This series highlights several of my favorite birds, all of which can be found in Wisconsin. I have found all of the birds included in the series (with one exception). Each cache is somehow related to the highlighted bird. In many cases you will find hints to finding the cache in the information provided about each bird. Each cache is hidden in roughly the environment the bird can be found. None of the caches are hidden in a nesting box or a fake nest (with one exception of a very non-standard nest), so if you find a nest or nesting box—please leave it alone it has nothing to do with the cache.
The Brown-headed Cowbird is named from its’ practice of following grazing animals looking for the insects that frequently accompany these animals. That, and the fact that this blackbird does indeed have a brown head.
Brown-headed Cowbird (Molothrus ater)
The cowbird is the only parasitic species of bird found in North America. The cowbird does not build its’ own nest, nor does it incubate its’ own eggs. The female cowbird carefully watches the nests of other birds waiting for a nesting bird to temporarily leaves its’ eggs and nest to search for food. In this brief moment, the female cowbird flies in to lay one of her own eggs. Sometimes, she will remove one egg from the host nest. The cowbird egg develops faster than those of the host species--typically hatching a day or more in advance of the host’s eggs. The unsuspecting host parent will treat the baby cowbird as its’ own. Occasionally the rapidly growing cowbird will push the young of the host species out of the nest.
Initially this behavior seems to save the cowbird all the work of building her own nest and feeding her own young. However, this approach does have its own draw backs. Frequently, the host bird recognizes the intruding egg and removes it from the nest. To insure that her eggs succeed, the female cowbird must monitor the nests in which she lays her eggs. If she discovers that her egg has been removed she will often destroy all the eggs in the nest forcing the host bird to lay a new set of eggs among which the cowbird will lay a new egg. The female cowbird will lay an average of 30 eggs in a season, with only 2-3 young successfully fledging. This number of eggs requires a huge amount of calcium. This need for calcium requires the female cowbird to spend large amount of time in search of calcium sources.
While studies have found cowbird eggs in the nests of over 220 species of birds, most females typically target the nest of just one species. Once a researcher even found a cowbird egg in the nest of a Ruby Throated Humming Bird--the egg was just about the size of the nest itself!
In the winter the Brown Headed Cowbird will join large mixed flocks of blackbirds whose numbers sometimes reach the millions. Ironically, many of the species of blackbirds making up these flocks are the same birds whose nests the cowbirds target for their eggs.
The cache is not at the posted coordinates. In order to find the Brown Headed Cowbird cache you will need to find the cache in which the cowbird laid her egg. The cowbird laid her egg in one of other caches in the Wisconsin Ornithology series. This egg will contain the coordinates for the cowbird final. Since a number of caches in series have already been published, I will email finders of the cache in which this egg is being placed. Then again, it might be in a cache yet to be published.
The Geocache Notification Form has been submitted to the Wisconsin DNR. Geocaches placed on Wisconsin Department of Natural Resource managed lands require permission by means of a notification form. Please print out a paper copy of the notification form, fill in all required information, then submit it to the land manager. The DNR Notification form and land manager information can be obtained at: http://www.wi-geocaching.com/hiding
There is a new bird book for the first to find.