BAYONNE (64) 16.03.2019

On 16 March 2019 at 01:55—not 3 or 15 March as mistakenly written in the questionnaire—a witness in his garden saw 7 silent points, each described as a somewhat blurred white disc. Their geometric formation crossed south-west to north-east in 4–5 seconds before his roof hid it. Only 1 account was collected. GEIPAN’s analysis considers white-plumaged birds, probably gulls travelling silently towards a nesting site, very likely (see the investigation report). The witness’s housing estate is surrounded by suitable wetlands. Non-migrating birds commute between coastal or riverside feeding grounds and nesting sites on inland waters. Spring is breeding and nesting season for some species, such as black-headed gulls, and migration season for others, such as little gulls. The straight, steady group flight fits gregarious gulls. Slightly adjusted angular-size and duration estimates produced calculated speeds and dimensions consistent with these birds flying at 20–30 m altitude. At this season, the suspected birds have dark parts on their heads and wings; only white undersides may be visible from below, leading to underestimated size and unseen wings or wingbeats. Distance, possible unconfirmed mist or reduced visual acuity, separately or together, could prevent recognition of their actual shape. Residual light and contrast against the dark sky would reveal their white plumage as pale or milky-white points. The account is concise, fairly precise, neutral and written promptly, but evidential strength remains moderate because there is only 1 witness and no photograph. GEIPAN considers the event only slightly unusual: linear motion and moderate speed, with appearance and behaviour matching ordinary birds seen under particular conditions. The case is classified B: probable observation of pale-plumaged birds flying in formation.