Oecologia

, Volume 86, Issue 3, pp 402–407

Discrimination among pinyon pine trees by Clark's Nutcrackers: effects of cone crop size and cone characters

  • Kerry M. Christensen
  • Thomas G. Whitham
  • Russell P. Balda
Original Papers

DOI: 10.1007/BF00317608

Cite this article as:
Christensen, K.M., Whitham, T.G. & Balda, R.P. Oecologia (1991) 86: 402. doi:10.1007/BF00317608

Summary

The influences of Colorado pinyon pine (Pinus edulis) cone crop size, cone and seed weight, cone length, number of seeds per cone, number of viable seeds, and percent viable seeds on the foraging behavior of avian seed dispersal agents were examined in field and laboratory settings. In the field, there was a significant positive relationship between cone number per tree and both the absolute number of cones and the percentage of the cone crop from which seeds were harvested. Cone weight and the number of viable seeds were also significantly related to seed harvest intensity. Laboratory experiments examined the relationship between crop size and cone characters on seed harvest by 18 Clark's Nutcrackers (Nucifraga columbiana). Nutcrackers were offered a choice of two tree types: one with 20 cones attached, and another with 10 cones attached. Significantly more birds chose to remove seeds first from the tree with 20 cones than the tree with 10 cones. In timed trials, they also harvested seeds from significantly more cones on the tree with the higher cone density. In the laboratory, cones chosen for seed removal by the nutcrackers had significantly more viable seeds, more seeds, and were longer compared to cones that were not chosen. Such discriminatory foraging behavior may increase avian foraging efficiency and result in differential reproductive success of pinyon pines. This behavior may therefore influence the evolution of pinyon pine reproductive traits.

Key words

Pinyon pine reproduction Discriminatory foraging behavior Clark's Nutcracker Nucifraga columbiana Pinus edulis 

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Kerry M. Christensen
    • 1
  • Thomas G. Whitham
    • 1
  • Russell P. Balda
    • 1
  1. 1.Department of Biological SciencesNorthern Arizona UniversityFlagstaffUSA

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