Current Zoology 61 (4): 773–780, 2015 Received Feb. 10, 2015; accepted May 17, 2015.  Corresponding author. E-mail: marmots@ucla.edu © 2015 Current Zoology Vivid birds do not initiate flight sooner despite their potential conspicuousness Nicholai M. HENSLEY 1,2 , Jonathan P. DRURY 2,3 , Theodore GARLAND, Jr. 4 , Daniel T. BLUMSTEIN 2* 1 Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA 2 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095-1606, USA 3 Institude de Biologie de l’ENS, 46 Rue d’Ulm, 75005, Paris, France 4 Department of Biology, University of California, Riverside, CA 92521, USA Abstract The distance from an approaching threat at which animals initiate flight -- flight-initiation distance (FID) -- is a sensi- tive metric of variation in risk, but the effects on FID associated with the risk of possessing highly detectable external coloration are unknown. We tested whether variation in the degree of plumage vividness in birds explained variation in flight-initiation dis- tance. After controlling for body mass, the distance at which the experimental approach began, and phylogenetic relatedness, plumage vividness was not a predictor of FID. Contrary to the expectation that vividness affects risk, and therefore risk assess- ment, these results suggest that birds do not compensate for greater visual conspicuousness by fleeing sooner from approaching threats [Current Zoology 61 (4): 773–780, 2015]. Keywords Antipredator behavior, Body size, Coloration, Comparative method, Conspicuousness, Flight Initiation Distance The distance from an approaching threat at which ani- mals initiate flight (i.e., flight-initiation distance; FID) is a metric of risk assessment that is sensitive to a va- riety of factors (Blumstein, 2003; Stankowich and Blumstein, 2005; Blumstein, 2006). Birds, mammals, and reptiles are particularly well-studied taxa (Stanko- wich and Blumstein, 2005; Cooper et al., 2014; Samia et al., 2015). For example, we know that various exter- nal factors influence FID, including speed of approach (Stankowich and Blumstein, 2005), habitat type (urban vs. rural; Møller, 2008; Bateman and Flemming, 2014), human activity (Price et al., 2014), and predation pres- sure (Møller et al., 2008). Factors inherent to organisms ("internal" factors) also influence FID, including body size, body temperature, reproductive status, and both individual and interspecific behavioral variation (Bau- wens and Thoen, 1981; Brodie, 1989; Bulova, 1994; Blumstein, 2006, Møller and Garamszegi, 2012). In addition to the factors just listed, an organism’s coloration would be expected to influence its predation risk, and hence its FID, in at least three ways (Cott, 1940). First, coloration may be aposematic and thereby signal unprofitability to potential predators (for a review see Baker and Parker 1979). Second, coloration could be cryptic whereby external coloration generally de- creases detectability by predators through background matching (Cott, 1946; Endler, 1978). Third, a color could increase the detectability of an individual while not providing any aposematic benefits, as in the case of social ornaments (Møller and Nielsen, 2006). Many animals have evolved such coloration as signals used in social communication (e.g., through sexual selection; Darwin, 1871), which are adaptive in spite of the sur- vival cost that comes with increased conspicuousness. These outcomes are also influenced by at least two ex- ternal factors: (1) the background habitats against which these colors are compared, and (2) the ability of receiv- ers (e.g., potential predators, mates, etc.) to discriminate between the signaler and background (Endler, 1978; Endler, 1990). Despite complex visual environments and selection from predators with different visual ecolo- gies, we still may expect conspicuous color to influence escape decisions. A few studies have examined the relationship be- tween conspicuous coloration and FID. Martín and López (1999) found that the males of the large, sexually dich- romatic lizard Psammodromus algirus with conspicuous head coloration had larger FIDs than both females and males with less coloration. By contrast, Cooper (2003) did not find that coloration intensity explained variation