A bark shield now in the British Museum can be identified from documentary and pictorial evidence as one collected by Captain Cook during his first voyage to Australia in 1770. Such shields often had special value to their Australian Aboriginal owners and hence might have been exchanged over considerable distances. This particular shield is known to have been collected in Kamay Botany Bay but analysis of the bark of which it is made revealed it to be of red mangrove, a tropical species found today more than 500km distant on the New South Wales north coast. It hence bears valuable testimony to the long-distance exchange networks operating in eastern Australia in the period before the disruption caused by European colonisation.