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Dead Recoveries (dead + recovery)
Selected AbstractsWithin- and between-year variation in the juvenile survival of Common Guillemots Uria aalgeIBIS, Issue 3 2007MICHAEL P. HARRIS We studied juvenile survival of 20 cohorts of Common Guillemot Uria aalge chicks colour-ringed on the Isle of May, Scotland, using both live observations at the colony and dead recoveries, allowing estimation of fidelity to the colony as well as survival. In this seabird, chicks leave the colony when only partly grown and are cared for by the male parent for several weeks afterwards. First-year survival varied strongly between cohorts, with a mean of 56% (range 30,91%). We did not identify any covariates which could explain this variation, whether relating to climate, population size or prey density. Survival was low during two regime shift episodes in the North Sea (1987,90 and 2000 onwards). Early hatched chicks were substantially more likely to survive than those hatching later in most years, whereas body condition at ringing had no detectable effect. Ringing recoveries indicated that mortality was highest in mid-winter, i.e. well after the cessation of paternal care. These results do not support the hypothesis that variation in prey quantity or energy content before fledging is a primary driver of variation in juvenile survival. Rather, it seems that chicks of high-quality parents are more likely to survive, as high-quality females tend to lay earlier in the season, and high-quality males presumably are better able to prepare their chicks to survive their first winter at sea. Very few (4%) Guillemots emigrated permanently before age 3 years, but from age 5 onwards 25,30% of birds annually left the colony or otherwise became unobservable. [source] Estimating survival and movements using both live and dead recoveries: a case study of oystercatchers confronted with habitat changeJOURNAL OF APPLIED ECOLOGY, Issue 1 2009Olivier Duriez Summary 1Animals facing partial habitat loss can try to survive in the remaining habitat or emigrate. Effects on survival and movements should be studied simultaneously since survival rates may be underestimated if emigrants are not considered, and since emigrants may experience reduced survival. 2We analysed movements and survival of adult wintering oystercatcher Haematopus ostralegus in response to the 1986,1987 partial closure of the Oosterschelde in the Dutch Delta. This reduced by one-third the tidal area of this major European wintering area for waders. 3We developed a novel variant of a multistate capture,recapture model allowing simultaneous estimation of survival and movement between sites using a mixture of data (live recaptures and dead recoveries). We used a two-step process, first estimating movements between sites followed by site-specific survival rates. 4Most birds were faithful to their ringing site. Winter survival was negatively affected by winter severity and was lowest among birds changing wintering site (i.e. moving outside of the Oosterschelde). 5During mild winters, survival rates were very high, and similar to before the closure in both changed and unchanged sectors of the Oosterschelde. However, the combined effect of habitat loss with severe winters decreased the survival of birds from changed sectors and induced emigration. 6The coastal engineering project coincided with three severe winters and high food stock, making assessment of its effects difficult. However, the habitat loss seems to have had less impact on adult survival and movements than did winter severity. 7 Synthesis and applications. Human-induced habitat change may result in population decline through costly emigration or reduced survival or reproduction of individuals that stay. Long-term monitoring of marked individuals helps to understand how populations respond to environmental change, but site-specific survival and movement rates should be integrated in the same model in order to maximize the information yield. Our modelling approach facilitates this because it allows the inclusion of recoveries from outside the study area. [source] Limited dispersal by Nazca boobies Sula grantiJOURNAL OF AVIAN BIOLOGY, Issue 1 2004Kathryn P. Huyvaert We documented natal and breeding dispersal at several spatial scales by Galápagos Nazca boobies Sula granti, a wide-ranging pelagic seabird. We found exceptionally low degrees of both types of dispersal despite these birds' vagility. Median natal dispersal distances were 26 m and 105 m for males and females, respectively. Median breeding dispersal distances for both sexes were 0 m. No natal or breeding dispersals occurred from our study site at Punta Cevallos, Isla Española to six other colonies in the Galápagos, but we did document four long-distance natal dispersals from Punta Cevallos to islands near the South American coast. Recaptures and dead recoveries of ringed birds showed long distance non-breeding movements to the Central American coast and elsewhere in the eastern Pacific, contrasting with the very limited dispersal to breeding sites. [source] | ||||||||||