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Effects of Exotic Lonicera and. Rhamnus on Songbird Nest Predation KEN.N, = A. SCHMIDT`-, AND CHRISTOPHER J. ''HELANT i 'Institute of Ecosystem Studies, Box AB, 'Ytillbrook, NY 12545, U.S.A. Illinois Natural History Survey, Midewin National Tallgrass Prairie.WMington,IL 60481, Abstract: Habitat fragmentation and disturbance exacerbate the invasion of exotic plant species that, in turn, may attract nesting songbirds by providing a branch structure suitable for nest sites. We document that n American Robin (I'urdus migratorius) nests in two exotic plants. Lonicera maackii and Rharnnus cathartics, ex- perienced higher predation than nests built in comparable native shrubs (Crataegus, Viburnum) and native tree species. This was due to a combination of lower nest height. the absence of sharp thorns on the exotic spe- cies, and perhaps a branch architecture that facilitated predator movement among the exotic species. In a more subtle interaction. nesting Wood Thrushes (Hylocichia mustelina) experienced apparent competition with robins for nest sites in Lonicera. and this interaction was further aggravated by an increased selectivity for Lonicera by nesting robins,possibly due to their early leaf flush and expansion. By documenting increased nest predation in songbirds nesting in exotic shrubs, our results suggest that restoring native plant communi- ties may benefit the surrounding avian community. • Efectos de las Especies Ex6ticas Lonicera y Rhamnas en la Depredaci6n de Nidos de Aves Cantoras Resumen: La fragmentation y perturbaci6n de hdbftats incrementan la invasion de especies de plantas ex6ticas que, en turno,pueden atraer ayes cantoras anidando al nidos del zorzai americano (rurdus migra- torius) en dos plantar ex6ticas, Lonicera maackii y Rhamnus cathartica. que experimentaron major depre- daci6n que los zor_-ales que construyeron nidos en arbusios nativos comparables(Crataegus,Viburnum)y en especies nativas de krboles. Esto se debid a la combinacidn de una altura del nido mas Baja, la ausencia de espinas filosas en Las especies ex6ticas y probablemente a una arquitectura de ramas que facilW el mov- imiento de depredadores entre Las especies ex6ticas.En una interacci6n mas sutil, el zorzalito maculado(Hy- locichla mustelina)experiment6 una aparente competencia con el zorzal americano por sitios de nidacidn en Lonicera, esta interaccion fue agravada aain mas por una creciente selectividad por Loniccra por zot-:al americano, Dosiblemente debido a site temprano desarrollo de bojas y expansion. Al documentar el incre- mento en la depredaci6n de nidos en ayes cantoras anidando en arbustos exdticos, nuestros resultados sugieren que La restauracidn de comuntdades de plantas nativas podria beneficiar las comunidades de ayes de los alrededores. Introduction of the Roche Mountains (Luken & Thierer 1996; Hutch- inson &Vanlcat 1997). Where they occur,Lonicera and Exotic plant species in the genera Lonicera and Rham- Rhamnus provide a branch structure suitable for nest nus have invaded numerous sites throughout much of construction within the range of heights used by many temperate, eas[em -North America. Lonicera maackii, songbird species (Whelan & Dilger 1992, 1995)- These for instance. is now widespread in at least 25 states east shrubs therefore may act as ecological traps if songbirds nesting in them experience higher predation than corn parable native shrubs(Gates&G-sel 19,8). :Current aaaress: Unwersay of.1lemDba, Department of Biology, Habitat fragmentation exacerbates both the invasion Ellington Hall. viempbts. nN,38152, (-'.S.A. 199 D' Paper submtsed fanuar_,, 29, 1999; revised manuscript accepted of exotic plant species (Hobbs & Huenneke Afav ZG, 1999. Hutchinson & Vankar 1997) and higher nest predation 1502 Conservation Biology.Pages i5o2-iioo n..............