Do Band-Tailed Pigeons Seek a Calcium Supplement at Mineral Sites?

Abstract

Abstract We tested the hypotheses that mineral sites in western Oregon are used by Band-tailed Pigeons (Columba fasciata) to supplement dietary calcium and sodium. We compared mineral composition of sites used by Band-tailed Pigeons, adjacent unused sites, and three major food items during the nesting season. Sixty-five percent of used mineral sites were low in calcium (<200 ppm), whereas mean concentrations in food items were high (1,960–2,290 ppm). All but one used mineral site were high in sodium (≥678 ppm), whereas mean concentrations in food items were low (20–254 ppm). Food items were high in mean concentrations of potassium (12,470–26,980 ppm) and potassium:sodium ratios (138–656). Used and adjacent, unused, estuary mineral sites were similar in calcium and sodium concentrations. We hypothesize that because of insufficient sodium intake and inefficient sodium retention, Band-tailed Pigeons seek a sodium source to supplement their diet during the nesting season. Use of mineral sites probably depends upon sodium concentration, but also vegetation structure, development, human activity, and congregation use by Band-tailed Pigeons. Used mineral sites appear to be scarce in western Oregon, and are seemingly essential resources for this species. Eighty-six percent of known currently-used mineral sites are privately owned and subject to possible alteration from land-use practices. Mineral sites used by Band-tailed Pigeons should be included in the overall management scheme for maintaining stable breeding populations of this species.