It’s been a summer of plentyRain and its profound effects on birds and their habitats in Kwa-Zulu Natal
Text and photographs Nicolette Forbes
The KZN climate
Rain approaching – a welcome sight in a water short country.
The beautiful result of rain in the air – light refraction separates the different wavelengths in sunlight creating a rainbow.
Rain – the blessing of Africa
Raindrops on grass stalks
In KZN, during the summer months, the region experiences the highest levels of rainfall, with average monthly falls ranging from 100 to 200 mm. The summer rainfall is often associated with thunderstorms, low pressure systems, cut-off lows and even southward wandering tropical cyclones. Some of the more extreme systems can cause heavy downpours and flash flooding in local areas while some can affect much larger areas. By contrast, the winter months from April to September are typically much drier, with average monthly rainfall ranging from 20 to 50 mm. While there may be occasional showers during the winter months, the rainfall is generally much less frequent and less intense than during the summer months.
Cumulonimbus cloud billowing up promising a significant thunderstorm
The emotive word – flood
The word or the concept of “flood” is a human construct and is often associated with powerful and intense emotions due to its association with destruction, loss, and danger. Floods can cause significant damage to homes, infrastructure, and communities, and can result in the loss of life and property. As a result, the term “flood” is often used in a highly emotive way, evoking feelings of fear, sadness, and anxiety.
An important concept is to understand that the flow in a river is defined as a continuum from low flows to high flows. Natural flows are characterised by both temporal and spatial heterogeneity in the magnitude, frequency, duration, timing, rate of change, and predictability of flow. These characteristics, for a specific river or a collection of rivers within a defined region, shape species life histories over evolutionary (millennial) time scales as well as structure the ecological processes and productivity of aquatic and riparian communities in short to medium term cycles.
So, it is important to note that ‘floods’ are usually considered destructive where infrastructure is damaged and the scale of damage is directly proportional to the level of inappropriate development and where ecological processes have not been given room to function. So while they may be described, or thought of, as destructive to infrastructure and human settlements, they are in general beneficial to the environment and biodiversity. Floods bring the inundation of large quantities of water to the landscape, which refreshes or resets aging systems, can create new habitats and provides a significant range of benefits to plants and animals.
High flow conditions rejuvenate natural systems
The ecological benefits of floods in aquatic habitats
One of the key benefits of floods is that they can create or expand wetland and aquatic habitats, which can support a wide range of plant and animal species. Wetlands are among the most productive and diverse ecosystems on the planet, and they provide important ecosystem services such as water purification, carbon storage, and flood control. Floods can also bring nutrients and sediment to the land, which can enrich the soil and support the growth of new plant communities.
In addition to creating new habitats, floods can also help to maintain existing habitats and ecosystems. In some cases, periodic flooding is essential for the survival of certain plant and animal species, as it provides important cues for reproduction and migration. For example, many species of fish and amphibians rely on seasonal flooding to trigger their breeding cycles and to create new spawning sites. Floods can also help to regulate populations of certain plant and animal species, by providing natural disturbances that promote biodiversity and prevent the dominance of any one species. In this way, floods can contribute to the resilience and long-term health of ecosystems, by maintaining a diverse range of species and preventing the spread of invasive or harmful organisms.
Therefore it is important to stress that while floods are often described as disruptive and damaging to human settlements, they can also be highly beneficial to the environment and biodiversity. By creating new habitats, enriching the soil, and regulating populations of plant and animal species, floods play an important role in supporting the ecological health and resilience of ecosystems.
River flow is a significant determining factor in aquatic habitat health
Rainfall in any amounts is an essential blessing to ensure changes in ecological functioning
Estuaries can react to floods in different ways. Floods can have a significant impact on estuaries in KwaZulu-Natal (KZN), both in terms of their physical characteristics and their ecological functioning. The physical characteristics of estuaries can be changed in several ways. They can deposit large amounts of sediment, which can alter the depth and shape of channels and the location of sandbars and mudflats. Floods can also erode banks and shorelines, creating new habitats and exposing new substrates for colonisation. The increase in water flow and flushing can flush water volumes and improve water quality. This increased water flow can also create new channels and pools, which can provide important habitats for birds and other organisms. Floods can change the composition of the benthic (bottom-dwelling) community in estuaries by redistributing sediment and exposing new areas for colonisation. These are an important base of the food-web and therefore improvements cascade through to everything including the birds. In general floods can increase the productivity of estuaries by depositing nutrient-rich sediment and creating new habitats for aquatic organisms. This can lead to increased biomass and diversity, which can in turn support a range of other species, including birds.
The September 1987 floods in KZN
In September 1987, KwaZulu-Natal experienced heavy rainfall that resulted in severe flooding. The floods were caused by a combination of factors, including a cut-off low-pressure system that moved over the region, as well as the topography of the area, which contributed to the rapid flow of water. Over a five-day period beginning on 25 September, parts of Natal province in eastern South Africa received as much as 900 mm (35 in) of rainfall. This should not be confused with the 1984 event of Cyclone Demoina which impacted areas of KZN north of the uThukela River. During the 1987 flood event many bridges were washed away but the destruction of the Mdloti and Tugela River bridges caused the greatest disruption for people. What was extremely interesting post-flood was the changes in bird abundance and species utilising areas not previously inhabited. Both White and Pink-backed Pelicans were the most obvious indicators of this with large groups of pelicans of both species found foraging and floating on what is now developed as Riverhorse Valley and was at the time the remnants of the wetlands of Sea Cow Lake.
As mentioned key benefits of floods is that they can create new wetlands and aquatic habitats, which can support a wide range of plant and animal species. Wetlands are among the most productive and diverse ecosystems on the planet, and they provide important ecosystem services such as water purification, carbon storage, and flood control. Floods can also bring nutrients and sediment to the land, which can enrich the soil and support the growth of new plant communities.
Possibly one of the most obvious groups to indicate changes in response to rainfall are the waterbirds. KwaZulu-Natal (KZN) is home to a diverse array of waterbirds, including herons, egrets, grebes, ibises, ducks, and flamingos. These birds are adapted to wetland and estuarine ecosystems that are prevalent in this wetter region, and their populations are often closely tied to the availability of water. Changing rainfall patterns and water levels can have a significant impact on the distribution, diversity and abundance of waterbirds in KZN. For example, prolonged low rainfall years can lead to a reduction in the availability of suitable habitats for waterbirds, which can lead to local declines in their populations. On the other hand, high rainfall and flood events can create new habitats and provide important feeding opportunities for waterbirds. Overall, the response of waterbirds to changing rainfall and water levels in KZN is complex and multifaceted, and depends on a range of factors including the timing, duration, and intensity of the changes, as well as the adaptability of the individual species.
Anyone visiting a local reserve in the highway area or further afield like the iSimangaliso Wetland Park will have observed differences in the birds present when water levels are low versus the situation after high flow events or a series of wetter years. This has indeed been the case since 2020 with KZN being subjected to a wetter cycle. This wet cycle followed quite a prolonged period of low rainfall years particularly in the northern part of the province. These larger climate cycles are influenced significantly by the El Niño-Southern Oscillation (ENSO), which affects weather patterns and ocean temperatures in the Pacific Ocean and beyond. El Niño, and its sister cycle La Niña can have significant impacts on the climate and environment of KwaZulu-Natal. During an El Niño event, KZN typically experiences hot and dry conditions, with reduced rainfall and an increased risk of drought. This can lead to a range of negative impacts, such as reduced crop yields, water shortages, and an increased risk of wildfires. On the other hand, during a La Niña event, KZN typically experiences cooler and wetter conditions, with increased rainfall and an increased risk of flooding. Overall, the impacts of El Niño and La Niña on KZN depend on a range of factors, including the timing, duration, and intensity of the events, as well as the specific geographic and ecological characteristics of the region. While both events can have significant impacts on the climate and environment of KZN, the exact nature and extent of these impacts can be difficult to predict and can vary from year to year. Unfortunately despite us experiencing the recent wet years as a result of La Niña there is a prediction that we are moving rapidly back to an El Niño cycle putting us into drier climatic conditions once again.
The amount of water currently seen in the Eastern and Western Shores Sections of the iSimangaliso Wetland Park has been mooted to be more than seen over the past 40 years. This is also linked to the restoration of the land parcels in these areas with the removal of plantations which are recognised Stream Flow Reduction Activities (SFRA). That restoration has provided the platform for the increased rainfall to have produced a very large and complex mosaic of aquatic habitats grading from estuary, brackish to fresh water and the birds have responded in abundance. The occurrence uncommon species such as White-backed Duck and African Pygmy Goose has multiplied from the historical situation.
Charismatic, uncommon and localised – a pair of African Pygmy Goose
Changes in abundance are obvious in resident species such as herons, egrets, and ibises, as well as migratory species such as waders and terns that travel to the park from as far away as Europe and Asia. The abundance of food and suitable breeding sites during periods of high rainfall can result in large concentrations of waterbirds, providing a stunning spectacle for visitors and an important source of ecological functioning within the wetland ecosystem. Rare and more localised birds such as Rufous-bellied Heron seem to have taken up more permanent residence in the wetlands while the estuary has hosted some interesting and remarkable birds such as three African Skimmer who spent quite a time feeding, roosting and resting in the mouth area over the summer alongside a range of other waterbirds with flocks of Greater and Lesser Crested, Caspian and Little Tern, Water Thick-knee, White Pelican, Reed and White-breasted Cormorant.
Great White Pelican soaring above a waterbody
Burchell’s Coucal, also affectionately known as ufukwe or the Rainbird, have increasingly become familiar to gardeners particularly where there is adjacent indigenous open space. It is a large and distinctive bird with a black body, reddish-brown wings, and a long, broad tail. It is known for its bubbling, repetitive call, which is thought to presage rain. This is likely from Zulu culture, where the bird is seen as a symbol of good luck and prosperity as its call is a sign of rain and fertility, a fact likely linked to the bird calling courtship and territory at the start of the rainy season.
In KwaZulu-Natal, the term “rainbird” is also sometimes applied to Purple-crested Turaco (Tauraco porphyreolophus), Grey-headed Bush Shrike (Malaconotus blanchoti) and Green Twinspot (Mandingoa nitidula). The first two of these are known for their distinctive and evocative calls, which are often heard in the rainy season during drizzly and misty conditions. Green Twinspot is a small bird found in forest margins, grasslands and savannas throughout southern Africa. It has a bright green body with black wings and a red bill. The male bird has a distinctive and musical call. Their calls are often seen as a sign of good luck and prosperity, particularly during the rainy season.
A female Green Twinspot
About the author
Nicolette Forbes was born in Durban and is passionate about all things KZN and its environments. With an interest in all things living from a young age it was no surprise that her chosen career path ended with her becoming a professional biologist having studied biological sciences at the University of Natal, Durban (now University of KwaZulu-Natal). Studying was followed by a lecturing stint to both biology and medical students for nine years before leaving the university to put her knowledge into practice with an ecological consultancy specialising in coastal habitat assessments.
Birding has been a passion from her high school days and birdwatching, atlassing. photography and being in the bush are her favourite things. Currently the Chair of BirdLife eThekwini KZN, the club covering the Greater Durban area, Nicolette has also through the non-profit EcoInfo Africa, partnered with Kloof Conservancy to run environmental courses focussed on birds, and these will continue once it is deemed safe to do so.