Methods:

We propose to capture 60 adult female gadwalls each year during October – November 2007 and 2008 on study sites in Louisiana and Texas and equip each female with a 40g implantable satellite transmitter (i.e., platform transmitter terminals [PTT]). We will attempt to distribute satellite transmitters evenly among capture sites, but will modify these plans if necessitated by trapping success. We will capture gadwalls using rocket nets fired from portable platforms over pre-established bait sites or swim-in traps. LeSchack et al. (1997) estimated mean body mass of adult female gadwalls during winter as 866g (range = 720 – 980g). We will mark only adult females whose body mass exceeds 800g, such that the transmitter weight will not exceed 5% of the female’s body mass. This cutoff point will minimize potential bias introduced by transmitter effects on female survival, behavior, or movements.

Satellite transmitters will be configured to produce an effective battery life of approximately 210 days (7 months). Transmitters will operate in repeating cycles of 6 hours ‘on’ and 32 hours ‘off.’ We chose a relatively short ‘off’ period to increase the number of transmissions per week and hopefully increase the frequency of high accuracy locations received during the winter study period. Radiomarked females will be monitored until they die or the transmitter battery expires; data will be received and processed weekly by project researchers. Dr. Alan Afton, USGS-Louisiana Cooperative Fish and Wildlife Research Unit at Louisiana State University (LSU) Agricultural Center, and Jacob Gray, LSU Master of Science student, will accept primary responsibility for implementing this study.