NECK COLLAR RETENTION IN DUSKY CANADA GEESE
--A total of 4965 Dusky Canada Geese (Branta canadensis occidentalis) were neckcollared on the Copper River Delta, Alaska, in 1984-1990. Collar retention rates for adult geese were obtained from examination of 910 recaptures. The effects of sex, collar age and collaring year on retention rates were determined using logit models. As there was a significant interaction between the effects of sex and collar age on retention rates, the sexes were modeled separately. The average annual retention rate for female geese (0.875 ___ 0.163 SE) was independent of all effects considered. Retention rates for males was influenced by collar age and the year collared. It is concluded that collar losses were substantial and that losses pecific to the years modeled should be considered in any population model. RETENCI•N DE ANILLOS EN EL PESCUEZO POR PARTE DE INDIVIDUOS DE BRANTA 1⁄2ANADENSIS OCCIDENTALIS Sinopsis.--Entre el 1984-1990 un total de 4965 individuos de gansos del Canada (Branta canadensis occidentalis) fucron anillados cn la pescuezo en el delta del Rio Copper, Alaska. La retenci6n de las anillas, pot parte dc adultos, fue obtenida del estudio de 910 individuos rccapturados. E1 efecto dcl sexo, edad dc la anilla y afio de la anillada, en la tasa de retcnci6n de anillas, fuc determinada utilizando modelos dc "logit." Como hubo una interaccion significativa entre el efecto del sexo y edad de la anilla, en la tasa de retenci6n, se hicieron modelos separados para ambos sexos. La retenci6n promcdio anual para hembras (0.875 + 0.163 EE) result6 set indepcndiente dc todos los otros efectos considerados. La tasa dc rctcnci6n cn los machos fue influcnciada pot la cdad de la anilla y el afio dc anillamiento. Sc concluye quc las p6rdidas de las anillas fue sustancial, y quc los extravlos en aftos particulates deben set consideradas en cualquier modelo poblacional. Neck collars have been used to mark geese for several decades (Marion and Shamis 1977). Observations of these birds have provided much valuable information about population dynamics (Hestbeck and Malecki 1989, Rusch et al. 1985), migration (Craven and Rusch 1983, Koerner et al. 1974, Raveling 1978, Trost et al. 1980), and behavior (Macinnes and Lieff 1968). Recently, observations of marked geese have been applied in methods used to estimate survival probabilities (Ebbinge and van Biezen 1987, Hestbeck and Malecki 1989, Raveling and Zezulak 1988, Rusch et al. 1985, Yparraguirre 1982), statistics that have traditionally been calculated from models utilizing band recovery data (Brownie et al. 1985). These models generally do not account for marker loss (Brownie et al. 1985, Pollock and Raveling 1982), which is probably of little consequence for-short lived species. In the case of potentially long-lived animals such as geese, however, marker loss may severely affect survival estimates (Nelson et al. 1980). The Dusky Canada Goose (Branta canadensis occidentalis), which nests primarily on the Copper River Delta, Alaska, and winters in the Willamitte Valley in Oregon and southwestern Washington, has steadily declined in number since 1979. Harvest was restricted in 1984 and is
Neckband loss and its effect on apparent survival estimates in Greylag Geese (Anser anser): variation with season, sex and age
Mark-recapture studies enable us to estimate population parameters such as survival, if marks do not impact survival and if marks are not lost. Mark loss can result from external wear and damage, but also behavioural factors may be important and could explain differences between seasons or sexes. We studied Greylag Geese (Anser anser) in eastern Netherlands, ringed with neckbands, leg bands and metal rings (912 geese), observed weekly during 1997–2019 (131,625 observations). Given the double marking and high annual resighting probabilities (neckbands: 0.974, leg rings: 0.639), we quantified neckband loss and the effect of neckbands on apparent survival, using multistate mark-recapture models. Annual neckband loss was 0.038, was higher in males (0.056) than females (0.021) and increased with years since marking, up to 0.098 for males more than 8 years after marking. Neckband loss tended to be higher during December–May than June–November, with most losses occurring in March–April. Both the higher loss in males and the peak in spring in both sexes could result from intraspecific fighting (pulling each other’s neck and neckband). Survival was underestimated in Cormack-Jolly-Seber models that did not account for neckband loss, by up to 0.096 for adult males 6–7 years after marking. Thus, ignoring neckband loss may give erroneous survival differences between sexes and seasons, and overestimate the effect of ageing on survival (i.e. senescence). We did not detect an effect of neckbands on mortality, but statistical power for this test was limited. Neckband loss, although lower nowadays than in studies of decades ago, still impacts survival estimates and should be considered in mark-recapture studies.
Protecting Marine Biodiversity on the Continental Shelf Beyond 200 Nautical Miles
States are expending significant effort to chart the extent of their continental shelves where these extend beyond 200 nautical miles. As more is understood about marine biodiversity on the outer continental shelf, states may wish to regulate the use of biodiversity for the purposes of conservation or for future exploitation. This article identifies potential threats to marine biodiversity on the continental shelf, explores whether conservation is a legitimate purpose for exercising coastal state rights over the outer continental shelf under the Law of the Sea Convention, and considers the various legal rules that coastal states may use to protect marine biodiversity. The article concludes that the continental shelf regime is undesirably vague in some instances but that coastal states have a legal basis for taking action to regulate activities that impact the marine biodiversity of the outer continental shelf.