The study looked at the sperm of different songbird species to understand why some birds have more twisted sperm heads. By examining 36 species, researchers found that birds with more helical sperm heads also had a higher rate of abnormalities in their sperm. The shape of the sperm head seemed to predict the likelihood of abnormalities better than the overall length of the sperm. Surprisingly, the level of competition for sperm between males of the same species did not seem to affect the number of abnormalities. This research suggests that there is a trade-off for songbirds between having fast-swimming sperm and maintaining the structural integrity of their sperm heads. In simple terms, having twisty sperm might help birds swim faster but could also make their sperm more prone to shape problems.