Steven W. Evans

Evaluating threats to an endangered species by proxy: air pollution as threat to the blue swallow (Hirundo atrocaerulea) in South Africa

Background, aim, and scopeThe blue swallow (Hirundo atrocaerulea) is one of the most threatened bird species in southern Africa. Among terrestrial birds, its plumage is known to be the most water repellent, an adaptation to foraging on the wing in dense fog. Despite this unique adaptation, the nesting success of the blue swallow at the Blue Swallow Natural Heritage Site (BSNHS) is lower during years with high incidence of fog. As the phenomenon is not observed at other nesting sites, we hypothesized that this is due to changes in the air chemistry at the BSNHS. In the immediate proximity of the BSNHS, plantations of exotic trees (e.g., pines and eucalypts), rich in volatile organic compounds (VOCs), are dominant features. In addition, air pollution from the Johannesburg area is transported with the surface winds and mix with VOCs released from exotic trees. Together with the high humidity and high elevation, these conditions may result in the formation of sulphonates. Sulphonates are strong detergents, and the presence of these in the fog could lead to decreased water repellence of the plumage. This study was performed in order to determine the occurrence and distribution of sulphonates in the BSNHS and to compare these with sulphonates formed in other locations in South Africa. Because the blue swallow is endangered, pine needles were used as proxy to detect formation of sulphonates.MethodsWe sampled pine needles with different exposure to air pollutants, in climates with different humidity, and at different elevation and analyzed these for sulphonates using mass spectrometry.ResultsPine needles from high elevations and the BSNHS, with high humidity, and exposure to air pollution contained significantly higher concentrations of sulphonates than pine needles from low elevations or from high elevations with a dryer climate or a different combination of air pollutants.ConclusionsThese findings lead to two conclusions. First, the occurrence and distribution of sulphonates may be explained by chemical reactions between sulphur dioxide and organic compounds in the humid air induced by ultraviolet radiation. Second, elevated concentrations of sulphonates in the fog could affect the water repellence of the blue swallow plumage, possibly decreasing their capacity to forage in the fog. We cannot prove conclusively that this is the reason why the number of blue swallows at the BSNHS has decreased dramatically, but for endangered species, we may have to rely on proxies to draw conclusions about outside threats. All such information should be valuable in devising protection plans for species under threat.Recommendations and perspectivesThe use of proxies to elucidate threats to endangered species should be evaluated in a broad scale. The mist-belt habitat in general is threatened by many human activities. These findings indicate that air pollution and the proximity of volatile organic compound (VOC) sources close to mist-belt habitat refuges may be an unrecognised conservation threat to the animals inhabiting them.

Historical and current distribution, population size and possible migration routes of the Blue Swallow Hirundo atrocaerulea in Africa

The Blue Swallow Hirundo atrocaerulea is restricted to sub-Saharan Africa, its population size previously estimated at fewer than 1,500 pairs, and is classified as Vulnerable. A better understanding of its current distributional range, population size, protection status and migration routes would improve our ability to conserve the species and the grassland and wetland habitat on which it depends. We now estimate that the Blue Swallow population in the 1850s may have numbered between 1,560 and 2,300 pairs. Based on an assessment of available data, we now estimate the total current Blue Swallow population at 1,006 pairs or 2,012 individuals, an estimated 36–56% decline over the last 150 years. There may be three separate Blue Swallow sub-populations and seven separate migratory routes between their breeding and non-breeding grounds. The Blue Swallow’s range in South Africa and Swaziland has contracted by 74%. The majority of Blue Swallows occupy unprotected areas on their non-breeding grounds in the Democratic Republic of the Congo, Uganda and Kenya. The Blue Swallow population in Africa will continue to decline unless the causes of reduction in Blue Swallow habitat quantity and quality can be stopped and sufficient and additional habitat set aside to sustain viable Blue Swallow populations throughout their range.

Developing a site selection tool to assist reintroduction efforts for the Southern Ground– Hornbill Bucorvus leadbeateri

The Southern Ground-Hornbill Bucorvus leadbeateri (SGH) is regarded as Vulnerable globally and Endangered in South Africa as a result of losing close to 70% of its range and 50% of its historic population in the country. One of the conservation tools being used to address this issue and restore the population to its historic range is reintroductions. The aim of this study was to identify and prioritise probable reintroduction sites in the Mopane Bioregion and the Limpopo and Mpumalanga sections of the Lowveld Bioregion of South Africa (all in the Savanna Biome), by using a niche-based modelling technique (Maxent) combined with GIS analyses. Suitable SGH habitat was determined for farms in the study area and evaluated for the absence of mappable threats. Three priority areas were identified for reintroductions. These areas are in a near-natural state, offer sufficient habitat, are free of mappable threats and are close to formally protected areas. Field surveys of these three priority areas are needed next to validate their suitability for reintroduction purposes. This is the first spatially explicit reintroduction plan for the SGH that has been developed and will contribute to conservationists’ efforts to conserve the SGH.

Current distribution and population size of the Blue Swallow Hirundo atrocaerulea in the southern Tanzanian highlands

Two surveys of Blue Swallows were conducted in the southern Tanzanian highland grasslands in order to determine the habitat preferences and estimate the size of this subpopulation. During the 2008/09 and 2012 surveys, a total distance of 3 635 km was travelled in search of Blue Swallows (at an altitude of above 1 400 m above sea level). Blue Swallows showed no preference for any altitude range above 1 400 m. The Blue Swallows showed a preference for natural pastures and for rural villages interspersed with crops and natural pasture. The buildings in the rural villages provide the nesting sites and, in close proximity, the crops, natural pastures, livestock and their dung possibly provide the food source for the aerial arthropods on which the Blue Swallows feed. In total, 151 Blue Swallows were recorded consisting of 62 males, 68 females and 21 unsexed individuals at 62 localities. These data along with environmental variables were used to construct an ecological niche model for the Blue Swallow. It was estimated that a mean of 12 791 km2 of suitable habitat was available for Blue Swallows. The 151 Blue Swallows recorded within the maximum perpendicular distance of 262 m on either side of the survey route resulted in a subpopulation estimate of 1 014 (338 to 507 pairs) Blue Swallows in the southern Tanzanian highland grasslands (12 791 km2). Mean densities were 0.023 to 0.035 pairs km − 2. A density of 0.13 pairs km − 2 recorded on a cattle farm consisting primarily of grasslands and wetlands was similar to the density of pairs found on sites in South Africa and Swaziland of compara- ble size and with matching characteristics to this site in Tanzania. Based on this new information the global Blue Swallow population estimate is updated to between 1 169 and 1 338 pairs.

Protection of marine birds and turtles at St Brandon’s Rock, Indian Ocean, requires conservation of the entire atoll

A survey of seabirds and turtles at St Brandon’s Rock, 400 km north of Mauritius, was undertaken in 2010. We estimated that 1 084 191 seabirds comprising seven breeding species and excluding non-breeders were present at the archipelago and we counted 279 turtle tracks and nesting pits of green turtles Chelonia mydas. Hawksbill turtles Eretmochelys imbricata were also present. Analyses of 30 different islets that make up the atoll showed that the seabird species mostly partitioned their use of islets based on islet size, with four species preferring larger islets and two species preferring smaller islets. Alien species introduced historically are still present and other threats, such as shipwrecks, remain. We propose conservation and other measures that should adequately protect the birds, turtles and coral reef by treating the atoll as a system.

An unusual nesting site of a Mascarene Martin Phedina borbonica on Mauritius

is restricted to Madagascar, Mauritius and La Reunion (Turner and Rose 1989, Cheke and Hume 2008) and the species is currently classified as Least Concern (IUCN 2010). The Mascarene Martin is described as being common on Madagascar and uncommon on Mauritius and La Reunion (Sinclair and Langrand 2003).On 21 and 22 October 2010 a pair of Mascarene Martins was observed flying in and out of the bow of a small boat. The boat was permanently moored, judging by the sea-life growing on its keel and mooring rope, approximately 20 m from the beach (20°17′38″ S, 57°21′47″ E) just south of the town of Flic en Flac on the western seaboard of Mauritius. On the morning of 21 October, SWE swam out to and boarded the small boat to inspect the nest and confirm breeding. The bow of the boat resembled an underground passage or cave (Figure 1). The bowl of the nest was approximately 0.5 m above the water. This nest appeared to be composed mostly of straw and very few dry twigs and no