Knowledge Gained from Video-Monitoring Grassland Passerine Nests

In the mid-1990s, researchers began to adapt miniature cameras to video-record activities :rt cryptic passerine nests in grasslands. In the subsequent decade, use of these video surveillance systems spread dramatically, leading to major strides in our knowledge of nest predation and nesting ecology of many species. Studies using video nest surveillance have helped overturn or substantiate many long-standing assumptions and provided insights on a wide range of topics. For example, researchers using video data have (1) identified an extensive and highly dynamic predator community in grasslands that varies both temporally (e.g., by time of day, nest age, season, year) and spatially (e.g., by habitat, edge, latitude); (2) shown that sign at nests is unreliable for assigning predator types and sometimes nest fates; (3) contributed to the n the 1990s, the plight of grassland birds received increased attention (Johnson and Schwartz 1993, Knopf 1994, Johnson and IgI 1995), as researchers began to recognize that grassland species were showing "steeper, more consistent, and more geographically wide-spread declines than any other behavioral or ecological guild" of North AmerIcan birds (Knopf 1994;251). Many grassland pas~erine populations had been declining for decades understanding of the risks and rewards of nest defense; and (4) provided information on basic breeding biology (e.g., fledging ages, patterns of incubation and brooding, and male/female roles in parental care). Using examples from grasslands, we highlight accumulated knowledge about activities at the nest documented with video surveillance; we also discuss the implications of this knowledge for our understanding of avian ecology. Like all tools, video nest surveillance has potential limitations, and users must take precautions to minimize possible sources of bias in data collection and interpretation.