Radio transmitters do not affect survival or behavior in songbirds
The reason we use radio telemetry to monitor animals is because it is difficult, if not impossible, to consistently find and observe individuals without help from technology. Therefore, comparing marked and unmarked animals is a frustrating challenge because if we could monitor unmarked individuals as well as we monitor marked individuals, we wouldn't mark any of them. This conundrum makes controlled tests of the effects of radio transmitters on behavior and survival of animals particularly challenging. Several groups before us found ways to compare marked and unmarked songbirds in aspects of annual survival and nesting behaviors. We compared reproductive parameters between radio-marked and unmarked female Golden-winged Warblers, and we found no impact of radio transmitters on any aspect of full-season productivity from clutch size through fledgling survival to independence from adult care. Our study demonstrated that, with carefully designed marking techniques, even 9-gram songbirds can be safely tracked through the entire breeding season with no discernable effects on their survival or reproductive output.