Disappearing Cactus and Wrens

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Zoo InternQuest is a seven-week career exploration program for San Diego County high school juniors and seniors.  Students have the unique opportunity to meet professionals working for the San Diego Zoo, Safari Park, and Institute for Conservation Research, learn about jobs, and then blog about their experience online.  Follow their adventure here!

In the San Diegian desert scrubland, there is a rare cactus wren that is native to California and requires this mild, cooler, coastal, Mediterranean climate. This desert scrubland is a habitat for many species, and the cactus wren has special requirement of cactus within this habitat. These wrens are picky about their cactus, as it must be the prickly pear or cholla cactus. The cactus has to be of a mature size and growing in clumps before the wrens can use them for their homes. It is an important fact that if the cactus disappears then the cactus wren will too.

The cactus wren species is least concern according to the IUCN (International Union for Conservation of Nature) red list, but the Californian subspecies, is not defined by the IUCN red list at all. This subspecies, coastal cactus wren, was named in 1990 by the state of California, but is not recognized federally, as its classification is controversial among ornithologists.  The coastal cactus wren is declining in numbers and becoming isolated due to urbanization (habitat loss), feral cats, and fires destroying the cactus.

The coastal cactus wren subspecies is different in appearance and song from the recognized species. Its feather coloration in the breast area is lighter tan without orange or yellow coloring. The song is lower pitched. The color variation in sub-populations may be habitat related. The coastal cactus wren has a limited year round range which may be contributing to the decrease in its population. It is unable to move when habitat is damaged; it can only travel about one kilometer.

The cactus wren uses twigs and small branches for building its nests. The nest is football sized, fully enclosed, and is used for laying eggs, raising young, and a roost for nighttime. The cactus the birds choose for nests must be three feet tall. The importance of cactus size is one of the species vulnerability; cactus can take seven years to grow to this height.

The cactus wren decline has increased the awareness of the loss of coastal sagebrush habitat. Urban development has taken over a large portion of the coastal sagebrush. The loss of wildlife areas due to development is causing fragmentation of this habitat, and isolating the wrens into very small populations. The 800 acre biodiversity preserve at the San Diego Safari Park has become the home of a program that protects the coastal sage habitat including the cactus wren and the prickly pear cactus. Some of these acres were damaged in recent wildfires and teams are now replanting cactus and protecting them until they reach maturity for the birds.

Colleen Wisinski, a Senior Research Technician at the Beckman Center, commented that we must be “good stewards of the land.”  For me being a good steward is continuing to preserve non- developed areas, protect our native plants and animals, and decrease human impact in our wildlife areas. Probably the most important part of being a good steward is to get educated on the issues and get involved.

Colton, Wildlife Conservancy Corner
Fall 2012, week three