Nectar-feeding by suburban Blue Tits: contribution to the diet in spring

The incidence of nectar feeding by 2 pairs of Blue Tits Parus caeruleus was investigated in relation to the availability of nectar and alternative food. Nectar was not the most preferred food and the occurrence of nectar feeding did not correlate significantly with most measures of nectar availability, but the Blue Tits selected the most productive flowers. Nectar feeding frequently occurred when the preferred peanuts were unavailable due to interspecific competition. The nectar resource was under-utilized by the Blue Tits except at the beginning of the flowering period. Despite this, nectar was a highly profitable food source, yielding 0.33-0.38 kJ min^?1 foraging. During the flowering period nectar was estimated to contribute up to 32.7% of the average daily metabolic rate (ADMR) of the male and up to 49.3% of the ADMR of the female, with means over the 2 years of 7.4% and 13.2% per day for the male and female, respectively. The importance of nectar in the ecology of Blue Tits is discussed.