A bird trespassing on train tracks at Brighton station caused an hour and a half of rush-hour disruption on Tuesday.
ThamesLink was forced to close three platforms for about half an hour from 7pm while power was switched off and the herring gull was removed.
Journeys affected included Brighton to London services and the Gatwick Express, with total disruptions lasting until about 8.20pm.
The rail operator posted on X, formerly Twitter, about the delay and advised travellers to allow an extra 20 minutes to complete journeys because of the presence of an “endangered species of bird (herring gull)”.
Several people replied to Thameslink asking if the post was a late April Fool joke, and questioning whether herring gulls are actually endangered.
One traveller complained that “numerous trains” had been cancelled and operators had left them “stranded in the rain”.
Although some said herring gulls are a common sight at the seaside, the species has been on the Birds of Conservation Concern’s (BCC) red list since 2009 because of ongoing population decline.
The list is compiled by the UK’s leading bird conservation organisations, including the RSPB, and identifies conservation priorities for birds.
Herring gulls’ red list status means they have been identified by the BCC as subject to “an increasing level of conservation concern”.
At 8.30pm Thameslink said the bird was safely away from the railway and apologised for any inconvenience.
Staff said the young bird “seems to be OK” and was “being well looked after”.
