Determinate vs. indeterminate laying in the House Sparrow

Kendra et al. (1988) have reopened the question of whether the House Sparrow (Passer domesticus) is a determinate or indeterminate layer. Determinate layers are species in which the number of ovarian follicles responding to the stimulation of the gonadotropic hormones is equal to the number of eggs laid, and this number is determined when egg laying begins. Neither the removal nor addition of eggs during the laying period will affect the number of eggs laid. Indeterminate layers are species in which the number of follicles that respond to hormonal stimulation is greater than the number of eggs laid normally. The follicles respond asynchronously to hormonal stimulation so that the development of some of the later-responding follicles may be inhibited during the laying cycle by the presence of eggs in the nest. If eggs are removed as laid, laying in these species continues beyond the normal clutch size to an indefinite number. ...I performed egg-removal experiments on 20 nests of the House Sparrow: 2 nests were in Poland in 1977 and 18 were in northern lower Michigan during the 1986-1988 breeding seasons.