• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of procbhomepageaboutsubmitalertseditorial board
Proc Biol Sci. Apr 22, 2003; 270(1517): 799–803.
PMCID: PMC1691309

Synergistic effects of food and predators on annual reproductive success in song sparrows.


The behaviour literature is full of studies showing that animals in every taxon balance the probability of acquiring food with the risk of being preyed upon. While interactions between food and predators clearly operate at an individual scale, population-scale studies have tended to focus on only one factor at a time. Consequently, interactive (or 'synergistic') effects of food and predators on whole populations have only twice before been experimentally demonstrated in mammals. We conducted a 2 x 2 experiment to examine the joint effects of food supply and predator pressure on the annual reproductive success of song sparrows (Melospiza melodia). Our results show that these two factors do not operate in an additive way, but instead have a synergistic effect on reproduction. Relative to controls, sparrows reared 1.1 more young when food was added and 1.3 more when predator pressure was low. When these treatments were combined 4.0 extra young were produced, almost twice as many as expected from an additive model. These results are a cause for optimism for avian conservation because they demonstrate that remedial actions, aimed at simultaneously augmenting food and reducing predators, can produce dramatic increases in reproductive success.

Full Text

The Full Text of this article is available as a PDF (142K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Krebs CJ, Boutin S, Boonstra R, Sinclair AR, Smith JN, Dale MR, Martin K, Turkington R. Impact of food and predation on the snowshoe hare cycle. Science. 1995 Aug 25;269(5227):1112–1115. [PubMed]
  • Scheuerlein A, Van't Hof TJ, Gwinner E. Predators as stressors? Physiological and reproductive consequences of predation risk in tropical stonechats (Saxicola torquata axillaris). Proc Biol Sci. 2001 Aug 7;268(1476):1575–1582. [PMC free article] [PubMed]

Articles from Proceedings of the Royal Society B: Biological Sciences are provided here courtesy of The Royal Society


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...