Insects found in birds’ nests from Argentina. Furnarius rufus (Gmelin, 1788) (Aves: Furnariidae) and their inquiline birds, the true hosts of Acanthocrios furnarii (Cordero & Vogelsang, 1928) (Hemiptera: Heteroptera: Cimicidae) 2700 Author Turienzo, Paola Author Iorio, Osvaldo Di text Zootaxa 2010 2010-12-03 2700 1 112 journal article 1175­5334 Ic. Mammalia Mammals and/or signs of their activity (fecal pellets and food remains) were found in 10 (3.98 %) of the 251 examined nests ( Table 1 , Appendix II). Didelphis albiventris Lund, 1840 [Marsupialia: Didelphidae ] Two previous records of Didelphis albiventris were made (Appendix Ia). Nevertheless, very probably these records were because of young opossums (an adult opossum can not enter the narrow entrance and the opossum is larger than the volume of the breeding chamber) ( Fig. 4 ). In fact, two young opossums were found, one from Entre Ríos (ER # 1) and the second from Buenos Aires (BA # 123). In the first case, the nest in which it was living was totally clean and devoid of any material. In the second, the original bed of grasses of F. rufus was still present. FIGURE 34. Eggs of Passer domesticus inside the nests of Furnarius rufus . Letters and numbers correspond to the nests in the Appendix IIc. FIGURE 35. Eggs of Sicalis flaveola pelzelni (BA # 27, BA # 28, BA # 65, BA # 125, BA # 135) and Troglodytes aedon (BA # 25) inside the nests of Furnarius rufus . Graomys griseoflavus (Waterhouse, 1837) [ Rodentia : Muridae ] ( Fig. 32 ) Graomys griseoflavus is an arboreal species, previously found in stick nests of other Furnariidae birds in Argentina ( Hershkovitz 1962 ). One nest of F. rufus from La Pampa was inhabited by three individual [MACN] of G. griseoflavus (Appendix IIc). The nest of this rodent is made with very small pieces of grasses (probably from the bed of F. rufus ), mixed with a great amount of small hairs and remains of food (broken endocarps of Prosopis caldenia Burkart [ Mimosaceae ] in the nests from La Pampa ) ( Fig. 32 ). Unidentified rodents In other cases, the rodents were not found or escaped, but their presence can be detected by fecal pellets, food remains (Appendix IIc), and/or the particular odour of the materials. Apparently, one nest of F.rufus was cleaned by the rodent because no remains of the bed of grasses were found (SF # 1). In a second case, the bed of grasses of F. rufus was covered by a layer of open endocarps of Melia azedarach L. [ Meliaceae ], mixed with fecal pellets (BA # 107). In a third nest, a small rodent, probably young (escaped), builds its own nest with the grasses of one abandoned nest of P. domesticus with five rotten eggs (BA # 141). In a fourth nest (BA # 171) three lactants were captured inside a nest of grasses, hairs, and yarns, recently built with the bed of F. rufus and a nest of S. f. pelzelni .