The Indirect Effect of Flight Demands on Egg Shape inMigratory and Sedentary Fork- tailed Flycatchers (Tyrannus savana)

ELIZABETH R. CHEN; MIGUEL ANGELO MARINI; VALENTINA GÓMEZ-BAHAMÓN; MARCELO ASSIS; D. T. TUERO; JOHN BATES

Alaska

Congreso; 137th Annual Meeting American Ornithological Society; 2019

Bird eggs haveevolved a wide variety of shapes including spherical, elliptical, and asymmetrical.Two mayor types of hypotheses have been proposed to explain such variation: 1) adaptivehypotheses, including life history traits and breeding ecology as major driversof egg shape, and 2) correlational evolution of egg shape with skeletal andmuscular features resulting from different flight demands. The former hasrecently been supported by evidence showing that at broad taxonomic scales, eggshape is correlated with flight capacity. Within species variation often spansthe spherical, asymmetrical and elliptical shapes found at themacroevolutionary level, yet studies that test the flight hypothesis at theintraspecific level are lacking. Migratory and sedentary birds differ onmorphological features such as wing length and shape, muscle fiber compositionand skeletal structure. The hypothesis of indirect effect of flight on eggshape would predict that egg shape is constrained in migratory birds, whereas insedentary populations, eggs it would have a wider variation resulting fromrelaxed selection on aerodynamics structures. In this study we present a novelmathematical method to quantify egg shape allowing comparisons across all eggshapes and test whether migratory and sedentary populations of Fork tailed Flycatchersdiffer as predicted. We aim to analyze shape parameters using cluster algorithmsto determine which account for the variation in our sample and conduct a normalmixture analysis to determine if migratory and sedentary eggs differ. To testwhether migratory egg shape is constrained we aim to conduct analyses ofvariance comparing with sedentary eggs.