In a new study published in Hormones & Behaviour, in collaboration with Dr. Alex T. Baugh (Swarthmore College), we measured circulating levels of the gut hormone peptide YY (PYY), a hormone known in mammals to signal satiety after feeding. We compared migrant and resident Common blackbirds (Turdus merula) on Helgoland during autumn migration and found that migratory individuals have significantly higher plasma PYY levels than residents. This pattern suggests differences in foraging intensity or digestive regulation during migration. Interestingly, PYY levels were unrelated to body condition or fat stores, indicating that this hormone may reflect short-term feeding dynamics rather than longer-term energy reserves.