Original article Effects of experimental reduction in nest micro-parasite and macro-parasite loads on nestling hemoglobin level in blue tits Parus caeruleus Robert Słomczyn 0 ski a , Adam Kalin 0 ski a , Jarosław Wawrzyniak a , Mirosława Ban 0 bura a , Joanna Skwarska a , Piotr Zielin 0 ski b , Jerzy Ban 0 bura a, * a Department of Experimental Zoology and Evolutionary Biology, University of Lódź, Banacha 12/16, 90237 Lódź, Poland b Department of Ecology and Vertebrate Zoology, University of Lódź, Banacha 12/16, 90237 Lódź, Poland ARTICLE INFO Article history: Received 8 December 2005 Accepted 27 April 2006 Available online 16 June 2006 Keywords: Wild birds Health Parasites Pathogens Nest ABSTRACT Theory suggests that macro- and micro-parasites may be important factors of selection for life-histories. They generate selection pressures by detrimental effects on host health. Nests of secondary cavity nesters provide a convenient habitat for an assemblage of para- sites exploiting nestlings. In this study, natural blue tit Parus caeruleus nests (26) were replaced with clean artificial nests, twice during the nestling stage. This treatment caused an increase of 7–10.5 g/l in hemoglobin level of 12-day-old nestlings in comparison with control nestlings. Nestlings that developed in parasite–pathogen-free nests improved their health status. The experimental sterilization did not affect a morphometric index of condition. Potential effects on condition indices might be masked by trophic conditions. © 2006 Elsevier Masson SAS. All rights reserved. 1. Introduction The constructing of nests that are used as the exclusive place to lay and incubate eggs and bring nestlings up to fledging is typical of altricial birds (Hansell, 2000). By binding parental birds and nestlings for the entire reproductive event, this characteristic may have important epidemiological conse- quences. Secondary hole nesters often use holes not only to nest, but also to spend nights during non-breeding periods (Perrins, 1979; Gosler, 1993; Hansell, 2000), which may facili- tate parasite and pathogen transmission among different holes (Loehle, 1995; Heeb et al., 1996). In addition, big nests of secondary hole-nesting birds, being complex structures isolated from many factors of the external environment, cre- ate an ideal habitat for different macro- and micro-organ- isms (Nordberg, 1936; Hart, 1997; Hansell, 2000; Heeb et al., 2000; Alabrudzińska et al., 2003). Some species belonging to this nest-related assemblage are opportunistic users of the nest structure, but some are parasites and pathogens that exploit either nestlings or both nestlings and adults (Roths- child and Clay, 1952; Pinowski et al., 1995; Clayton and Moore, 1997; Singleton and Harper, 1998; Berger et al., 2003; Gwinner and Berger, 2005; Lucas and Heeb, 2005). Such coex- istence undoubtedly generates mutual pressures on life-his- tories of all organisms involved at both physiological and evolutionary levels (Combes, 2001; Frank, 2002; Simon et al., 2004). At the physiological level, pathogens and parasites may influence health of individual hosts by the exploitation of their body resources, which, therefore, generates a selec- tion pressure for some anti-parasite strategies (Goater and Holmes, 1997). Birds evolved different anti-parasite–pathogen strategies, like, for instance, a selected set reported for tits: avoidance of infested nests (Rytkönen et al., 1998), nest sanitation (Christe et al., 1996; Hurtrez-Boussès et al., 2000; Bańbura et ACTA OECOLOGICA 30 (2006) 223 – 227 * Corresponding author. Tel.: +48 42 635 4493; fax: +48 42 678 1364. E-mail address: jbanb@biol.uni.lodz.pl (J. Ban 0 bura). 1146-609X/$ - see front matter © 2006 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.actao.2006.04.003 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/actoec