A bonanza for fruit eaters

Fall must be like Christmas for Cedar Waxwings and Robins, who gorge themselves on the super-abundance of tree fruits available at this time of year.  We found a small flock of adult and juvenile Cedar Waxwings doing just that at the MN Valley National Wildlife Refuge last week.

Adult Cedar Waxwing showing off his red and yellow dipped feathers (for which he gets his name?).

Adult Cedar Waxwing showing off his red (wing) and yellow (tail) capped feathers (for which he gets his name?).

Like all young of the year, the juvenile Cedar Waxwings await instructions from their parent on where to forage.

Like all young of the year, the juvenile Cedar Waxwings await instructions from their parent on where to forage.

The youngsters wear the black mask of the adult, but lack the colorful yellow breast feathers and wax dipped feather tips.

The youngsters wear the black mask of the adult, but lack the colorful yellow breast feathers and wax dipped feather tips.

Here?  Is this a good fruit?

Here? Is this a good fruit?  Is a red-colored fruit a warning or an invitation?

Learning by trial-and-error which fruits are not only nutritious, but won’t poison you, is a long process; copying what your parents feast on is much easier and safer.

Not all fruits are equal: some plants have co-evolved with fruit-eating birds and mammals that aid in disseminating the plants’ seeds; other plants evolved disseminating mechanisms that involve propelling their seeds through pressure-driven or wind-driven means and protect their valuable offspring with toxic chemicals.  In addition, fruits are generally low in caloric value (compared to a nut), and may lack sufficient nitrogen for their consumers’ diets.

So, how does a Cedar Waxwing survive on a fruit diet?

Photo by Debbie Reynolds

Photo by Debbie Reynolds

Cedar Waxwings seem to be inordinately fond of high-sugar fruits, and they have exceptionally good absorptive capacity for sugars, not only in their small intestine, but in the proximal part of their colon as well (an unusual place to transport sugar).  It is thought that the accelerated sugar transport capacity of their intestine actually enhances amino acid transport as well, because these birds can actually remain in positive nitrogen balance on fruit diets that cause other frugivores (like robins) to lose nitrogen via excretion.

An interesting corollary of this high fruit diet is that cowbirds (brood parasites written about in an earlier post) that lay their eggs in the nests of Cedar Waxwings have doomed their offspring, because cowbird chicks can’t survive on a fruit diet, like the waxwing chicks can.

7 thoughts on “A bonanza for fruit eaters

  1. Very interesting! I am a new birder in southeast Florida, and was fortunate to see a large flock of cedar waxwings in my neighbor’s trees for two days last spring. I hope to see them again this year. I enjoy learning more about avian biology. Can you recommend any books?

    • Thanks for visiting the blog. I think a good way to get started learning about birds is doing some selective reading about the birds you see on the Cornell bird lab website: http://allaboutbirds.org

      You can use their bird guide to learn more about familiar species, or search for the ID of unfamiliar ones by matching some features.

      If you have a smart phone or an iPad, you can download the Audubon guide which includes images and songs, as well as basic info about the birds. Playing the song on your phone to a bunch of birds in a tree sometimes brings them right up close for a good photo (this works better in the spring than the fall).

  2. Wonderful shots, Sue, especially of the young birds, which I have never seen before. I really like the coloration of the Cedar Waxwing and think that it is one of the coolest looking birds. Now I have to try to find some this fall before it’s too late.

  3. Lovely captures. I have only seen these beautiful birds when on your side of the Pond. I enjoyed watching a flock in Vermont a couple of years ago. Spectacular.

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