Nesting and foraging ecology of interior least terns (Sterna antillarum athalassos) nesting on reclaimed surface coal mine spoil in east-central Texas

A thorough understanding of the breeding ecology of Interior Least Terns (Sterna antillarum athalassos) is necessary for the conservation of this endangered species. Foraging ecology of the species is understudied in interior populations. Studies are lacking for interior nesting at artificial sites, which are inherently different from natural sites. This study examined the foraging and nesting ecology of Interior Least Terns nesting on reclaimed surface coal mine spoil at Big Brown Mine in Freestone County, Texas. In an experiment testing the effects of fish density on tern use, artificial stocking of sediment ponds was used to establish ponds with different fish densities, with 9 ponds used in 2000 and 12 in 2001. Fish density was not important in determining pond use by Least Terns on the mine. However, the physical characteristics of the ponds were very important in determining which ponds were used and the manner in which terns utilized them. Foraging ponds were old, clear ponds in old reclamation while loafing ponds were young, turbid ponds with mudflats or floating objects in newly reclaimed landscapes. Turbidity, wind, water surface conditions, and sky conditions, and time of day affected foraging success, with reduced effects of weather at clear ponds, suggesting that tern preference for foraging at clear ponds is reinforced by the effects of abiotic factors. Tern nest success was limited each year, with May rainfall causing egg-sticking and predation by mammals (primarily coyotes) contributing to nest failure. Sites used for nesting at Big Brown were larger in area, more recently disturbed, and had less silt in soils than unused potential sites. In 2002, 13 colonies were found around Texas on the Red River, reservoirs, and a gravel quarry. Big Brown colony sites were larger and farther from loafing sites, with more grasses present than at other Texas sites. Big Brown colony sites also had less sand and gravel than other Texas sites. Big Brown and other Texas colony sites were both in very recently disturbed landscapes, with human disturbance of the landscape creating nesting habitat throughout the state.