Background Least terns (Sternula antillarum) are fish-eating birds that nest in a variety of open habitats on rivers and coasts (Thompson et al.

1997).

The interior population of the Least Tern (ILT) is defined as all Least Terns nesting >50 miles from the Gulf of Mexico on

credit:

rivers of the Great Plains and in the Lower Mississippi Valley (USFWS 1985, 1990).

Most individuals of this population nest on sandbars with little to no vegetation that are located on large rivers, primarily the Mississippi, Red, Arkansas, Canadian, Missouri, and Platte (Lott 2006).

ILT was listed as endangered by the United States Fish and Wildlife Service (USFWS)in 1985 due to concerns about breeding habitat loss and degradation associated with water resource development projects, which affect a large proportion of this population (USFWS 1985).

Large multi-purpose dams, engineered navigation systems, bank stabilization projects, and wells or canals that remove water for irrigated agriculture affect ILT nesting habitat across much of their range (USFWS 1990).

Many of the large dams and navigation systems in the range of ILT are operated by USACE (U.

S.

Army Corps of Engineers 1999, 2002, 2003, 2004a, 2004b, 2005) as detailed in the incidental take statement of the 2016 PBO in accordance with the Endangered Species Act (ESA) (USFWS 2016).

Historically, sandbar nesting habitat on many rivers throughout the range of ILT has been lost or strongly degraded due to channel responses to large dam placement or channelization for navigation (Friedman et al.

1998, Funk and Robinson 1974, Williams 1978, Stinnett et al.

1988, Tommelleri 1984, and Knoll 2006).

In addition to this initial (and in some cases, ongoing) pulse of habitat loss during channel adjustment to large-scale river engineering, multi-purpose dam operations continue to have direct effects on ILT reproductive success (e.g., nest and chick mortality due to flooding) that are strongest directly below 8 large multi-purpose dams on the Arkansas, Red, Canadian, and Missouri Rivers (USFWS 2003, 2005a).

For this project all efforts will be concentrated on the Arkansas River between Fort Smith and the Mississippi River.

In addition to the Arkansas River, least terns have been documented nesting on rooftops within the Arkansas River Valley.

These are flat rooftops, fully or partially covered with small river rock or pea gravel, at least superficially resembling riverine, island/sandbar nesting habitat of Least Terns (Forys and Borboen-Abrams 2006).

These sites are also monitored with the appropriate permissions.

Brief Description of Anticipated Work It was determined that traditional navigation and hydroelectric operations on the Arkansas River from Oklahoma to Arkansas has had detrimental effects on the ILT population.

Once we understood how our actions were impacting the ILT bird population we needed to ascertain through research how badly as well as exploring different conservation measures that would stabilize and support the remaining birds.

Field work includes conducting breeding season, nest monitoring and inventory as well as habitat assessments of the interior least terns.

The research will cover monitoring at least 12 river colony locations and 3-5 rooftop colonies within the Arkansas River Valley from downstream of Wilbur D.

Mills Dam at river mile (RM) 10 to roughly RM 285 of the MKARNS in Arkansas.