Geoscience Reference
In-Depth Information
RADIOTRANSMITTERS
Radiotelemetry is an important tool for the study
of avian biology (Kenward 1993; Kenward and Walls 1994; Custer et al.
1996). Radiomarking and use of recording devices (e.g., for flight velocity, div-
ing depth) on birds has generated considerable study of effects of these mark-
ers because they are large compared to most other bird markers. The effect of
transmitter or device size on birds can be influenced by where the package is
placed or how it is attached. Packages have been placed on legs, necks, wings,
backs, retrices and other feathers, under the skin, in the body, by banding, col-
laring, wing tagging, harnessing, gluing, tying, suturing, clamping, and
implanting (Kenward 1987; Samuel and Fuller 1994). Since the earliest uses
of radiomarking in birds, it has been recognized that the transmitter attach-
ment method can affect a variety of aspects of behavior and survival. For
instance, neck collars were shown to be effective in some cases (Marcstrom et
al. 1989; Meyers 1996), but in other cases their use was accompanied by neg-
ative effects (Sorenson 1989). In one series of studies, tail-mounted transmit-
ters did not affect mass or survival of northern goshawks (
Accipiter gentilis;
Kenward 1978, 1985), but it is understood that such transmitters must be
light (2 percent or less of bird body mass), thereby limiting battery size and
transmitter longevity. Reid et al. (1996) describe a method for replacing a tail-
mounted transmitter when individuals can be recaptured. As with legbands
and dyes, transmitter color also must be considered: Wilson and Wilson
(1989) and Wilson et al. (1990) found that penguins pecked significantly less
at black recorders (attached to the dorsal feathers by tape) than at other colors.
Radiotransmitters are similar to other markers in having variable effects
that are influenced by attachment method, and the bird's species, age, and sex
are necessary considerations. In an effort to securely attach large packages to
birds, a number of researchers have experimented with various harness designs
to hold transmitters on the bird's back. Several authors (Houston and Green-
wood 1993; Kenward and Walls 1994; Kenward et al. 1996; Neudorf and
Pitcher 1997) failed to show differences in survival or behavior of birds carry-
ing various harness transmitter packages, but other examples show that such
transmitters can have negative effects on bird behavior or survival (Hooge
1991; Klaasen et al. 1992; Pietz et al. 1993; Gammoneley and Kelly 1994;
Ward and Flint 1995; table 2.3).
In an attempt to minimize the deleterious effects of harnesses on birds,
researchers have experimented with different types of implants. Partial-
implant (Mauser and Jarvis 1991; Pietz et al. 1995) as well as full-implant
transmitters (Dzus and Clark 1996) have been used with some success, but
such implants can result in short-term preening over the incision site and cause
