Valentina AlaasamCantarero Carmona, AlejandroMatteo BeccardiAlejandro Corregidor-CastroFuertes Recuero, ManuelMatteo SchiavinatoLia ZampaAlessandro GrapputoMatteo GriggioJenny Q. OuyangAndrea PilastroDavide Baldan2025-12-112025-12-112025Alaasam, V., Cantarero, A., Beccardi,M., Corregidor-Castro, A., Fuertes-Recuero, M., Schiavinato,M., Zampa, L., Grapputo, A., Griggio, M., Ouyang, J. Q.,Pilastro, A., & Baldan, D. (2025). Mate desertion affectsoffspring survival, development and physiology in a songbirdwith multiple parental strategies. Functional Ecology, 00,1–15. https://doi.org/10.1111/1365-2435.701940269-846310.1111/1365-2435.70194https://hdl.handle.net/20.500.14352/128774Author Contributions Alejandro Cantarero, Matteo Griggio, Jenny Q Ouyang, Andrea Pilastro and Davide Baldan conceived the ideas and designed the methodology; Alejandro Cantarero, Matteo Beccardi, Manuel Fuertes-Recuero, Matteo Schiavinato, Lia Zampa and Davide Baldan collected the data; Valentina Alaasam, Alejandro Corregidor-Castro and Alessandro Grapputo analysed the data; and Valentina Alaasam, Jenny Q Ouyang and Davide Baldan led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.Sexual conflict affects the amount and duration of offspring care each parent invests, resulting in multiple parental care strategies sometimes coexisting within a single population. Understanding the persistence of multiple parental care strategies requires a precise estimate of the benefits and costs associated with parental decisions. Even though the benefits of brood desertion are well known, the reproductive costs of desertion (i.e., nestlings' physiological conditions and survival), are less explored. We use rock sparrows, Petronia petronia, a species in which both uniparental and biparental care occur in the same population, to investigate the costs of brood desertion. Specifically, we continuously monitored breeding attempts to explore the behavioural mechanisms (desertion decision and compensatory responses) and the reproductive and physiological consequences (offspring corticosterone concentrations, oxidative stress, telomere attrition) of parental care strategies. We show that male desertion was not related to the initial value of the brood (clutch size, brood size) but was associated with a reduction in the survival probability of the nestlings. Females caring alone increased their per capita feeding rate, partially compensating for the lack of male care. Nestlings deserted earlier also experienced higher oxidative stress and had higher corticosterone concentrations during the early stages of development, but these effects did not persist to fledging, and there were no differences in telomere attrition. Our findings indicate combined reproductive and physiological costs associated with brood desertion. Considering these costs is essential to understand the evolution and persistence of polymorphic patterns of care.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/journal article1365-2435https://doi.org/10.1111/1365-2435.70194https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.70194open access636.09Brood desertionCorticosteroneDevelopmental stressOxidative stressParental strategiesSexual conflictTelomere attritionVeterinaria3109 Ciencias Veterinarias