SGER: Use of Small Remote Video Systems to Provide the First Test of the Skutch Hypothesis

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Food limitation is widely accepted as the primary evolutionary driver of life history traits of birds, particularly clutch size. A half century ago, it was argued that small clutch sizes of tropical and southern hemisphere birds were caused by nest predation constraining parental visits to the nest during the nestling stage (Skutch hypothesis). Recent broad comparative studies suggest that nest predation may, in fact, represent a much stronger determinant of life history strategies of birds than food limitation. However, the Skutch hypothesis has never been directly tested. A direct test will gain enormous attention, because the hypothesis is a longstanding, but untested and has major ramifications for our current understanding of life history evolution in birds.Direct tests of the Skutch Hypothesis depend upon quantitatively measuring parental visitation rates to the nests. Video cameras provide a means for obtaining broad quantitative measures of parental visitation rates. However, standard video camera systems are too large and have been found to influence parental visitation rates in some species because they are cautious about approaching the nest with a large camera setup on a tripod with the distance (ca. 10m) needed to monitor the nest. Birds in Latin America, where these tests need to be made, appear to be particularly sensitive to presence of cameras, possibly because of high predation there. This bias severely compromises tests of the Skutch Hypothesis. Dr. Martin has developed a small remote camera system that is camouflaged and appears to be ignored by even sensitive bird species. However, this system has not been tested in Latin America and responses of birds there are not yet known. Dr. Martin will conduct a test of this system in Latin America (Argentina) to validate whether this approach can provide an unbiased measure of parental visitation rates even among the most sensitive species. He will simultaneously directly test the Skutch Hypothesis for the first time by examining whether parental visitation rates are negatively correlated with nest predation rates across 8 species in Argentina for which he has already measured nest predation. This group of species includes broad variation in nest predation rates (varying from 24 to 76% of nests lost to predation), thereby increasing statistical power for examining a negative correlation. Ultimately, if this approach works, it will provide strong support or rejection of the Skutch Hypothesis for the first time and will provide a new approach that will rapidly catalyze changes in the way a large number of research groups are approaching field work in tropical and southern hemisphere regions of the world.