Any study of nature and its ecosystems finds millions of stories to be told. From plant lifecycles to habit adaptations each species has a tale of history, survival and incredulity to be shared. The challenges that many of these species have faced, experienced or overcome in order to pass on their genes reveal the complexity, cruelty and competition of nature. As human beings, we are so far removed from nature that I think it is easy to lose perspective of life itself.
I have a subtle African print entitled "Essence of Survival" that reads, "Every morning in Africa, a gazelle wakes up. It knows it must run faster than the fastest lion or it will be killed...every morning a lion wakes up. It knows it must outrun the slowest gazelle or it will starve to death. It doesn't matter whether you are a lion or a gazelle...when the sun comes up, you'd better be running." In nature, there is no such thing as a day off.
Fortunately, not all methods of survival are so straightforward, even if the competition is no less intense. To illustrate one of any number of examples, the Brown-headed Cowbird has adopted interesting survival skills, both promiscuous and parasitic- although by no means eccentrically unique by nature's standards.
A regular to the area in general and our backyard in particular, it seems quite normal in its disposition. The name comes from, as one might guess, its affinity to cows and other livestock (actually it was known as the "buffalo bird," but after human beings killed all the buffalo, the birds adapted to cows). The birds would follow the herding animals, eating the insects disturbed in its path. The travel made nesting difficult and required some adaptation on the bird's part.
Brown-headed Cowbirds do not build nests; rather the females lay their eggs in the nests of other (usually smaller) birds. She enters the nest and in less than one minute, she disposes of a one or two of the hosts' birds' eggs and lays hers in their place. The cowbird eggs hatch slightly before the rest of the nest and develop faster. The host bird often takes in the misplaced chick, even though it may kill or have killed her offspring. Over 150 documented species of birds have raised Brown-headed Cowbird young, as the female may lay as many as 40 eggs per season. The Brown-headed Cowbirds do not commit to another as a mate (although some dispute this), build a nest, or raise their own offspring. (Hmm, maybe they do live the "good life"- no spouse, no house, no kids!)
The Brown-headed Cowbird has been successful not only in its clever adaptations, but also thanks to humans, which have opened new habitats through deforestation (cowbirds prefer the fields). The potential impact of cowbirds is to the many songbirds whose nests they damage and whose offspring they kill. Several species are becoming threatened by its parasitic nature, such as Kirtland's Warbler, Black-capped Vireo, and Least Bell's Vireo. Some songbirds, however, have caught on and have begun displacing the cowbird eggs. (Imagine the conversation between songbird mates... "Honey, where did this egg come from?")
Unfortunately, as the tale too often goes, humans decide which birds we do and do not like, and in preference of the songbirds, the Brown-headed Cowbirds are now trapped and killed in some areas- even if many of the scientific facts surrounding its nature are disputable. The Audubon, as late as 1997, disputed some of the negative claims made against cowbirds, while noting that nearly $800,000 is spent annually protecting other species from cowbirds. Perhaps this observation by Stephan I Rothstein of the University of California, sums it up best, "People hate cowbirds, yet people love hawks. Hawks catch adult birds and rip them to pieces. Maybe people hate cowbirds because they're tricky."
Brown-headed Cowbirds are just one of thousands of fascinating species that engage scientists and the public alike. Its beauty or its nuisance, I suppose, is a matter of perspective and preference. Personally, it appears that they are making practical use of their competitive and adaptive advantages. I think every species and each individual deserves a fair chance- for that is the best deal nature can afford to offer.