Includes bibliographical references. / African Black Oystercatchers (Haematopus moquini) have a modal clutch size of two eggs but occasionally lay one or three eggs. It has been noted that an increase in frequency of larger threeand even four-egg clutches has occurred over the last few decades. By analysing extensive historical nest records dating back five decades I verified the occurrence of this increase in three-egg clutches over many of the sites within their breeding range. As African Black Oystercatchers are very territorial, co-operative polygyny was rejected as a sole cause (through observations). As eggs were found to be significantly similar (through intra-clutch egg shape comparisons) within clutches egg-dumping as a cause was also rejected. It was thus established that the increase in three-egg clutch frequency was indicating an increase in breeding effort. On further analysis of this increase, it was discovered that three-egg clutches offer no benefit to species fitness or breeding success as they do not result in an increased fledgling output to those of the smaller two-egg clutches. This is primarily due to inefficient incubation as a result of the extra egg, and the inability to maintain and feed a larger brood size. This study validates previous assertions that three-egg clutch frequency is increasing for African Black Oystercatchers.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/12975 |
| Date | January 2014 |
| Creators | Paijmans, Dane Matthew |
| Contributors | Ryan, Peter G, Hockey, Phil A R |
| Publisher | University of Cape Town, Faculty of Science, Department of Biological Sciences |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
Page generated in 0.0016 seconds