Influence of residual tree density on predation of artificial and natural songbird nests A. Kari Stuart-Smith * , John P. Hayes Department of Forest Science, Oregon State University, Corvallis, OR 97331-7501, USA Received 20 October 2002; received in revised form 23 November 2002; accepted 12 February 2003 Abstract Variable retention, or the retention of live (residual) trees within logged stands, is thought to reduce the impact of clearcutting on wildlife. However, it has been suggested that this practice may increase nest predation for songbirds nesting within these stands, resulting in an ‘‘ecological trap’’. We tested this hypothesis using experimental (artificial nests) and observational (natural nests) approaches in the montane forests of the Rocky Mountains in southeastern British Columbia, Canada. In each of 2 years, we placed 720 artificial nests in 24 stands (16 logged, 8 burned by wildfire) of similar age which varied in residual tree density from 0 to 180 trees/ha (residual basal area 0–19.0 m 3 /ha). Natural nests of ground and shrub-nesting songbirds were monitored in four additional logged stands that varied in residual tree density from 8 to 64 trees/ha (residual basal area 0.5– 4.6 m 3 /ha). There was no strong or consistent evidence that predation on nests of ground and shrub-nesting birds increased in association with residual tree density. Predation on artificial nests increased moderately with residual tree density in logged stands, but in only one of 2 years. In burned stands there was no relationship in either year. There was no difference in overall predation rates on artificial nests in logged and burned stands. Predation was caused mainly by birds, squirrels and small mammals, and predation by birds showed the strongest relationship with residual tree density. Predation on natural nests was less frequent than that on artificial nests, and did not increase with residual tree density. Thus, there was no indication that variable retention stands acted as ecological traps for songbirds. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Nest predation; Songbirds; Rocky Mountains; Residual trees; Variable retention; Artificial nests 1. Introduction Leaving varying densities of residual (green) trees within harvested areas is emerging as one strategy for integrating ecological and economic objectives of forest management in temperate forests (Hansen et al., 1995a; Franklin et al., 1997). Known as variable or green-tree retention, this practice is thought to reduce the impacts of forest harvesting on wildlife and make harvested areas more closely resemble those created by natural disturbances. For birds, recent studies have shown that leaving dispersed trees or patches of trees within cutblocks can increase abun- dance and richness of songbirds (passerines) relative to levels in clearcut stands in aspen-dominated (Nor- ton and Hannon, 1997; Merrill et al., 1998; Schieck et al., 2000; Tittler et al., 2001), and conifer-domi- nated (Hansen et al., 1995b; Seip and Parker, 1997; Forest Ecology and Management 183 (2003) 159–176 * Corresponding author. Present address: Tembec Inc., BC Division, 220 Cranbrook St. North, P.O. Box 4600, Cranbrook, BC, Canada V1C 4J7. Tel.: þ1-250-426-9380; fax: þ1-250-426-5372. E-mail address: kari.stuart-smith@tembec.com (A.K. Stuart-Smith). 0378-1127/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0378-1127(03)00104-X