Keep your distance — how humans are diminishing shorebirds’ breeding success
We might not even notice them, but getting within even 30m of some shorebirds drastically lessens their ability to take their eggs to term.
“We don’t know what our impacts are — if no one’s going to tell us what they are, then we probably will continue in our ignorance,” said conservation scientist Brittany Arendse at the second Plett Marine Science Symposium last week.
While strolling on the beach you might not even notice them — Arendse likes to call these shorebirds, white-fronted plovers, “masters of concealment” — as they are very well camouflaged against the sand throughout all phases of life, from adults to chicks and even eggs.
“If you weren’t really looking to find these birds, you might not see them at all,” Arendse said, explaining that white-fronted plovers often make their nest in an indent of sand, sometimes near vegetation, covering part of their eggs (typically two) with a bit of sand.
But they are there — and our presence on the beach, even within 30m of them, is seriously affecting their ability to breed.
And with six billion people globally projected to live within 100km of the coast by 2025, and thousands of South Africans flocking to the beach every summer, we’re going to have to learn to coexist with the species that are trying to live along our coastlines.
A 2012 study on coastal bird communities in the Western Cape found that while species like oystercatchers and Egyptian geese are doing well, there was a 40% decline in small-bodied waders like white-fronted plovers over the 30-year study period.
One part of NVT’s #ShareTheShores programme is protecting beach breeding birds, which initially started as part of Selena Flores’ PhD thesis that she is completing at UCT in collaboration with the NVT, which has found evidence to suggest white-fronted plovers’ ability to breed is under threat from humans’ presence on beaches
While Flores’ research started seven years ago, the project has continued, with NVT setting up a small team to investigate how these birds are responding to disturbances on beaches from Robberg to Nature’s Valley, and what we can learn from these responses.
The initial study that NVT conducted at Robberg Beach, Lookout Beach, Keurbooms Beach and Nature’s Valley found that, like some other shore-breeding plovers around the world, white-fronted plovers have a low breeding success because of human and dog disturbances to incubation.
What impact do people have on beaches?
From disturbance tests NVT conducted over three breeding seasons, they figured out how close humans/dogs could get to white-fronted plovers before they fled and how long it would take for them to come back.
The interns would observe an incubating bird for a two-hour period three times a day (morning, midday and afternoon) during their breeding period, from August to March.
They’d observe instances when a person, sometimes with a dog, would walk through the bird’s nesting territory and how often the bird would get off its nest (be flushed off), and how close people needed to get to the nest before the birds left their eggs.
Data collected from the 2014/2015 and 2015/2016 summer seasons found that over a two-hour period more than 1,000 people went through a nesting territory (their counter only went to 1,000), and 34 and 51 dogs, respectively. The birds were flushed out of their nests 15 and 19 times, respectively.
Arendse said, “This is the level of disturbance that you can expect in peak summer when the beaches are full.”
The NVT also conducted manipulated disturbance trials, where they would wait for a bird to start incubating and then approach the bird from a distance, recording when the bird first noticed them, how far they had to be for the bird to feel threatened enough that it got off its eggs, and once it left the nest how long it took to come back.
They found that on average at about 29-30m approach distance, the bird would get off its eggs and that it would take the bird about 4.5 minutes to return to its nest and continue incubating its eggs, given that the threat had continued past the nesting area.
This is a problem, “because it’s so hot, and the sand is often hotter than the ambient temperature, they actually shade the eggs most of the time during peak heat,” Arendse explained.
“So it’s important for them to stay on those eggs as long as possible, otherwise, the development of the eggs [is compromised].”
Once the eggs reach the 42°C threshold, the embryo will be unviable — and on a hot day, the eggs can reach that temperature within the first five to six minutes of a bird leaving its eggs, and quicker if it’s a really hot day.
So if a bird gets flushed off its nest 15-19 times in a two-hour period, and it takes more than four minutes to get back, it makes it very difficult for them to produce viable offspring.
And the initial results from this study reflect this. Over the first breeding season they monitored 83 nests, which had 35 breeding pairs that laid 152 eggs. Out of the 152 eggs, only 15 made it to fledge — a 9.8% breeding success rate.
“Shorebirds usually nest in a very harsh environment, so you’d expect it to be low anyway,” Arendse said, “but in general, they should experience around 30 to 40% breeding success. So this is extremely low for a species.”
This impact happens with people getting within 30m of the birds. “At this point, you probably haven’t even noticed the birds, your dogs definitely haven’t noticed the birds, Arendse said.
“There is this misconception that [conservationists] are really worried about dogs chasing birds down and eating eggs… but it is more about the birds’ inherent response to disturbance by a four-legged mammalian predator.”
The NVT launched the #ShareTheShores programme in 2017 to address aspects of concern in the Greater Plettenberg Bay area, one of which was the pressures people and companion animals place on shore-breeding birds like white-fronted plovers.
As Arendse said, we typically aren’t even aware of the impact we are having — especially with a species that is as camouflaged as these plovers.
NVT used community outreach days, social media campaigns and signage that showed where the nesting territory was, and where possible, closed off 60x60m areas where the nests were (with signage ideally 30m from the nests).
NVT collaborated with the local community, the Bitou Local Municipality, CapeNature, SANParks and other authorities on beach management possibilities.
“We wanted to be involved in the management as far as we can, because we have that data and feel that it’s important to base your management processes on actual facts and data,” Arendse said.
At the time, the NVT had three breeding seasons worth of data, which gave it information about where most of the birds were nesting and where most of the conflict areas were.
The tags mark the hotspot breeding areas for this section of beach — red tags mark nests that failed, and green tags mark nests that made it to fledge.
Arendse said the beach management process was long, with the initial zoning of the beaches taking about 18 months, and they were still working with authorities to make the management more efficient.
“The goal was never to save every bird on every beach, because that is not possible. But we wanted to speak to enough people to understand what they needed from the beaches and how we could get a win-win for our birds and our people and our dogs,” Arense said.
Before this project, Plettenberg Bay didn’t have any systems to control dogs on beaches, but from the data collected, the municipality has zoned several beaches (red is where dogs are not allowed, orange is where dogs have to be leashed, and green is where dogs can run free but under the control of their owner).
For example, Keurbooms peninsula is a red zone because it has very big breeding colonies, not just of white-fronter plovers but of other birds including gulls, egrets, spoonbills, ibises and thick-knees.
Arendse took over from Flores in 2017/2018, when they started the awareness campaign and put up rope and signage.
This resulted in the percentage of breeding success in Nature’s Valley doubling (from about 15.4% to 30.6% two breeding seasons later).
Lookout Beach improved from 10% breeding success in 2017/2018 to 14% two breeding seasons later. Despite being a red-zoned beach, it still has many dogs and people visiting.
However, the last breeding season (2022/2023) at Lookout Beach had the highest success at 20.8%.
Arendse acknowledged that along with anthropogenic impacts (caused by humans), breeding success is also affected by natural factors, and due to sea level rise and an increase in storm surges, many nests are lost in flooding events.
“[The white-fronted plover is] also not a very sexy species in terms of status — it’s not critically endangered, it’s not even endangered, it’s only declining,” Arendse reflected at the end of her talk at the symposium to Plett locals and scientists.
“But I think it’s important for us to be proactive in instances like this and not reactive and actually start doing something now before we look back in 30 years’ time and the bird is extinct.” DM