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♦ 1Krebs, J. R., & Avery, M. I. (1985).
Central place foraging in the European bee-eater, Merops apiaster. The Journal of Animal Ecology, 459-472.
♦ 2Diet composition and prey choice by the red-backed shrike Lanius collurio in western Poland, Piotr Tryjanowski, Malgorzata Karolina Karg, Jerzy Karg, Belg. J. Zool., 133 (2) : 157-162 (2003)