Answers are grounded in this paper and cite their sources.
As was to be expected after the 1978/79 cold winter, many resident passerines were down in numbers. Some summer migrants were also less in evidence (especially Swallow and Spotted Flycatcher), though there was a welcome increase of Redstarts.
No takes yet. Share an insight, caveat, or question.
Marchant et al. (1980) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: