Ruiying Han

1 Introduction Nestlings of altricial birds usually seek parental care using begging behavior, including making begging calls and giving begging gestures (Ottosson et al. 1997; Wright and Leonard 2007). While begging behavior is of direct benefit (i.e., food) to nestlings, they pay direct (energy consumption or predation risk) or indirect costs (sibling fitness reduction). Thus, begging is usually considered an honest signal (Cotton et al. 1996; Mock et al. 2011).

Conflicts of Interest The authors declare no conflicts of interest. Supporting Information Filename Description cbf70088-sup-0001-2025_6_3_Clean_version_Supplemental_Information.docx5 MB 2025.6.3-(Clean version)(Supplemental Information). References 1, , , , , and , “A Programmable Dual-RNA–Guided DNA Endonuclease in Adaptive Bacterial Immunity,” Science 337, no. 6096 (2012): 816–821. 2, , , et al., “The CRISPR/Cas Bacterial Immune System Cleaves Bacteriophage and Plasmid DNA,” Nature 468, no.