Nectar alkaloids of tree tobacco can reduce Palestine sunbird foraging performance in a colour discrimination task Rainee L. Kaczorowski, Shai Markman * Department of Biology & Environment, University of Haifa e Oranim, Tivon, Israel article info Article history: Received 29 April 2015 Initial acceptance 1 July 2015 Final acceptance 26 April 2016 MS number 15-00352R Keywords: anabasine behaviour bird cognition colour foraging memory nicotine pollinator secondary metabolites Many plant species contain plant secondary metabolites (PSMs), such as alkaloids, in their tissues for protection against herbivore attack, but PSMs can also be found in floral nectar. Some pollinators have been shown to discriminate against floral nectar with PSMs and consuming PSMs may have negative fitness effects on pollinators. However, only a few studies have investigated the effects of ecologically relevant levels of PSMs on pollinator foraging performance. Here, we addressed the question of whether the natural concentrations of the alkaloids, nicotine and anabasine, found in tree tobacco, Nicotiana glauca, nectar affect foraging performance in Palestine sunbird, Nectarinia osea, pollinators that use the plant's nectar as a food source. We trained foraging sunbirds to discriminate between rewarding and nonrewarding artificial flowers based on colour. We measured sunbird foraging performance through their accuracy at distinguishing the two colours immediately after training (pretreatment), and again the following day after consuming sucrose solutions with or without alkaloids (post-treatment). We also explored other potential effects of PSM consumption by assessing bird activity level and flower visit rate. Birds that consumed alkaloids did not significantly change their activity level or flower visit rate across time (pre- and post-treatment) compared to birds that did not consume alkaloids (no significant time by treatment interaction). However, alkaloid consumption significantly decreased sunbird foraging perfor- mance in terms of their accuracy in distinguishing the rewarding colour, potentially due to reduced memory retention and/or other cognitive or physiological impairments following alkaloid consumption. We also found that sunbirds discriminated against higher, in favour of lower, ecologically relevant alkaloid concentrations in the nectar of tree tobacco and that previous exposure to alkaloids reduced overall consumption of alkaloid solutions. Reduced foraging performance due to PSM ingestion could greatly affect a pollinator's foraging efficiency, which could, in turn, affect both pollinator and plant reproductive fitness. © 2016 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Plant secondary metabolites (PSMs), such as alkaloids, can be found in many plant species (Irwin, Cook, Richardson, Manson, & Gardner, 2014) and are important for deterring herbivores from consuming plant tissues (Bennett & Wallsgrove, 1994; Rosenthal & Berenbaum, 1992; Wink, 1998, 2010). PSMs are also found in the nectar of many flowers (Adler, 2000; Baker, 1977; Irwin, Adler, & Brody, 2004; Irwin et al., 2014), exposing mutualist pollinators to various levels of PSMs (Irwin et al., 2014; Kessler et al., 2012). Pollinators are often found to discriminate against nectars con- taining PSMs (Detzel & Wink, 1993; Kessler, Gase, & Baldwin, 2008; K€ ohler, Pirk, & Nicolson, 2012; Tadmor-Melamed et al., 2004). However, PSM concentrations in nectar are typically much lower than in other plant tissues (Adler & Irwin, 2012; Cook, Manson, Gardner, Welch, & Irwin, 2013; Detzel & Wink, 1993; Irwin et al., 2014; Manson, Rasmann, Halitschke, Thomson, & Agrawal, 2012, 2013), and may be less than concentrations that affect pollinator foraging behaviour (Elliott, Irwin, Adler, & Williams, 2008; Manson et al., 2013; Singaravelan, Nee'man, Inbar, & Izhaki, 2005; Tiedeken, Stout, Stevenson, & Wright, 2014). In addition to potential effects on pollinator foraging behaviour, PSM consumption has also been found to limit activity (Cook et al., 2013; Manson et al., 2013), reduce oocyte development (Manson & Thomson, 2009) and increase mortality (Detzel & Wink, 1993; K€ ohler et al., 2012; Singaravelan et al., 2006; Tan et al., 2007) in different bee species. In Palestine sunbird pollinators, PSMs have been shown to reduce gut transit time and sugar assimilation, even at nondeterrent concentrations (Tadmor-Melamed et al., 2004), illustrating that PSM consumption can have physiological effects even when they apparently do not affect foraging behaviour. * Correspondence: S. Markman, Department of Biology & Environment, University of Haifa e Oranim, Tivon, 36006, Israel. E-mail address: markmans@research.haifa.ac.il (S. Markman). Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav http://dx.doi.org/10.1016/j.anbehav.2016.05.015 0003-3472/© 2016 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Animal Behaviour 119 (2016) 59e68