Kleptoparasitism as a problem of prey choice:A study on mudflat-feeding curlews, <i>Numenius arquata</i>

Curlews feeding on intertidal flats attacked mainly conspecifics for prey, whereas they themselves also fell victim to kleptoparasitic attacks from gulls. There is no convincing evidence that robbers obtained other benefits, such as access to a good feeding site, besides the stolen prey itself. The data are consistent with the view that kleptoparasitism should be treated as a problem of prey choice, where attacks are initiated so as to maximize the net rate of energy gain. Attacks were directed mainly towards conspecifics handling large prey animals. There was no evidence of a simple producer-scrounger dichotomy. Instead, a dominance hierarchy seems more likely, where each individual could initiate attacks, but did so predominantly towards subdominant individuals, according to immediate profitability