Invasive ecosystem engineers both positively and negatively affect their recipient ecosystems by generating novel habitats. Many studies have focused on alterations to ecosystem properties and to native species diversity and abundance caused by invasive engineers. However, relatively few studies have documented the extent to which behaviors of native species are affected. The red seaweed Gracilaria vermiculophylla (Rhodophyta) invaded estuaries of the southeastern United States within the last few decades and now provides abundant aboveground vegetative cover on intertidal mudflats that were historically devoid of seaweeds. We hypothesized that G. vermiculophylla would affect the foraging behavior of native shorebirds positively for birds that target seaweed‐associated invertebrates or negatively for birds that target prey on or within the sediment now covered with seaweed. Visual surveys of mudflats >1 ha in size revealed that more shorebirds occurred on mudflats with G. vermiculophylla relative to mudflats without G. vermiculophylla. This increased density was consistent across 7 of 8 species, with the one exception being the semipalmated plover Charadrius semipalmatus. A regression‐based analysis indicated that while algal presence predicted shorebird density, densities of some bird species depended on sediment composition and infaunal invertebrate densities. At smaller spatial scales (200 m2 and <1 m2), experimental removals and additions of G. vermiculophylla and focal observations showed strong variation in behavioral response to G. vermiculophylla among bird species. Birds preferentially foraged in bare mud (e.g., C. semipalmatus), in G. vermiculophylla (e.g., Arenaria interpres), or displayed no preference for either habitat (e.g., Tringa semipalmata). Thus, while the presence of the invasive ecosystem engineer on a mudflat appeared to attract greater numbers of these predators, shorebird species differed in their behavioral responses at the smaller spatial scales that affect their foraging. Our research illuminates the need to account for species identity, individual behavior, and scale when predicting the impacts of invasive species on native communities.

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Native predators can confer biotic resistance through consumption of invasive prey. However, early in the invasion process, native predators may initially ignore an invader when it is rare and only increase consumption once it becomes abundant. Furthermore, the willingness of native predators to consume novel invasive prey may be in uenced by the similarity of the invader to other native prey species that are favored or familiar. Here we examined whether a native predator (the common mudcrab, Panopeus herbstii) consumes the invasive lter-feeding crab, Petrolisthes armatus as a function of Pe. armatus abundance relative to native prey and the similarity of Pe. armatus to native prey. Using choice experiments, we quanti ed consumption of invasive Pe. armatus when its abundance was either rare, equal, or more abundant than native prey that were either taxonomically similar (crab, Eurypanoepus depressus) or dissimilar (mussel, Geukensia demissa) to the invader. We found that the absolute consumption of invasive Pe. armatus increased as its relative availability increased, but only in treatments where the alternative prey was a native crab. This suggests that prior experience of the native predator with a similar prey may prime the predator to consume more invasive Pe. armatus. A hierarchical Bayesian analysis determined that both native prey species were preferentially consumed by the native predator Pa. herbstii even when native prey were rare or equal in abundance to invasive Pe. armatus. These results suggest that density-dependent predation plus a persistent preference for native prey by native Pa. herbstii predators may help explain how Pe. armatus escapes its natural enemies.

Although scientists strive to accurately communicate their research, disconnects can arise between results and rhetoric. Some have regarded invasion scientists as particularly prone to using value-laden language incommensurate with the scientific facts or results. We addressed how authors used 10 near synonyms (words for which usage is similar but not completely overlapping) of the negative-value word invasive. We asked whether study findings (effect sizes) or other factors predicted language use. The use of negative-value words such as invasive was not associated with study findings but, instead, with contextual factors. For example, plant and invertebrate biologists used more negative language to describe nonnatives than did those studying vertebrates. The authors also tended to use more negative language in recently published papers than in older studies. Although many have called for impartial language when communicating research, some scientists use language imbued with value that may be inappropriate. Such use may affect how the public perceives scientific findings.