Breeding biology of the Karoo Prinia Prinia maculosa

We studied the breeding biology of Karoo Prinias Prinia maculosa at Botrivier, Western Cape, South Africa, where they have become hosts to brood-parasitic Brown-backed Honeybirds Prodotiscus regulus since the mid-1980s. We monitored prinias breeding in a 120ha site over 7 years. Individually colour-ringed territorial prinias exhibited high fidelity to partners, breeding together for up to 4 years. Males constructed nest frames from green and/or dry grass, showing strong individual preferences in plant species selected for nest placement. Both sexes lined nests with fluff. Most nests were concealed in dense vegetation, facing north-east, away from rain-bearing westerly winds. Mean nest height (n = 217) was 62 ± 23 cm above the ground (range 3–170 cm). Clutch size was 3.3 ± 0.6 (n = 77). Incubation bouts averaged 14 ± 9 minutes (n = 173). Females were responsible for all incubation and brooding of nestlings, while both sexes fed nestlings. Faecal sacs were seldom removed in the first three days, but were subsequently removed by both sexes on 27% of nest visits (n = 116). Nestlings gained mass until 12 days post-hatching, with a slight decrease before fledging. Post-fledging parental care continued for up to 46 days. Nests where the outcome was determined (n = 71) had a 39% success rate in raising at least one fledgling. Of the 224 eggs monitored, 39% resulted in fledged chicks. Mammals, snakes, birds, or ants predated 30% of eggs and 21% of nestlings; other causes of nest failure (10%) were infertile or abandoned eggs, nest desertion caused by flooding of nests, or interference by mice, birds, humans, or spiders. Seven pairs successfully fledged two broods in one season. These findings provide a baseline against which nests parasitised by honeybirds can be compared.