Investigating the possible change in breeding strategy of African black oystercatchers

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.

Grantor dc:publisher.institution

Department of Biological Sciences

Year dc:date.issued

2014

Author dc:creator

• Paijmans, Dane Matthew

Advisors dc:contributor.advisor

• Ryan, Peter G
• Hockey, Phil A R

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/12975

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/12975