Meeting Abstract
Eggshells of many bird species have distinctive maculation patterns that have led biologists to pose a number of adaptive hypotheses. The signature hypothesis proposes that eggshell patterns allow females to recognize their own eggs in the face of inter- and intraspecific brood parasitism. In barn swallows (Hirundo rustica erythrogaster), which are colonially nesting passerine birds, 17% of nests are subject to intraspecific brood parasitism. Our research aims to better understand the range of maculation patterns on the surface of barn swallow eggs. We asked whether eggs in the same nest exhibit a “signature” maculation pattern that was quantifiably more similar to the other eggs in the nest than to eggs in other barn swallow nests. We photographed 23 clutches of eggs, and after uniformly filtering all the images, we analyzed the images in SpotEgg and NaturePatternMatch. SpotEgg quantifies many features of an individual egg, including shape of the egg and the color, shape, size, and dispersion of spots, whereas NaturePatternMatch generates similarity scores between eggs. From these data, we could identify how closely an egg resembled another egg within a given set of eggs. Based on a preliminary data set, we found that 31% of eggs matched most highly to other eggs in the nest of origin, and 54% of eggs included an egg from the nest of origin among the top three best matches. Our work revealed substantial variation in egg maculation patterns among barn swallow clutches which may provide evidence for the signature hypothesis.
