Reproductive success of the interior least tern (Sterna antillarum) in relation to hydrology on the Lower Mississippi River

Abstract

The annual hydrograph of large rivers, including flood pulses and low-flow periods, is believed to play a primary role in the productivity of biota associated with these ecosystems. We investigated the relationship between river hydrology and Interior least tern (Sterna antillarum) reproductive success on the Lower Mississippi River from April to July 1986-1993. The number of fledglings produced per adult pair was negatively correlated with July mean (r= −0.95, p=0.0004) and July maximum river elevation (r= −0.97, p=0.0001), but no other aspects of river hydrology were related to tern reproduction. Low-water elevations in July may benefit least tern reproductive success by increasing sand island area or the area of shallow-water habitat that surrounds islands. Loss of deep-water habitats in conjunction with an increase in shallow habitat during stage decreases may concentrate fish prey in shallow-water habitats and backwater areas, thereby increasing food availability during chick-rearing.

Effects of temperature and precipitation on grassland bird nesting success as mediated by patch size

“…In these cases, wetter than normal conditions could directly affect nest survival through flooding or decreased foraging efficiency (Dugger et al. ; Moreno & Møller ; Skagen & Yackel Adams ). There is increasing recognition that precipitation is an important component of grassland bird range shifts (McCauley et al.…”

Changes in hydrologic regime by dams

“…But adjustments to high flows are not the exclusive cause of diminished ecological integrity. Other components of the hydrograph and flow duration curve also have corresponding ecological responses, especially those associated with changes in the timing and duration of flows and in the rates of change and frequency of hydrograph rises and falls (Richter et al, 1996;Poff et al, 1997;Hadley and Emmett, 1998;Puckridge et al, 1998;Dugger et al, 2002). For example, sudden increases in bar saturation by rapid flow releases during hydropower production enhance bar erosion through abrupt changes in pore water pressure leading to sapping.…”

Short-Term Assessment of Morphological Change on Five Lower Mississippi River Islands

“…For example, Least Terns are highly impacted by increases in river stage that decrease available nesting site area; thus, only higher elevation islands may provide useful nesting grounds for this endangered species (Dugger et al 2002). Likewise, a strong relation exists between vegetation and fluvial dynamics (Cooperman and Brewer 2005), with the two main driving variables of vegetation being the flood/flow pulse and sediment dynamics (Steiger et al 2005).…”