How individual birds schedule their movements and use different sites during the non-breeding season are fundamental issues in avian migration ecology, and studies have often revealed strong seasonal variation in such strategies. Using geolocators we tracked Common Ringed Plovers Charadrius hiaticula from northern Norway to West Africa and back to assess whether there were differences in migratory speed, duration and stopover use between autumn and spring migration and whether birds used multiple sites during the non-breeding season. Although the pace of migration was similar between autumn and spring, the length of flight bouts and duration of the preceding stopovers were positively correlated only in autumn. Four of five birds showed a marked southward movement in mid-winter.

Investigating space use of wild birds provides important knowledge of bird behavior and ecology, which is crucial in the management and conservation of threatened species. In the present study, we used GPS satellite telemetry to investigate space use and movements of seven adult Eurasian Eagle-Owls (Bubo bubo) in Norway during breeding and post-breeding seasons. Breeding adults had a mean home range size of 42.9 km 2 (SD 6 35.1 km 2 ; 95% kernel density estimation H ad hoc ), and five individuals performed long (.20 km) excursive movements away from their breeding territories during autumn. Such wide-ranging behavior has not previously been reported for adults of the nominate subspecies B. b. bubo. The study demonstrates the need to investigate seasonal movements of species, populations, and age groups even if they are considered residents, and provides valuable information for management and conservation of the Eurasian Eagle-Owl.

International audienceIn recent decades, data loggers and radio- and satellite transmitters have become an important technological part of research on free living animals. Loggers to track movements and behaviour are especially useful in seabird studies, as seabirds often travel considerable distances at sea where visual observations are challenging. The potential negative effects of these devices on mortality, behaviour and reproduction of birds have received some attention, but few studies have investigated the physiological effects of instrument attachment. In the present study, effects of global positioning system (GPS) loggers on black-legged kittiwakes Rissa tridactyla were investigated by obtaining behavioural and physiological parameters of stress (nest attendance, plasma levels of the avian stress hormone corticosterone [CORT], relative leucocyte counts, body mass and reproductive success) during 2 d of GPS-deployment. GPS-equipped kittiwakes had significantly elevated levels of CORT at recapture and also significantly extended the duration of feeding trips compared to controls. Kittiwakes with low body condition index (BCI) attended nests less than controls, and this pattern was more pronounced among GPS-equipped birds. The study underlines the need to take device effects into consideration when instrumenting seabirds. Potentially, effects may become more evident in birds with low body condition or in years where food is limited, and results from GPS-equipped birds should be viewed with this in mind

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Abstract. The use of tracking devices to monitor birds is extensive, but the effects of such instruments on equipped individuals are still insufficiently taken into account. Here we evaluate potential effects of backpack-mounted satellite transmitters (platform terminal transmitters; PTTs) on survival of 28 Snowy Owls Bubo scandiacus. Six confirmed deaths were all probably related to natural and human-induced causes. Although PTT operational time was significantly shorter than expected lifetime of Snowy Owls, five owls were observed alive after transmissions ceased. Additionally four PTTs stopped due to low battery levels, indicating end of transmitter life and not owl mortality. We found no evidence of mortality caused by PTTs, but sample sizes are relatively low and detrimental effects on equipped Snowy Owls cannot be excluded. We recommend caution when instrumenting large owls.