八色鳥(Pitta nympha)在巢內放置哺乳動物糞便的行為探討

Abstract

The rate of nesting success in birds is directly in relation to an individual’s fitness and population size. A nest is composed of materials collected by the adults, and the nesting material determines its safety and thus nesting success. It’s uncommon for birds to place or utilize animal dung in nests; however, the presence of mammalian dung was discovered in the nests of Fairy Pitta (Pitta nympha, family Passeriformes). In order to understand the generality of this behavior and the probable functions of mammalian dung and other mammalian dung-like substance (both are denominated as MDS) in Fairy Pitta nests, I used video recording, photograph taking and regular nest checking to observe nests in the Linnei Township of Yunlin County from May to July of 2009 and 2010. The types, placed period, location, quantity and quality of MDS were recorded. To ascertain the role of MDS, I examined the behavior by testing anti-predation hypothesis and heating hypothesis. The anti-predation hypothesis proposed that MDS could decrease the predation risk of eggs and chicks in nests, and thus increase the survival rate of nests, while the heating hypothesis proposed that MDS had the potential to produce heat and increase the temperature of nests. Within 33 Fairy Pitta nests, including 76 stages (which include building, egg-laying, early-incubation, late-incubation, early-nestling and late-nestling stages), 76.3% of nests (n=25) were observed with MDS using behavior. The types of MDS can be divided into three categories: mammalian dung, soil and others, with mammalian dung appearing most frequently (67%). The mammalian dung was later determined as the dung of Formosan macaque (Macaca cyclopis) and Masked Palm Civet (Paguma larvata). The placed stage of MDS was most frequent in the late-incubation, early-nestling and late-nestling stages (87.5%, 90.9%, and 100%). The location of MDS was mostly at the region which is zero to five centimeters inside the entrance of the nests (56.9%), and the second most common region was zero to five centimeters outside the entrance of the nests (34.5%). I used artificial nests and quail eggs to test the anti-predation hypothesis and the heating hypothesis, with the dung of Formosan macaque as the MDS. The daily survival rates of artificial nests supported the anti-predation hypothesis. Nests with the dung of Formosan macaque (n=71) have significantly higher daily survival rate (0.934±0.0013) than those without dung (n=71, daily survival rate= 0.923±0.0014; p<0.001). The temperature of nests with or without the dung of Formosan macaque did not show a significant difference. Results from my field observation did not support the heating hypothesis. In conclusion, the majority of breeding Fairy Pittas do in fact place mammalian dung and mammalian dung-like substance inside their nests and the function of this behavior may be related to anti-predation.