H.B. Tordoff, W.R. Dawson (1965). “The influence of daylength on reproductive timing in the red crossbill”, The Condor67 (5), p. 416–22. doi:10.2307/1365634.
T.P. Hahn (1995). “Integration of photoperiodic and food cues to time changes in reproductive physiology by an opportunistic breeder, the red crossbill, Loxia curvirostra (Aves: Carduelinae)”, J. Exp. Zool.272, p. 213–26. doi:10.1002/jez.1402720306.
