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Observations of unusual feeding behavior of white-winged dove on Chinese tallow.

White-winged doves (Zenaida asiatica asiatica) have become a common nonmigratory species in many urban areas of Texas including major cities such as Corpus Christi, San Antonio, and Waco (Schwertner et al., 2002; Small et al., 2006). Several factors have been attributed to their expansion into urban areas, including concentration of human habitation using landscape-promoting large shade trees, microhabitat warming from supplemental fossil-fuel heat sources, absorption and radiation of solar energy from asphalt and concrete, and backyard bird feeding (Schwertner et al., 2002). Though whitewinged doves consume a variety of native seeds such as doveweed (Croton setiger), leatherweed (Croton pottsii), and wild sunflower (Helianthus species; George et al., 1994), in San Antonio, large flocks of white-winged doves utilize neighboring agriculture fields to feed during the breeding season (West, 1993). Agricultural seeds include sorghum (Sorghum bicolor), commercial sunflower (Helianthus species), corn (Zea mays), and wheat (Triticum species) as well as mast from ornamental species during the breeding season (Schwertner et al., 2002). It remains unclear what white-winged doves feed on during the postbreeding season when grain fields used for foraging are unavailable. In south Texas, a majority of agricultural fields are disked after the crop is harvested and remain fallow until spring when planting of various agricultural crops resumes. The large white seeds of Chinese tallow (Triadica sebifera) have only been reported once as a relevant food source to white-winged doves (Schwertner et al., 2002), though other food sources include gum bumelia (Sideroxylon lanuginosum lanuginosum) and crushed or fragmented pecan (Carya illinoinensis). Chinese tallow is an exotic, invasive species that has expanded along the Texas coastal and prairie regions during the past several decades, converting natural habitat into monotypic stands of tallow trees (Conway et al., 2002; Burns and Miller, 2004). There is concern that avian species may continue to facilitate its spread through seed dispersal (Conway et al., 2002).

During the postbreeding months from october to January in 2013-2015, we observed the feeding behavior of white-winged doves on Chinese tallow seeds at two separate residential locations, one near Mathis (28.094[degrees]N 97.827[degrees]W) and the other in Corpus Christi, Texas (27.743[degrees]N 97.452[degrees]W). We made ~10 random observations of feeding by white-winged doves, generally in the late afternoon from 1630h to 1800h. We did not record the minimum number of birds, though at the Corpus Christi location in January, >30 white-winged doves were present in one tree. At the beginning of each postbreeding period, Chinese tallows had seeds. At each location, there were bird feeders, but they remained empty for the duration of the postbreeding season. Chinese tallow seeds ripen from September to October (Duke, 1983). The pods of the Chinese tallow were no longer green and closed, but instead, their outer black shells were open or in some cases had fallen to the ground. The large white seeds were available for birds to forage on without having to break the shell open.

[FIGURE 1 OMITTED]

White-winged doves appeared to employ two methods to attain the seeds from Chinese tallow trees. Most commonly, they would perch atop a branch using their tail for balance. As they attempted to maintain balance by moving their tail feathers up and down, they plucked the white seeds with their beaks from the seed pods one at a time, sometimes in an upside-down manner (Fig. 1). White-winged doves consumed each seed wholly and individually; Conway et al. (2002) noted that other bird species that consume tallow seeds usually scrape the seed coating before consuming the seeds. At other times, white-winged doves used their tail feathers to shake seeds free, and other doves consumed the seeds on the ground directly beneath the trees. It is unclear if the doves were working collaboratively or if the dove on the ground just happened to be beneath the branch when it occurred. All of the white-winged doves appeared to be adults, based on Fedynich et al. (2013).

As the postbreeding season progressed, white-winged doves began to feed in larger numbers at a single tree. By the end of January, a majority of seeds had been removed from every Chinese tallow tree on the two properties. Although white-winged doves remained within the neighborhoods after each tree was depleted of seeds, it remains unclear what other food sources they used until spring when native vegetation as well as agricultural crops became more available. Conway et al. (2002:554) noted "energy demands likely revolve around body maintenance and survival" during postbreeding months. The pulp of Chinese tallow seeds is composed mostly of saturated fatty acids (42.5-75.1% of total fatty acids) with a high-energy value of 33.5 kJ/g (Baldwin et al., 2008). Under these circumstances, the high oil and fatty-acid levels in Chinese tallow seeds may be important for whitewinged doves that remain as postbreeding residents.

White-winged doves, as well as other seed-eating avian species, feeding on Chinese tallow seeds may pose a serious ecological problem through seed dispersal. Goddard et al. (2009) documented Benghal dayflower (Commelina benghalensis) seed survivability in the guts of mourning dove (Zenaida macroura; a species closely related to white-winged doves), while Olin et al. (1989) suggested the possibility that some saguaro cactus (Carnegiea gigantea) seeds survived digestion by whitewinged doves. These suggest that the possibility may exist for seeds to survive digestion and later germinate, possibly because they are not being thoroughly crushed by the gizzard. This might lead to further loss of native grasslands and brushland by colonization of the invasive Chinese tallow plants (Conway et al., 2002). As whitewinged dove postbreeding grounds continue to expand into more northern areas, or if additional nonmigratory populations occur, it might lead to a feedback loop whereby most seeds are utilized by doves but a few survive digestion to germinate, creating an increased postbreeding food supply. Further complicating this problem is that many urban communities already have been planted with Chinese tallow because it is considered a suitable shade tree that is relatively free from disease and other pests (Jubinsky and Anderson, 1996; Burns and Miller, 2004). Additional studies concerning white-winged dove nutrition during the postbreeding months are needed to further understand this relationship and any impact it may pose for native habitat.

The authors wish to thank K. Bung and B. Bung for the use of their property. This is Caesar Kleberg Wildlife Research Institute manuscript #15-109.

LITERATURE CITED

BALDWIN, M. J., W. C. BARROW, JR., C. JESKE, AND F. C. ROHWER. 2008. Metabolizable energy in Chinese tallow fruit for yellow-rumped warblers, northern cardinals, and American robins. Wilson Journal of Ornithology 120:525-530.

BURNS, J. H., AND T. E. MILLER. 2004. Invasion of Chinese tallow (Sapium sebiferum) in the Lake Jackson area, Northern Florida. American Midland Naturalist 152:410-417.

CONWAY, W. C., L. M. SMITH, AND J. F. BERGAN. 2002. Avian use of Chinese tallow seeds in coastal Texas. Southwestern Naturalist 47:550-556.

DUKE, J. A. 1983. Handbook of energy crops. Purdue University Department of Horticulture and Landscape Architecture, West Lafayette, Indiana. Available at: https://www.hort. purdue.edu/newcrop/duke_energy/dukeindex.html. Accessed 1 October 2015.

FEDYNICH, A. M., W. C. COLSON, D. G. HEWITT, S. R. KREMER, AND C. D. MASON. 2013. Pilot study: aging classification criteria for fledged juvenile white-winged doves. Journal of Fish and Wildlife Management 4:290-297.

GEORGE, R. R., E. TOMLINSON, R. W. ENGEL-WILSON, G. L. WAGGERMAN, AND A. G. SPRATT. 1994. White-winged dove. Pages 29-50 in Migratory shore and upland game bird management in North America. Second edition (T. C. Tacha and C. E. Braun, editors). International Association of Fish and Wildlife Agencies, Washington, D.C.

GODDARD, R. H., T. M. WEBSTER, R. CARTER, AND T. L. GREY. 2009. Resistance of Benghal dayflower (Commelina benghalensis) seeds to harsh environments and the implications for dispersal by mourning doves (Zenaida macroura) in Georgia, USA. Weed Science 57:603-612.

JUBINSKY, G., AND L. C. ANDERSON. 1996. The invasive potential of Chinese tallow-tree (Sapium sebiferum Roxb.) in the Southeast. Castanea 61:226-231.

OLIN, G., S. M. ALCORN, AND J. M. ALCORN. 1989. Dispersal of viable saguaro seeds by white-winged doves (Zenaida asiatica). Southwestern Naturalist 34:281-284.

SCHWERTNER, T. W., H. A. MATHEWSON, J. A. ROBERSON, M. SMALL, AND G. L. WAGGERMAN. 2002. White-winged dove (Zenaida asiatica). Account 710 in The birds of North America (A. Poole and F. Gill, editors). Academy of Natural Sciences, Philadelphia, Pennsylvania; and American Ornithologists Union, Washington, D.C.

SMALL, M. F., C. L. SHAFFER, AND J. T. BACCUS. 2006. Historic and current distribution and abundance of white-winged doves (Zenaida asiatica) in the 48 United States. Texas Ornithological Society, Occasional Publication No. 6, San Antonio.

WEST, L. M. 1993. Ecology of breeding white-winged doves in the San Antonio metropolitan area. Ph.D. dissertation, Texas Tech University, Lubbock.

Submitted 10 July 2015. Acceptance recommended by Associate Editor, Gary D. Schnell, 5 February 2016.

William Colson *, Alan Fedynich

Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville, Kingsville, TX 78363

* Correspondent: willccolson@aol.com
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Title Annotation:NOTES
Author:Colson, William; Fedynich, Alan
Publication:Southwestern Naturalist
Article Type:Report
Date:Jun 1, 2016
Words:1493
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