Experimental mass-marking of waterfowl wintering on the Southern High Plains of Texas
Godfrey, Ralph D
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The use of fluorescent particles for marking waterfowl was assessed using captive mallards (Anas platyrhynchos), 30 July 1985 through 26 August 1986. Additionally, field studies were conducted November 1984 to March 1986 on the Southern High Plains of Texas. Wild waterfowl were captured November 1984 to March 1985 and October 1985 to March 1986. Caged mallards were in alternate plumage throughout most of the study. None of the feathers shed during molt had fluorescent particles adhering, thus m o U was not a limiting factor for determining the marked index on captive mallards. Captive mallards exposed to pigment solutions for 60 minutes marked equally well as ducks exposed for periods up to 480 minutes. The period of particle retention on plumage of captive mallards was highly correlated (P s 0.001) with the initial marked index of an individual (y = 4.24x, r^ = 0.94, df = 35). There were no differences between sexes in the period of particle retention. Wings of captive mallards retained fluorescent particles longer than other body regions. Application of 7 kg of fluorescent pigment/ha-m of water (3 lbs/ac-foot) was sufficient to mark waterfowl for 5 weeks. However, low marked indexes from 2 lakes suggested that waterfowl need to be examined soon after the initial pigment application to determine if additional pigments should be applied. The marked index was not influenced by sex or species for mallards, American wigeons (A. americana), northern pintails (A. acuta), and green-winged teals (Ã‚. crecca). Waterfowl on lakes ^ 1 m in depth, and those not receiving feedlot runoff, had higher marked indexes than did waterfowl from other lakes. Unmarked waterfowl (n = 383), captured and confined in cages on lakes containing fluorescent pigments, received marked indexes highly correlated (P ^ 0.0001) with the concentration of fluorescent particles in water samples collected from within the cages (y=0.66x,r^2=0.67). The distribution of fluorescent particles throughout lakes was not affected by prevailing winds, but particles did sink. Lakes s 1 m in depth, and those not receiving feedlot runoff, maintained higher concentrations of particles over time than did other lakes. The average size of fluorescent particles did not change between weeks in each lake. Observers, with limited instruction, were capable of relatively accurate scoring of particles on waterfowl wings. Extent of observer experience with wildlife, waterfowl, or viewing fluorescent pigments had little effect on the accuracy of scoring wings. However, individuals with previous particle viewing experience could distinguish particles with greater ease than novice observers.