A bad day for Blue Cranes: The impact of fences
In the Overberg’s agricultural landscape, fences are a common sight. But while they play an important role in managing livestock, there’s a flip side to them. In the past two weeks, the Endangered Wildlife Trust (EWT) and Overberg Crane Group have experienced this downside firsthand.
On the same day early in March, OCG partners came across two Blue Cranes, both killed when they became entangled in fences.
The first crane was found in the Overberg by Nuwejaars Wetlands Special Management Area (NWSMA) conservation staff. The second, a Blue Crane tagged in the NWSMA in September 2020, was found dead in a fence close to Humansdorp.
Powerlines are highlighted as a major concern to the viability of Blue Crane populations. While fences don’t always make the list of top concerns, Blue Cranes and other birds can easily become caught in fences. Once they’re trapped, it’s virtually impossible for them to escape.
Here’s what BirdLife South Africa found…
In 2013, a BirdLife South Africa survey found that a third of bird species killed in fences are threatened globally or regionally. Owls in particular are vulnerable to fences.
BirdLife SA’s research found there are six ways birds are impacted:
- Snagging: A bird’s body part, like a wing, is impaled on razor wire, and the bird can’t free itself. It will die of thirst and exhaustion.
- Snaring: A bird’s leg is trapped between two overlapping wires. This seems to be the reason for both our Blue Crane deaths.
- Impact injuries: The bird flies into the fence – either being killed through the force of the impact, or injuring itself.
- Snarling: A bird becomes trapped in fence material while passing through wire strands or wire mesh.
- Electrocution: Not many fences are electrified across the Overberg. But those that are could kill or severely injure birds.
- Barrier effect: Young cranes that can’t fly can become trapped behind fences that serve as a barrier. These prevent them from escaping predators or getting to feeding areas.
There are ways to mitigate against these threats – but it requires constant attention from Overberg landowners. Here’s Birdlife South Africa’s suggestions:
- Simply remove fences that aren’t needed anymore.
- Rather use smooth wire for the two top strands of the fence (as opposed to barbed wire).
- And increase the space between these two top strands (at least 30 cm).
- Re-tension loose wires, which helps to prevent snaring.
- Put markers on fences to make them more visible.
- Where possible, leave gates open so that flightless birds can still move between areas.
(The Endangered Wildlife Trust and the Overberg Crane Group work in partnership to protect Blue Cranes in the Overberg. The EWT and the International Crane Foundation work together in furthering conservation of cranes and their habitats throughout Africa. The EWT Western Cape project is supported by the Leiden Conservation Foundation and Eskom.)