Mixed effects of an introduced ecosystem engineer on the foraging behavior and habitat selection of predators

• Published in: Ecology
• Main Authors: Haram, Linsey E., Kinney, Kaitlin A., Sotka, Erik E., Byers, James E.
• Other Authors: National Science Foundation, National Oceanic and Atmospheric Administration
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Arenaria interpres
• Online Access: http://dx.doi.org/10.1002/ecy.2495; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fecy.2495; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ecy.2495; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ecy.2495; https://onlinelibrary.wiley.com/doi/am-pdf/10.1002/ecy.2495; https://esajournals.onlinelibrary.wiley.com/doi/am-pdf/10.1002/ecy.2495; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecy.2495

Abstract 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 m 2 and <1 m 2 ), 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 ...