Factors Affecting Home Range Size and Movements of Post-Fledging Grassland Birds

Abstract

We describe post-fledging movements and evaluate the effects of local vegetation, temporal, and biological factors on home range size for two species of declining grassland birds in southwestern Missouri from 2002 to 2004. We obtained ≥30 detections for 74 individual juvenile Dickcissels (Spiza americana) and 64 juvenile Eastern Meadowlarks (Sturnella magna) during the post-fledging period. Juvenile Eastern Meadowlarks had a greater total number of days (6.7 ± 0.6) with large (>300 m) movements than juvenile Dickcissels (5.0 ± 0.5 days). Average Dickcissel home range size was larger and three times as variable in 2002 (77.0 ± 22 ha) compared to 2003 (31.4 ± 7.5 ha) and 2004 (34.9 ± 7.5 ha). There were year-specific effects of the variability in vegetation height on home range size of juvenile Dickcissels. Home range size was similar among years for juvenile Eastern Meadowlarks (2002, 109.4 ± 39.2 ha; 2003, 82.7 ± 29.4 ha; 2004, 70.7 ± 11.6 ha), but there was a year-specific effect of variability in grass cover on home range size of juvenile Eastern Meadowlarks. Local vegetation conditions are important factors affecting home range size and movements during the post-fledging period.