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Résumé :
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Nectar passage and digestive tract morphology of two unrelated nectarivorous bird species, the Malachite Sunbird, Nectarinia famoso, and the Black-capped Lory, Lorius Iory, were examined. X-ray techniques were used to determine the gross anatomy, and the flow of nectar (an artificial sugar solution) along the gastrointestinal tract. The Black-capped Lory has a crop while Malachite Sunbirds do not. X-ray analyses showed that labelled meals were briefly stored in the crops of lorys but flowed directly from the oesophagus to the ventriculus in Malachite Sunbirds. Gut morphology of Malachite Sunbirds and a Black-capped Lory were also examined. The sunbirds have a simple gastrointestinal tract anatomy without a crop, whereas the Black-capped Lory has a well-developed crop. We hypothesize that in nectar-feeding birds, the presence of a crop confers foraging flexibility. We predict that the presence of a crop allows lorys to take larger meals, and hence reduce feeding rate defined as meals/time. Sunbirds on the other hand, must feed frequently.
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