Key points are not available for this paper at this time.
Tore Slagsvold, Bird Song Activity in Relation to Breeding Cycle, Spring Weather, and Environmental Phenology, Ornis Scandinavica (Scandinavian Journal of Ornithology), Vol. 8, No. 2 (Nov. 15, 1977), pp. 197-222
Tore Slagsvold (Tue,) studied this question.