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

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 hav...

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Bibliographic Details
Published in:	Ecology (Durham) 2018-12, Vol.99 (12), p.2751-2762
Main Authors:	Haram, Linsey E., Kinney, Kaitlin A., Sotka, Erik E., Byers, James E.
Format:	Article
Language:	eng
Subjects:	Abundance Algae Animal behavior Aquatic birds Biodiversity Birds Density ecosystem engineers Ecosystems Engineers Estuaries Estuarine environments Foraging behavior Foraging habitats foundation species Habitat selection Habitats habitat‐modifying species Historical account Impact prediction Indigenous species Introduced species Invasive species Invertebrates Mud Mud flats Native species niche non‐native species novel ecosystems Predators Prey Regression analysis Seaweeds Sediment composition Sediments shorebirds soft sediment Species diversity
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Summary:	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
ISSN:	0012-9658 1939-9170