Impacts of disturbance and development on coastal and water birds
Human population densities are greatest in coastal areas and around wetlands. As a result, many coastal and water birds face significant threats from direct human disturbance. Some species appear to be able to tolerate disturbance, whereas others are decreasing in numbers. A key question is how tolerance develops among populations; is it learned, or is it the result of selection for more tolerant individuals? This programme considers the impacts of disturbance and development on coastal and water birds.
This programme had two active projects in 2016: MSc student Andrew de Blocq is advising CapeNature on the sustainability of boat-based tourism on De Hoop Vlei, a Ramsar wetland which is a key component of their of flagship De Hoop Nature Reserve. And in the Garden Route area, MSc student Selena Flores is studying the factors causing population decreases in coastal populations of White-fronted Plovers Charadrius marginatus.
Activities in 2016
Andrew de Blocq continued to monitor the impact of tourist boat trips on waterbirds at De Hoop Vlei throughout the first half of 2016. By comparing the numbers of birds affected by boat trips with the total population on the vlei he showed that the two routes currently used for boat tours impact at most 10-20% of the vlei’s bird populations. Few species of conservation concern were affected by the current tour routes.
Flight initiation distances varied greatly among species, but most species were surprisingly intolerant of boats, reacting when the boat was around 80-100 m away. Added to this, most species failed to return to an area within one hour after being displaced by a boat. By comparing bird responses to the tour boat with their responses to a kayak, Andrew showed that most birds were disturbed more by the kayak. Kayak tours also are harder to control in terms of routes, and can penetrate into shallower water (which support high bird concentrations), and are not practical at De Hoop Vlei given the frequent strong winds, and thus were not recommended as a tourist activity.
Andrew conducted similar approaches by kayak at Rietvlei, a coastal wetland in Cape Town with a long history of boat use. Surprisingly, there was little difference in flight initiation distances between the two wetlands, suggesting that there is little habituation to the passage of small boats. However, his comparison was complicated by the need to sample both in the open access and reserve areas at Rietvlei. Habituation of waterbirds at De Hoop Vlei is unlikely for most species because it requires repeated exposure of the same individuals, yet regular counts at De Hoop show regular changes in bird populations, suggesting frequent movement in and out of the system. Accordingly, Andrew advised caution in the implementation of boat tours at De Hoop Vlei.
Selena Flores monitored White-fronted Plovers on the coast around Plettenberg Bay for the third breeding season in succession. She is testing how plover breeding behaviour differs over a disturbance gradient. Overall breeding success is low (<10%), especially during the busy holiday season. Incubating plovers respond to an approaching person from up to 50 m away, and typically leave their nests when the person is 30 m away, remaining away from the nest until the person has moved at least this distance past the nest. Her trials with dummy eggs show that unattended eggs can reach a potentially lethal 45°C in under 15 minutes during summer midday temperatures.
In 2016 the project initiated an intervention and awareness programme to help mitigate human disturbance on the plovers, planned and implemented in conjunction with the Nature’s Valley Trust. Information boards highlighting conservation concerns and responsible beach usage have been installed at beach entrances, and signage placed around White-fronted Plover nests to encourage visitors to be aware of ground-nesting shorebirds and avoid of active breeding areas. Awareness campaigns also are being conducted using public talks and workshops, social media and directly with beach visitors. The research team also is conducting a questionnaire survey to gather public opinion and general rates of compliance with and enforcement of beach regulations. The findings will be presented to municipal government and nature conservation agencies.
- MSc student Andrew de Blocq completed his field studies at De Hoop Nature Reserve and will submit his thesis in early 2017.
- The project final report was given to CapeNature in December 2016. The report recommended that at current water levels it is acceptable to allow boat tours to continue on the current two routes at De Hoop Vlei, provided specific conditions are met. Kayak tours should not be permitted.
- Selena Flores upgraded her MSc to a PhD in December 2016.
- A documentary featuring White-fronted Plover research was filmed by Cape Town's Homebrew Studios in February 2016. The segment is part of upcoming Smithsonian Earth series Wildlife Odyssey, with final production for airing in North America and online planned for 2017.
- White-fronted Plover samples were contributed to Josie Jackson's PhD study with the University of Bath and Cardiff University, on genetic diversity and gene flow within populations of southern African shorebirds.
BirdLife Plettenberg Bay; Cape Nature; DST-NRF CoE grant; Keurboomstrand Property Owners’ Association; Knysna Toyota; Table Mountain Fund; Wader Quest.
Prof. Peter Ryan (FIAO, UCT)
Dr Mark Brown (Nature’s Valley Trust)
Dr Robert Thomson (FIAO, UCT)
Students: Andrew de Blocq (MSc, UCT), Selena Flores (MSc, UCT)
Research assistants: Jesse Beck, Taylor Frerichs, Andrea Gress, Amber Hatch, Aurora Hood, Christina Marques; Carissa Wasyliw.