Bird Watchers Digest - November/December 2010

blackmail explains the evolution of producing such eggs in all cases. It may well be the case in some situations, however, and it is not necessarily mutually exclusive with other suggested hypotheses.

One thing is certain. A good number of bird species indeed lay highly conspicuous eggs, and the reason(s) for this phenomenon have bewildered scientists for more than 100 years.

Reader Observations

Patricia Kenyon of Yuma, Arizona, has a horde of great-tailed grackles nesting in trees in her backyard, and she has noted that a fair number of nestlings fall out of the nest prematurely. The wayward nestlings end up standing silently on the ground in the protection of tall grasses, bushes, and trees. When humans or potential predators approach a fallen youngster, a mob of a half-dozen or more adults fly about making noise and threatening to attack until the danger passes. But what Patricia has never seen is a parent landing near the youngster

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to offer food to it. She reports that virtually 100 percent of such young die of dehydration or starvation, and she wonders why the grackles have evolved such a vigorous defensive tactic toward predators but not a behavior to assist the fallen nestling with food.

I checked The Birds of North America series for this species and discovered it is not only common for grackle nestlings to fledge from the nest and spend several days on the ground, but the female parent also readily feeds the begging fledglings for several weeks. Either the grackles in Patricia’s backyard are reluctant to fly down to the ground to feed the prematurely fledged nestlings, perhaps because of lurking predators, or they are simply not interested in investing any time and effort into such birds. a