Site-Specific Heavy Metal Concentrations in Blood of South Island Pied Oystercatchers Haematopus ostralegus finschi from the Auckland Region, New Zealand

Concentrations of mercury, lead and cadmium were determined in whole blood samples from South Island pied oystercatchers Haematopus ostralegus finschi from two over-wintering sites within the Auckland region, New Zealand. The sites chosen reflected divergent pollutant regimes; South Kaipara Harbour was relatively free of urbanisation and associated pollution, whilst Mangere Inlet within Manukau Harbour in central Auckland was considered relatively polluted. Mercury concentrations in bird blood samples were relatively low (maximum concentration=102.4 ng g −1 wet weight in a juvenile from Mangere Inlet), and exhibited no differences between age categories, nor between the two sites. Mercury concentrations measured in oystercatchers were highly unlikely to result in any deleterious toxicological effects. Mean lead concentration was markedly and significantly higher in birds from Mangere Inlet (overall mean=143.1 ng g −1 wet weight) compared to that in birds from South Kaipara (overall mean=58.2 ng g −1 wet weight). Within birds from Mangere Inlet, juveniles exhibited a significantly higher mean lead concentration (184.0 ng g −1 wet weight) compared to that in adults (113.0 ng g −1 wet weight). Some individuals sampled at Mangere Inlet exhibited blood lead concentrations above the 200 ng g −1 wet weight ‘threshold’ generally considered to define the concentration at and above which there is potential for toxicological effects. Cadmium concentrations were uniformly low in birds from both sites, often below detection limits, and pose no toxicological threat. The suitability of analysing heavy metals in blood from South Island pied oystercatchers in order to elucidate patterns of metal contamination over relatively small spatial scales is discussed.