Acorn Woodpecker

Melanerpes formicivorus

Order:
Piciformes
Family:
Picidae
Sections

Tables and Appendices

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Table 1

Summary of reproductive parameters in 3 Acorn Woodpecker populations.

  Hastings Reservation, California Water Canyon, New Mexico Research Ranch, Arizona
Clutch size
Single female groups only 4.37
All groups 4.98
Percent of groups not attempting a nest 18.9 26.2 37.1
Percent of groups with second nests 9.8 8.8 0.0
Fall nests
Percent of groups 4.8 0.0 0.0
Percent of years 34.4 0.0 0.0
Annual reproductive success (all nests)
Young/group/year 2.53 1.67 1.06
Young/bird/year 0.61 0.58 0.49
Young/breeding attempt 2.42
Annual reproductive success (successful nests only)
Young/group/year 3.63
Young/bird/year 0.87
Young/breeding attempt 3.17
Percent of groups that successfully rear
1 brood 60.1
2 broods 10.1  
3 broods 0.1
≥ 1 brood 70.3 60.1 48.5
Sample size (no. of group years) 1784 164 33

  • Sources: Koenig and Mumme 1987, Koenig and Stahl 2007, unpublished data of the authors.

Table 2

Within-population variation in breeding group composition (breeders and nonbreeding helpers) among 3 Acorn Woodpecker populations. Listed are means (range).

 
  Hastings Reservation, California Water Canyon, New Mexico Research Ranch, Arizona
Mean breeding group size 4.60 (2–15) 2.64 (2–5) 2.15 (2–3)
Male breeders/group 1.82 (1–8) 1.23 (1–3) 1.05 (1–2)
Female breeders/group 1.30 (1–3) 1.00 1.00
Male nonbreeding helpers/group 0.87 (0–8) 0.24 (0–2) 0.10 (0–1)
Female nonbreeding helpers/group 0.61 (0–7) 0.08 (0–1) 0.00
Percent of groups a pair only 16.2 59.8 85.4
Percent of adult nonbreeding helpers 32.2 12.0 5.0
Sample size (no. of group years) 1641 164 33

  • Sources: Koenig and Stacey 1990, unpublished data of the authors.

Table 3

Mass (g) and linear measurements (mm) of Acorn Woodpeckers at Hastings Reservation, central coastal California (MTS, WDK unpubl. data).

Mean ± SDRangen
Mass
Male80.9 ± 4.961–97706
Female77.2 ± 5.063–95646
Exposed culmen
Male31.7 ± 1.726–40642
Female29.6 ± 1.524–34579
Wing chord
Male143.8 ± 4.2130–159674
Female142.8 ± 4.0130–153605
Tail
Male79.7 ± 3.968–89413
Female80.0 ± 3.961–92338


Recommended Citation

Koenig, W. D., E. L. Walters, P. B. Stacey, M. T. Stanback, and R. L. Mumme (2019). Acorn Woodpecker (Melanerpes formicivorus), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.acowoo.02