Thirty female five-to-eight-day old European starlings (Sturnus vulgaris) were collected from nest boxes in late-April to early-May 2015 from a native colony in Upper Bavaria, South Germany (47° 58′ N, 11° 13′ 142 E) and brought into an animal care facility at the Max Planck Institute for Ornithology (MPIO), Seewiesen, Germany. We chose to focus on female starlings as they may face unique physiological challenges during migration in relation to their reproductive success. Migratory birds prepare to breed shortly after spring migration and depositing antioxidants into eggs has been shown to lead to higher hatching and fledging rates for offspring [128 (link), 129 (link)]. Female birds may thus face substantial oxidative tradeoff during migration, as they must balance preventing oxidative damage with their future reproductive success [44 (link)]. Hatchlings were hand-raised and fed a high protein diet consisting of bee larvae, crickets, wax worms, green bottle fly larvae (pinkies and buffaloes), beef heart with vitamin mixture and calcium carbonate powder. Once hatchlings were able to feed independently, we additionally offered them live mealworms, fresh fruits and vegetables. The diet has been successfully used to hand-raise starlings at the MPIO in previous experiments [32 (link), 73 (link), 130 (link)]. From about the age of 35–100 days, the starlings were moved to outdoor aviaries, kept under a natural light cycle, and maintained on an MPIO diet that consisted of insect powder, lettuce, fresh apples and oranges, dried fruit pellets, and mealworms.
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