Establishing Salvage Incubation Protocols for Abandoned Eggs of the Brown Shrike Lanius cristatus superciliosus.

Abstract

Integrating in situ and ex situ actions is essential to prevent the loss of reproductive output when passerine nests are abandoned. We developed and tested a two‑phase salvage incubation protocol for the endangered Japanese Brown Shrike Lanius cristatus superciliosus. During 2023-2025 in Nagano Prefecture, Japan, eggs judged to be abandoned were placed in modified portable incubators near nest sites for first‑phase bridging incubation and then transferred to Toyohashi Zoo and Botanical Park for second‑phase controlled incubation and hatching under stable conditions. Across 20 nests, 83 eggs were salvaged; 73 showed visible embryonic development, and 41 hatched, yielding a hatching success rate of 0.562 among eggs with visible embryonic development. Generalized linear models with AIC‑based selection supported three predictors of hatching success: (i) more days of parental incubation prior to abandonment, (ii) higher minimum temperature during periods of parental absence in the field, and (iii) a second‑phase regime of 37.8°C with one 5 min cooling event per day, which outperformed no cooling and twice‑daily cooling. These results show that a standardized field-to-facility pipeline can recover reproductive output that would otherwise be lost and provide operational guidance for linking field-based egg salvage with ex situ artificial incubation in passerines.