Supplementary feeding advances laying in red-winged blackbirds Agelaius phoeniceus and may increase polygyny at two ponds in Washington, USA

  • Published source details Wimberger P.H. (1988) Food Supplement Effects on Breeding Time and Harem Size in the Red-Winged Blackbird (Agelaius phoeniceus). The Auk, 105, 799-802


This study is summarised as evidence for the following.

Action Category

Provide supplementary food for songbirds to increase reproductive success

Action Link
Bird Conservation
  1. Provide supplementary food for songbirds to increase reproductive success

    A randomised, replicated and controlled experiment around two lakes in Washington state, USA, in 1981 (Wimberger 1988), found that red-winged blackbirds Agelaius phoeniceus from territories supplied with supplementary food laid eggs 8-13 days earlier than blackbirds from control (unfed) territories, for first, second, third and fourth nests of the year (20 territories studied). Each lake was divided in half, with one half provided with sunflower seeds from the 4th April. The average number of females in each territory was increased by feeding on one lake (average of 9.0 females/territory on fed territories vs. 6.5 females/territory on controls, eight territories studied) but not the other (average of 5.2 females/territory on fed territories vs. 4.7 females/territory on controls, 12 studied).


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