Double-brooding in a Western Australian population of the Silver Gull, Larvus novaehollandiae Stephens

Abstract

The Australian silver gull is one of a number of marine bird species which show a bimodal nesting regime along the Western Australian coast. The author had previously established that in captivity the same individuals bred in the autumn and in the spring of the same year (i.e. were double-brooded). Il he present paper, confirms that, at a nesting island off Fremantle in 1972, a similar nesting regime operated under natural conditions. No other species of gull is known to be double-brooded, and among silver gulls in the wild the phenomenon is known only in Western Australia. It may occur in South Africa, but apparently not in eastern Australian or New Zealand populations.