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Trophic overlap between sexes in the dimorphic A frican black oystercatcher foraging on an alien mussel
Author(s) -
Kohler Sophie A.,
Connan Maëlle,
Kolasinski Joanna,
Cherel Yves,
McQuaid Christopher D.,
Jaquemet Sébastien
Publication year - 2014
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/aec.12117
Subject(s) - sexual dimorphism , foraging , biology , predation , ecology , trophic level , mussel , rocky shore , habitat , zoology
Sex‐specific feeding segregation related to sexual bill dimorphism has been described in several oystercatcher species, including the A frican black oystercatcher. For the latter, studies concerned only a small number of breeding pairs and were done prior the invasion of the S outh A frican rocky shores by the M editerranean mussel, which is believed to have benefited oystercatchers by increasing overall biomass. Here, we investigated geographic variability in the segregation of diet, biometrics and body condition between sexes in the A frican species, in relation to changes in foraging habitats along the S outh A frican coastline, using stable isotope analyses. Males and females and their potential prey (mussels, limpets, polychaetes and ascidians) were sampled on the southern A frican west, south‐west and south‐east coasts for stable isotope analyses and biometrics and body conditions of birds were measured. Bill dimorphism occurred throughout the study area and south‐west males had lower body conditions than other males and females in general. Sexes displayed little differences in their δ 13 C ratios and in the relative consumption of the different prey throughout the study area, except on the south‐east coast where males were slightly depleted in 13 C relative to females and the most abundant prey elsewhere (the M editerranean mussel) is rare. Females were slightly but significantly enriched in 15 N by 0.3‰ compared to their breeding partners and this did not link clearly to differences in diet. We argue that the combined effect of biogeographic variations in rocky shores diversity and biomass, heterogeneous invasion by the Mediterranean mussel on the S outh A frican coastline and bill dimorphism may have altered the sex‐specific feeding behaviour of oystercatchers differently between coastal regions and possibly had an additional cost for male oystercatchers faced with lower prey biomass and diversity on the south‐west coast.