Breeding Biology of the White-Throated Cacholote Pseudoseisura gutturalis ochroleuca, an Endemic Bird of the Monte Desert

Abstract

The White-throated Cacholote Pseudoseisura gutturalis is a little studied, socially monogamous furnariid, endemic to arid Argentina. Here we provide novel information to characterize the breeding biology of the northern subspecies ochroleuca in the Monte Desert, Argentina, and discuss the similari ties and differences with other Pseudoseisura species. Nests were bulky enclosed structures constructed with thorny sticks and twigs of native plant species (n = 15) and 47% of them had objects used as external decorations. Nests had an entrance tube oriented preferentially towards the northeast, prob ably to avoid the prevailing south-southeast winds at the study site, and were placed at a mean height of 2.1 m above the ground (n = 13). Most of the active nests (93%) were built in columnar cacti Trichocereus atacamensis that were healthier and with fewer branches than nearby available conspecifics. Mean clutch size was 3.2 white eggs (n = 9) and the incubation period was c. 18–20 days. Brood size ranged from one to three hatchlings (n = 12) and nestlings remained in the nest for 24–26 days until fledgling. Nests with complete clutches were found between 29 October and 1 February and nestlings were found between 1 November and 5 February. Nestlings were attended by both parents and were fed with arthropods (n = 63) and vertebrates (n = 7). Nest visitation rate per nestling was similar among nests with three and two nestlings and lower than for a nest with one nestling. The breeding success was high during the incubation (73%) and nestling rearing (82%) stages. Our data show that Pseudoseisura species are similar in some aspects of their breeding biology (e.g. nest dimensions, nest decorations, mating system, clutch size), whereas other aspects, such as nest-site selection, nestling period and nest attendance rate, are more variable among species.