Thursday, March 29, 2012

Cactus Wren on Cholla: Best Buddies

Cactus Wren on Cholla: Best Buddies


Introduction:
The Cactus Wren, also known as  Campylorhynchus brunneicapillus, is the largest bird found in parts of North America such as Southern California, Southern Nevada, Arizona, New Mexico, Utah, Western Texas, and Northern Mexico [1]. The normal size of a wren is about 8 inches long [1]. Campylorhynchus brunneicapillus is distinguished from other birds because it's belly has spots, and speckled brown, black and white feathers on its back, wings and head. It also has black feathers on its throat and a long stripe of white feathers [1]. Campylorhynchus brunneicapillus lives in desert areas such as a large cactus known as Cylindropuntia, commonly known as 'cholla' [2]. Campylorhynchus brunneicapillus  finds its food from the ground using its long bill. They usually eat ants, beetles, grasshoppers, wasps, fruits and seeds. However, it also eats small frogs and lizards. The wren is adapted to the life in the desert and gets most of the water from the food it eats in order to survive [1]. Cylindropuntia  are found in North American deserts with more than 20 species found in the Southern America [3]. "Cholla" is the term used to describe shrubby cacti with cylindrical stems that have segmented joints [3].  The cactus wren lives on large cacti like the 'cholla' in order for the cholla to hold its large nests.There is a commensalistic relationship between the cholla cactus and wren.


Relationship:
Commensalism is a relationship in which one of the organism's benefits (gets what it needs) while the other organism neither benefits nor is harmed. In the relationship between the cactus wren and cholla, the cactus wrens build their nests in cholla cacti. The spines of the cactus help by protecting the nest from predators. In this relationship, the cactus wren receives what it needs, i.e. nest protection [4]. The cholla cactus neither benefits nor is harmed by the nests that the cactus wrens form [4].


Cost/Benefit Analysis:
There is no cost in this relationship for the cactus wren. The wren benefits from the cholla by gaining shelter without harming the cholla. The wren builds its nest inside the cholla so that it has a cooler place to live in rather than the hot weather outside in the desert. The cholla also helps the wren by protecting it from predators through its spines. The cholla has no cost because the wren does not harm the cholla in any way. The cholla helps the wren by providing it shelter.

References:
[1]  http://www.nhptv.org/natureworks/cactuswren.htm
[2]  http://en.wikipedia.org/wiki/Cylindropuntia
[3]  http://www.desertusa.com/mag99/may/papr/chollas.html
[4]  http://www.azgfd.gov/i_e/ee/resources/wild_kids/relationships46.pdf





1 comment:

  1. Wouldn't a cactus with a steady family of wrens benefit from their presence from the the waste produced by the bird, not only its droppings but food scraps. Not all birds are super fastidious and carry their chick waste away from the nest in tidy packages. Doing so in a desert is probably more risky than a forest, because your comings and goings are more obvious to hawks Etc. I bet this bird takes care of business simply by propping their butt over the edge of the nest to poop. Beyond that, it would accumulate more nitrogen rich waste in general from wrens who had chosen a particular cactus as their home even out of nesting season. In a desert fertilizer can be hard to come by, and a bird regularly providing some would be a huge plus for a cholla. Then there is the fact that a wren inhabited cholla should have far fewer bug pests eating away at it, since wrens love to eat bugs.

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