Our inquiries went from the Department of Conservation Hokitika to Wellington Head Office and resulted in an explanation with a request for permission to use these photos as a national reference of NZ shag ballast stones.

The NZ Ornithological Society published the photos with explanation in the March 2009 Magazine, Southern Bird. Several species of shags (Pied, Black, Little and Spotted) often swallow small stones as ballast, used in the same way as human divers use lead weight belts, to control buoyancy. The stones are stored in the gizzard and are often regurgitated at roost before the birds fly off to feed again. They may only be used when the bird is feeding in shallow water and seem to be less necessary on deeper dives. The foot prints identify the shags, most likely the three Spotted shags on the nearby rock.
Recently fourteen species of shorebirds were seen by our birding guests at the river mouth. Join us for a wilderness birding tour!