{"paper":{"title":"Localized inhomogeneity and position-dependent stability of migratory bird formations","license":"http://creativecommons.org/licenses/by-nc-nd/4.0/","headline":"Changing one bird's wingspan keeps a formation stable only within position-specific limits, with tighter tolerance at the outer wing than near the leader.","cross_cats":["physics.flu-dyn"],"primary_cat":"nlin.PS","authors_text":"Jiang Hui, Nariya Uchida","submitted_at":"2026-05-13T21:27:27Z","abstract_excerpt":"We investigate how localized inhomogeneity affects the geometry and stability of migratory bird formations. We use a lifting-line model with a horseshoe-vortex representation to describe the longitudinal dynamics of aerodynamic interactions. As a reference case, we first analyze homogeneous formations and show that their steady states exhibit a U-shaped geometry with hierarchical streamwise spacing, in which adjacent birds become progressively closer toward the leader. We then introduce localized inhomogeneity by modifying the wingspan of a single bird, with its physical properties determined "},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The stability range depends strongly on the position of the modified bird, being narrower near the outer wing and broader near the leader.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The lifting-line model with horseshoe-vortex representation accurately captures the longitudinal dynamics of aerodynamic interactions among the birds.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"In a modeled bird formation, the allowable wingspan variation for stability is narrower for a modified bird at the outer wing than near the leader.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Changing one bird's wingspan keeps a formation stable only within position-specific limits, with tighter tolerance at the outer wing than near the leader.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"295bc9ef4eb3fa292646a97492014769b780a9edf231e5554faff5d3d25c8e46"},"source":{"id":"2605.14127","kind":"arxiv","version":1},"verdict":{"id":"41216f13-0ba3-4e7f-932f-469ed7fcc545","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-15T05:23:09.339040Z","strongest_claim":"The stability range depends strongly on the position of the modified bird, being narrower near the outer wing and broader near the leader.","one_line_summary":"In a modeled bird formation, the allowable wingspan variation for stability is narrower for a modified bird at the outer wing than near the leader.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The lifting-line model with horseshoe-vortex representation accurately captures the longitudinal dynamics of aerodynamic interactions among the birds.","pith_extraction_headline":"Changing one bird's wingspan keeps a formation stable only within position-specific limits, with tighter tolerance at the outer wing than near the leader."},"references":{"count":46,"sample":[{"doi":"","year":2017,"title":"B. Voelkl and J. Fritz, Philos. Trans. R. Soc. B372, 20160235 (2017)","work_id":"2b6cdd6e-35e0-4a8b-abbc-be276caddcc6","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2004,"title":"M. Andersson and J. Wallander, Behavioral Ecology15, 158 (2004)","work_id":"548de5a5-6bbe-4d90-9abb-34f690b75079","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2009,"title":"I. L. Bajec and F. H. Heppner, Anim. Behav.78, 777 (2009)","work_id":"5b5aca86-55b3-4bb6-835f-25093bf78436","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1978,"title":"P. Ward, Anim. Behav.26, 1273 (1978)","work_id":"35280ec6-b727-4c74-b7ee-9b6428851e07","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1974,"title":"F. H. Heppner, Bird-Banding45, 160 (1974)","work_id":"46c301c9-a6e3-4cc3-a207-0ea39bd2b132","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":46,"snapshot_sha256":"b85c5095780235a2fd7dc94519250f0228df84bf633b650e77319efc4619ef8c","internal_anchors":0},"formal_canon":{"evidence_count":1,"snapshot_sha256":"2916b8d2f71ac8c4555baefe3ea6e9c1ca260ff68fc9187d5417217321d5e8e1"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}