Investigating the possible change in breeding strategy of African black oystercatchers

Paijmans, Dane Matthew

Investigating the possible change in breeding strategy of African black oystercatchers

Master Thesis

2014

Publisher

University of Cape Town

Department

Department of Biological Sciences

Faculty

Faculty of Science

Abstract

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.

Description

Includes bibliographical references.

Keywords

Ornithology

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