Dataset Information

Foraging patterns of acorn woodpeckers (Melanerpes formicivorus) on valley oak (Quercus lobata Nee) in two California oak savanna-woodlands.

ABSTRACT: Landscape characteristics and social behavior can affect the foraging patterns of seed-dependent animals. We examine the movement of acorns from valley oak (Quercus lobata) trees to granaries maintained by acorn woodpeckers (Melanerpes formicivorus) in two California oak savanna-woodlands differing in the distribution of Q. lobata within each site. In 2004, we sampled Q. lobata acorns from 16 granaries at Sedgwick Reserve in Santa Barbara County and 18 granaries at Hastings Reserve in Monterey County. Sedgwick has lower site-wide density of Q. lobata than Hastings as well as different frequencies of other Quercus species common to both sites. We found acorn woodpeckers foraged from fewer Q. lobata seed source trees (K(g) = 4.1 ± 0.5) at Sedgwick than at Hastings (K(g) = 7.6 ± 0.6) and from fewer effective seed sources (N(em)* = 2.00 and 5.78, respectively). The differences between sites are due to a greater number of incidental seed sources used per granary at Hastings than at Sedgwick. We also found very low levels of seed source sharing between adjacent granaries, indicating that territoriality is strong at both sites and that each social group forages on its own subset of trees. We discovered an interesting spatial pattern in the location of granaries. At Sedgwick, acorn woodpeckers situated their granaries within areas of higher-than-average tree density, while at Hastings, they placed them within areas of lower-than-average tree density, with the outcome that granaries at the two sites were located in areas of similar valley oak density. Our results illustrate that landscape characteristics might influence the number of trees visited by acorn woodpeckers and the locations of territories, while woodpecker social behavior, such as territoriality, shapes which trees are visited and whether they are shared with other social groups.

SUBMITTER: Scofield DG

PROVIDER: S-EPMC3074073 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Publications

Foraging patterns of acorn woodpeckers (Melanerpes formicivorus) on valley oak (Quercus lobata Née) in two California oak savanna-woodlands.

Scofield Douglas G DG Alfaro Victor Ryan VR Sork Victoria L VL Grivet Delphine D Martinez Edith E Papp Jeannette J Pluess Andrea R AR Koenig Walter D WD Smouse Peter E PE

Oecologia 20101124 1

Landscape characteristics and social behavior can affect the foraging patterns of seed-dependent animals. We examine the movement of acorns from valley oak (Quercus lobata) trees to granaries maintained by acorn woodpeckers (Melanerpes formicivorus) in two California oak savanna-woodlands differing in the distribution of Q. lobata within each site. In 2004, we sampled Q. lobata acorns from 16 granaries at Sedgwick Reserve in Santa Barbara County and 18 granaries at Hastings Reserve in Monterey C ...[more]

PMID: 21107869

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Project description:Tree cavities provide a critical resource for cavity-nesting animals, and high quality cavities can be difficult for animals to acquire in habitats where competition is high. We investigated the breeding performance of Lewis's Woodpeckers in three habitat types in British Columbia, Canada in 2013 and 2014. We also assessed whether the number of nest competitors and cavity availability influenced the habitat specific breeding performance of this threatened cavity nesting species. We found that daily nest survival rate was lower in burned habitat (0.15 ± 0.08 (0.05-0.37)) than in live pine (0.72 ± 0.10 (0.51-0.87)) or cottonwood (0.69 ± 0.09 (0.51-0.83)) habitats. However, hatching success (the proportion of eggs that hatch) was lower in live pine habitat (0.59 ± 0.09 95% CI) than burned (0.77 ± 0.19 95% CI) or cottonwood (0.80 ± 0.07 95% CI) habitat, and the fledging success of successful nests in live pine and burned habitat (1.86 ± 0.31 and 1.88 ± 0.59 95% CI, respectively) was slightly lower than in cottonwood habitat (2.61 ± 0.45 95% CI). Consequently, Lewis's Woodpeckers in cottonwood habitat produced more fledglings per nesting attempt (2.05 ± 0.49 95% CI) than in live pine (1.53 ± 0.35 95% CI) or burned (0.79 ± 0.49 95% CI) habitat. Habitats differed in the number of nesting competitors and the number of suitable cavities surrounding active Lewis's Woodpecker nests. Our results showed that cavity density best explained breeding performance differences although the mechanisms remain unclear. There was no evidence that the number of heterospecific nest competitors, including the invasive European Starling (Sturnus vulgaris), explained or influenced Lewis's Woodpecker breeding performance. Cavity density influenced the productivity of successful nests but did not explain habitat differences in hatching success or daily nest survival. Further work is required to understand the mechanistic basis for the habitat specific breeding performance of Lewis's Woodpeckers. Habitat differences in breeding performance in British Columbia are not consistent with those in other regions, highlighting the importance of regionally-specific demographic data for managing species at risk.

Dataset Information

Foraging patterns of acorn woodpeckers (Melanerpes formicivorus) on valley oak (Quercus lobata Nee) in two California oak savanna-woodlands.

Publications

Foraging patterns of acorn woodpeckers (Melanerpes formicivorus) on valley oak (Quercus lobata Née) in two California oak savanna-woodlands.

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