The birds in the film aren't actually Tawny Pipits, they are Meadow Pipits. Tawny Pipits are very rare in the UK (even more so in wartime when this film was made) and it wasn't possible to find any to film. The rarity of the Tawny Pipit is a major thread to the story. It was decided to photograph a pair of ordinary meadow pipits and keep to shots which showed the back view only; the tawny has a plain breast and the meadow a speckled one, but their back plumage is very similar.
Nancy, the character played by Jean Gillie, is referred to as a "land girl". During WW II, these were girls from London, Manchester, and other big cities who went to the country to work on farms, since all the men were serving in the war.
Tawny Pipit (1944) features a rare appearance on film of a pair of Covenanter tanks. Designed by the LMS railway and Nuffield, they were delivered after the fall of France, but suffered from insufficient cooling making them unsuitable for use in warm climates like North Africa so were used for training in Britain by divisions who were often waiting to be sent abroad, then handed down to the next division before they were moved. By the time of D-Day when a front opened up with a suitable climate for the Covenantor the design had been rendered obsolete.
Once the watchers have been chosen from the students, Reverend Kingsley speaks some lines of poetry: "East and west and south and north / The messengers ride fast, / And tower and town and cottage / Have heard the trumpet's blast". These lines are from "Horatius" by Thomas Babington Macaulay, Lord Macaulay. Kingsley does make an error in using 'hamlet' instead of 'cottage'.
This film received its initial USA telecast in Los Angeles Monday 10 April 1950, leading off Triple Feature Theatre on KECA (Channel 7) , hosted by Art Baker; it first aired in New York City Saturday 30 September 1950 on WCBS (Channel 2), and in San Francisco Saturday 13 January 1951 on KGO (Channel 7).