A Bird’s-eye view of our coastline

9 October 2019

White fronted plover 3 for digital3Sandy shores are a direct result of erosion of rocks in the sea. Sand grains are carried by wave action and deposited on the beach resulting in a somewhat undulating topography. It is an extremely dynamic and harsh environment where water, sand and sea are always in motion, resulting in quite a different scene at every visit. These conditions often determine species diversity, biomass and community structure.

Coastal environments such as sandy beaches face extreme pressures in areas like the Garden Route where tourism and accompanying development can often be the driving life blood of a town. Currently there are about 3 Billion people living along the coastline, globally, and this is set to double by the year 2025. With such an influx of people, what are the effects on wildlife?

This is a question that Nature’s Valley Trust is very interested in. Specifically looking at the White-fronted Plover, what are the pressures they face and how are these disturbances impacting the success of the species, locally. This work stemmed from 2 surveys done about 30 years apart, in which it was found that our white-fronted plovers had decreased by 40% in the Western Cape and have suffered a further 70% reduction in density over that period. Further they are no longer breeding on at least 3 beaches near Cape Town and are basically on the brink of local extinction in those areas. One of the main drivers of this reduction was thought to be an increase in people and companion animals on beaches.

In Plettenberg Bay, for the 2015-2016 breeding season, it was discovered that our little plovers only have a 9.8% breeding success. This number should be closer to 30-35% in a healthy and stable population. That is for the 152 eggs laid that season, across 4 of our main beaches, only 15 individuals made it to an age where they are completely independent of their parent and fully capable of flight, what we would call a fledgling.

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A true reflection of what 10% breeding success means.

During the initial studies we did many experiments to help us ascertain the impact we have on our beach breeding birds and also that of our companion animals. We conducted 2-hour observation periods during different times of the day, where we recorded the total amount of people and dogs in a nesting area as well as the number of times an incubating parent would get flushed off the nest by disturbance. We also did what we call manipulated disturbance trials, where we (with or without canine sidekick) would walk up to an incubating parent and record responses to us as the disturbance.

What did we learn from this?

  • 2-hour observation periods:

During one day in 2014/2015 and one day in 2015/2016, both in peak summer, we had the following results:

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Two mid-summer observational periods (2 hours) and their results

We observed at least 1000 people (we capped the count at 1000) walking through a nesting area, a further 34 and 51 dogs, respectively, and the incubating adults was flushed off its nest 15 and 19 times on each day within a 2-hour period.

  • Manipulated Disturbance Trial

Here we learnt that, on average, an incubating bird will leave its eggs when we are 29m away. On average, this bird will return to its nest after about 4.5 minutes, given you are walking through the area and not making it a sunbathing spot. They also only come back to their nest when the ‘threat’ is 40m away. Often at the 29m mark the bird has not even been noticed by the human or dog so this really has very little to do with weather your dog is chasing down birds on the beach or trampling or eating eggs and is wholly about the response of the bird to a perceived danger. Really a response to you and the dog that is the shape and the size of what these birds have evolved to fear - an array of natural predators.

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Graphic demonstrating that on average plovers leave their nests when we are 29m away. Not that this is an average so some individuals may leave their nests sooner or later.

  • Temperature loggers

We were also very interested to know what extreme temperatures these eggs experienced during mid-summer. iButtons, temperature loggers, were place into model eggs and left in two environments, one where the eggs are shaded for 2 hours (from 11am to 1pm) and one where eggs are exposed to direct sunlight for 2 hours. Within the first 20 minutes of sun exposure the temperature inside the egg reaches 46.5 °C. Why is this important? What a lot of people don’t know is that these birds incubate their eggs to keep them cool; by shading the eggs they can lower its temperature to one that is much more conducive to development. Also note that an eggs thermal capacity, the peak heat it can withstand before egg death occurs, is 42 °C. On this particular day the egg exceeded 42°C within 5-6 minutes in the sun.

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Graph illustrating the heat experienced by model eggs, placed in direct sunlight and in shade, for a two hour period during the peak of the day.

Now imagine a warm summers day, it’s about 28°C outside – fantastic weather for a beach day. A lonely White-fronted plover nest is nestled into the hot sand with a proud momma keeping it cool. The day creeps on and it seems to just get hotter, it reaches 30°C ambient temperature and the sand is burning hot at close to 40°C. If there are about 1000 people walking past, accompanied with 30 odd dogs entering the nesting area, your adult is flushed off her nest 15 times and it takes her about 4.5 minutes to get back to her eggs, also keeping in mind that temperatures can reach critical within 5-6 minutes of direct sun exposure - the window for egg survival gets smaller and smaller with every flush off the nest.

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Graphic illustrating the fate of an egg left unattended by parents, due to human disturbance.

Some of this information is probably new to you, many may not even know what a white-fronted plover is or what our impacts on their survival could be and this is not completely your fault. These birds are extremely well camouflaged at all stages of their lives, from egg to fledge to adult. It is very easy to miss them on the beach and even easier to trample their eggs or young. This is an added anthropogenic threat that we pose to these little ones along our coastline.

But what is NVT doing to alleviate the pressure we all pose to the White-fronted Plover?

  • Awareness and Education!

We have launched a strong awareness campaign since 2017/2018 - you may recognise the hashtag, #ShareTheShores. This campaign focuses on various human impacts on the marine and coastal environment: marine debris, shore-based line-fishing and of course the White-fronted Plover breeding success. These three pillars of our three-legged campaign are all focused on awareness and education and this is based on our strong belief that most of us want the best for our environment and often don’t recognise the negative impacts we have on our surroundings. By clear, locally relevant, research-based education we are able to inform those to make better and more sustainable decisions for their environment.

This education process is ongoing and coincides with in situ interventions we implement in each nesting area. The measures we take are relatively basic and entails erecting 4-5 signs around the nest, about 30m (where we can) away from the nest. As you will recall the average distance we have to be from a nest before the adult gets up is 29m, therefore the 30m bubble we place around the nest works very well. The signs are connected with some rope to encourage people to walk around instead of through the nesting area.

We have also, with the assistance of the relevant ratepayer’s associations, CapeNature, SANparks, Bitou and Animal Welfare (PAWS) informed management plans, based on three seasons of plover breeding data, to colour zone beaches for dogs. This has allowed residents and visitors to, for the first time EVER, be allowed to legally walk their dogs on beaches in the Greater Plettenberg Bay area – before the by-laws stated no dogs on any beach at any time! From our perspective this is a fantastic win-win solution for all beach users, and their fur children. Please find individual maps for beaches in your area here.

Earth First

Doggie transition zone signs (top), billboards at beach entrances (bottom left), the difference nest signage and rope makes to foot traffic in a nesting area (Bottom right)

But of course, without your compassion, support and compliance the education and awareness would all come to naught. On Nature’s Valley the birds have done very well in response to our #ShareTheShores interventions and appear to be somewhat steady around 30% breeding success for the last two seasons. Unfortunately, Lookout beach has not done well, due to severe storm surges and questionable placement of nests, as well as an increase in egg predation. Additionally, Lookout has a clear red zone designation but with no enforcement comes little compliance. Compassion in some are low and the ease of access for locals and their dogs (even though kilometer stretches of off-leash beaches are a 10 minute drive away) trumps the success of what I believe to be a secret treasure on our beaches – the White-fronted plover. 

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Graph and table with raw values used to calculate breeding success in White-fronted plover across two beaches in Plett.

As a conservation NPO we will continue to do our best for the birds on our stretch of coastline and we know you will do the same. Thank you for your commitment to #ShareTheShores and going above and beyond what is expected. Thank you for joining us on coastal clean-up days, on local greening and community clean-ups. There is so much value in every little bit you do – catchment to coast, everything is connected!

thankyou

The plovers thank you!

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