Bioenergetics of White-Winged Dove Reproduction in the Lower Rio Grande Valley of Texas

Availability of high-quality food has been proposed as a primary factor limiting productivity of eastern white-winged doves (Zenaida asiatica asiatica) in the Lower Rio Grande Valley (LRGV) of Texas where populations have declined 75-90% since the 1920's. We studied variation in body composition among prenesting and first- and second-nesting attempts (nesting status levels); laying, hatching, and prefledging periods (nest stages) within nesting attempts; and between sexes and years of breeding white-winged doves during May-July 1991 and 1992 in the LRGV of Texas. Effects of nesting status, nest stage, sex, and/or year on habitat use and selection, frequency of occurrence of food items, and diet composition also were studied. We tested the hypothesis that production of young from multiple nesting efforts is energy or protein limited. Spring and summer rainfall was near to above average during both years of this study, and productivity did not appear to be limited by availability of energy or protein in the diet. We observed no net losses of lipid, protein, or ash in either year between first-nesting doves that layed eggs and second-nesting doves that had young within 4 days of fledging. Lipid, protein, and ash masses (g) differed (P ≤ 0.072) among nest stages, and there was an interaction effect of nesting status and nest stage on lipid mass (P = 0.032) in 1991. Body composition did not vary (P > 0.10) in 1992. In 1991, dove lipid mass was lowest at prenesting, increased after laying, peaked at hatching, and declined between hatching and fledging of young during the first nest. Lipid masses increased during incubation and peaked at hatching in doves from second nestings in 1991, but did not decline during brooding of young. Patterns of changes in lipid mass suggest that doves were capable of maintaining a positive energy balance in both years of this study. Habitat use and selection, frequency of occurrence of foods, and diet composition of doves indicated that doves used habitats containing high-energy grains and seeds heavily, and consumed those foods when available. Grains were important food sources for nesting doves, with sorghum accounting for 28-40% of dry-weight crop contents and sunflower accounting for 22-38%. Improvement in condition through the nesting cycles was directly related to the availability and use of these high-energy agricultural grains. We recommend conservation of native woodlands throughout the LRGV, not only as stable nesting habi