Phoebe Barnard

Phenological changes in the southern hemisphere.

Current evidence of phenological responses to recent climate change is substantially biased towards northern hemisphere temperate regions. Given regional differences in climate change, shifts in phenology will not be uniform across the globe, and conclusions drawn from temperate systems in the northern hemisphere might not be applicable to other regions on the planet. We conduct the largest meta-analysis to date of phenological drivers and trends among southern hemisphere species, assessing 1208 long-term datasets from 89 studies on 347 species. Data were mostly from Australasia (Australia and New Zealand), South America and the Antarctic/subantarctic, and focused primarily on plants and birds. This meta-analysis shows an advance in the timing of spring events (with a strong Australian data bias), although substantial differences in trends were apparent among taxonomic groups and regions. When only statistically significant trends were considered, 82% of terrestrial datasets and 42% of marine datasets demonstrated an advance in phenology. Temperature was most frequently identified as the primary driver of phenological changes; however, in many studies it was the only climate variable considered. When precipitation was examined, it often played a key role but, in contrast with temperature, the direction of phenological shifts in response to precipitation variation was difficult to predict a priori. We discuss how phenological information can inform the adaptive capacity of species, their resilience, and constraints on autonomous adaptation. We also highlight serious weaknesses in past and current data collection and analyses at large regional scales (with very few studies in the tropics or from Africa) and dramatic taxonomic biases. If accurate predictions regarding the general effects of climate change on the biology of organisms are to be made, data collection policies focussing on targeting data-deficient regions and taxa need to be financially and logistically supported.

Climate change and birds: perspectives and prospects from southern Africa

Global climate warming, now conclusively linked to anthropogenically-increased CO2 levels in the earths atmosphere, has already had impacts on the earths biodiversity and is predicted to threaten more than 1 million species with extinction by 2050. Climate change in southern Africa is expected to involve higher temperatures and lower rainfall, with less predictability and a greater frequency of severe storms, fires and El Niño events. The predicted changes to birds in Africa — the continent most at risk from climate change — have hardly been explored, yet birds and many other vertebrates face uncertain futures. Here, in one of the first focused analyses of the correlates of climate change vulnerability in southern African birds, we offer a wide-ranging perspective on which species may be most at risk, and explore which traits may influence the adaptability or extinction risk of bird species. Our review suggests that small nomadic species with short generation times may be least at risk. While larger-bodied species may be physiologically buffered against environmental change, their longer generation times may make them less able to adapt evolutionarily to climate change. Migrant species, and those with specialised feeding niches such as pollinators, are also predicted to be at risk of population declines, based on low ability to adapt to new environments when introduced there as aliens. Species with small ranges (<50 000km2) restricted to the two southern African biodiversity hotspots most at risk from climate change — the Cape Floral Kingdom and the Succulent Karoo — are ranked according to low, medium or high risk of extinction. Those restricted to mountain slopes, mountain tops or islands, and those occurring mainly at the southern or western extremes of these biomes, are ranked as highest risk. These include endemic sunbirds, warblers and rock-jumpers — none of which are currently recognised Red Data species. Using climate envelopes we modelled the possible range shifts by 2050 of three pairs of species found in habitats considered to be at risk: fynbos, mountain and arid Karoo. All six species lost substantial portions of their range (x = 40%), with the montane Drakensberg Rock-jumper Chaetops aurantius losing most (69%). Significant reductions of available climate space in all species may interact with life history characteristics to threaten many southern African bird species unable to shift geographic range or adapt to novel resource conditions. We conclude with a list of research priorities and testable hypotheses which may advance our understanding of the complex influence that climate change is likely to have on African, particularly southern African, birds.

A 2017 Horizon Scan of Emerging Issues for Global Conservation and Biological Diversity

We present the results of our eighth annual horizon scan of emerging issues likely to affect global biological diversity, the environment, and conservation efforts in the future. The potential effects of these novel issues might not yet be fully recognized or understood by the global conservation community, and the issues can be regarded as both opportunities and risks. A diverse international team with collective expertise in horizon scanning, science communication, and conservation research, practice, and policy reviewed 100 potential issues and identified 15 that qualified as emerging, with potential substantial global effects. These issues include new developments in energy storage and fuel production, sand extraction, potential solutions to combat coral bleaching and invasive marine species, and blockchain technology.

Novel methods reveal shifts in migration phenology of barn swallows in South Africa

Many migratory bird species, including the barn swallow (Hirundo rustica), have advanced their arrival date at Northern Hemisphere breeding grounds, showing a clear biotic response to recent climate change. Earlier arrival helps maintain their synchrony with earlier springs, but little is known about the associated changes in phenology at their non-breeding grounds. Here, we examine the phenology of barn swallows in South Africa, where a large proportion of the northern European breeding population spends its non-breeding season. Using novel analytical methods based on bird atlas data, we show that swallows first arrive in the northern parts of the country and gradually appear further south. On their north-bound journey, they leave South Africa rapidly, resulting in mean stopover durations of 140 days in the south and 180 days in the north. We found that swallows are now leaving northern parts of South Africa 8 days earlier than they did 20 years ago, and so shortened their stay in areas where they previously stayed the longest. By contrast, they did not shorten their stopover in other parts of South Africa, leading to a more synchronized departure across the country. Departure was related to environmental variability, measured through the Southern Oscillation Index. Our results suggest that these birds gain their extended breeding season in Europe partly by leaving South Africa earlier, and thus add to scarce evidence for phenology shifts in the Southern Hemisphere.

When to stay, when to go: trade-offs for southern African arid-zone birds in times of drought

Introduction Prolonged spells of drought pose dilemmas for most organisms, even those adapted to hyper-aridity. For birds, reproduction, feeding, dispersal and moult are all activities which may need careful timing in relation to fluctuations in ecological productivity. In arid and semi-arid ecosystems, rainfall often triggers events in the life cycle which may be suppressed for months or even years during dry periods. In times of very low productivity or harsh conditions, birds, like many other animals, can move to escape local conditions and improve their chances of feeding or reproduction. However, some resident species may not move, but simply adjust their activities to ‘ride out’ difficult periods. Semi-arid ecosystems are characterised by wet or dry states that are patchy in time and space. This patchiness is particularly true of southern Africa, where much of the region is semi-arid and the environment experiences extremes in weather, from periods of intense and prolonged drought to exceptionally high rainfall events. Rainfall in arid and semi-arid ecosystems in the southern hemisphere, including southern Africa, is greatly affected by El Niño Southern Oscillations (ENSO), leading to large variability in rainfall and prolonged droughts. Similarly, extensive wet periods (La Niña events) have concomitant effects on ecosystem functioning. The effects of El Niño and La Niña have been well studied in a few organisms, particularly birds, where changes in species richness and density and reproduction are correlated with the wet–dry cycles of ENSO years. Birds, other animals and plants respond to increased rainfall in similar ways, and both birds and plants tend to increase reproductive effort with more rain. The response by biota to extended dry periods in semi-arid environments, however, differs markedly between and within invertebrate and vertebrate phyla, and markedly between most animals and plants. Plants cope with droughts by dying after depositing dormant propagules (ephemerals) or becoming dormant and restricting their internal water use by discarding leaves or leaves and stems. Although death and propagule dormancy are options taken by plants and some invertebrate taxa, viz. brine shrimp (Artemia), these options are not available to vertebrates, leaving escape and water conservation as the alternatives. Drought-induced dormancy in vegetation therefore has effects on animals. Animals in general, and birds in particular, cope with droughts and changes in vegetation by using behavioural and physiological tactics, including opportunistic movement away (in birds), shifts in habitat and deferred hatching or dormancy in eggs (in locusts). It is not known in detail whether birds make dietary shifts during extended droughts, but many species are opportunistic in their foraging and feeding in the Karoo and it is very likely that such shifts do occur. Our questions in this review are: (1) what is the influence of variability in rainfall on avian populations, including breeding and movements? and (2) how resilient are bird populations to extended dry periods? While we do not explicitly review climate change per se, our conclusions should be of value in predicting species-specific responses and levels of vulnerability to changing rainfall patterns in Africa.

What precipitates influxes of wetland birds to ephemeral pans in arid landscapes? Observations from Namibia

Simmons, R.E., Barnard, P.E. & Jamieson, I.G. 1998. What precipitates influxes of wetland birds to ephemeral pans in arid landscapes? Observations from Namibia. Ostrich 70 (2): 145–148 The ability of wetland birds to rapidly find and exploit ephemeral pans is well known in and lands, but the episodic nature of such events means that the methods employed are poorly understood. Birds may: (i) wander randomly until wetlands are found; (ii) predict rainfronts and rainfall using changes in pressure gradients as cues; or (iii) follow rainfronts directly and descend onto pans as they fill. Observations from isolated pans in Namibia during the first rains indicate that wetland birds follow rainfronts, and descend onto pans as they fill. In one 30 ha pan, 37 birds of 5 species had arrived one day after filling and in another 50 ha pan over 300 birds of 13 species were attracted within 3 days of filling. Wetland birds, like migratory raptors, therefore, follow rainfronts, andMaywander locally thereafter. How specie...

Endemic birds of the Fynbos biome: a conservation assessment and impacts of climate change

The South African Fynbos biome, a global biodiversity hotspot with high endemism and species richness, has six endemic bird species. These are important not only intrinsically, but also for ecological functioning and as flagships for South Africa’s economically valuable avitourism sector. Little is known about population sizes or realised distribution ranges of these six species, but projected range modelling based on occurrence from the South African Bird Atlas Project (SABAP) has suggested these species are vulnerable to climate change. We estimate global population sizes for these six endemics based on densities calculated from two intensive biome-wide point count surveys in 2012. We modelled regions of suitable climatic space, from which we established that mean annual temperature and the temperature of the warmest quarter of the year appear to limit Cape Rock-jumper Chaetops frenatus and Protea Canary Serinus leucopterus ranges. Both species have seen an apparent > 30% decrease in range and reporting rates (a proxy for abundance) in the twenty years between SABAP atlas periods (1987–1991 and 2007–ongoing). The Cape Rock-jumper result is unexpected: encounter rates are higher in shorter vegetation, dry slopes and habitats with more recent occurrence of fire – all proxies for proximate causes of climate change on the Fynbos. Although coastal plains are highly transformed, mountain Fynbos is the best protected of all the world’s Mediterranean-climate habitats, with relatively little anthropogenic land transformation. Long term weather datasets from the Fynbos demonstrate significant warming since 1960. We conclude from these lines of evidence that these decreases are consistent with the loss of suitable climate space and inability of these species to adjust physiologically to increasing temperatures.

Nutrient Addition and Moisture Promote the Invasiveness of Crimson Fountaingrass (Pennisetum setaceum)

Abstract We conducted a greenhouse study to examine the effects of different habitat conditions and environmental resources on the growth rates of crimson fountaingrass, an invasive, alien, perennial grass in South Africa. To help understand the factors promoting the spread of this emergent alien grass, we investigated the effects of temperature regimes, nutrient and moisture addition, and soil type on seedling growth rates and biomass allocation. Our results suggest that crimson fountaingrass seedlings do not tolerate drought because they died within 1 mo without water. Additional nutrients and extra water increased seedling growth rates throughout the study period. Higher temperatures with extra moisture increased seedling growth rates and the development of belowground biomass throughout the study period. This study demonstrates the importance of available environmental resources and their interaction with some habitat conditions in promoting crimson fountaingrass growth. We suggest that soil moisture and nutrient availability are critical factors affecting successful establishment of crimson fountaingrass in arid environments. Managers should target seedlings for removal following precipitation and in areas of nutrient enrichment, such as near rivers and at road–river crossings. Nomenclature: Crimson fountaingrass, Pennisetum setaceum (Forsk.) Chiov. PESSA

Population metrics for fynbos birds, South Africa: densities, and detection and capture rates from a Mediterranean-type ecosystem §

Estimates of bird numbers through quantification of density and range sizes are necessary for decisions regarding conservation status, yet counts of birds are often confounded by uncertainty of detection. The status of the endemic birds of the Fynbos biome is of interest due to their conservation value in a global biodiversity hotspot, the ecological services they provide, and their importance for the avitourism industry. We conducted an extensive repeated point-count survey across the Fynbos biome, South Africa, to determine probability of detection and covariates of site occupancy for 27 bird species. Detection of most species was influenced by time of day, temperature or vegetation height. Important covariates influencing site occupancy were vegetation height, altitude, time since fire and habitat type. Site occupancy for four fynbos-endemic species was positively associated with increasing altitude. We further conducted point counts and mist-netting in eastern regions of the Fynbos biome to calculate local density and standardised capture rates. A linear regression analysis showed that capture rates were a function of bird densities, but that several species were captured at higher rates than expected, notably nectarivorous species. During mist-netting a relative abundance count was conducted. We expected deviation of the fit of the regression of capture rates on relative abundance to correlate with detection probability, because we expect this index to underestimate skulking and cryptic species, but there was no correlation. Estimated species richness indices were highest for the biome-wide survey, and lowest for mist-netting due to the body size limit imposed by the capture technique. Overall, we showed that point counts are an effective method for surveying birds in the fynbos and that mist-netting can be used to create an index of relative abundance for smaller species, but can be significantly affected by net placement.

Aspects of the ecology and morphology of the protea seedeater, Crithagra leucopterus, a little-known Fynbos endemic

The protea seedeater, Crithagra leucopterus, is one of six passerine birds endemic to the Fynbos Biome, South Africa. It is the least known of these, and there is very little information on breeding and habitat use. Through nest observations and a bird ringing scheme in the eastern sections of the Fynbos, we provide updated information on habitat use, breeding and population biometrics. We document changes in capture rates for a suite of birds in relation to a fire event and use of burnt and unburnt sites within Blue Hill Nature Reserve, South Africa. Protea seedeaters were recorded nesting in mature Fynbos, but feeding in recently burnt Fynbos on freshly released protea seeds, suggesting the species benefits from small-scale burns that create a landscape of mixed veld ages. Protea seedeaters weighed less and had shorter wings compared to those of the western Fynbos. Further habitat-use and life-history information on protea seedeaters is needed to help guide conservation management plans, especially in the light of changing fire regimes in the Fynbos.