Local and Migratory Movements of Radio-Tagged Juvenile Harriers
ABSTRACT
To determine post-fledging movements of the juvenile Northern Harrier (Circus cyaneus) hatched on the Buena Vista Marsh, central Wisconsin, I radio-tagged both adult and nestling harriers. I followed the local movements of 7 radio-tagged juveniles from 3 nests, inest in 1976 and 2 in 1977, and the early migratory movements of 3 of these juveniles in 1977. All 7 remained within 1.4 km of their nests for about 3 weeks after their first flights. They did little if any hunting during this period. Five of the 7 left the study area between 20 and 23 days after fledging. One juvenile was killed near its nest by a predator 32 days after fledging, and the last one left the study area 50-51 days after fledging.
I obtained information on 4 of the 6 juveniles that left the study area. All 4 left alone, rather than with parents or siblings. Three were located during migration. Their migratory movements were interrupted by the establishment of temporary home ranges that were used for 2-3 weeks. One juvenile was located once 71 km southeast of her nest. Another was monitored in two temporary home ranges, one 85 km east-southeast and another 171 km southeast of his nest. A third juvenile was tracked continuously until she was in a temporary home range 164 km southeast of her nest. All known locations of the migrating juveniles were in the southeast quarter of Wisconsin. Case histories of the movements of these 3 juveniles are presented in detail.
