A critical analysis of ‘false-feeding’ behavior in a cooperatively breeding bird: disturbance effects, satiated nestlings or deception?
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‘False feeding,’ where helpers arrive at nests with food but fail to provision the young, has been reported in several cooperative species. This and other potentially ‘deceptive’ behavior has been interpreted as indicating that helping may operate as a signal within such social groups. We critically examine these phenomena in the provisioning behavior of the bell miner Manorina melanophrys. Excessively close observation distances can artificially elevate the rate of false feeding in this (and other) species, but once this had been accounted for, there was little evidence for any ‘deceptive’ behavior by helpers or breeders. Natural and experimentally induced variation in the presence of a potential conspecific audience at the nest did not have any consistent influence upon the rate of false feeds, which was low at 7.94% of 6,880 nest visits. Instead, encountering unexpectedly low levels of brood demand provided a more parsimonious explanation for those visits where helpers failed to feed nestlings or ate the food themselves. Failure to completely transfer a load to nestlings was more likely when the load contained a high proportion of sticky lerp, indicating a simple prey-transfer problem. Finally, individuals that arrived at nests without prey were often members of neighboring breeding pairs, suggesting that these few non-feeding visits may instead involve an information-gathering function. We, therefore, suggest that future studies explicitly exclude the possibility of observer disturbance and all aspects of normal provisioning behavior before applying the terms ‘false feeding’ or ‘deceptive’ and inferring anything more than straightforward helping at the nest.
KeywordsBell miner White-winged chough Carrion crow Helping at the nest Signaling hypotheses
Nick and Joan Hoogenraad and the La Trobe University Wildlife Reserve kindly allowed field work to be undertaken on their land. We thank Maria Pacheco, Luc te Marvelde, James O’Connor, Dean Ingerson, and Amanda Dare for their assistance with the fieldwork. Anna Lashko, Mike Double, and Andrew Cockburn provided facilities for and carried out the molecular analyses. Robert Gibson, Robert Heinsohn, and an anonymous reviewer commented on an earlier version of this manuscript. Leg bands were provided by the Australian Bird and Bat Banding Service. This research was carried out under a BBSRC grant (5/S19268) to J.W. and the University of Wales, Bangor, and was approved by the La Trobe University Animal Ethics Committee (license AEC01/19(L)/V2) and the Department of Sustainability and Environment (license 10002082).
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