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Borgmann, K. L., C. J. Conway, and M. L. Morrison. 2013. Breeding phenology of birds: mechanisms underlying seasonal declines in the risk of nest predation. PLoS ONE8(6): e65909. doi:10.1371/journal.pone.0065909.


Seasonal declines in avian clutch size are well documented, but seasonal variation in other reproductive parameters has
received less attention. For example, the probability of complete brood mortality typically explains much of the variation in
reproductive success and often varies seasonally, but we know little about the underlying cause of that variation. This
oversight is surprising given that nest predation influences many other life-history traits and varies throughout the breeding
season in many songbirds. To determine the underlying causes of observed seasonal decreases in risk of nest predation, we
modeled nest predation of Dusky Flycatchers (Empidonax oberholseri) in northern California as a function of foliage
phenology, energetic demand, developmental stage, conspecific nest density, food availability for nest predators, and nest
predator abundance. Seasonal variation in the risk of nest predation was not associated with seasonal changes in energetic
demand, conspecific nest density, or predator abundance. Instead, seasonal variation in the risk of nest predation was
associated with foliage density (early, but not late, in the breeding season) and seasonal changes in food available to nest
predators. Supplemental food provided to nest predators resulted in a numerical response by nest predators, increasing the
risk of nest predation at nests that were near supplemental feeders. Our results suggest that seasonal changes in foliage
density and factors associated with changes in food availability for nest predators are important drivers of temporal patterns
in risk of avian nest predation.


Current Staff

Federal Staff: 2

Masters Students: 9

Phd Students: 1

Post Docs: 1

University Staff: 43

5 Year Summary

Students graduated: 21

Scientific Publications: 48

Presentations: 95



June 2013

Unit Authors

Arizona Cooperative Fish and Wildlife Research Unit Cooperators

  1. Arizona Game Fish Department
  2. U.S. Fish and Wildlife Service
  3. U.S. Geological Survey
  4. University of Arizona
  5. Wildlife Management Institute