeding species. The dominant species were Ring-necked Dove Streptopelia capicola (14.2%), Helmeted Guineafowl Numida meleagris (9.3%), White-browed Sparrow-Weaver Plocepasser mahali (9.3%) and Blue Waxbill Uraeginthus angolensis (8.3%). Nine other species were classified as subdominant, comprising a further 27.7% of all breeding birds.

Mountain Wheatear Myrmecocichla monticola: comparative biometrics, moult and breeding data, and criteria for the determination of age and sex

2022-11-12T08:26:41+00:00

In this article we present measurement and moult data from over 160 Mountain Wheatear (Myrmecocichla monticola) of the subspecies atmorii (Tristram, 1869) ringed in Namibia, as well as two individuals of the adjacent northerly subspecies M. m. albipileata (Bocage, 1867) from Angola, and discuss our findings from these subspecies. We gathered nesting, breeding and moulting records for Namibia from published literature and photographic records, and compared our observations of the moult process and our records of active brood patches with breeding records, gathered by Brown et al. (2017), to gain insight into the timeline of physical processes. On the basis of photographs, we describe the nestling and compare juvenile and immature plumage and other features which help to distinguish these age groups. We add notes on the overall numbers observed in the last fifteen years and notes on recaptures, site fidelity and parasites. We discuss the white covert-patch as an indicator of age and document undescribed plumage details such as signs of a second-year plumage, spots on the coverts of first-year birds, white supercilium in grey males, the occurrence of grey or black greater coverts in grey males and features from both sexes in one plumage. This article is intended to supplement published data and encourage further research and discussion.

Red-backed Shrike (Lanius collurio) Linnaeus, 1758 on its non-breeding grounds: comparative biometrics, moult data and criteria to determine age and sex

2022-11-10T20:06:12+00:00

Much is still unknown or unpublished in the Afrotropical literature concerning the complexity of the plumage features of the Red-backed Shrike (Lanius collurio). We present measurements, moult data and related observations for about 300 Red-backed Shrikes collected while ringing them in their non-breeding range in southern Africa. We discuss our findings on timing and progress of primary moult in adults and birds in their first year of life. We describe in detail plumage features for the determination of age and sex, and discuss colour and plumage variations in both sexes, especially females, and the occurrence of white wing patches in males. We give photographic evidence of the change of the bill colour during the non-breeding season and add notes on age and sex ratio, retraps and site fidelity. We also discuss the long-standing claims of Red-backed Shrike breeding in the southern hemisphere. Our field excursions between 2002 and 2022 were based mainly in Namibia during the Austral summer months, from November to April. We have included supplementary records of this species from Botswana and Zambia.

Tractrac Chat Emarginata tractrac: comparative biometrics, moult data and criteria for the determination of age and sex

2022-10-27T06:50:37+00:00

Data on the Tractrac Chat (Emarginata tractrac) (Wilkes), 1817 are scarce and widely scattered in the literature. We present measurement and moult data from 97 Tractrac Chats of the subspecies E. t. albicans ringed in Namibia over 20 years. We gathered published data of nesting, breeding and moulting, and compare our observations of the moult process and our records of active brood patches with breeding records compiled by Brown et al. (2017). On the basis of photographs, we describe the nestling of the ssp. E. t. albicans and its development to immature and then adult. We compare young and adult plumage and other features which help to distinguish these age groups. We also document several cases of irregular primary moult. We add observations on site fidelity; on changes in habitat and subsequent changes in numbers of territories; on the development of overall numbers of the species in our research area; on behaviour and on parasites and injuries. We also point out errata in the literature from Levaillant that remain in use, as well as discuss the elevation of the distribution range

How well do CHIRPS precipitation estimates relate to measured rainfall in Namibia?

2022-09-07T13:13:57+00:00

Measured rainfall data from 33 ground-based rainfall stations were compared with rainfall estimates from CHIRPS (Climate Hazards Infrared Precipitation with Stations) across a rainfall gradient in central Namibia. There was close agreement between the two datasets across the interior of the country from the escarpment eastwards. However west of the escarpment the two datasets diverged. In this zone all CHIRPS estimates were higher than measured values and the seasonal variability of CHIRPS estimates declined towards the coast whereas measured rainfall variability rose. Quality assessments of CHIRPS in the literature have suggested there is a tendency for the model to overestimate the frequency of rainfall events, and to record low rainfall rather than zero rainfall in low rainfall areas. These effects may be exacerbated in Namibia by the prevalence of coastal fog. Increasing the number of reliable ground-based stations across the coastal zone may go some way to addressing the discrepancy in Namibia between CHIRPS estimates and ground measurements.

First records for Namibia of Lesser Masked Weaver Ploceus intermedius subsp. beattyi

2022-08-13T19:57:04+00:00

The presence in Namibia along the Kunene River and border of Angola of the beattyi subspecies of Ploceus intermedius (Lesser Masked Weaver) is reported for the first time. Observations suggested that beattyi probably grades into birds of the cabanisii subspecies from Epupa Falls and further upstream along the Kunene River, while typical cabanisii occurs south of the Kunene River.

Analysis of records from community game guards of human-elephant conflict in Orupupa Conservancy, northwest Namibia

2022-05-05T07:09:44+00:00

Competition between local people and elephants (Loxodonta africana) for water and vegetation is an increasing concern in many conservancies in northwest Namibia. Many livestock were lost during droughts in 2018-2019, and there are risks of more severe droughts in the future because of climate change. Little research has been published on elephants in the Northern Highlands, although the community game guards have been collecting data for many years in Event Books, as part of their role within conservancies. These include records of human-elephant conflict incidents. The objective of this study was to assess in detail the data on human-elephant conflict in Event Books for Orupupa Conservancy. In addition to analysis of Event Book data, consultations were carried out with community game guards in 2021 and 2022. Incidents involving elephants tend not to be frequent, but damage at water points can have a major impact on a local community because of the time taken and expenses of repairing the infrastructure. In 2019 and 2020 there was a changing dynamic in which some local communities set up vegetable gardens near water points or springs. The number of incidents of elephant damage at vegetable gardens greatly increased in 2020. Our study demonstrates that detailed analysis of Event Book data for additional conservancies would be useful. Combined with local ecological knowledge, the Event Book data can be used to inform the planning of local actions to reduce human-elephant conflict, including conservation of elephants and their habitats, in line with the actions in Namibia’s National Elephant Conservation and Management Plan. The study also confirmed the substantial knowledge of community game guards and their important work in keeping records in Event Books. The expansion of their monitoring role to identify specific elephant herds would provide benefits in terms of improving knowledge on the elephant population and movements, and the potential for early warning between villages about the more problematic herds.