Is mate choice based on mate size or physiological condition?

Scatter plot of z-scores for paired male and female goshawks showing (A) body mass and (B) heat map of the smoothed total number of fledglings per pair in 423 breeding attempts (not limited to initial year of pair formation) by 147 male and 151 female goshawks of known-mass on the Kaibab Plateau, Arizona, USA. Solid lines depict one-to-one relationships.