Our subject this week is a the Bohemian Waxwing.  I learned several things about this bird, but the one that stuck out the most to me was the word “altricial.”  Waxwing chicks are born altricial, as opposed to precocial.  Altricial species are underdeveloped at birth and must be cared for more extensively than precocial species, which are born more capable and in some cases may be able to walk or even fly within a day of being born.  Of course, before any hatchlings get altricial, we’ve gotta do a mating display, and once again dry, academic language makes the male waxwing’s lack of success sound funny: “The male may repeatedly present a gift of a small item, often food, to his partner, placing it in her open bill. In about 90% of cases, this display does not lead to copulation.”

Because their diet of berries isn’t very nutrient-rich, waxwings have to eat a whole lot of them, sometimes twice their bodyweight in a day.  One absolute unit of a bird “was recorded as eating between 600 and 1,000 cotoneaster berries in six hours, and defecating every four minutes.”  Waxwings have a large liver to help them convert sugar from berries into energy.  Although their liver is more efficient than a human’s, they are still capable of eating enough fermented berries to become drunk.  Finally, this diet provides an advantage besides facilitating cute photos.  Due to feeding its young berries, the species doesn’t fall victim to brood parasites like the cuckoo or brown-headed cowbird. Brood parasites such as these leave their own eggs in a different bird’s nest to be raised by an unaware parent of another species. This strategy doesn’t work with waxwings because brood parasite hatchlings can’t live on such a fruit-heavy diet.  

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