Ce. Moorman et Dc. Guynn, Effects of group-selection opening size on breeding bird habitat use in a bottomland forest, ECOL APPL, 11(6), 2001, pp. 1680-1691
An increase in timber removals from southern bottomland forests of the Unit
ed States has been predicted, warranting investigations of the effects of s
ilvicultural alternatives on avian breeding habitat. We;studied the effects
of creating group-selection openings (man-made canopy gaps) of various siz
es on breeding bird habitat use in a bottomland hardwood forest in the Uppe
r Coastal Plain of South Carolina, USA. We used spot mapping and mist netti
ng to estimate bird abundance at 0.06-, 0.13-. 0.26-, and 0.5-ha gap's and
at uncut control areas during the 1996, 1997, and 1998 breeding seasons (I
May-1 August). There were significant increases in the number of species ma
pped (P = 0.0001) and netted (P = 0.0001) with successive increases in gap
size. The greatest number of total spot-map detections (P = 0.0002) and mis
t net captures (P = 0.0004) also occurred in and around the large gaps. The
se patterns were the result of increased use of larger gaps by field-edge s
pecies, primarily Brown-headed Cowbird (Molothrus ater), Common Yellow-thro
at (Geothlypis trichas), and Indigo Bunting (Passerina cyanea), and some fo
rest-edge species, such as White-eyed Vireo (Vireo griseus) and Northern Pa
rula (Parula americana). Conversely, Acadian Flycatcher (Empidonax virescen
s) Was less abundant in and adjacent to gaps. Because there were few differ
ences in vegetation among gaps of different sizes, it is likely that birds
that were detected more frequently in and adjacent to larger gaps selected
those gaps based on other factors correlated with size. Creation of 0.5-ha
group-selection openings in southern bottomland forests should provide bree
ding habitat for some field-edge species in gaps and habitat for forest-int
erior species and canopy-dwelling forest-edge species between gaps. provide
d that sufficient mature forest is maintained.