Observations of unusual feeding behavior of white-winged dove on Chinese tallow.
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.
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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: email@example.com
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|Author:||Colson, William; Fedynich, Alan|
|Date:||Jun 1, 2016|
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