Flexibility in Nest-site Choice and Nesting Success of Turdus Rufiventris (turdidae) in a Montane Forest in Northwestern Argentina

—We studied the consequences of nest-site choice on nesting success under differing disturbance levels for the Rufous-bellied Thrush (Turdus rufiventris). We compared nest-site choice and nest success between a disturbed site and an undisturbed site in a montane subtropical forest in northwestern Argentina. We found no overall difference in daily predation rate (DPR) between the disturbed and undisturbed sites. However, DPR of nests on bromeliads was significantly lower at the microhabitat level than on other types of subtrates at the disturbed site. T. rufiventris used bromeliads for nesting more often than expected by chance at the disturbed site. DPR did not differ between substrates at the undisturbed site and T. rufiventris used all substrates according to their availability. Nests had higher predation at the disturbed site when DPR on non-bromeliad substrates was compared between disturbed and undisturbed sites. Nest fate was independent of nest height. Our results suggest T. rufiventris’ flexibility in nest-site choice, as reflected by increased use of the safest sites, i.e., bromeliads, in the disturbed site compared to the undisturbed site, may allow this species to survive in an otherwise much riskier habitat. Our results illustrate how microhabitat-scale effects can mediate landscape scale effects. Received 24 October 2009. Accepted 7 April 2010. Understanding habitat influences on nesting success of birds may be key to their successful conservation, given the sensitivity of this life stage to habitat disturbance (Martin 1992, Easton and Martin 2002). Nest success is influenced by nest-site choice in large part because nest-site characteristics can influence nest predation rates (Martin and Roper 1988, Martin 1993, Holt and Martin 1997, Martin 1998, De Santo et al. 2002, Easton and Martin 2002, Mezquida and Marone 2002, Kellett et al. 2003, Fontaine et al. 2007). Nest predation may be one of the main agents of natural selection influencing evolution of life history traits and nest-site choice (reviewed by Lima 2009, Martin and Briskie 2009). Flexibility in choosing a nest site may allow birds to optimize fitness by exploiting safer substrate types in disturbed conditions, but studies of nesting flexibility and their consequences for nest success are rare. Nest-site choice, including nesting substrate and nesting height, may be evolutionarily conservative in many species (Martin 1988, Martin and Roper 1988), which may constrain plasticity of choices. Some bird species use the same nest sites in disturbed and undisturbed forest patches, even though this increases predation in disturbed forest patches (Holt and Martin 1997, Easton and Martin 2002). Plastic changes in nest-site selection in response to predation risk have been observed in some species (e.g., Marzluff 1988, Eggers et al. 2006, Peluc et al. 2008). Variation in predation risk is often associated with disturbance of habitats, which also generally reflects differing habitat structure; both differing predation risk and habitat structure could influence nest-site choice (Martin 1992). Few studies have compared nest site choices under differing predation risk or differing habitat structure. Plasticity of nest-site choice is particularly interesting for tropical and subtropical birds, because they are often thought to have more specialized niches (MacArthur 1972). Consequently, their flexibility of nest-site choice to varying predation risk or habitat structure may be constrained. No study has examined plasticity of nest-site choice by a tropical or subtropical bird. Thus, examination of flexibility of nest-site choice and consequences of that choice on nesting success under differing disturbance levels for tropical or subtropical birds is needed. Our objective was to test whether nest-site choice and nesting success of the Rufous-bellied Thrush (Turdus rufiventris; Turdidae) differed 1 IADIZA–CCT MENDOZA, CONICET, Avenida Ruiz Leal s/n, CC 507, 5500 Mendoza, Argentina. 2 Universidad de Puerto Rico, Departamento de Biologı́a, CN 235, P. O. Box 70377, San Juan, PR 00936, USA. 3 LIEY-IER, Universidad Nacional de Tucumán, Argentina, CC 34, Yerba Buena, 4107 Tucumán, Argentina. 4 USGS, Montana Cooperative Wildlife Research Unit, Avian Studies Program, 205 Natural Science, University of Montana, Missoula, MT 59812, USA. 5 Corresponding author; e-mail: [email protected] The Wilson Journal of Ornithology 122(4):674–680, 2010