The dunnock song repertoire comprises of multiple song types, and during bouts of singing males repeats a song type several times before switching. Several hypotheses suggest that the rate at which males switch song types may function in male–male aggression, mate attraction, or both. Dunnocks switch song types 10 times faster when searching for a receptive female than during male–male interactions. Polyandrous and polygynandrous males switch song types significantly faster than monogamous and polygynous males when separated from a fertile female, but there is no difference in switching rates during song duels or spontaneous song bouts outside the fertile period. Thus males are more likely to switch song types if they are competing to attract a receptive female than if they have exclusive access to females (Langmore 1997).
In many species, a female’s reproductive success is limited by her access to resources whereas a male’s reproductive success is limited by his access to females. Mating systems, therefore, should often be related to the ability of males to control access to females. The degree of control will depend on two main factors; Firstly ecological conditions such as the dispersion of food, nest sites and predators will influence female distribution which, in turn, will determine their economic defend-ability by males. Secondly, the ability of males to monopolize females will depend on the amount of competition for mates at any one time, which will be reflected by the operational sex ratio (the local ratio of receptive females to sexually active males). In Dunnocks, food distribution influences the range size of a female and this then determines the ease with which she is monopolized by males. Where food patches are dense, female ranges are small, they are easily monopolized and the mating combinations reflect high male mating success (polygyny and polygynandry). Where food patches are sparse, female ranges are large and they are then less easily monopolized giving rise to lower male mating success (polyandry) (Davies and Lundberg 1984).
Dunnocks (Prunella modularis) inhabit dense scrub where females defend small, exclusive territories. Individuals have one to two mates depending on how the territories of males overlap the female territories, resulting in monogamy, polygyny, polyandry or polygynandry, as previously stated.The congeneric alpine ancestor (Prunella collaris) inhabits high mountains where food is more patchily distributed. Two to five females have large, overlapping ranges defended by two to five males in a polygynandrous group. At regular feeding sites, where food is provided each day, dunnocks defended small, exclusive territories. At variable feeders, where food is allocated at random each day to one of several adjacent sites, dunnocks adopted larger, overlapping ranges typical of alpine ancestors, with two to five males overlapping two to four females. Unlike their alpine ancestors, however, the dunnocks with variable feeders did not have a consistent dominance hierarchy over the whole of the shared range and females did not gain mating access to more males. It is suggested that whereas ecological conditions influence the spacing system, social relationships are affected by individual conflicts of interest (Davies and Hartley 1996).
Reference List:
- Davies.N.B., & Lundberg.A., (1984) Food Distribution and a Variable Mating System in the Dunnock, (Prunella modularis). Journal of Animal Ecology, 53, 895-912.
- Davies.N.B., & Hartley.R.I., (1996) Food Patchiness, Territory Overlap and Social Systems: An Experiment with Dunnocks (Prunella modularis). Journal of Animal Ecology, 65, 837-845.
- Langmore.E.N., (1997) Song switching in monandrous and polyandrous dunnocks, Prunella modularis. Animal Behaviour, 53, 757-766.
