On the breeding biology of the Dusky-tailed Canastero Pseudasthenes humicola in central Chile

Abstract

The main habitat of the Dusky-tailed Canastero (Pseudasthenes humicola) is semiarid to arid zones cover with thorny bush thickets or cacti. Egg-laying started at the end of August and ended at the end of December. Its basket type nest varied between 26 to 76 cm in length and on average it was placed at about 1.8 m above the ground (n=58). Build mainly with thorny sticks and primarily in Espinos (Vachellia caven) (55,2%) or Trevos (Trevoa trinervis) (36,2%), (n=58). Its eggs were white non-shiny and their main shape was subelliptical (34,7%) short subelliptical (22,1%), and oval (20%). Its clutch size was between 3-4 eggs but mainly 3 (56,4%) eggs, n=62. Both adults incubate and the incubation period was 20,7 days, range 20-22 days (n=10) which is long for a small passerine. The nestlings at hatching were typical altricial and they departed the nest between 14-16 days, mainly at 15 days. The main food for nestlings were larvae of Lepidoptera: Geometridae. From 82 eggs, 39 (47,5%) nestlings left the nest successfully, which is within the range of altricial nestlings with cover nests. It is worth to mention that seven grown nestlings of 53 nestlings (13,2%) from different nests, were found dead on the nest, body intact but with large hematomas on body but mainly on head. It seems a type of direct but passive infanticide.