Both federal (permit MB019065) and state (permit: 10TRb2006) permits were acquired prior to testing.
On December 14th, 2010 20 European Starlings were captured at a cattle feedlot outside of Platteville, CO (40°12' 39.84"N by104°52' 15.84"W) using modified Australian Crow traps. All birds were transported to the USDA-NWRC Outdoor Aviary Research Facility (OARF) and housed in individual testing cages (0.9 m × 1.8 m × 0.9 m). A maintenance diet was provided daily (ad libitum) to all birds. Water was also provided daily (ad libitum) to all birds throughout the study. Both food and water were simultaneously presented to the birds through the left hand door of the cage
Along with the maintenance diet, Russian olive fruits were presented to the birds in a free choice mannor. In free choice, birds were presented with 25 Russian olive fruits at a time in small clay dishes, through the right hand door of the cage and left for 24 hours. The birds were given the option to freely feed on the seeds at their leisure. Depending upon the bird feeding behaviors, each bird was held until it had consumed a total of 50 seeds for the test, or a grand total of 1000 seeds. Free choice testing was carried out over a 1-week period. Water, maintenance diet, and test fruits were checked every morning at 0700 hours (7:00 am MST).
Feeding was monitored using a camcorder mounted on a tripod facing the cages for further analysis on feeding behaviors. Video cameras were positioned either on tripods on top of the cage or were attached to the sides of the cage. Video was recorded over an 11 hour time period, just after seeds were introduced to the birds in the morning. Video was screened after the testing to determine feeding behaviors.
Paper tray liners were removed from the cages every other day for seed collections from the fecal matter and regurgitations. Seed passage was determined by screening the feces and regurgitated seeds for those that had been stripped of the fleshy perianth, which constituted a "cleaned" seed. Seed passage was determined by screening the feces and regurgitations by collecting the respective sample from fecal trays. Russian olive seeds were identified from the feces and distinguished from other seeds consumed. Seeds were considered scarified if they were defecated or regurgitated, based upon their morphology and the digestive processes that occurred.
This is the first of two videos from the the testing. In this video, we see a European Starling activly feeding upon Russian olive seeds. This video was captured 10 seconds after the feed dish had been placed inside of the cage. We see the European Starling activly gulp down seeds until its crop has been filled and then fly away. In the field, this same behavior was observed from our game camera trials examining wild European Starlings feeding upon Russian olive trees. Birds would swarm on a particular tree, feed for several minutes, and then fly away after their crops had been filled. This action (from both the video and the game cameras) indicate that the potential for European Starlings to act as a dispersal agent for Russian olive is both real and may explain a invasive quaility of the trees that deserves further study.
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Ramon, New Mexicoby wdrazo134 views
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