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Open Access Publications from the University of California

Breeding Red-Winged Blackbird Response to Conspecific Models Placed in Pre-Copulatory Position: Implications for Reproductive Control

  • Author(s): Moulton, Laurel L.
  • Linz, George M.
  • Bleier, William J.
  • et al.

Sunflower producers in the northern Great Plains are annually plagued by feeding flocks of blackbirds, especially red-winged blackbirds (RWBL). Past techniques aimed at reducing blackbird damage have had varying degrees of success, but the estimated annual loss of sunflower remains at ≥$10 million. Thus, there is a need for new innovative approaches to managing blackbird damage. One approach is to find non-lethal species-specific methods of lowering reproduction by discovering vulnerable behavioral tendencies in the reproductive cycle of RWBL. Male RWBL are a good candidate for reproductive control because of their territorial and polygynous reproductive behavior. We have designed a study to assess the male RWBL response to a model placed in pre-copulatory position under different treatment scenarios. Our objective is to discover the conditions under which we can attract the largest numbers of males to the model, keeping in mind that these models could potentially be used as a delivery system for a reproductive inhibitor. While we had nearly no response from territorial males, we found that floater males (those that do not hold territories) readily copulate with conspecific models. Floater intrusion and copulation occurs more often in the early part of the breeding season and while females were most fertile. Of the floater males that attempted to copulate with a model, 96% were SY (second-year) males; SY males are considered “non-breeding”. Preliminary results show that reproductive management would be most successful in the floater male population. Since the majority of floaters are SY males, it is likely that they will attain territories in future breeding seasons. This would require the use of a long-term sterilant. This method has the potential to target specific breeding populations, but more research is needed on movement patterns of floater males.

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