Shorebird feeding on stranded giant Gastropod egg capsules of Adelomelon brasiliensis (Volutidae) in coastal Argentina

PABLO E. PENCHASZADEH; FLORENCIA BOTTO; OSCAR IRIBARNE

JOURNAL OF SHELLFISH RESEARCH

Año: 2000 p. 901 - 904

0730-8000

We report predation by shorebirds on large eggs of the gastropod Adelomelon brasiliana. This gastropod inhabitant of sandy substrates in the northern coastal area of Argentina and is the only South American volutid known to have free unattached egg capsules. These capsules are commonly found strewn on beaches, specially after storms. Two shorebirds were observed feeding on embryos inside capsules, the American oystercatcher (Haematopus ostralegus) and the South American Stilt (Himantopus melanurs). Duing periods when egg capsules were stranded both birds switched to pey on embryos inside capsules stranded on the sandy beach. Field observations and a field experiment showed that birds prefer o prey on capsules that have embryos in advanced development stages. It I interesting to note that of all the shorebirds observed at the study site, only the local non-migratory species preyed on capsules