3 – the number of decades between successful breeding attempts in the 1,200 square kilometres of the SBSG recording area (from the 1950s to 1984).
3 – the average number of chicks fledged from the St George’s nest over the last 5 years; also the average number of chicks that fledge from urban nests according to Esther Kettel’s PhD research (cf. average of 2 from rural nests).
3 – the temperature (in degrees celsius) here in Sheffield as I write, following some snow flurries this afternoon, evident in the screengrab below, with the male sitting tight.
And finally – 3 – the number of eggs visible as the female takes over incubating duties just now: her bigger body size will be more effective, especially on a cold night.