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�I - �J Effects of Exotic Lonicera and Rbamnus on Songbird Nest Predation HENti= A. SCHMIDT— _N,D CHRISTOPHER T. NX'HELAN 'Institute o?Ecosystem Studies. Box AB. Ntillbrook. NY 12545, L..�"A. ? 'Illinois Natural Historn•Survey. `fidewin National Tallgrass Prairie. Willington,IL 6,3481. I..s.A. 1 a j i Abstract: Habitat fragmentation and disturbance exacerbate the invasion or exotic plant species that, in turn, may,attract nesting songbirds by providing a branch structure suitable for nest sites. We document that American Robin (rurdus tnigratonus) nests in two exotic plants. Lonicera maackii and Rhantnus cathartica. ex- perienced higher predation [ban nests built in comparable native shrubs (Ctataegus, 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 Derhaps a branch architecture that facilitated Dredator movement among the exotic species. In a more subtle interaction. nesting IrVood Thrushes (Hylocichia mustelina) experienced aDDarent 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 Especics Ex6licas Lonicera y Rhamnus cr.1a Depredaci6n de Nidos de Aves Cantotas Resumen: La fragmentation 11 perturbaci6n de htibitats incrementan la invasion de especies de plantar ex6ticas que, en turno,pueden atraer aves cantoras anidando al nidos del zor_-al americano (I'urdus migra- torius) en dos plantas exdticas, Lonicera maackii y Rhamnus cathartics, que experimentaron major depre- daci6n que los zorzales que construveron nidos en arbustos nativos comparables (Crataegus, Vibumum)y en especies nativas de arboies. Esto se debi6 a la combination de una altura del nido mas baja, la ausencia de espinas filosas en Las especies exdticas y probablemente a una arquitectura de rarnas que facilit6 el mov- imiento de depredadores entre Las especies exdticas. En una interacci6n mas sutil, el zorzalito maculado(Hy- locichla mustelina) exDerimentd una aDarente competencia con el zor_-al americano por sitios de nidact'6n en Lonicera, esia interaction fife agravada aun mas por una creciente selectividad por Lonicera por zor_-al americano.Dosiblemente debido a site temprano desarrollo de bojas y expansion. Al documentar el incre- mento en is depredation de nidos en aves cantoras anidando en arbustos exdticos, nuestros resultados sugieren que La restauracidn de comunidades de plantar nativas Dodria beneficiar las comunidades de ayes de Los alrededores. Introduction of the Rockv Mountains (Luken :- Thieret 1996; Hutch- inson 3 Vankat 1997). W'here they occur.Lonicera and Exotic plant species in the genera Lonicera and Rbam- Rhamnus provide a branch structure suitable for nest nus have invaded numerous sites tnroughout much of construction within the range of heights used by man' temperate, eastern North America. Lonicera maackii, songbird species (Whelan & Dilger 1992. 1995). These i for instancc. is now widespread in ai least 25 states east shrubs therefore mail act as ecological traps if songbirds nesting in them experience higher predation than com- Current eauaress: Un:versi:y of Membbu. DeDanment of Biology, a ble natlVe Shlrubs(Gates & G}'sel 19-8). Ellington Hall.,11emObu. T,%, 38152, L. . i. Habitat fragmentation exacerbates both the invasion Paper suom:aed fanuan_ 29, 1999, revised manuscript acceDted of exotic olant species (Hobbs & Huenneke 1992; Stay ZG, 1999. Hutchinson & vankat 1997, and 1502 � higher nest predation Conserv2rion Biology.Pages 1502-1;O6