Cardinal Woodpecker (Dendropicos fuscescens) utilises wildebeest carcass horns as a foraging substrate

Woodpeckers are known to be preferentially omnivorous foragers that feed primarily on insects and their larvae as well as other arthropods, with many species relying, to a greater or lesser extent, on plant products such as nuts, fruits and tree sap (Winkler et al. 1995, Winkler and Christie 2002). The foraging substrates that woodpeckers utilise include bark, wood, epiphytes, vines, soil, mud, fruits and flowers (Winkler et al. 1995, Winkler and Christie 2002). The Cardinal Woodpecker (Dendropicos fuscescens) is considered to be Africa’s most widespread woodpecker, occurring across most of the continent south of the Sahara, including the Serengeti National Park (SNP) in Tanzania (Winkler et al. 1995, Zimmerman et al. 2001, Winkler and Christie 2002). Cardinal Woodpeckers feed on insects and insect larvae, including certain beetles; termites (Isoptera), grasshoppers (Orthoptera) and fruits are among the food items they are known to consume (Winkler et al. 1995, Winkler and Christie 2002, Hockey et al. 2005). Cardinal Woodpeckers usually forage alone, in pairs or in mixed species flocks, and they utilise trees, vines, bushes, reeds, euphorbias, dry stalks of cultivated maize, and seed pods as foraging substrates. Cardinal Woodpeckers search mostly in the lower strata of these substrates for food (Winkler et al. 1995, Winkler and Christie 2002, Hockey et al. 2005). Other publications on the feeding or breeding biology of this species contain no further information with regard to exploited feeding substrates (e.g. Attwell 1952, Dean 1974). Here we report a series of observations of Cardinal Woodpeckers foraging on the horns of a wildebeest carcass, which until now, has not been documented as a foraging substrate for this species or for any other species of woodpecker. The observations were made by BPF in the vicinity of the Seronera Research Centre, SNP, Tanzania (2°26’S, 34°51’E; 1 535m). The prevailing habitat type at this study site is open woodland savanna. Several weeks prior to the observation, the skull of a blue wildebeest (Connochaetes taurinus) carcass was placed by BPF upside down on the porch of the research centre. The outer keratin layers of the horns were perforated by moth grubs of the genus Ceratophaga (Tineidae, Lepidoptera). These larvae are highly specialised scavengers, which forage and live inside the keratin layers of the horns, creating characteristic foraging tracks: keratin convolutions rising from the external surface of the horns. Throughout the study period for another project (October–December 2005), Cardinal Woodpeckers were observed almost daily around the house. On 22 October 2005 at 18:20, a female Cardinal Woodpecker was observed landing on the wildebeest skull. This individual carefully inspected its surroundings for 2–3min before it began to show typical foraging behaviour by tapping on the horns of the skull and probing into the moth larvae holes. A Cardinal Woodpecker female was observed on the following day at 17:10, as well as on 18 November 2005 at 18:15, at the same skull. Each visit lasted for c. 2–5min, consisted only of one continuous visit to the skull, and the individual exhibited the same typical foraging behaviour, although no items were observed to be extracted during these observations. To our best knowledge, this is the first report of the utilisation of a mammalian skull, i.e. its horns, as a foraging substrate by the Cardinal Woodpecker in particular, and by woodpeckers in general. About 25 000km in size, the SNP is home to the largest herd of migrating ungulates in the world, with about 1.2 million wildebeests (Packer et al. 2005). In savannas, trees as the more traditional Cardinal Woodpecker foraging substrate are comparably scarce; mammalian horns inhabited by (presumably) highly nutritious moth larvae might therefore be a foraging substrate of more than merely incidental importance to woodpeckers.