We hypothesized that prey consumed by bats in maternity colonies differed b
y season and perhaps by time of day during postnatal development of young.
Such was based on information that availability of prey to aerial-foraging
bats differs spatially and temporally, some bats are selective of prey, and
activity of lactating females varies with stage of development of young an
d their demands for energy. We identified prey in fecal samples collected a
t 2400 and 0600 h at weekly intervals from beneath two clusters of big brow
n bats (Eptesicus fuscus) in a maternity colony in a barn in Benton County,
Oregon during postnatal development of young. Only consumption of moths (L
epidoptera) differed significantly by week; neither percent frequency nor a
verage percent volume for any taxon of prey differed significantly by time
of day. The overwhelming preponderance of caddisflies (Trichoptera) consume
d possibly obscured variation in frequency and volume of other taxa of prey
eaten. A maternity colony more distant from a single abundant, highly desi
rable, source of easily captured prey possibly would exhibit greater differ
ences in prey consumed during postnatal development of young.