Shorebird feeding on stranded giant gastropod egg capsules of Adelomelon Brasiliana (Volutidae) in coastal Argentina

PABLO E. PENCHASZADEH; F. BOTTO; O. IRIBARNE

JOURNAL OF SHELLFISH RESEARCH

NATL SHELLFISHERIES ASSOC

Año: 2000 vol. 19 p. 901 - 904

0730-8000

We report predation by shorebirds on large egg capsules of the gastropod Adelomelon brasiliana. This gastropod is a common 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, especially after storms. Two shorebirds were observed feeding on embryos inside capsules, the American oystercatcher (Haematopus palliatus) and the South American stilt (Himantopus melanurus). During periods when egg capsules were stranded both birds switched to prey on embryos inside capsules stranded on the sandy beach. Field observations and a field experiment showed that birds prefer to prey on capsules that have embryos in advanced developmental stages. It is interesting to note that of all the shorebirds observed at the study site, only the local non-migratory species preyed on capsules.