To female coastal plain swamp sparrows, male bill size matters. When looking for a mate outside of their pair bond, female coastal plain swamp sparrows (Melospiza georgiana nigrescens) choose males with large bills, according to a University of Maine-led study conducted along Delaware Bay. Small-billed males are more at risk of being cheated on by read more Sexual Selection May Result in Bigger-Billed Male Birds, says UMaine Researcher