Honeyguides and other brood parasitic birds are famous for tricking host parents by laying eggs that mimic their own. Honeyguide eggs mimic host eggs in size yet, surprisingly, bee-eater hosts are undiscriminating and readily accept mismatched eggs. This study shows that honeyguide egg size adaptation has probably rather evolved to trick other honeyguides, not host parents: honeyguides selectively puncture any mismatched egg already present in the nest when they lay their own, lest it be the offspring of another honeyguide female and brutally kill their own chick when it hatches.
Read the full paper in Biology Letters [Open Access], or Ed Yong’s excellent article about the study. Here are some other nice articles and podcasts online covering this study: The Behaviour, Ecology & Evolution Podcast | Take Part blog | Earth Times.
Our paper ‘Why and how to apply Weber’s Law to coevolution and mimicry’ has been published in the journal Evolution. This perspectives paper, written by Tanmay Dixit, Eleanor Caves, Claire Spottiswoode, and Nicholas Horrocks, argues that Weber’s Law of proportional processing can lead to otherwise counterintuitive predictions about the evolutionary trajectories of mimicry systems. Weber’s Law states that when the magnitude of a stimulus is large, it is more difficult to discriminate a change or difference from that stimulus. In other words, relative differences are more salient than absolute differences. We show that Weber’s Law could have implications for mimicry: when stimulus magnitudes are high, it should be more difficult to discriminate a model from a mimic. This leads to testable predictions about evolutionary trajectories of models and mimics. We also present a framework for testing Weber’s Law and its implications for coevolution.