Department of Statistical Sciences
University of Cape Town
| Avian Demography Unit
Department of Statistical Sciences University of Cape Town |
|
Projects of the Avian Demography UnitInventory of South Africa's waterbird breeding colonies
Many birders may be familiar with this scene: a reedbed or clump of trees packed with cormorants, egrets, herons, spoonbills, darters and/or ibises all busy building nests, sitting on nests, or feeding chicks. These sometimes impressive bird assemblages are often large, noisy and smelly but generally there is always a lot of activity taking place at any one time - adult birds leaving the nest on their way to look for food or nesting material, birds arriving at the nest to relieve the other parent of nest duties or to feed chicks, young chicks squawking for food in the nest, etc. This 'hustle and bustle' is what usually accompanies the establishment of a breeding site by many colonial waterbird species, and the selection of the site is the first important step to ensuring that they will maximise their reproductive effort for that season.
Although breeding together in large numbers and in close association with other species provides a 'safety in numbers' component, there are five fundamental site requirements shared in all colonial species (Perennou et al. 1996): (e.g. strong wind); (there should be sufficient to maintain both parents and chicks throughout the breeding season) Once these or some of these requirements are met, the first few pairs begin to build their nests and this usually provides the catalyst for other individuals and/or species to add to the foundation of the ever-growing colony. Once established, and if a successful site, the birds will re-use the site in following years, but if the site becomes unsuitable (due to flooding or felling of trees) or the breeding productivity was low, the birds will usually abandon and look for an alternative site. Whereas with non-colonial breeding waterbirds (e.g. ducks), if a nest is lost the population is not generally under the threat, but the loss of a heronry could mean the loss of a (or part of a) population, particularly if alternative sites are not available. This can have serious conservation implications especially if species within the colony comprise Red Data species or species' whose population numbers are thought to be declining.
Shorebird (or ground-nesting) colonies are well known and have been fairly well researched and documented. This has been done mainly through extensive monitoring programmes of Marine and Coastal Management of the Department of Environmental Affairs & Tourism. In contrast, little is known about the status of inland (or tree-nesting) colonies in South Africa. In fact, we don't even know where most of these are located, how many are located within protected areas and/or how successful these heronries are from one year to the next? The revised Nest Record Card Scheme (NERCS), launched in 1995 by the ADU and BirdLife South Africa, attempted to answer these questions through the production of colony/heronry cards, but to date only 65 cards have been submitted to the scheme. These cards are in the process of being computerised and await analysis. A lot more data needs to be collected in order to fully assess the distribution, status and potential management of heronries in South Africa.
In order to achieve this, the ADU has launched a national colony/heronry initiative whereby we would like to collect as much information as possible over the next two years in order to start producing an inventory of heronry/colony sites in South Africa. We would like to focus more on heronries (i.e. inland colonies), although information on marine breeding colonies can also be submitted. Hopefully, if enough information is collected a preliminary report can be published in 2005. Although this initiative would aim to be an intensive excercise over the next two years, the continual submission of records would be encouraged. A start was made in December 2001, when colony/heronry cards were sent to all CWAC compilers and selcted observers. The CWAC network provided an ideal opportunity to launch this initiative and numerous cards have already been returned following the 2001/02 season. However, there are probably hundreds of additional heronries that have, as yet, not been reported and this is where we would like you to get involved. By keeping an eye open for active heronries in your area, and participating in this initiative, you will be making a significant contribution to waterbird conservation, and in particular to the preservation of colonial breeding sites, in South Africa.
All you need to do is find an active colony or heronry, record your observations on a NERCS colony/heronry card and submit it to NERCS, ADU, University of Cape Town, Rondebosch, 7701. It's that easy!. For internet users the colony/heronry cards are available in pdf format here, or you can contact Doug Harebottle and he will gladly post you some. It is important to bear in mind that you will need to refer to the Nest Record Card Scheme handbook (ADU Guide No. 3) for habitat, human impact and nest position codes. The handbook is available as two pdf files, Handbook: cover & contents (52 138 Kb) and Handbook: full text (353 399 Kb), or copies can be posted to potential participants. As many of these heronries could be located while travelling and one may be limited by time to record details about the colony, the following minimum information should be noted: For additional information and answers to frequesntly asked questions please consult the Nest Record Card Scheme handbook (pages 27-31) Heronries and colonies can be spectacular events to witness and to record interesting observations, but please be aware of these important guidelines: This initiative hopes to focus on the significance of these breeding sites for colonial waterbirds in South Africa and how they contribute to the reproductive output and long-term survival of these populations. These sites hold a special fascination for many people; we now have a chance to make an important contribution to their conservation and management and thereby ensure their protection and continued fascination for future generations. Enjoy participating and have fun! Any queries or questions can be directed to Doug Harebottle
Reference Perennou, C., Sadoul, N., Pineau, O., Johnson, A.R. & Hafner, H. 1996. Management of nest sites for colonial waterbirds.Conservation of Mediterranean wetlands - Number 4. Tour de Valat, Arles (France), 114 pp. |
Photo Les Underhill 
