34 
THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124. No. 1. March 2012 
Mean pole touches per understory (<3 m) height interval 
FIG. I. Seasonal foliage-gleaning bird caplures plotted against mea 
Caro^na P USA nderSt0ry hdght ** CaCh " Ct loca,ion in a 
understory foliage density (mean vegetation pole 
bottomland forest during 2001-2002 in South 
density was greater at gap edges than in g; 
except during the breeding season when densit 
were greater in gaps (Table 2). The five m. 
frequently encountered arthropod Orders rep 
senting at least 150 individuals, were Arane; 
Coleoptera, Homoptera, Hymenoptera. and Lei 
doptera. Aramds. hymenopterans, and lepidoptt 
ans followed the same general pattern as . 
arthropods combined, but coleopteran densi 
decreased from spring to fall migration. Lepido 
tera density was highest in the forest during sprii 
migration, breeding, and post-breeding perioc 
but densities were similar among sampli, 
locations during fall migration. 
Bird and arthropod relationships were inconsi 
tent across the four seasons (Table 3). Folia* 
g eanmg bird abundance was positively associate 
«th lol.age dwelhng arthropods during the brecc 
periods ^ 
1-2, P = 0.28) (Table 3). Foliage-gleaning birds 
were positively associated with understory vegeta¬ 
tion density during all periods (Table 4; Fig. 1). 
DISCUSSION 
Seasonal shifts in relative bird use of gaps and 
forest understory in bottomland hardwood forests 
W'ere not driven by changes in arthropod avail¬ 
ability. Bowen et al. (2007) documented a 
seasonal shift in habitat use for several bird 
groups at our site with relative bird use of mature 
forest habitat greatest during the breeding period: 
they speculated these shifts may correspond to 
seasonal changes in arthropod abundance among 
habitats. However, arthropod abundance remained 
greater in forest understory than in gaps in all 
seasons, and we did not document an increase in 
total arthropods or any arthropod Order in die 
lores! during the breeding season when relative 
bird use of torest understory was greatest. The 
highest arthropod densities in gaps occurred 
during the breeding season, the period when birds 
least used gaps. Foliage-gleaning birds on our 
study site, based on crop flushes, consumed 
