Is the Starling Sturnus vulgaris a determinate layer?

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Abstract
European Starlings Sturnus vulgaris have been said to be determinate layers, that is, they do not react to egg removals by laying extra eggs nor to egg additions by laying fewer eggs. Especially in species with a relatively small clutch‐size, such as the Starling, it is important to start these experiments early during the laying period to give the laying female the possibility of reacting to these additions and/or removals. I report here addition (n= 11 nests) and removal experiments (n= 35) early in laying period in a captive Starling colony. Additional information is presented about the development of incubation behaviour, a good predictor of clutch‐size. When three eggs were added to nests at 1500h on the first day of laying, females laid the normal number of eggs, and incubation behaviour developed regularly. Egg removals (one egg on three successive days) that started early in the laying period (at 1500h on the first day or at 0800h on the second day) arrested the development of incubation behaviour and resulted in the laying of extra eggs. Removals later in the laying period had no effect on the number of eggs laid nor on incubation behaviour. Following Kennedy's (1991) terminology, the starling is an addition‐determinate, and appears to be a removal‐indeterminate, layer.