Short communication Nest and nestling data for Barlow’s lark, Calendulauda barlowi Derek Engelbrecht 1 * & Johann Lonzer 2 1 School of Molecular and Life Sciences, University of Limpopo, Private Bag X1106, Sovenga, 0727 South Africa 2 Port Nolloth Museum, P.O. Box 187, Port Nolloth, 8280 South Africa Received 19 February 2008. Accepted 1 October 2008 Barlow’s lark is one of southern Africa’s least known lark species. This study is the first to report on the structure and dimensions of this species’ nest and aspects of the nestling period. The ontogenetic devel- opment of the nestling is described with regard to plumage development, increase in mass and growth of the head and tarsus. The parameters of the logistic growth curve for the increase in mass and growth of the tarsus are also provided. The nestling period lasted 13 days and both sexes contributed to feeding nestlings exclusively on invertebrates. Key words: Barlow’s lark, Alaudidae, Calendulauda, nestling period, breeding biology. U ntil recently, Barlow’s lark, Calendulauda barlowi, was considered a subspecies of the Karoo lark Calendulauda albescens complex. Follow- ing analyses of genetic, morphological and call data of the different subspecies in the Karoo lark complex, Barlow’s lark was elevated to full specific status (Ryan et al. 1998). However, there are reports of hybridisation between Barlow’s and Karoo larks from the southern edge of the species’ range, particularly in the vicinity of Port Nolloth (Ryan et al. 1998). Since most of its relatively small global range of approximately 18 000 km 2 falls within diamond-mining exclusion areas, very little is known about the general biology of this species (Hockey et al. 2005), and it is currently listed as near-threatened (Barnes 2000). This paper presents new information on the nesting and nest- ling growth of Barlow’s lark. On 7 September 2007, a nest with two nestlings was found in the coastal dunes of Port Nolloth (29°14’25.1”S, 16°51’39.6”E). The nestlings’ mass, selected biometric measurements (head length, tarsus length and wing length) and the extent of feather development indicated that they were one day old. The aging of the nestlings was based on D.E.’s experience with lark nestlings, namely the short-clawed lark (Certhilauda chuana), Sabota lark (Calendulauda sabota) and monotonous lark (Mira- fra passerina). One nestling was found lying dead approximately 10 cm from the nest at age five days. We recorded the growth and plumage develop- ment of the surviving nestling daily between 07:00 and 08:00 until the nestling was nine days old. In order to obtain an accurate nestling period, handling the nestling was stopped after day nine to avoid it fledging prematurely. The growth parameters recorded were mass (g), head length (mm) and tarsus length (mm), as described by De Beer et al. (2001). The growth rate of the nestling was determined by fitting the growth curve by a logistic equation, having the form: W(t)+ A/(1 + e (–K(t–ti)) ), where W(t) is the mass/length at age t, A is the asymptote of the growth curve, e is the base of the natural logarithm, K is the growth rate constant, and ti is the age at the inflection point of the growth curve, i.e. 0.5 of the asymptotic mass/length on a logistic growth curve (Ricklefs 1967, 1968). Fitting a growth curve is also compli- cated by sexual size dimorphism in the species (Hockey et al. 2005) and the possibility of differential growth rates of males and females of the species. The growth curve parameters for head length were not calculated as the head lengths of adult birds are not known. The t10–90, i.e. the time required to complete growth from 10% to 90% of the asymp- tote, was also calculated. For a logistic growth curve this is calculated as t10–90 = 4.394/K. Nest site, structure and dimensions The nest was situated in the coastal dunes, approximately 150 m from the shore, under a Seriphium plumosum shrub that was approximately African Zoology 44(1): 00–00 (April 2009) Author for correspondence. E-mail: engelbrechtd@ul.ac.za