title: The influence of density on frequency-dependent food selection: a comparison of four experiments with wild birds.
abstract: We compare the results of four experiments, conducted at different times and with different protocols, that explored the relationship between frequency-dependent selection and prey density in wild birds feeding on artificial populations of coloured baits. One (experiment 4) used pastry baits that differed only in the presence or absence of a red stripe, and this experiment provided no evidence for any kind of selective behaviour. The other three experiments used green and brown baits, and they all provided evidence for a trend towards increasing anti-apostatic selection with high densities (>100 baits m-2). However, one of these (experiment 3) provided no evidence for frequency-dependent selection at low densities (0.5-20 baits m-2), while the other two experiments concurred in suggesting a trend towards increasing apostatic selection with low densities (down to 2 baits m-2). Together, these experiments both support and qualify the published findings of experiment 1 that frequency- dependent selection by wild birds on bait populations is modified by density. Experiment 4 indicates that frequency-dependent selection may break down entirely if bait types are too similar, while experiment 3 indicates that some details of this trend with density will depend either on the protocol used or on exogenous changes in the birds' feeding behaviour.
authors.affiliation: Biodiversity and Ecology Division, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK e-mail: jaa@soton.ac.uk Tel.: +44-23-8059-4388, Fax: +44-23-8059-4269, , , , , , GB.
authors.forename: M E
authors.initials: ME
authors.lastname: Weale
authors.affiliation: Biodiversity and Ecology Division, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK e-mail: jaa@soton.ac.uk Tel.: +44-23-8059-4388, Fax: +44-23-8059-4269, , , , , , GB.
authors.forename: D
authors.initials: D
authors.lastname: Whitwell
authors.affiliation: Biodiversity and Ecology Division, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK e-mail: jaa@soton.ac.uk Tel.: +44-23-8059-4388, Fax: +44-23-8059-4269, , , , , , GB.
authors.forename: H E
authors.initials: HE
authors.lastname: Raison
authors.affiliation: Biodiversity and Ecology Division, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK e-mail: jaa@soton.ac.uk Tel.: +44-23-8059-4388, Fax: +44-23-8059-4269, , , , , , GB.
authors.forename: D L
authors.initials: DL
authors.lastname: Raymond
authors.affiliation: Biodiversity and Ecology Division, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK e-mail: jaa@soton.ac.uk Tel.: +44-23-8059-4388, Fax: +44-23-8059-4269, , , , , , GB.
authors.forename: J A
authors.initials: JA
authors.lastname: Allen
keywords: Anti-apostatic selection; Apostatic selection; Artificial prey; Key words Frequency-dependent selection; Selective predation