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.

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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	plate,mask,shield limpets	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	3.5	3.2
5.8	3.5	3.2
5.8	3.5	3.3
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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Last Updated on 3/14/00
By Erin K.

Return to the Field Lab directions
Return to the Taxonomy file on Black Oystercatchers