Ecological Applications, 22(7), 2012, pp. 1989–1996 Ó 2012 by the Ecological Society of America Anthropogenic noise is associated with reductions in the productivity of breeding Eastern Bluebirds (Sialia sialis) CAITLIN R. KIGHT, 1,2,4 MARGARET S. SAHA, 3 AND JOHN P. SWADDLE 1 1 Institute for Integrative Bird Behavior Studies, Biology Department, College of William and Mary, Williamsburg, Virginia 23187-8795 USA 2 Centre for Ecology and Conservation, Biosciences, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Tremough, Penryn TR10 9EZ United Kingdom 3 Biology Department, College of William and Mary, Williamsburg, Virginia 23187-8795 USA Abstract. Although previous studies have related variations in environmental noise levels with alterations in communication behaviors of birds, little work has investigated the potential long-term implications of living or breeding in noisy habitats. However, noise has the potential to reduce fitness, both directly (because it is a physiological stressor) and indirectly (by masking important vocalizations and/or leading to behavioral changes). Here, we quantified acoustic conditions in active breeding territories of male Eastern Bluebirds (Sialia sialis). Simultaneously, we measured four fitness indicators: cuckoldry rates, brood growth rate and condition, and number of fledglings produced (i.e., productivity). Increases in environmental noise tended to be associated with smaller brood sizes and were more strongly related to reductions in productivity. Although the mechanism responsible for these patterns is not yet clear, the breeding depression experienced by this otherwise disturbance-tolerant species indicates that anthropogenic noise may have damaging effects on individual fitness and, by extraction, the persistence of populations in noisy habitats. We suggest that managers might protect avian residents from potentially harmful noise by keeping acoustically dominant anthropogenic habitat features as far as possible from favored songbird breeding habitats, limiting noisy human activities, and/or altering habitat structure in order to minimize the propagation of noise pollution. Key words: anthropogenic disturbance; bioacoustics; breeding; Eastern Bluebird; fitness; noise; Sialia sialis; Williamsburg, Virginia, USA. INTRODUCTION Anthropogenic activities can introduce significant noise pollution into the environment. The loudest noise pollution generally exceeds levels achieved by natural sources of noise, and may permeate the habitat to a greater degree. For example, noise levels in roadside forests may reach 98 dB at the edge nearest the road (5 m away) and remain at detectable levels several hundred meters into the trees (Are´valo and Newhard 2011). Further, the timing and pattern of human-made noise may be unpredictable and differ significantly from those found in nature (Warren et al. 2006, Barber et al. 2010, Pijanowski et al. 2011). Exposure to noise pollution has the potential to increase physiological stress levels in animals (Kight and Swaddle 2011), reduce foraging success (Siemers and Schaub 2011), alter species’ behavioral time budgets (Quinn et al. 2006), mask acoustic communication (Slabbekoorn and Peet 2003, Patricelli and Blickley 2006), and alter community structure (Francis et al. 2009, 2011b). An increasing number of anthropogenic noise studies have shown that adult animals are remarkably flexible, over both the short and long term (Barber et al. 2010, Verzijden et al. 2010, Hanna et al. 2011), when it comes to responding to the presence of anthropogenic noise. For example, species of frog, fish, bird, and whale have all been shown to alter their vocalizations in order to reduce masking by anthropogenic noise (Sun and Narins 2005, Vasconcelos et al. 2007, Francis et al. 2011a, Hanna et al. 2011, Parks et al. 2011). European Robins (Erithacus rubecula) in noisy areas have been found to sing more at night, when it is quieter (Fuller et al. 2007), while mouse-eared bats (Myotis myotis) preferentially hunt in quieter habitats (Schaub et al. 2008). Thus, by altering how, when, and where they perform certain behaviors (i.e., their phenotypes), many animals appear capable of tolerating the presence of noise pollution. Even among the most phenotypically plastic species, however, noise may have negative effects over the long term. A study in a Canadian population of Ovenbirds (Seiurus auroapillus) found that older males claimed quieter territories and left noise-polluted sites to first- Manuscript received 24 January 2012; revised 5 April 2012; accepted 6 April 2012. Corresponding Editor: R. L. Knight. 4 Present address: Centre for Ecology and Conservation, Biosciences, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Tremough, Penryn TR10 9EZ United Kingdom. E-mail: caitlin.r.kight@gmail.com 1989