By A Mystery Man Writer
Blue tit guide: how to identify, what they sound like, and what type of nest box they use - Discover Wildlife
Blue Tit or Great Tit: What Are The Differences?
Eurasian blue tit - Wikipedia
Frontiers Variation in Diurnal Patterns of Singing Activity Between Urban and Rural Great Tits
BBC Springwatch 2016: Blue Tits and Great Tits - GardenBird
Susan D. Healy's research works University of St Andrews, Saint Andrews and other places
Great tit - Wikipedia
Blue Tit or Great Tit: What Are The Differences?
Eurasian blue tit - Wikipedia
Christopher TEMPLETON, Professor (Associate), PhD, Pacific University Oregon, Forest Grove, Department of Biology
Mean ± SE call rate of (a) blue tits and (b) great tits in response to