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Birding at the Chico

The Chico Basin Ranch is a major flyway for migratory birds, due to the abundant springs, lakes and bird habitat on the ranch. The ranch works closely with Rocky Mountain Bird Observatory and has over 300 birds on the ranch bird list. Many people come to the ranch in the spring and fall to bird.

Bill Maynard is one of birders that comes most frequently. When we asked him if he would keep the ranch birding journal, he was pleased and agreed to do it. Thank you Bill! Bill has taught high school biology, worked as a naturalist for the National Park Service and as a biologist for a variety of government agencies. He has also worked for the American Birding Association at their national headquarters in Colorado Springs. 

Click Here to download the Ranch Bird Checklist

Click Here to download the Birding Trail Map (4mb PDF)

Click Here to download the Ranch Dragonfly and Damselfly Checklist



Wednesday, Jun 18, 2008
Brown-headed Cowbirds - Egg Factories
No more migrant birds at the Chico.  Only the breeders remain.  The most intereting bird in North American (and least attractive) is arguably Brown-headed Cowbird.  Native to the short-grass prairie where it was historically tied to the vast herds of American bison, Brown-headed Cowbird has spread with deforestation, moving east into cleared areas, as settlers moved west.  

Brown-headed Cowbird is a brood  parasite, never building its own a nest, but relying on the nests of other songbirds.  The female can lay up to 40 eggs in a season and in captivity one layed 71 eggs.  This equates to trouble for nesting birds.  Cowbird females spend a lot of time watching.  They know where all of the local nests are located.  Usually, they wait until the hour before first light, fly to the nest they have chosen and lay one or sometimes two eggs in the host species nest.  When the host is a larger bird, the female cowbird often pierces one of the host species eggs, and then either drops it to the ground or eats it.  If they remove too many of the host species eggs, the host will abandon its nest, ending the chance that either species will have any young produced from that nest.

Because the western expansion is a relatively new event, songbirds have not yet been able to evolve to compensate with the massive increase in numbers of Brown-heaed Cowbirds.  Some songbird species that are already listed as Endangered Species, such as Black-capped Vireo in Texas and Kirtland's Warbler in Michigan, could become extinct if biologists did not spend considerable amount of time and money trapping and euthanizing cowbirds in the areas where these endangered species breed.  However, this is a never-ended process that has to be repeated each year to ensure that the endangered species will raise a brood as more cowbirds fill in the gaps where other cowbirds have been removed.

Because Brown-headed Cowbirds do not tend to their own young, they are able to forage at great distances from the areas where they lay their eggs, often alongside livestock.  Some songbird species have begun the evolution process in response to the increase in cowbirds, and Yellow Wablers, for example, will usually build a new nest on top of the egg of a cowbird.  More likely the host species is  unable to tell a cowbird egg from their own, even in instances when cowbird eggs are twice as large, with the result being that the host feeds the larger, more aggressive cowbird chicks, while their own young starve.  To date, over 220 bird species have been parasitised by Brown-headed Cowbirds.  Species that breed early or very late, and cavity nesters seem to be the only ones not affected by this brood parasite.  Birds that live exclusively in large forested areas are not affected by cowbirds, unless there is a large meadow or pasture in the center.  Cowbirds  are now associated with livestock and feed on waste grains not consumed by horses, pigs, cattle, or goats.  On the Chico, cowbirds are often seen riding the backs of cattle.

Although strongly disliked by nature lovers, Brown-headed Cowbirds only do what they evoved to do; they are extremely successfuly at  laying eggs in other species' nests.  They are so successful that winter flocks are reported to be in the millions.
Posted by Bill M. on 06/18/2008

   
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CONTACT US 719.683.7960 info@chicobasinranch.com