Conservation Implications When the Nest Predators Are Known

Conservation and management of passerines has largely focused on habitat manipulation or restoration because the natural communities on which these birds depend have been destroyed and fragmented. However, productivity is another important aspect of avian conservation, and nest predation can be a large source of nesting mortality for passerines. Recent studies using video surveillance to identify nest predators allow researchers to start evaluating what methods could be used to mitigate nest predation to help passerines of conservation concern. From recent studies, we identified latitudinal and habitat-related patterns in the importance of predator groups that depredate passerine nests. We then reviewed how knowledge of specific nest predators can benefit conservation of bird species of concern. Mammals were the dominant predator group in northern grasslands. Snakes were the dominant predator group in southern habitats. Fire ants were only a nest predator in southern latitudes. Differences in the importance of predator species or groups were likely the result of both their geographic patterns of distribution and habitat preferences. Some direct and indirect predator control measures developed for waterfowl management potentially could be used to benefit passerine productivity. We reviewed three examples-cowbirds, snakes in shrublands, and ground squirrels in grasslands-to illustrate how different predator control strategies may be needed in different situations. Mitigation of passerine nest predation will need to be based on knowledge of predator communities to be effective. This requires large samples of predation events with identified predators; video technology is essential for this task

Baseline for beached marine debris on Sand Island, Midway Atoll

Baseline measurements were made of the amount and weight of beached marine debris on Sand Island, Midway Atoll, June 2008–July 2010. On 23 surveys, 32,696 total debris objects (identifiable items and pieces) were collected; total weight was 740.4 kg. Seventy-two percent of the total was pieces; 91% of the pieces were made of plastic materials. Pieces were composed primarily of polyethylene and polypropylene. Identifiable items were 28% of the total; 88% of the identifiable items were in the fishing/aquaculture/ shipping-related and beverage/household products-related categories. Identifiable items were lowest during April–August, while pieces were at their lowest during June–August. Sites facing the North Pacific Gyre received the most debris and proportionately more pieces. More debris tended to be found on Sand Island when the Subtropical Convergence Zone was closer to the Atoll. This information can be used for potential mitigation and to understand the impacts of large-scale events such as the 2011 Japanese tsunami

Nocturnal Activity of Nesting Shrubland and Grassland Passerines

Nocturnal behaviors and sleep patterns of nesting passerines remain largely undocumented in the field and are important to understanding responses to environmental pressures such as predation. We used nocturnal video recordings to describe activity and quantify behaviors of females with nestlings of four shrub land bird species and three grassland bird species (n = 19 nests). Among the shrubland birds, Blue-winged Warbler (Vermivora pinus), Prairie Warbler (Setophaga discolor), and Indigo Bunting (Passerina cyanea) returned to the nest for the night at the same time, around sunset. Among the grassland birds, Eastern Meadowlark (Stumella magna) returned the earliest before sunset and Grasshopper Sparrow (Ammodramus savannarum) returned the latest after sunset. All species exhibited back sleep with the bill tucked under scapular feathers, and individuals awoke frequently for vigils or peeks at their surroundings. Sleep of all species was disrupted by nestling activity. Average duration of sleep bouts varied from 6 min (Grasshopper Sparrow) to 28 min (Blue-winged Warbler; Field Sparrow, Spizella pusilla). Mean overnight duration on the nest varied from 6.4 hr (Field Sparrow) to 8.8 hr (Indigo Bunting). On average, adults woke in the morning (the last waking before departing the nest) 20-30 min before sunrise. The first absence from the nest in the morning was short for all species, and nestlings were fed within 12 min of a parent\u27s departure. Our study highlights the need for further video research on sleep patterns of nesting birds in the field to better understand basic natural history, energetic cost-benefits of sleep, and behavioral adaptations to environmental pressures

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 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

Bird Productivity and Nest Predation in Agricultural Grasslands

Effective conservation strategies for grassland birds in agricultural landscapes require understanding how nesting success varies among different grassland habitats. A key component to this is identifying nest predators and how these predators vary by habitat. We quantified nesting activity of obligate grassland birds in three habitats [remnant prairie, cool-season grass Conservation Reserve Program (CRP) fields, and pastures) in southwest Wisconsin, 2002-2004. We determined nest predators using video cameras and examined predator activity using track stations. Bobolink (Dolichonyx oryzivorus) and Henslow\u27s Sparrow (Ammodramus henslowii) nested primarily in CRP fields, and Grasshopper Sparrow (A. savannarum) in remnant prairies. Eastern Meadowlark (Sturnella magna) nested evenly across all three habitats. Daily nest survival rate for Eastern Meadowlark varied by nesting stage alone. Daily nest survival rate for Grasshopper Sparrow varied by nest vegetation and distance to the nearest woody edge; nest survival was higher near woody edges. In CRP fields, most predators were grassland-associated, primarily thirteen-lined ground squirrels (Ictidomys tridecemlineatus). In pastures, one-third of the nest predators were grassland-associated (primarily thirteen-lined ground squirrels) and 56% were associated with woody habitats (primarily raccoons, Procyon lotor). Raccoon activity was greatest around pastures and lowest around prairies; regardless of habitat, raccoon activity along woody edges was twice that along non-woody edges. Thirteen-lined ground squirrel activity was greater along prairie edges than pastures and was greater along nonwoody edges compared to woody edges. In CRP fields, raccoon activity was greater along edges compared to the interiors; for ground squirrels these relationships were reversed. Using video camera technology to identify nest predators was indispensable in furthering our understanding of the grassland system. The challenge is to use that knowledge to develop management actions for both birds and predators

Monitoring of a southern giant petrel Macronectes giganteus population on the Frazier Islands, Wilkes Land, Antarctica

Since 1956, Southern Giant Petrels on the Frazier Islands, East Antarctica, have been counted with different census techniques, sometimes varying within seasons and among islands, which hindered analysis of the data. Protective measures for the islands from 1986 onwards have increased the need for reliable long-term census data, but reduced the ways to collect these data. Published and unpublished data were re-examined, and population trends were reconstructed based on two relatively standardised techniques: the number of active chicks (AC) and the number of apparently occupied nests (AON) around hatching. AC-values from Nelly Island from 1959 to 1998 indicate substantial periodic fluctuations, but no consistent long-term change. Since the late 1970s, AC-values on the other two islands and AON-values suggest that the breeding population may have grown by 35%. This recent growth, however, is within the extent of periodic fluctuations observed in Southern Giant Petrel population that is stable over the long ter