Feathering the Nest: Food Supplementation Influences Nest Construction by Blue ( Cyanistes Caeruleus ) and Great Tits ( Parus major )

Food supplementation can potentially provide additional energy and/or liberate time usually devoted to foraging, enabling birds to invest more in activities, such as nest construction, that provide long-term fitness benefits. Although nest construction can represent large temporal and energetic investments in a breeding attempt, few studies have investigated how it is influenced by food supplementation. We studied the effects of food supplementation on nest construction by Blue Tits ( Cyanistes caeruleus) and Great Tits ( Parus major). We found that food supplementation advanced nest construction and egg laying in both species. Food supplementation also resulted in truncation of the nest construction period of Blue Tits, but not Great Tits. The duration of the nest-lining period was not influenced by food supplementation in either species. Unexpectedly, food supplementation resulted in significantly shallower nests in Blue Tits but not in Great Tits. We conclude that food availability can constrain nest construction behaviour and that these constraints can be released by the provision of supplementary foods prior to and throughout nest construction.