Type: report

Article abstract: This report documents the 2007 Nature Reserve of Orange County funded study to outfit fledgling cactus wrens with radio transmitters and to use a hand-held receiver and antenna to relocate the juvenile wrens as they attempted to disperse from their natal territories. It was initially planned to radio mark up to 14 juvenile wrens from several study sites located throughout the reserve system. However, the lack of nesting attempts and low productivity, likely due to low precipitation during the previous rainy season, provided few fledglings to radio mark. We radio tracked 7 fledglings and 3 adult males for 3 to 48 days. We also monitored a pair of banded wrens that were relocated to Upper Newport Bay in 2006. We tracked two hatch-year wrens for more than 45 days. One moved away from its natal territory (area where the parents were located) and roamed the study site, but did not leave it, and the other was not observed to have left its natal territory. Three other young wrens? signals were lost after 14 to 24 days and another lost its transmitter after 10 days. None were ever relocated during the season. Another young wren?s partially eaten remains were found after three days of tracking. Two radio marked adult male parents were followed until the batteries failed and a third lost its transmitter after 21 days, but was resighted up to 48 days later. A banded male that was relocated to Upper Newport Back Bay in 2006 made a 0.7 km breeding dispersal and mated with a relocated female producing one fledgling in 2007. In this report, the wren radio tracking observations from this study are compared to movement records from two multi-year cactus wren banding studies conducted in coastal Southern California. Cactus wrens near or at their adult size initially appear to be robust enough to tolerate having a small radio transmitter temporarily placed on them. They also appear to tolerate the translocation procedure and initially appear to quickly adjust to their new location. These activities do expose the wrens to an increased risk of injury and mortality and it is unknown what the impacts are on their long term survival and reproductive success; they should be used and conducted judiciously. It is important to understand cactus wren dispersal patterns in a fragmented landscape in order to manage and conserve their populations in the region and further study is encouraged. However, cactus wren habitat and populations in the reserve appear to continue to decli