Avian consumption and seed germination of the hemiparasitic mistletoe Agelanthus natalitius (Loranthaceae)

We documented avian consumers of the mistletoe Agelanthus natalitius in the field and quantified their effects on seed germination in captive studies. Seven bird species were frequently observed to feed on mistletoe fruits in the field, namely Cape Batis (Batis capensis), Cape White-eye (Zosterops virens), Red-fronted Tinkerbird (Pogoniulus pusillus), Red-winged Starling (Onychognathus morio), Dark-capped Bulbul (Pycnonotus tricolor), Speckled Mousebird (Colius striatus) and Village Weaver (Ploceus cucullatus). Of the four bird species used in captive feeding trials (Red-winged Starling, Speckled Mousebird, Village Weaver and Cape White-eye), most of the birds removed the pulp-cover of the mistletoe fruits and left the exposed seeds in potentially germinable condition. Red-winged Starlings ingested but then regurgitated the seeds and wiped their bills on a twig to dislodge the sticky viscin-covered seeds individually. Mistletoe seeds obtained from cages of Red-winged Starlings had the highest germination success of all the seeds obtained from the captive bird study. The handling of mistletoe fruits applied by all species of birds both in the field and in captivity showed that mistletoe dispersal is likely to occur over short distances, although the seeds are likely to be dispersed to safe sites due to directed dispersal on parental host trees. Such autoinfection and local aggregation increase the interaction with already parasitised hosts, which through time may enhance local specialisation on the most frequently parasitised host species.