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Sex and the Birds: 10. Dunnock’s mixed bag of breeding systems

on 22nd December 2013

Dunnocks (Punella modularis) are common garden and hedgerow birds found throughout temperate Europe and into Asia. It has a drab appearance, looking much like a sparrow, thus commonly known as Hedge Sparrow. On closer inspection it is rather attractive as it’s grey-blue head and breast become apparent. The sexes are alike although the female is less richly coloured.

What is remarkable about the Dunnock is its colourful sex life. It has evolved a unique breeding system that is extremely variable (Hatchwell, 2005):

1. Monogamy (42%) – a male and a female stay together for at least one breeding cycle.
2. Polygny (4%) – a male mates with several females during a mating season.
3. Polyandry (30%) – a female mates with several males during a breeding season.
4. Polygyandry (24%) – both the male and the female of the pair mate with more than one sexual partner during a breeding season.

In a territory with only a male and a female, the pair will cooperate to rear the chicks, thus adopting a monogamous relationship. If the territory is larger than usual, he may take in one or two more females and becomes polygynous, but this is rather uncommon. A more common scenario is where the female tries to mate with more than one male. This polyandrous breeding system is considered favourable to the female as the males she mated with will help in looking after her chicks.

In such a polyandrous situation, if the two or more males (who are not relatives) share a territory, they will compete for the female. The dominant male will naturally guard the female, not allowing any other males to copulate with her. Invariably he will fail as she will sneak off to mate with the other males. However, before copulation, the male will peck at her cloaca numerous times to stimulate her to eject the sperms from an earlier copulation (Davies, 1983), see video HERE.

As mentioned above, the advantage of a female copulating with more than one male is that she will have more than one male to care for her chicks. This will ensure an increased success of the chicks fledging, especially when food is scarce. On the other hand, a male copulating with more than one female allows him to produce more chicks, thus spreading his genes. However, the success of his chicks fledging will be reduced as they will be cared for by the usual two adults, without the help of one or more males.

Credit: YC Wee (text) & Dr Eric Tan (image of Dunnock).

References:
1.
Davies, N. B., 1983. Polyandry, cloaca-pecking and sperm competition in dunnocks. Nature, 302: 334-336.
2. Hatchwell, B. J., 2005. Family Prunellidae (Accentors). In: del Hoyo, J., Elliott, A. & D. A. Christie (eds.), Handbook of the birds of the world. Vol. 10. Cuckoo-shrikes to Thrushes. Lynx Editions, Barcelona. Pp. 496-513.

If you like this post please tap on the Like button at the left bottom of page. Any views and opinions expressed in this article are solely those of the authors/contributors, and are not endorsed by the Lee Kong Chian Natural History Museum (LKCNHM, NUS) or its affiliated institutions. Readers are encouraged to use their discretion before making any decisions or judgements based on the information presented.

YC Wee

Dr Wee played a significant role as a green advocate in Singapore through his extensive involvement in various organizations and committees: as Secretary and Chairman for the Malayan Nature Society (Singapore Branch), and with the Nature Society (Singapore) as founding President (1978-1995). He has also served in the Nature Reserve Board (1987-1989), Nature Reserves Committee (1990-1996), National Council on the Environment/Singapore Environment Council (1992-1996), Work-Group on Nature Conservation (1992) and Inter-Varsity Council on the Environment (1995-1997). He is Patron of the Singapore Gardening Society and was appointed Honorary Museum Associate of the Lee Kong Chian Natural History Museum (LKCNHM) in 2012. In 2005, Dr Wee started the Bird Ecology Study Group. With more than 6,000 entries, the website has become a valuable resource consulted by students, birdwatchers and researchers locally and internationally. The views and opinions expressed in this article are his own, and do not represent those of LKCNHM, the National University of Singapore or its affiliated institutions.

Other posts by YC Wee

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