Predation by the Black Oystercatcher….1999

In September of 1999, the students of the Environmental Systems Class collected the shells in the midden surrounding the nest of a pair of Black OysterCatchers at Race Rocks, They analysed the size, species diversity, and species frequency of the shells. The following data and charts are presented in order to provide information about the role of this seabird in the intertidal ecology of Race Rocks.

Numbers of Shells Collected Near Black Oyster Catcher’s Nest
    Limpets: Mask, Shield, and Plate 350    
    Limpets: Whitecap 70    
    Limpets: Fenestrate 19    
    Limpets: Rough Keyhole 2    
    Chitons: Black Katy 73    
    Chitons: Mossy 13    
    Chitons: Lined Red 7    
    California Mussels 342    
    Ribbed Whelk 5    
    Amphisia Snail 1    
         

Average Size of the Oyster Catcher’s Food california mussels –5.2875 cm plate,mask,shield limpets–3 cm whitecap limpets 5.2875 cm 3 cm 2.985 cm Size of Oyster Catcher’s Food: Raw Data, in cm

california mussels plate, mask and shield limpets white cap limpets
3 2 1.7
4 2.2 2.1
4.2 2.5 2.3
4.5 2.8 2.4
4.6 2.8 2.5
4.6 2.8 2.6
4.7 3 2.7
5.2 3 2.8
5.25 3.1 2.9
5.3 3.2 3
5.5 3.4 3.2
5.5 3.4 3.2
5.5 3.5 3.2
5.8 3.5 3.2
6. 3.5 3.3
6.5 3.5 3.6
6.6 3.6 3.7
7.5 3.8 3.8
7.8 3.8 3.8
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Garry Fletcher and Ecoguardian Carol Slater examining sorted shells of black oystercatcher prey from on midden.

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