Short communications Nestling growth, plumage development and rate of prey delivery at a nest of the desert cisticola, Cisticola aridula Derek G. Engelbrecht & Susan M. Dippenaar* School of Molecular and Life Sciences, University of Limpopo, Private Bag X1106, Sovenga, 0727 South Africa Received 8 December 2003. Accepted 18 March 2004 Despite the widespread occurrence of the desert cisticola, Cisticola aridula, little is known about its general biology and, in particular, the nestling period. We studied the nestling period, chick development and rate of prey delivery at a single nest in the Polokwane Nature Reserve, Limpopo Province. A nest with three naked chicks and an egg was discovered on 6 February 2003 and the following day, the fourth egg had also hatched. Data collection commenced on 7 February 2003. The nestlings were weighed, selected biometric measurements were taken and the state of feather development was recorded every second day for the duration of the nestling period. We also determined the rate of prey delivery to nestlings every fourth day. The nestling period in this study (13 days) differed from that reported in the literature (18 days). Nest- lings were fed by the female only. The rate of food delivery increased from 50 visits (day 2) to 115 (day 10) for a 12.5-hour observation period. The one-day- old chicks’ mass ranged from 1.1 g to 1.7 g (average = 1.45 g) and they fledged at an approximate mean mass of 8.8 g (8.4–9.5 g). Key words: Cisticola aridula, nestling growth, rate of prey delivery, nestling period, asynchronous hatching. D espite its widespread distribution throughout the arid and semi-arid interior of southern Africa, the general biology of the desert cisticola (Priniidae) is poorly known (Urban et al. 1997). Furthermore, nestling growth and plumage development are undescribed for most species. Here we provide the first description of the growth and plumage development of desert cisticola nest- lings, which may serve as a benchmark for future inter- and intraspecific comparative studies on the growth rates of nestlings. A nest (23°58’S, 29°31’E) with three chicks and an egg was discovered at 11:00 on 6 February 2003 (day 0) in the Polokwane Nature Reserve, Limpopo Province, South Africa. At 6:30 the next day, 7 February 2003 (day 1), the remaining egg had hatched. Observations of breeding desert cisticolas revealed that they lay eggs at one day intervals and incubation commences after the third egg is laid. The hatching asynchrony observed in the present study confirms these observations and, together with state of physical development of the nestlings, we can accurately assume that the first three chicks hatched the day before the last nestling hatched. All the nestlings were weighed and individually marked on the tarsometatarsus with a non-toxic colour marker pen to aid identification during the nestling period. From 8 February 2003 (day 2), and every second day thereafter, the chicks were weighed, selected biometric measurements were recorded using a vernier calliper, and plumage development was described. For comparative purposes, mass and biometric measurements are only reported for the three nestlings that had hatched on the same day, i.e. 6 February 2004. The nestlings were always weighed and measured between 06:00 and 06:30. The biometric measurements taken included: head length (from the back of the skull to the tip of the bill), gape flange width (at the widest points) and tarsus length (from the notch of the intertarsal joint to the point where the foot is turned 90° to the tarsus). The rate of prey delivery was recorded every fourth day. Observations were made from a temporary hide approximately 20 m from the nest and calculated over 30 min. intervals for the pe- riod 06:00 to 18:30. Furthermore, observations were made on the directions as well as approxi- mate distances from the nest where prey was collected. Description of newly hatched nestlings The newly hatched nestlings were naked and flesh coloured. The gape flange, bill and inside of the mouth were yellow. The tongue was also African Zoology 40(1): 151–153 (April 2005) *Author for correspondence. E-mail: susand@unorth.ac.za