Anthropogenic disturbance on shore breeding birds
Coastal regions of South Africa face various threats, from widespread global issues like climate change, to remarkable rates of encroachment due to human development. Along with these larger concerns, it is also necessary to examine and address the cumulative impacts of smaller, everyday forms of disturbance, such as effects of recreational beach use on coastal wildlife and habitats. Despite hefty economic and ecological importance, environmental policy and enforcement often neglect sandy beaches. Shorebirds that nest on the ground are notably vulnerable to beach visitors in high-tourism areas.
The White-fronted Plover (Charadrius marginatus) has undergone considerable reduction in its numbers, up to 40-60%, over the last three decades, following the unfortunate worldwide trend of shorebird population decline. The Garden Route shoreline, being a popular holiday destination, is continuously experiencing increases in tourism and development, among the natural areas it is so well-known for. NVT’s shorebird conservation research aims to use field observations, experiments, and monitoring to determine the influence of humans (and dogs) on shorebird survival on our local beaches. The outcome of the project is to emphasize current applications of research, by drafting conservation management recommendations to minimize our impact on shorebirds and coastal habitats. Suggestions from a sound scientific standpoint will assist those driving our community to make appropriate decisions, taking into consideration both economic development and environmental conservation.
Here's what three years of data tells us...
White-fronted Plover disturbance observations in 2015 indicated that an average of 51 people and 6 dogs entered a nesting area at a given time of day (morning, midday or evening) over a two-hour period, during peak holiday season. These intrusions into a nesting area caused an average of three flushes of the incubating bird off its nest. Throughout the 2015 breeding season there was a maximum of 1000 people and 34 dogs observed and a maximum of 15 birds being disturbed off their nests.
The manipulated disturbance trials suggested that on average the incubating parent notices approaching threats at an average distance of 38m and at 29m leaves the nest as an evasive tactic to lure intruders away from their eggs. African Black Oystercatchers notices threats at 50-60 m away and leaves the nest when the threat is at least 30m away. This distance varies more dramatically within oystercatchers than plovers as the former may leave the nest at a 60m distance from threat. The trials further indicated that for plovers the threat must be at least 40m away before the incubating parent will return to its nest. On average it took 4.5 minutes for such an adult to return, given that the threat did not linger in the territory. Oystercatchers too a maximum of 9 minutes on average to return to incubating their eggs. Have a closer look at the work we have done on the impacts of people and dogs on the breeding success of sensitive beach breeding birds like African Black Oystercatchers and comparing this to the more adaptable Kelp Gulls.
Temperature experiment, using false eggs, indicated that eggs exposed to the sun may reach 47°C in 15 minutes and eggs peak at 49°C. Additionally, we found that shaded eggs experience consistent temperatures between 26-31°C. Given that the thermal capacity of eggs average around 41°C it is imperative that incubating birds return to their nest to shade their eggs as soon as possible, as on hot summers day it may take less than 5 minutes for eggs to overheat and die.
Across the 2015/2016 breeding season we encountered 83 nests with a total of 152 eggs from 35 pairs of White-fronted Plovers. Of the 152 eggs only 58 chicks hatched successfully and a mere 15 fledged. This initial season suggested a fledge rate of 26% and an overall breeding success rate of 9% across the Greater Plettenberg Bay area.
NVT has decided to take a socio-environmental approach to this dire situation shore-breeding birds face on our stretch of coastline. From our point of view, it was a lack of education and awareness around the issue which caused this seemingly apathetic behaviour contributing to the decline in success of the species. We have made accurate and locally relevant information available to the public, this stretched from large billboards on beaches to small pamphlets as well as articles in local papers. NVT also launched a strong, positive media campaign ranging from dramatic and gripping soap operas episodes, Sands of Change, on the life and times of plovers and oystercatcher on our beaches. We also developed cute cartoon characters called Sandy and Rocky, who are the ambassadors for our campaign. Furthermore, we allowed for naming and adoption of these tiny chicks, where you walk away with a certificate with ring numbers and pictures as well as the satisfaction of contributing to the conservation of your newly adopted feather child. In short, we are increasing visibility of the issue on all platforms we can think of, to increase awareness around the birds on our shores.
In terms of the shorebirds research on the beaches we implemented nesting area signs, placed at least 30 m away from an active nest and also conducted over 100 surveys with beach users over the 2016/2017 breeding season.
Armed with the sound scientific research we are in a prime position to influence management strategies. By engaging authorities, inclusive of all stakeholders, we were able to adjust management of beaches by implementing a new colour-coded system in December 2017. Beach entrances of Robberg, Central/Hobie Beach, Lookout/Poortjies, Keurbooms Peninsula/GooseMarsh, Keurbooms Beach and Nature's Valley, are now equipped with a large board with colour coded areas indicated, green: dog off leash, orange: leashed zone and red: no dogs zone. Each transition zone, where one section of beach goes to the next also has smaller boards indicating the change in zones.
These zones were based on our scientific research on breeding bird abundance as well as the Blue Flag status of some of the beaches.
For the 2017/2018 breeding season we focussed on improving the breeding success of the White-fronted Plover on two highly utilised beaches: Nature’s Valley beach, Nature’s Valley and Lookout beach, Plettenberg Bay. Again, we implemented nesting area signs on both beaches and cordoned off nests on Nature’s Valley. The in situ intervention as well as public awareness and education and the new dog regulations, together appear to have had a fantastic outcome for the plovers.
Comparing data from the 2017/2018 breeding season to that of previous breeding seasons showed a marked increase in overall breeding success form, 10.6% (2015/2016) to 14.3% (2017/2018) on Lookout beach, and 8.6% (2014/2015) to 30.5% (2017/2018) on Nature’s Valley beach.
The results strongly suggest that increased public awareness of nesting areas as well as the reduction of dogs in hotspot breeding areas have increased breeding success by some degree. What should be noted is that natural predation as well as tidal events, e.g. extreme spring tides and flooding events, also play a major role in the success of the birds that breed in the transition between land and see.
It is clear that the all-inclusive efforts we have applied over the course of this research programme has picked up momentum in terms of increasing the breeding success of the White-fronted Plover. It is important that we continue this work to reach a breeding rate that can be sustained over the long term to the benefit of the species. For the coming seasons we also want to apply more effort into the success of the African Black Oystercatcher.
Kelp Gull project
We are studying the various Kelp Gull colonies in and around Plettenberg Bay. This includes the largest land-based breeding colony of the species in the country (1500 pairs). Notably, we were the first researchers in Africa to use a UAV drone to count birds! We are also assessing urbanisation effects on gulls, by using GPS units to track where they go, and how much they forage in urban areas. In addition, we have been quantifying how much rubbish gulls line their nest with and how much they ingest (by dissecting regurgitated pellets). We have also investigated micro-habitat effects on breeding, by measuring incubation temperatures in exposed, partially exposed and shaded nests, and by comparing breeding success between micro-habitats. Be on a look out for ringed and color ringed birds! We are frequently encountering birds ringed over 10 years ago, with the oldest individual photographed on Robberg being an 18 year old gull from Port Elizabeth! The data for this project was collected by Minke Witteveen. (Click here to view the published paper)