December 16, 2011

Clean-up on aisle 12...!

(Photo by Mark Havnes | The Salt Lake Tribune) An Eared Grebe waits in a box on
Wednesday to be released after crash-landing in Cedar City on Monday night
apparently thinking some areas were water. At least 1,000 birds died
and 2,000 survived to be transferred to reservoirs in Washington County
(text from the Salt Lake Tribune).
Making news this week: the crash-landing of thousands of grebes in a Walmart parking lot in Cedar City, Utah.  The death toll looks to be about 1,500 birds according to press accounts.

Evidently, the birds were migrating in a storm and mistook the parking lot for a lake surface.  There have been myths about ducks mistaking the blue football field at Boise State (Idaho) for a lake, but they appear to be untrue.

Ecological traps are situations in which animals respond to cues, which normally would lead to enhanced survival or reproduction.  But, in an altered landscape, those cues can be misleading---leading to the 'trap' of misinterpreting the cue.

A typical example of an ecological trap--birds respond to the density of non-native, cool-season grasses in the spring to build a nest.  Throughout recent history, native cool-season grasses were mixed with warm-season grasses and forbs, which provided cover and sources of insects (for food for chicks) later in the season.  Early growth of grass would normally indicate an area that would be good for nesting and rearing young.  But, where non-native brome grass has overtaken a pasture, for example (wonderful forage grass for cattle), the forbs and warm-season grasses will not 'show up' later in the nesting season.  The birds, of course, do not know this, and the situation may result in reduced productivity...hence, a trap.

As my research lab continues to work with habitat selection of grassland birds, we may find more examples of ecological traps.  But, none will probably seem as harsh as the reality of crash-landing on pavement. 

1 comment:

  1. I vividly remember an American coot running across the Walmart parking lot in Starkville, MS. I can only imagine it was a similar scenario. Funny thing was it ran straight into the bushes at the Popeye's Chicken!