Bird Reactions to Observer Clothing Color: Implications for Distance-Sampling Techniques

• Published in: The Journal of wildlife management 1997-07, Vol.61 (3), p.935-947
• Main Authors: Gutzwiller, Kevin J., Marcum, Heidi A.
• Format: Article
• Language: English
• Subjects: Animal behavior; Animal ethology; Animal, plant and microbial ecology; Applied ecology; Aves; Biological and medical sciences; Birds; Cardinal points; Colors; Conservation, protection and management of environment and wildlife; Fundamental and applied biological sciences. Psychology; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Psychology. Psychoanalysis. Psychiatry; Vegetation; Vertebrata; Vests; Warblers; Wildlife habitats; Wildlife management; Wildlife observation; Woodlands; Woodpeckers
• ISSN: 0022-541X; 1937-2817
• DOI: 10.2307/3802203

The species-confidence hypothesis asserts that birds prefer mates whose colors match those of their species and avoid potential mates whose colors are atypical of conspecifics. Earlier point-count research indicated this mate-choice hypothesis also may explain avian reactions to observer clothing color. In central Texas, during January and February 1993, we tested further whether the species-confidence hypothesis holds for reactions to observer clothing color by determining how close an investigator could get to individuals before they flushed (approach distance) and how long individuals remained visible near their initial flush point (detectability period). The same investigator experimentally wore or did not wear a hunter-orange vest, which some wildlife biologists wear as a safety precaution during hunting-season field studies. The vest did not affect approach distance for species with red or orange on their bodies (American robin [Turdus migratorius], P = 0.247; northern cardinal [Cardinalis cardinalis], P = 0.196; ruby-crowned kinglet [Regulus calendula], P = 0.434; red-bellied woodpecker [Melanerpes carolinus], P = 0.113). In contrast, approach distances for species without red or orange were longer when the vest was worn than when it was not worn (Carolina chickadee [Parus carolinensis], P = 0.032; northern mockingbird [Mimus polyglottos], P = 0.033; yellow-rumped warbler [Dendroica coronata], P = 0.001). Differences in detectability period between vest conditions depended on air temperature for American robins (P = 0.003) and on the variation in visibility within habitats for northern cardinals (P < 0.001). Detectability period was shorter when the vest was worn than when it was not worn for Carolina chickadees (P = 0.057) and yellow-rumped warblers (P = 0.060). Thus, for several species this matechoice hypothesis seems to apply to garment color as well. Some species' reactions demonstrated that, if birds respond significantly to clothing color, important assumptions of distance-sampling techniques used to estimate avian richness, density, and abundance will be violated, and these parameters will be underestimated. Wildlife scientists will be more likely to draw valid inferences and recommend effective management practices from avian data gathered via distance-sampling methods if reactions to clothing color are precluded.