Inter-specific kleptoparasitism between gulls and hosts with different foraging strategies: a comparative approach

GARCÍA GERMÁN OSCAR; FAVERO MARCO; VASSALLO ALDO IVÁN

EMU

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2012 p. 1 - 15

0158-4197

Kleptoparasitism is a well-known foraging strategy used opportunistically by many seabirds. Our study compares the strategies performed by a facultative kleptoparasite species (Brown-hooded Gull Chroicocephalus maculipennis) associated with two hosts with different foraging strategies (American Oystercatcher Haematopus palliatus and Red-gartered Coot Fulica armillata). Ninety-seven percent of the prey kleptoparasitized from oystercatchers were identified as the clam Tagelus plebeius, and all prey kleptoparasitized from coots as the crab Cyrtograpsus angulatus. The attack rate (number of kleptoparasitic attacks by unit time) did not differ significantly according to the host species, but the attack success rate (proportion of successful kleptoparasitic attacks out of total attacks registered) was greater for attacks on coots than on oystercatchers. Mean feeding (ingestion) rate by gulls did not differ according to the host. A strong selection for large kleptoparasitized prey was observed. The comparison of net intake (cost-benefit balance) for each kleptoparasite-host system showed that profitability was 3.5 times higher in the Gull-Coot system compared to the Gull-Oystercatcher system. Future work should address in more detail the costs and benefits for kleptoparasites with multiple hosts in similar systems elsewhere.