Abstract. The extent to which resource subsidies affect food web dynamics is poorly understood in anthropogenic landscapes. To better understand how species interactions are influenced by subsidies, we studied breeding birds and nest predators along a rural-to-urban landscape gradient that varied in subsidies provided to generalist predators. We hypothesized that resource subsidies in urban landscapes would decouple predator-prey relationships, as predators switch from natural to anthropogenic foods. From 2004 to 2009, we surveyed nest predators and monitored 2942 nests of five songbird species breeding in 19 mature forest stands in Ohio, USA. Eighteen species were video-recorded depredating nests. Numbers of avian and mammalian nest predators were positively associated with the amount of urban development surrounding forests, with the exception of Brown-headed Cowbirds (Molothrus ater). Although nest survival strongly declined with detections of nest predators in rural landscapes, nest survival and predator numbers were unrelated in urban landscapes. Thus, the strength of interaction between breeding birds and nest predators diminished as landscapes surrounding forested parks became more urbanized. Our work suggests that decoupling of predator-prey relationships can arise when synanthropic predators are heavily subsidized by anthropogenic resources. In this way, human drivers can alter, and completely disarticulate, relationships among species that are well established in more natural systems.

Optimal defense theory (ODT) predicts antiherbivore defensive compounds will be allocated so that the most valuable or most susceptible tissues will be best defended. The growth-differentiation balance hypothesis (GDBH) predicts that defense allocation will be a result of trade-offs between growth and defense. Thus, these two theories predict opposite allocation patterns with respect to ''valuable,'' actively growing meristematic and reproductive tissues. ODT predicts that meristems and reproductive tissues should have higher defense levels than nonmeristematic vegetative tissues; the GDBH predicts the defense levels of meristems and reproductive tissues will be lower than vegetative tissues. We examined allocation patterns of phlorotannins in 21 species of kelps (Order Laminariales) and rockweeds (Order Fucales) from nine sites on the west coast of the United States to determine if allocation patterns better matched the predictions of ODT or the GDBH and to look for differences in allocation patterns among sites. Within-species differences in phlorotannin levels occurred in 10 of the 21 species examined. Meristems of both kelps and rockweeds had higher phlorotannin levels than nonmeristematic vegetative tissues, consistent with ODT. Phlorotannin levels in reproductive tissues of kelps were higher than vegetative tissues, but levels in reproductive tissues of rockweeds were lower than vegetative tissues, indicating that allocation strategies may follow taxonomic lines. Allocation patterns differed among sites in four of the 16 species collected from more than one site. Differences in allocation patterns among sites were usually changes in the ratios of phlorotannins in well-defended compared to poorly defended tissues, rather than changes in which tissues were well defended or poorly defended. We concluded that environmental variability can have large effects on the concentration of phlorotannins in algae but has limited effects on allocation patterns among tissues.

Estimating the population density of deer is an essential task for public agencies that plan a herd reduction. Distance sampling has been increasingly utilized to estimate population density, and is used by the National Park Service to estimate white‐tailed deer (Odocoileus virginianus) densities throughout the eastern United States. Many of these surveys are conducted along public roads due to limited resources and accessibility, which may violate a critical assumption of distance sampling and potentially introduce sampling bias. We used infrared cameras to confirm deer activity with respect to survey roads at 2 national parks in Maryland, USA (Catoctin National Park and Antietam National Historic Battlefield), during 2005 and 2006 and compared results with the predicted distributions. The number of deer observed during road surveys declined with distance intervals at Catoctin, but there was a similar amount of deer activity at each distance interval. At Antietam, survey observations maintained a constant level of activity beyond 200 m from the survey route, while deer activity was inconsistent between distance intervals. The mean number of deer photographs/day/sample point did vary significantly across distance intervals from the survey route at Antietam, but not at Catoctin. In Antietam, the uneven distribution of agricultural fields and public roads were significant predictors of deer activity detected during the camera surveys. At Catoctin, the fit of the detection function was improved by expanding the first distance interval. Although density estimation using DISTANCE can account for most sources of error introduced by use of public roads, our data indicate bias is likely to occur in landscapes with high road densities and long sight distances. © 2011 The Wildlife Society.

In urban landscapes, predators are often more abundant or diverse than in rural areas, but few studies have examined how the identity of actual nest predators varies with urbanization. From 2007 to 2010, we used time-lapsed video to record activity at nests of the Northern Cardinal (Cardinalis cardinalis). Acadian Flycatcher (Empidonax virescens). Gray Catbird (Dumetella carolinensis), and Wood Thrush (Hylocichla tnitstelina) in riparian forests in urban and rural landscapes of Ohio, and we examined the extent to which predator identity was predicted by landscape composition. In 99 records of depredation, we identified 21 species of nest predators (17 in rural, 15 in urban). No single species dominated, though the Brown-headed Cowbird {Molothrus ater; 18% of recorded depredations) and northern raccoon {Procyon lotor; 11%) were the most commonly recorded predators. Birds were responsible for 62% of depredations, followed by mammals (36%) and snakes (2%). By category of predator, mesopredators were the most likely to remove all nest contents, depredate nests at night, and concentrate on the nestling stage. Mesopredators also were most important in urban landscapes, accounting for 35% of urban but only 13% of rural depredations. Small birds (46%), including the cowbird. Common Grackle (^Í/MCÍZ/ÍW quiscula), and House Wren {Troglodytes aedon), plus raptors (21%), were responsible for most rural depredations. The relative proportion of nests depredated by mesopredators increased as the landscape surrounding a forest urbanized. These data indicate that the composition of the actual predator community may not mirror patterns of abundance or diversity along the rural-to-urban gradient. Cambio de Depredadores de Nido Dominantes a lo largo de un Gradiente Rural-UrbanoResumen. En paisajes urbanos, los depredadores son generalmente más abundantes o más diversos que en áreas rurales, pero pocos estudios han examinado como varia la identidad de los depredadores con la urbanización. Desde 2007 a 2010, utilizamos grabaciones de video para registrar la actividad en nidos de Cardinalis cardinalis, Empidonax virescens, Dumetella carolinensis y Hylocichla mustelina en bosques ribereños en paisajes rurales y urbanos de Ohio. También examinamos el grado ai cual era posible predecir la identidad de los depredadores con base en la composición del paisaje. En 99 registros de depredación, identificamos 21 especies de depredadores de nidos (17 en la localidad rural y 15 en la urbana). Ninguna especie fue dominante, aunque Molothrus ater (18% de las depredaciones registradas) y Procyon lotor (11% de las depredaciones registradas) fueron los depredadores más comunes. Las aves fueron responsables del 62% de las depredaciones, seguidas por los mamiferos (36%) y las serpientes (2%). Por categoria de depredador, los de mediano porte fueron los que tuvieron mayor probabilidad de remover todo el contenido del nido, de depredar los nidos en la noche y de concentrar su actividad durante el periodo de pichones. Los depredadores de mediano porte tambi...

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