Polygynous Blue Tits and Monogamous Great Tits: Does the Polygyny-Threshold Model Hold?

Abstract

Using the polygyny-threshold model as a starting point, and knowing that great tits are monogamous and blue tits occasionally polygynous, I test the hypothesis that quality differences between habitats should be larger for blue tits than for great tits. Comparisons are made among study plots at Ghent (10-30 ha) differing in habitat and hence in density and among 10 subplots of about 1 ha each in a single study plot of optimal habitat for tits near Antwerp. Both analyses show a larger difference in reproductive rate for blue tits than for great tits. In the Antwerp study, polygyny was found only on the subplots where monogamous females produced more surviving offspring. Production of offspring surviving for at least 3 mo was greatest for monogamous females in the better subplots, next greatest for polygynous females, and least for monogamous females in the poorer subplots. My data support the polygyny-threshold model.