Artificial nest experiments have been used in an attempt to understand patterns of predation affecting natural nests. A growing body of literature suggests that neither relative rates nor patterns of predation are the same for artificial and natural nests. We studied nest predation and daily mortality rates and patterns at real and artificial ground and shrub nests to test the validity of artificial nest experiments. We monitored 1667 artificial and 344 natural nests, over seven trials, in three regions, across 58 sites in Ontario. We controlled for many of the factors thought to be responsible for previously reported differences between predation rates on natural and artificial nests. Although artificial nests in our study resembled natural nests, contained eggs of appropriate size, shape, and color of target bird species, and were placed in similar microhabitats as natural nests, the rates of predation on these nests did not parallel rates on natural nests for any region in terms of absolute rate or pattern. Predation rates on artificial nests did not vary between years, as they tended to for natural nests, and the magnitude of predation pressure on artificial ground nests compared with shrub nests did not show the same pattern as that on natural nests. In general, rates of predation on artificial nests were significantly higher than on natural nests. Our results suggest that conclusions derived from artificial nest studies may be unfounded. Given that many influential ideas in predation theory are based on results of artificial nest experiments, it may be time to redo these experiments with natural nests.Resumen: Se han utilizado experimentos con nidos artificiales con la intención de entender los patrones de depredación que afectan a los nidos naturales. La bibliografía sugiere que ni las tasas relativas ni los patrones de depredación son iguales para nidos artificiales y naturales. Estudiamos las tasas y patrones de depredación de nidos y de mortalidad diaria en nidos reales y artificiales sobre el suelo y en matorrales para probar la validez de los experimentos con nidos artificiales. Monitoreamos 1667 nidos artificiales y 344 nidos naturales, en siete pruebas, en tres regiones, en 58 sitios en Notario. Controlamos muchos de los factores que se piensa son responsables de diferencias entre tasas de depredación en nidos naturales y artificiales reportadas previamente. Aunque los nidos artificiales en nuestro estudio se asemejaron a nidos naturales, contenían huevos de tamaño, forma y color adecuados para la especie de ave y fueron colocados en microhábitats 382 Predation Patterns on Artificial and Real NestsBurke et al.similares a los de nidos naturales, las tasas de depredación en estos nidos no fueron similares a las tasas en nidos naturales en ninguna región en términos de tasa o patrón absoluto. Las tasas de depredación en nidos artificiales no variaron de un año a otro, como fue la tendencia en nidos naturales, y la magnitud de la presión de depredación en nidos sobre el suelo comparada con nidos en arbu...

. ~e w r n a s t e r l f~The effects of thinning on growth and survival of white pine (Pinus strobus L.), white ash (Fraxinus americana L.), and red oak (Quercus rubra L.), and understory plant diversity were examined in a young red pine (Pinus resinosa Ait.) plantation. Five years after thinning, seedling diameter, height, and stem volume were positively correlated with thinning intensity and the size of canopy openings. Percent survival did not differ among thinning treatments, but was significantly higher in white ash and white pine than red oak. Understory vegetation included 113 species, with species richness increasing with thinning intensity and proximity to neighbouring plant communities. Thinning to create relatively large canopy openings in combination with underplanting can promote the natural succession of young pine plantations to native forest species.Keywords: direct seeding, plant diversity, natural regeneration, red oak, restoration, white ash, white pine Les effets de 1'Cclaircie sur la croissance et la survie du pin blanc (Pinus strobus L.), du frCne d'AmCrique (Fraxinus americana L.) et du chCne rouge (Quercus rubra L.) et sur la diversit6 des plantes en sous-6tage ont 6t6 CtudiCs dans une jeune plantation de pin rouge (Pinus resinosa Ait.). Cinq annkes aprks l'Cclaircie, le diamktre, la hauteur et le volume de la tige des semis ont Ct C corrklks positivement avec l'intensitk de 1'Cclaircie et la taille des ouvertures dans le couvert des cimes. Le pourcentage de sumie n'a pas diffkrk selon les traitements d'kclaircie, mais il Ctait significativement plus Clev6 pour le fr&ne d' AmCrique et le pin blanc que pour le chCne rouge. La vCgCtation en sous-Ctage comprenait 113 espkces, et la diversit6 des espkces augmentait selon I'intensitC d'kclaircie et la proximite de communautks de plantes avoisinantes. Une tclaircie r6alisCe dans le but de cr6er d'importantes ouvertures dans le couvert en association avec un regarnissage peut promouvoir la succession naturelle des plantations de jeunes pins vers des espkces forestikres indigknes.

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Periodic partial harvesting of trees is an important economic activity within the highly fragmented woodlands of southern Ontario. We studied the population density, age structure, food abundance, productivity, and nest survival of Rose-breasted Grosbeaks (Pheucticus ludovicianus) nesting in 35 deciduous woodlots with varying intensities of harvest. Heavily cut woodlots contained higher densities of territorial males and greater abundances of fruit-bearing shrubs compared with standard cut and reference sites (uncut for >13 years). Results based on insect sampling were mixed, depending on the sampling technique and sample date. All treatments were demographic sinks, with populations in this landscape showing annual declines of 19%–24%. Though the proportion of parasitized nests tended to be higher in heavily cut sites, harvesting had little effect on nest survival, nest initiation dates, clutch size, age structure, or the number of young fledged from a successful nest. Our results indicate that within the fragmented woodlots of southern Ontario, partial harvesting does not further degrade breeding habitat for Rose-breasted Grosbeaks. However, further research is needed to determine the underlying causes of population declines.