Population change among Pacific, kelp and silver gulls using natural and artificial feeding sites in south-eastern Tasmania

Abstract

The kelp gull, Larus dominicanus, which is widely distributed around the southern hemisphere, has become established in Australia only in the past half-century. The greatest numbers of kelp gulls in Australia are now found in south-eastern Tasmania in sympatry with the two endemic species, the morphologically similar Pacific gull, L. pacificus, and the smaller silver gull, L. novaehollandiae. We examined populations of the three species in this area. We surveyed large refuse tips and specific shoreline sites in the Hobart area regularly during the winter months in 1981 and again in 1992, recording numbers of each species, and age classes of kelp and Pacific gulls. Between the two survey periods, the number of Pacific gulls and the total number of all gulls present at refuse tips remained unchanged. There was, however, a marked increase in the number of kelp gulls at tips, equivalent to an annual rate of increase of 22.8%, and a corresponding decrease in the number of silver gulls. Kelp gulls of all ages were over-represented at refuse tips, while adult Pacific gulls fed preferentially at more natural shoreline sites. At shoreline sites, adult Pacific gulls appeared to exclude kelp gulls from small bays in 1981, but kelp gulls were present in most of these bays eleven years later. Reducing access to food at refuse tips may be an effective means of controlling the kelp gull population in this area.

Biomass and biodiversity of nocturnal aerial insects in an Adelaide City park and implications for bats (Microchiroptera)

“…Synanthropic research has focused on quantifying differences in animal species diversity and/or abundance between urban areas and natural or rural areas, or along urban gradients with vertebrate (Geggie and Fenton 1985;Coulson and Coulson 1998;Kirsten and Klomp 1998;Legakis et al 2000;Duchamp et al 2004;Hwang and Turner 2005) and invertebrate species indicators (Blair and Launer 1997;Zapparoli 1997;Denys and Schmidt 1998;Barros 2001;McIntyre et al 2001;Alaruikka et al 2002;Braks et al 2003;Ishitani et al 2003;Rickman and Connor 2003;Hwang and Turner 2005;Piel et al 2005). Urbanisation is known to affect biodiversity negatively (in South Australia for example Turner 2001;Department for Environment and Heritage 2003;Reardon and Tait 2005), yet comparing wildlife trends in highly urbanised areas, such as cities, to those trends in increasingly distant non-urban controls may not be relevant in all instances (Garden et al 2006).…”

First Breeding Records of Kelp GullsLarus Dominicanus Vetulaat Robben Island, Western Cape, South Africa

“…In addition, in some years the island supports the largest breeding colonies of two taxa endemic to southern Africa: Hartlaub's gull and swift tern Sterna bergii bergii. Although there is currently no need to implement control measures for kelp gulls on Robben Island, this is an option that might soon need to be considered, noting the problems associated with increases in numbers of the same species off New Zealand and Australia (Fordham 1967, Coulson andCoulson 1998).…”

Urbanization of the Silver Gull: Evidence of Anthropogenic Feeding Regimes from Stable Isotope Analyses

“…Silver Gull populations in Australia have increased for over 50 years, both in number and size of colonies (Smith 1992;Smith andCarlile 1992, 1993b). However, populations of Silver Gulls in southeast Tasmania show an overall decreasing trend (Coulson and Coulson 1998;Wakefield 2005;Wakefield and Hayward 2006). Whether the decrease is due to improved garbage dump management, competition with naturalized Kelp Gulls (Coulson and Coulson 1998), or decreasing individual and reproductive fitness is unclear.…”

“…However, populations of Silver Gulls in southeast Tasmania show an overall decreasing trend (Coulson and Coulson 1998;Wakefield 2005;Wakefield and Hayward 2006). Whether the decrease is due to improved garbage dump management, competition with naturalized Kelp Gulls (Coulson and Coulson 1998), or decreasing individual and reproductive fitness is unclear. Synanthropy between humans and Silver Gulls has also been reported in Tasmania for over 30 years (Skira and Wapstra 1990).…”