USING TELEMETRY AND DNA ANALYSES TO DETERMINE NATAL DISPERSAL RATES OF WOOD 
THRUSHES

Jason Hass1, Lara Scott1, Abigail Garner1, Larkin Powell2 and Justin Streit3
1Department of Environmental Science, University of Dubuque, Dubuque IA  52001; 
2School of Natural Resources, University of Nebraska, Lincoln, NE  68583
3Department of Biology, Northland College, Ashland, WI  54806   

Natal dispersal of excess juveniles from growing, or "source" populations can be 
critical for the support of declining, or "sink" populations.  The distance of, 
and habitat used for, natal dispersal is unknown for most birds, and 
conservation efforts to preserve critical habitats can be enhanced by such 
knowledge.  We studied wood thrushes (Hylocichla mustelina), a neotropical 
migrant, in the Mines of Spain Recreation Area near Dubuque, IA.  We monitored 
nests and activity during the summer of 2001.  Nest were found by visual 
observation and by radio-marking adult female wood thrushes, captured in mist 
nets.  We tracked juveniles using radio transmitters during their natal 
dispersal.  DNA analyses were used to determine the gender of the wood thrush 
fledglings.  Seventy percent of the nests (n=10) were parasitized by brown-
headed cowbirds (Molothrus ater), including 2 nests with no host eggs.  The 
daily nest success rate was 0.9612 (SE=0.0189), and daily juvenile survival was 
0.9703 (SE=0.0169).  Three successful juveniles dispersed 270 m, 980 m and 746 
m.  High predation rates, combined with high parasitism rates indicate that our 
study area was a region of low productivity for wood thrushes, reinforcing the 
need for further information on natal dispersal of successful fledglings.  Our 
analyses of dispersal during the summer of 2001 will be helpful to managers of 
critical habitat for the wood thrush species.

Keywords: dispersal, survival, nest success, wood thrush, Hylocichla mustelina