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 facto r limiting productivity of eastern white-winged doves (Zenaida asiatic a asiatica) in the Lower Rio Grande Valley (LRGV) of Texas where popul ations have declined 75-90% since the 1920's. We studied variation in body composition among prenesting and first- and second-nesting attemp ts (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 h abitat use and selection, frequency of occurrence of food items, and d iet composition also were studied. We tested the hypothesis that produ ction of young from multiple nesting efforts is energy or protein limi ted. 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 loss es of lipid, protein, or ash in either year between first-nesting dove s that layed eggs and second-nesting doves that had young within 4 day s of fledging. Lipid, protein, and ash masses (g) differed (P less tha n or equal to 0.072) among nest stages, and there was an interaction e ffect of nesting status and nest stage on lipid mass (P = 0.032) in 19 91. Body composition did not vary (P > 0.10) in 1992. In 1991, dove li pid mass was lowest at prenesting, increased after laying, peaked at h atching, and declined between hatching and fledging of young during th e first nest. Lipid masses increased during incubation and peaked at h atching in doves from second nestings in 1991, but did not decline dur ing brooding of young. Patterns of changes in lipid mass suggest that doves were capable of maintaining a positive energy balance in both ye ars of this study. Habitat use and selection, frequency of occurrence of foods, and diet composition of doves indicated that doves used habi tats containing high-energy grains and seeds heavily, and consumed tho se foods when available. Grains were important food sources for nestin g doves, with sorghum accounting for 28-40% of dry-weight crop content s and sunflower accounting for 22-38%. Improvement in condition throug h 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 tat but also as a primary source of food during prenesting and early f irst-nesting periods. We also recommend planting food plots of high-qu ality grain that will mature during the arrival (mid- to late April) o f prenesting white-winged doves.