J. Avian Biol. 42: 429433, 2011 doi: 10.1111/j.1600-048X.2011.05326.x # 2011 The Authors. J. Avian Biol. # 2011 Nordic Society Oikos Subject Editor: Wesley M. Hochachka. Received 31 August 2010, accepted 11 April 2011 Great spotted woodpeckers Dendrocopos major exert multiple forms of phenotypic selection on Scots pine Pinus sylvestris L  ukasz Myczko and Craig W. Benkman L  . Myczko, Inst. of Zoology, Poznan ´ Univ. of Life Sciences, Wojska Polskiego 71C, PL-60-625 Poznan ´, Poland.  C. W. Benkman (cbenkman@uwyo.edu), Dept of Zoology and Physiology, Univ. of Wyoming, Laramie, WY 82071, USA. Relatively few animal species extract seeds from closed conifer cones because of the forces required to spread apart or penetrate the woody scales. Those species that forage on seeds in closed cones tend to forage selectively, and therefore act as selective agents on cone structure. However, little is known about the foraging preferences and thus phenotypic selection that is exerted on conifers by many species that forage extensively on seeds in closed cones, including especially woodpeckers (Picidae). Great spotted woodpeckers Dendrocopos major are one of the main predators of seeds in closed cones of Scots pine Pinus sylvestris in central and eastern Europe. To estimate the cone preferences of these woodpeckers foraging on Scots pine, we contrasted traits of cones that were and were not foraged on by woodpeckers. Woodpeckers preferred to forage on shorter cones when scales were thin (smaller apophyses) but preferred cones of intermediate length when scales were thicker, providing evidence for correlational selection. The preference for intermediate-sized cones indicates that woodpeckers exert disruptive selection on cone length when cones have thicker scales, but the overall selection on cone length across all scale types indicates directional favoring the evolution of longer cones. Woodpeckers avoided cones with thicker scales, which would lead to directional selection favoring the evolution of thicker scales. Preferences for intermediate-sized cones have been found in tree squirrels and directional selection favoring the evolution of cones with thicker scales may be a common outcome of the foraging behavior of birds. Species interactions structure ecological communities, and natural selection experienced during these interactions drives much of adaptive evolution (Thompson 2005). Consequently, evolutionary ecologists have invested a tremendous amount of effort characterizing natural selec- tion (Brodie et al. 1995, Kingsolver et al. 2001, Siepielski et al. 2009). Studies of phenotypic selection exerted by conifer-seed-eating animals provide one such set of studies. These studies have demonstrated that several seed pred- ators, namely red or common crossbills (Loxia curvirostra complex), Clark’s nutcrackers Nucifraga columbiana, tree squirrels (Sciurus spp. and Tamiasciurus spp.), and cone borer moths Eucosma recissoriana, have had consider- able impacts on conifer cone evolution (Benkman et al. 2001, 2003, 2010, Siepielski and Benkman 2004, 2007, Benkman and Parchman 2009, Mezquida and Benkman 2010). Although these studies show that variation in selection exerted by these animals can account for geo- graphic variation in cone structure in a number of conifer species, many other seed predators forage extensively on seeds in the closed cones and may further alter the evolution of conifer cones. One Eurasian species, the great spotted woodpecker Dendrocopos major, is well known for foraging on seeds in closed conifer cones. However, the extent to which woodpeckers exert selection on conifer cone structure is unknown. Such selection should result in evolution because various cone traits, including those measured in our study, are heritable in various species of conifers (references in Benkman et al. 2010). During winter, great spotted woodpeckers forage mainly on conifer seeds in central and eastern Europe (Hogstad 1971, Osiejuk 1998, Ke ˛dra and Mazgajski 2001). A single great spotted woodpecker removes seeds from up to 50 Scots pine Pinus sylvestris cones per day (Pulliainen 1963, Winkler and Christie 2002). In comparison, the average annual production of cones by a Scots pine tree varies from 40 to a maximum of 650 cones per tree (Tyszkiewicz 1952). Woodpeckers therefore have the potential to consume a large fraction of the standing seed crop. Although some studies have analyzed the sizes of cones foraged on by these woodpeckers (Hordowski 1995, Ke ˛dra and Mazgajski 2001), the structure of cones available in the environment was not quantified. Thus, these studies do not allow us to estimate cone preferences and the form of selection exerted by woodpeckers. Here, we estimate the cone use by great spotted woodpeckers, and infer the form of selection they exert on Scots pine, the most widely distributed pine in the World (Critchfield and Little 1966), and discuss the 429