Food Caching in the Tropical Frugivore, Macgregor's Bowerbird (Amblyornis macgregoriae)

Abstract

-Males of MacGregor's Bowerbird (Amblyornis macgregoriae) cache fruit. In a study population in eastern Papua New Guinea we found 437 cache sites at 39 bowers. Adult males stored an average total of 17.6 fruits (range 0-82) at 13.6 sites (range 0-55), significantly more than immature males. All sites were located in vegetation above ground within 13 m horizontal and 9 m vertical distance from the males' bowers. For 3 males studied intensively, the rate of replacement of caches averaged 0.13 replacements-site-l day-1, with no significant differences among males. Caching occurred only during the seasonal periods of bower attendance and breeding activity. Females did not store fruit and did not take fruit stored by males. We suggest that by extending the time males can remain at their bowers, caching may increase interaction time with females and decrease rates of bower marauding by rival males. There was no evidence that cached fruits served as bower decorations. Received 7 May 1984, accepted 4 October 1984. FOOD storing refers to the deposition of food items in a particular location for later consumption. It has been observed in a number of bird and mammal species (Roberts 1979, Vander Wall and Balda 1981, Smith and Reichman 1984). In birds, food storage occurs as either a long-term strategy, to yield food during times of scarcity, or on a short-term basis for temporary retention or accumulation of items that cannot be eaten at one time. Long-term food storage occurs predominately in nonmigratory species and in habitats with seasonal fluctuations in resource abundance (Roberts 1979, Smith and Reichman 1984). The food stored is generally durable and particulate, such as seeds. Birds for which longterm food storage is an important contribution to reproductive success and winter survival include woodpeckers (Koenig 1978), corvids (Tomback 1977, Bossema 1979, Vander Wall and Balda 1981), and parids (Ulfstrand 1976, Sherry et al. 1982). Short-term food storage is known primarily in shrikes (Lanius spp., Craig 1974) and birds of prey (Newton 1979, Walter 1979) and in some cracticids, parids, and corvids (Pizzey 1980, Smith and Reichman 1984). Long-term food storing apparently is more common in temperate than in tropical avifaunas (Smith and Reichman 1984). This may reflect both the greater importance of seasonal 1 Present address: Department of Biology, C-016, University of California at San Diego, La Jolla, California 92093 USA. changes in food abundance in temperate habitats and the cooler temperatures that allow for storage of perishable items over a longer period of time (Roberts 1979, Vander Wall and Balda 1981). Nonetheless, tropical jays (Turcek and Kelso 1968) and woodpeckers (Skutch 1969) store food, as do their temperate counterparts, particularly in montane areas. In this paper we describe food-storing behavior in MacGregor's Bowerbird (Amblyornis macgregoriae), a frugivorous species found in montane rain forest in New Guinea. This behavior is separate from fruit gathering by males for bower decoration. We present data on occurrence, type, location, and replacement rates of stored food items and discuss caching in relation to the species' social organization and bower-building behavior. Food storing has not been described previously in any bowerbird or, to our knowledge, any tropical frugivorous