title: Asymmetric competition for nectar between a large nectar thief and a small pollinator: an energetic point of view.
abstract: There are two alternative hypotheses related to body size and competition for restricted food sources. The first one supposes that larger animals are superior competitors because of their increased feeding abilities, whereas the second one assumes superiority of smaller animals because of their lower food requirements. We examined the relationship between two unrelated species of different size, drinking technique, energy requirements and roles in plant pollination system, to reveal the features of their competitive interaction and mechanisms enabling their co-existence while utilising the same nectar source. We observed diurnal feeding behaviour of the main pollinator, the carpenter bee Xylocopa caffra and a nectar thief, the northern double-collared sunbird Cinnyris reichenowi on 19 clumps of Hypoestes aristata (Acanthaceae) in Bamenda Highlands, Cameroon. For comparative purpose, we established a simplistic model of daily energy expenditure and daily energy intake by both visitor species assuming that they spend all available daytime feeding on H. aristata. We revealed the energetic gain-expenditure balance of the studied visitor species in relation to diurnal changes in nectar quality and quantity. In general, smaller energy requirements and related ability to utilise smaller resources made the main pollinator X. caffra competitively superior to the larger nectar thief C. reichenowi. Nevertheless, sunbirds are endowed with several mechanisms to reduce asymmetry in exploitative competition, such as the use of nectar resources in times of the day when rivals are inactive, aggressive attacks on carpenter bees while defending the nectar plants, and higher speed of nectar consumption.
authors.affiliation: Biology Centre, Institute of Entomology, Academy of Sciences of the Czech Republic, Branišovská 31, 370 05, Ceske Budejovice, Czech Republic. paddysek@gmail.com.|Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 31, 370 05, Ceske Budejovice, Czech Republic. paddysek@gmail.com.|Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, 128 44, Prague 2, Czech Republic. paddysek@gmail.com.
authors.forename: Eliška
authors.identifier: 0000-0003-3994-2161
authors.initials: E
authors.lastname: Padyšáková
authors.affiliation: Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 31, 370 05, Ceske Budejovice, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Okrouhlík
authors.affiliation: School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.
authors.forename: Mark
authors.initials: M
authors.lastname: Brown
authors.affiliation: Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, 128 44, Prague 2, Czech Republic.|Institute of Botany, Academy of Sciences of the Czech Republic, Dukelská 135, 379 82, Třeboň, Czech Republic.
authors.forename: Michael
authors.initials: M
authors.lastname: Bartoš
authors.affiliation: Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, 128 44, Prague 2, Czech Republic.|Institute of Botany, Academy of Sciences of the Czech Republic, Dukelská 135, 379 82, Třeboň, Czech Republic.
authors.forename: Štěpán
authors.initials: Š
authors.lastname: Janeček
mesh_terms: D000818:Animals; D001516:Bees; D005247:Feeding Behavior; D035264:Flowers; D046109:Passeriformes; D057048:Plant Nectar; D054817:Pollination; D012919:Social Behavior
chemical_list: D057048:Plant Nectar
keywords: Africa; Carpenter bee; Cinnyris; Hypoestes; Sunbird; Xylocopa