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January 3 - Febuary 28, 2021

Meeting Abstract

5-9  Sat Jan 2  Nest substrate and tool shape significantly affect mechanics and energy requirements of avian eggshell puncture Clark, DL*; Hauber, ME; Anderson, PSL; University of Illinois at Urbana-Champaign; University of Illinois at Urbana-Champaign; University of Illinois at Urbana-Champaign

Some host species of avian obligate brood parasites reject the parasitic eggs whereas others accept them, even though they recognize them as foreign. One hypothesis to explain this seemingly maladaptive behavior is that acceptors are unable to pierce and remove the parasitic eggshell. Previous studies reporting on the force and energy required to break brood parasites’ eggshells were typically static tests performed against hard substrate surfaces. Here, we considered host nest as a substrate to simulate this potentially critical aspect of the natural context for egg puncture to occur while testing the energy required to break avian eggshells. Specifically, as a proof of concept, we punctured domestic chicken eggs under a series of conditions: varying tool shape (sharp vs. blunt), tool dynamics (static vs. dynamic), and the presence of natural bird nests (of three host species). The results show a complex set of statistically significant interactions between tool shapes, puncture dynamics, and nest substrates. Specifically, the energy required to break eggs was greater for the static tests than for the dynamic tests, but only when using a nest substrate and a blunt tool. In turn, in the static tests, the addition of a nest significantly increased energy requirements for both tool types, whereas during dynamic tests, the increase in energy associated with the nest presence was significant only when using the sharp tool. Characterizing the process of eggshell puncture will help in understanding whether and how hosts of brood parasites evolve to reject parasitic eggs.