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.

Biology Centre Institute of Entomology Academy of Sciences of the Czech Republic Branišovská 31 370 05 Ceske Budejovice Czech Republic

Department of Ecology Faculty of Science Charles University Prague Viničná 7 128 44 Prague 2 Czech Republic

Department of Zoology Faculty of Science University of South Bohemia Branišovská 31 370 05 Ceske Budejovice Czech Republic

Institute of Botany Academy of Sciences of the Czech Republic Dukelská 135 379 82 Třeboň Czech Republic

School of Life Sciences University of KwaZulu Natal Durban South Africa

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PLoS One. 2013 Apr 10;8(4):e59299 PubMed

Ecol Lett. 2007 Feb;10(2):115-26 PubMed

Science. 1972 May 12;176(4035):597-602 PubMed

Oecologia. 1993 May;94(1):87-94 PubMed

Behav Processes. 2014 Mar;103:138-44 PubMed

J Exp Biol. 2004 Oct;207(Pt 22):3959-68 PubMed

Biol Lett. 2005 Sep 22;1(3):346-9 PubMed

Oecologia. 1998 Oct;116(4):519-527 PubMed

Ecology. 2007 May;88(5):1202-9 PubMed

Am J Physiol Regul Integr Comp Physiol. 2010 Oct;299(4):R1068-74 PubMed

Am J Bot. 2001 Nov;88(11):1960-5 PubMed

Oecologia. 1985 May;66(2):161-167 PubMed

Ann N Y Acad Sci. 2012 May;1256:66-88 PubMed

Am Nat. 2003 Oct;162(4 Suppl):S63-79 PubMed

Proc Biol Sci. 2003 Mar 22;270(1515):557-62 PubMed

Oecologia. 2004 Apr;139(2):246-54 PubMed