Population biology of the common ground dove and ecological relationships with mourning and white-winged doves in south Texas

Abstract

Breeding biology, behavior, and food habits of the common ground dove (Columbina passerina) in native brushlands of Live Oak County, Texas were investigated during 1978-80. Comparative data from mourning (Zenaida macroura) and white-winged doves (Zenaida asiatica) also were obtained for some aspects of breeding biology and food habits. Nesting records and gonadal sizes of collected birds indicated ground and mourning doves nested from late March through mid-October, while whitewings nested from May-August. The whitewing breeding pattern apparently was correlated with the ripening and harvesting of wheat and sorghum crops. Mourning dove nests were found most frequently (62") in mesquite (Prosopis glandulosa) and colima (Zanthoxylum fagara), while ground doves most often (47%) nested in blackbrush (Acacia rjgidula) and prickly pear (Opuntia sp.). Forty ground dove nests averaged 1.5 m above the ground, while 32 mourning dove nests averaged 2.1 m high. Incubation patterns of male and female ground doves were typical of the pigeon family; males attended the nest from late morning to late afternoon while females were on the nests the remainder of the day. Nest exchange in ground doves occurred without ritualized "greeting" behavior as reported for other species. Courtship calls increased from March through mid- June, then remained constant until mid-September when a decline occurred. No calls were heard after October. Copulation, which was observed twice in ground doves, followed the "bow-coo" display with no food-solicitation behavior. Chase flights consisting of a female, her mate, and 1-3 male pursuers frequently were observed during the breeding season. Chase flights in the ground dove were more analogous to rape flights of waterfowl rather than the territorial pursuits reported for mourning doves. Hatching dates of juvenile ground doves backdated from primary feather molt indicated a peak in hatching during late April-early May. One-third of the juveniles captured during June-August were hatched between 1-LO May. Age ratios increased from 0 juveniles per adult in April to 1.5 juveniles per adult in September. Peak numbers of adults were captured during 1101-1200, while the highest numbers of juveniles were captured during 1301-1400. Ground doves frequented watering sites nearly exclusively during mid-day (0900-1600) in contrast to mourning and white-winged doves, which visited watering sites mainly during early morning and late afternoon. Based on gonadal inspections of collected ground doves, breeding by juveniles contributed an additional 12-21% to the annual recruitment in a simulated population model. Juveniles were capable of breeding when approximately 79 days old. Gonadal activity in juveniles terminated in mid-October, similar to the adult pattern. Adult juvenile males replaced their primary feathers at faster rates than females of their respective age classes. Primary feather molt in adults began during May and apparently terminated in October or November. Food habits were determined from analysis of crop contents from 107 ground, 72 mourning, and 45 white-winged doves. All species consumed large quantities of doveweed (Croton spp.) seeds. Ground and mourning doves mainly utilized native seeds of forbs and grasses while white- wings were dependent on agricultural crops, especially wheat, sorghum and corn. Ground doves expended over 75% of their feeding time during the spring consuming very small seeds such as wood-sorrel (Oxalis sp.) and copper!eaf (Acalypha radians). Niche breadth for food utilization varied from 1.00 for whitewings in the fall (100% for doveweed) to 9.45 for ground doves in the spring. Food niche overlap indicated similar food habits between mourning and whitewings in the spring, but different from ground dove use. Overlap among all 3 species was high during the summer because of the increased use of doveweed by all doves. Ground doves were classed as generalists, whitewings relative specialists, and mourning doves somewhat ambiguous in their food habits. Snail shells were consumed by all species possibly to offset losses of calcium during the reproductive season.