Berthold, P. (1976). "Animal and vegetable nutrition of omnivorous songbird species: food preferences, annual cycle of food choice, physiological and ecological significance". Journal of Ornithology. 117: 145–209. doi:10.1007/BF01643586. S2CID11393458.
Witmer, Mark (2001). "Nutritional interactions and fruit removal: cedar waxwing consumption of Viburnum opulus fruits in spring". Ecology. 82 (11): 3120–3130. doi:10.1890/0012-9658(2001)082[3120:NIAFRC]2.0.CO;2.
Levey, Douglas; Grajal, Alejandro (1991). "Evolutionary implications of fruit-processing limitations in cedar waxwings". The American Naturalist. 138 (1): 171–189. doi:10.1086/285210. S2CID84391877.
Karasov, William; Levey, Douglas (1990). "Digestive system trade-offs and adaptations of frugivorous passerine birds". Physiological Zoology. 63 (6): 1248–1270. doi:10.1086/physzool.63.6.30152643. S2CID88368753.
Berthold, P. (1976). "Animal and vegetable nutrition of omnivorous songbird species: food preferences, annual cycle of food choice, physiological and ecological significance". Journal of Ornithology. 117: 145–209. doi:10.1007/BF01643586. S2CID11393458.
Levey, Douglas; Grajal, Alejandro (1991). "Evolutionary implications of fruit-processing limitations in cedar waxwings". The American Naturalist. 138 (1): 171–189. doi:10.1086/285210. S2CID84391877.
Karasov, William; Levey, Douglas (1990). "Digestive system trade-offs and adaptations of frugivorous passerine birds". Physiological Zoology. 63 (6): 1248–1270. doi:10.1086/physzool.63.6.30152643. S2CID88368753.