The hoopoe is not a nocturnal bird, nor a forest bird - it's a daylight lover found in open areas. So why are they crashing around the woods at midnight recording it?
When three of the birdwatchers are trying to identify a random bird from a hide in the forest, they suggest in turn the yellow-rumpled warbler, black-throated green warbler, Lucy's warbler, and redstart. While these birds have similar body shapes, they have distinctive plumage, difference enough for these experienced birdwatchers with powerful lens to make a more definitive identification. Perhaps it's meant as a joke or Easter egg for birders in the audience.
The program/brochure that was on the wall of the room of the obsessed fan misspelled "Starring" Nina which was spelled "Staring" Nina.
Mobile phones receiving a mass text message at the beginning of the programme all show the time the text was sent quite blatantly; however, the formatting would've been different, even on 2012-era phones. Time stamps would've been more accurate, but would've made this time line clue less clearly visible.