Camouflage and Clutch Survival in Plovers and Terns.
Animals achieve camouflage through a variety of mechanisms, of which background matching and disruptive coloration are likely the most common. Although many studies have investigated camouflage mechanisms using artificial stimuli and in lab experiments, less work has addressed camouflage in the wild. Here we examine egg camouflage in clutches laid by ground-nesting Snowy Plovers Charadrius nivosus and Least Terns Sternula antillarum breeding in mixed aggregations at Bahía de Ceuta, Sinaloa, Mexico. We obtained digital images of clutches laid by both species. We then calibrated the images and used custom computer software and edge detection algorithms to quantify measures related to three potential camouflage mechanisms: pattern complexity matching, disruptive effects and background color matching. Based on our image analyses, Snowy Plover clutches, in general, appeared to be more camouflaged than Least Tern clutches. Snowy Plover clutches also survived better than Least Tern clutches. Unexpectedly, variation in clutch survival was not explained by any measure of egg camouflage in either species. We conclude that measures of egg camouflage are poor predictors of clutch survival in this population. The behavior of the incubating parents may also affect clutch predation. Determining the significance of egg camouflage requires further testing using visual models and behavioral experiments.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.|Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
Mary Caswell
MC
Stoddard
Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria.
Krisztina
K
Kupán
Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
Harold N
HN
Eyster
Laboratorio de Biología Evolutiva, Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Carretera Tlaxcala-Puebla Km. 1.5, 90070, Tlaxcala, México.
Wendoly
W
Rojas-Abreu
Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Unidad Académica Mazatlán, Av. Joel Montes Camarena S/N, 82040, Mazatlán, Sinaloa, México.
Medardo
M
Cruz-López
Laboratorio de Biología Evolutiva, Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Carretera Tlaxcala-Puebla Km. 1.5, 90070, Tlaxcala, México.|Posgrado en Ciencias Biológicas, Universidad Autónoma de Tlaxcala, México.
Martín Alejandro
MA
Serrano-Meneses
Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria.
Clemens
C
Küpper
D000818:Animals; D000067558:Biological Mimicry; D046091:Charadriiformes / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D013045:Species Specificity; D016019:Survival Analysis