phaidra.vetmeduni.ac.at o:3664 DOI 10.1098/rspb.2024.1173 Small energy benefits of in-wake flying in long-duration migratory flights During long-distance migrations, some bird species make use of in-wake flying, which should allow them to profit from the upwash produced by another bird. While indirect evidence supports energy saving as the primary benefit of in-wake flying, measurements are still missing. We equipped migrating northern bald ibises (Geronticus eremita) with high-precision global navigation satellite system data loggers to track their position in the flock. We estimated birds' energy expenditure through different proxies, namely dynamic body acceleration (DBA), heart rate and effective wingbeat frequency. During active flapping flight, DBA estimates dropped off when in-wake compared with when not-in-wake. In addition, effective wingbeat frequency decreased, suggesting an increased use of intermittent gliding flight during in-wake periods. Heart rate varied greatly among individuals, with a clear decrease during gliding-corroborating its energy-saving function. Furthermore, we found consistent proof for decreased heart rate during in-wake flying, by up to 4.2%. Hence, we have shown that flying in the wake of another individual reduces birds' DBA, heart rate and effective wingbeat frequency, which could reflect reduced energy requirement. eng Animals; Flight; Animal Migration; Energy Metabolism; Birds; Heart Rate; Wings; Acceleration 2024-10-29T09:22:06.810Z LOMv1.0 Author BEGIN:VCARD VERSION:3.0 N:Perinot;Elisa; FN:Elisa Perinot X-ORCID:https://orcid.org/0000-0003-0379-8508 END:VCARD BEGIN:VCARD VERSION:3.0 N:Voelkl;Bernhard; FN:Bernhard Voelkl X-ORCID:https://orcid.org/0000-0001-5454-2508 END:VCARD BEGIN:VCARD VERSION:3.0 N:Fusani;Leonida; FN:Leonida Fusani X-ORCID:https://orcid.org/0000-0001-8900-796X END:VCARD BEGIN:VCARD VERSION:3.0 N:Ruf;Thomas; FN:Thomas Ruf X-ORCID:https://orcid.org/0000-0002-9235-7079 END:VCARD BEGIN:VCARD VERSION:3.0 N:Vyssotski;Alexei; FN:Alexei Vyssotski END:VCARD BEGIN:VCARD VERSION:3.0 N:Nobile;Marco Salvatore; FN:Marco Salvatore Nobile X-ORCID:https://orcid.org/0000-0002-7692-7203 END:VCARD BEGIN:VCARD VERSION:3.0 N:Rewald;Ortal Mizrahy; FN:Ortal Mizrahy Rewald X-ORCID:https://orcid.org/0000-0003-1909-0459 END:VCARD BEGIN:VCARD VERSION:3.0 N:Fritz;Johannes; FN:Johannes Fritz X-ORCID:https://orcid.org/0000-0003-4691-2892 END:VCARD https://w3id.org/kim/hcrt/scheme https://w3id.org/kim/hcrt/text Textdokument Text LOMv1.0 yes https://creativecommons.org/licenses/by/4.0 application/pdf 1059390 https://phaidra.vetmeduni.ac.at/o:3664 https://phaidra.vetmeduni.ac.at/api/object/o:3664/thumbnail LOMv1.0 discipline