THE SUMMER DIET OF THE YELLOW RAIL IN SOUTHERN QUEBEC

摘要

We documented Yellow Rail (Coturnicops noveboracensis) food habits through the use of tartar emetic, a non-destructive method to collect stomach contents. A total of 71 rails were forced to regurgitate during 9 Jun.-25 Aug. 1994 and 16 May-31 Jul. 1995, from which we obtained 105 emetic samples. Almost 95% (99/105) of samples contained food items. Overall, mean number of taxa within one sample was 4.7 (SD = 3.2; Range = 1-13; N = 99): 1.1 (SD = 1.6; Range = 0-7) for seeds and 3.6 (SD = 2.1; Range = 0-8) for invertebrates. Sand grit, feather fragments, and plant fragments were also identified in many samples. Totals of 1169 organisms from 52 taxa were identified and counted in the samples: 372 seeds from 18 taxa and 797 invertebrates from 34 taxa. Invertebrates and seeds had relative frequencies of 68.1% and 31.9%, respectively, and the mean number of individuals counted within samples was significantly higher (P < 0.001) for invertebrates (Mean = 8.1; SE = 0.8; Range = 0-44) than for seeds (Mean = 3.8; SE = 0.9; Range = 0-44). Among the first group, Coleoptera (beetles) were by far the most important food, representing almost two-thirds of invertebrates eaten and having a relative frequency of 42.5%. Araneae (spiders) were second, with a relative frequency of 13.3%, while other taxa ranked far lower. Of seeds identified, Cyperaceae (sedges) and Juncaceae (rushes), particularly genera such as Carex, Juncus, and Eleocharis, were the most important food items, with relative frequencies of 12.7%, 6.5%, and 3.1%, respectively. According to our results, during summer the Yellow Rail is mostly an arthropod-feeder that complements its diet with seeds. Effects of tartar emetic on birds were negligible and this technique appeared to be very successful, suggesting that it could be used as an alternative to sacrificing rails in future dietary studies.