Western Cape wheatlands threaten blue crane breeding success

A recent study suggests that intensive agricultural landscapes in the Western Cape may be reducing the breeding success of the iconic Blue Crane, South Africa’s national bird.

The study, conducted by researchers from the University of Cape Town’s (UCT) FitzPatrick Institute of African Ornithology and the International Crane Foundation/Endangered Wildlife Trust, raises concerns about the long-term viability of one of the country’s most important populations.

The study showed that Blue Cranes’ breeding in the Western Cape’s wheat-growing regions is producing far fewer chicks than populations in other parts of the country. The findings indicate that these agricultural areas may have become an “ecological trap” – a habitat that appears suitable for wildlife but ultimately undermines their survival and reproduction.

The study, published in Ostrich: Journal of African Ornithology, compared the breeding of Blue Cranes in the Western Cape wheatlands in the Overberg and Swartland, Karoo and eastern grasslands of South Africa. It found that the birds bred more frequently in the grasslands and the Karoo than in the Overberg or Swartland.

Breeding success lower in wheatlands

The researchers analysed breeding-monitoring data collected over several years to determine how many chicks Blue Crane pairs successfully raise. Their findings showed a contrast between agricultural areas and more natural habitats.

Blue Crane pairs in the Karoo and eastern grasslands produced close to one fledgling per breeding attempt, while pairs in the Western Cape wheatlands produced roughly half as many. In addition, fewer breeding pairs in the wheatlands successfully raised chicks at all. Around two-thirds of pairs in the grasslands and Karoo produced at least one chick, compared with only around 40% in the Overberg and Swartland.

“These differences are worrying because the Western Cape wheatlands hold some of the highest densities of Blue Cranes anywhere in the world.”

“These differences are worrying because the Western Cape wheatlands hold some of the highest densities of Blue Cranes anywhere in the world. If breeding productivity remains low, it could help explain the population declines observed in the region in recent years,” said Dr Christie Craig, the study’s lead researcher and a UCT alumna. She is a conservation scientist at the International Crane Foundation/Endangered Wildlife Trust.

Dr Craig completed her PhD at UCT in 2024, under the supervision of Emeritus Professor Peter Ryan. For her PhD, she did an assessment of the conservation status of the agriculturally adapted Blue Crane, focusing mainly on population trends, survival, movements and the threat of powerline collision to the species.

Declining recruitment signals deeper problem

The team also examined winter flocks of Blue Cranes to estimate how many young birds are joining the population each year. The results were equally concerning.

Between 2019 and 2021, juveniles made up only about 4% of winter flocks in the Overberg and 3.6% in the Swartland – roughly half the proportion recorded three decades ago. Such low recruitment suggests that fewer young cranes are surviving to join the adult population.

Craig said: “If fewer chicks are fledging and fewer juveniles are entering the population, it becomes increasingly difficult for populations to sustain themselves. This pattern raises serious conservation concerns for what has historically been one of the species’ strongholds.”

Neglected conservation law threatens SA’s farmland

Agricultural landscapes may act as ecological traps

Although Blue Cranes have adapted well to farmland and are commonly found in agricultural areas, the study highlights how these modified environments can create hidden risks. In conservation biology, an ecological trap occurs when animals are attracted to habitats that appear suitable but ultimately reduce their survival or reproductive success.

In the case of Blue Cranes, the wheatlands provide open landscapes that resemble their natural habitat and may appear ideal for nesting. However, farming activities and landscape features can disrupt breeding and increase chick mortality.

“Even small disturbances during the breeding season can have significant consequences for reproductive success.”

For example, nests may be destroyed during harvesting when wheat fields are cut and collected. Disturbance around nests can also increase the likelihood of predation by species such as Pied Crows.

Craig said these pressures may be limiting the number of chicks that survive to fledging.

“Blue Cranes have adapted remarkably well to agricultural landscapes, but these environments are complex. Even small disturbances during the breeding season can have significant consequences for reproductive success.”

The dangers do not end once eggs hatch. Anecdotal evidence and field observations suggest that young Blue Cranes may die from several hazards common on farms. These include entanglement in fencing, drowning in water troughs and food shortages or physical abnormalities.

Craig said that while some causes of chick mortality are known, others remain poorly understood and require further investigation. “There is still much to learn about why chicks fail to survive in these landscapes. Focused research on chick mortality would help identify the most effective conservation interventions.”

Farmers play a key role in conservation

Despite these challenges, the study emphasises that collaboration with farmers is essential to protecting Blue Crane populations.

Many conservation measures could be implemented relatively easily, particularly during the breeding season. These include reducing disturbances near nests, modifying water troughs to allow chicks to escape if they fall in and adjusting fence designs to reduce entanglements.

“Engaging with landowners is crucial,” said Craig. “Because most breeding cranes occur on farmland, conservation efforts must work in partnership with farmers to improve breeding outcomes.”

However, relationships between farmers and cranes can sometimes be complicated. In some areas, farmers report crop damage caused by cranes, which may influence attitudes toward the species.

Craig concluded: “Addressing these concerns while promoting conservation-friendly practices will be essential for long-term success.”