Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens.

The wind power plant on the island of Smøla, western Norway, is currently the largest in Norway; it has 68 turbines with nominal capacity of 2-2.3 MW each, hub height of 70 m and rotor blade radius of 38-41 m,. It was constructed in two phases between 2001 and 2005. Approximately 60 White-tailed Eagle Haliaeetus albicilla territories are found in the whole Smøla archipelago. Before construction there were 13 Eagle pairs holding territories in the wind farm area and within 500 m of it, whereas in 2009 this was reduced to only five. Since 1996, baseline data on the White-tailed Eagle population size and reproduction have been collected.In a post-construction study, 50 fledglings were satellite-tagged during 2003-2009, of which 45 provided more than 80 000 GPS positions in total. In addition to the geographical location, data on altitude and flight speed were provided by the transmitters (Microwave Telemetry, Inc., Columbia, MD, USA). Juveniles of both sexes stayed within the Smøla archipelago during their first winter. Most individuals moved away from the area during spring in their second year (April-May). Females dispersed further than males, often more than 800 km during summer, generally to the north. There was a return movement to the natal area during the second autumn. The same pattern was repeated in the third and fourth years for females, while the males showed more philopatry (Bevanger et al., 2009).From August 2005 to May 2010, four of the satellite-tagged birds were killed by collisions with turbines, of 36 White-tailed Eagles in total, involving 20 adults, nine immatures and seven juveniles. April and May are the months with the highest collision frequencies, with 13 (c. 36%) and nine (c. 25%) of the known fatalities.Risk assessments were performed based on GPS positions during the different months of the year and the age of the birds. The transmitters were programmed to transmit their positions at different intervals. Long time intervals (up to 24 h) were used during winter, 3-6 h during spring and autumn, and 1-3 h during summer. An analysis of moves showed that the birds changed positions on average 15 times per day, using a 100-m difference between positions as an indicator of movement. Every change in position was considered to involve a collision risk when the birds were at Smøla and its archipelago. Moves when they were elsewhere were not considered. Monthly 95 and 50% utilization distributions (UDs) (Worton 1989) were produced using the positions from the Smøla archipelago only, with all birds in each month and age-class pooled. The expected number of moves by each bird was estimated by weighing the number of obtained positions by a factor equal to 15 divided by the preprogrammed number of positions taken for each transmitter and month. The total number of expected moves (Me) was then obtained by summing over all birds for each calendar year and month. Kernel UD (95 and 50%) areas by calendar year and month (Ak95 and Ak50) were produced via ArcView 3.3, by using cross-validation and

Abstract The postfledging period is the least-studied stage of avian life cycles. Survival during this period has crucial effects on population dynamics. Survival of fledged young may be influenced by dispersal from their nest sites, because juveniles must cope with the hazards of novel environments. To better understand this important life stage, we used radiotelemetry techniques to study postfledging movements and survival of 50 juvenile Eastern Meadowlarks (Sturnella magna) at Prairie Ridge State Natural Area in Jasper County, Illinois, in 1999 and 2000. Juveniles began to move away from the nesting area in the third week after fledging. Most juveniles moved only 1–5 km from their birth site by the end of the study (90 days). Juvenile survival for the first 90 days after fledging was estimated as 56–69%. Mortality was greatest during the first week of the postfledging period, likely because of high rates of predation. Juvenile meadowlarks are flightless at fledging and thus are vulnerable to predators. We did not observe a second peak of mortality, as other studies have shown, at independence or when juveniles began to move away from their nest areas. The present study suggests that immediate postfledging movements may not be related to dispersal to future breeding sites, but rather occur in response to immediate needs for food resources and security from predators. Furthermore, the data suggest that presumed mortality patterns and estimated levels of juvenile survival are suspect; that interspecific variability of juvenile survival and postfledging movements may be considerable; and that detailed, longer-duration field studies are necessary to elucidate this important demographic period.

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