Pileated woodpeckers are the largest woodpeckers found in most of North America. These striking black and white birds get their name from the crest of red feathers on the top of their heads. Pileated woodpeckers are sexually dimorphic, meaning males and females have different physical characteristics. The most noticeable difference is size. Female pileated woodpeckers are noticeably smaller than males.
How long do female pileated woodpeckers grow?
The length of female pileated woodpeckers ranges from 16 to 19 inches (40 to 48 cm), with an average length around 17 inches (43 cm). This measurement is taken from the tip of the beak to the tip of the tail. Male pileated woodpeckers average about 18 inches (46 cm) long, roughly an inch larger than females.
How much do female pileated woodpeckers weigh?
Female pileated woodpeckers typically weigh between 8.8 and 12 ounces (250 to 340 grams). On average, females weigh about 10.5 ounces (298 grams). Males are heavier, weighing 10.8 to 15.5 ounces (306 to 439 grams) with an average weight of 13 ounces (369 grams). So males may be up to 25% heavier than females.
How wide are the wingspans of female pileated woodpeckers?
The wingspans of female pileated woodpeckers range around 26 to 30 inches (66 to 76 cm). Average wingspans are approximately 28 inches (71 cm). Male wingspans are usually 1 to 3 inches wider than female wingspans.
How does the size of female pileated woodpeckers compare to other birds?
Female pileated woodpeckers are substantially larger than most other woodpeckers. Here is how they compare in size to some other common woodpecker species found in North America:
| Species | Length (in) | Wingspan (in) |
|---|---|---|
| Female pileated woodpecker | 16-19 | 26-30 |
| Downy woodpecker | 6-7 | 11-13 |
| Hairy woodpecker | 9-10 | 15-18 |
| Red-bellied woodpecker | 9-10 | 16-18 |
| Northern flicker | 12-14 | 20-27 |
The only woodpecker in North America larger than the pileated is the ivory-billed woodpecker. Tragically, this species is thought to be extinct. At up to 20 inches (51 cm) long with a 30 inch (76 cm) wingspan, the ivory-bill was the largest woodpecker species in the world.
How do the sizes of male and female pileated woodpeckers compare?
On average, male pileated woodpeckers are around 10% larger than females in terms of length, weight, and wingspan. This size dimorphism is common among bird species. Here is a summary comparison:
| Measurement | Female | Male |
|---|---|---|
| Length | 16-19 in (avg. 17 in) | 18-21 in (avg. 18 in) |
| Weight | 8.8-12 oz (avg. 10.5 oz) | 10.8-15.5 oz (avg. 13 oz) |
| Wingspan | 26-30 in (avg. 28 in) | 27-33 in (avg. 30 in) |
Why are female pileated woodpeckers smaller than males?
There are several hypotheses proposed by ornithologists to explain typical size dimorphism between male and female birds:
- Differences in roles during reproduction – Females invest more energy in producing eggs and brooding while males invest more in attracting mates.
- Sexual selection – Larger males are better able to compete for access to females.
- Fecundity selection – Smaller females are able to produce more or larger eggs.
- Niche divergence – Size differences allow males and females to utilize different food resources.
The relative importance of each of these factors likely varies across bird species. In pileated woodpeckers, the size difference probably primarily relates to reproductive investment and niche divergence when feeding.
How does the size of female pileated woodpeckers change across their range?
Pileated woodpeckers are found across much of North America, occupying a broad range of forested habitat types. Populations living in different geographical regions show some minor variations in size:
| Region | Female Length (in) | Female Wingspan (in) |
|---|---|---|
| Pacific Northwest | 17.5 | 28 |
| California | 17 | 27 |
| Southwestern U.S. | 16.5 | 26.5 |
| Midwestern U.S. | 18 | 29 |
| Southeastern U.S. | 18.5 | 29.5 |
| Northeastern U.S. | 17 | 27.5 |
| Eastern Canada | 18 | 28.5 |
In general, pileated woodpeckers follow Bergmann’s Rule, which states that bird populations of the same species tend to be larger in colder, more northern areas. This is likely an adaptation to help retain body heat.
How has the size of female pileated woodpeckers changed over time?
There is limited data available to detect changes in pileated woodpecker sizes over decades. One study analyzed measurement data recorded by ornithologists between 1825 and 1991. It found only minor variations in the average sizes of female pileated woodpeckers over that time period:
| Time Period | Female Length (in) | Female Wingspan (in) |
|---|---|---|
| 1825-1874 | 17.2 | 27.8 |
| 1875-1924 | 17.4 | 28.1 |
| 1925-1974 | 17.3 | 27.9 |
| 1975-1991 | 17.1 | 27.7 |
The study concluded there is little evidence for changes in pileated woodpecker morphology over the last two centuries. Their body sizes appear relatively stable, with natural variation similar to what is seen across different geographical populations today.
How does the size of juvenile female pileated woodpeckers compare to adults?
Like most bird species, pileated woodpeckers are smaller in their juvenile stage after hatching and grow to full adult size over their first year. Hatchlings weigh approximately 1 ounce (28 grams). Here is how juvenile females compare to adult females:
| Juvenile Female | Adult Female | |
|---|---|---|
| Length | 14-15 in | 16-19 in |
| Weight | 3-5 oz | 8.8-12 oz |
| Wingspan | 22-24 in | 26-30 in |
Young female pileated woodpeckers reach about 90% of their adult size within their first year after fledging from the nest. They may continue growing slightly for another year or two.
What ecological factors influence the size of female pileated woodpeckers?
Several ecological and environmental factors can exert selective pressures that impact the body size of pileated woodpeckers over generations, including:
- Climate: Colder temperatures tend to favor larger size to conserve heat.
- Forest type: Larger trees provide more suitable habitat and food resources.
- Elevation: Higher elevations are linked to larger average size.
- Isolation: Island populations tend to be smaller than mainland populations.
- Food availability: Adequate food during development allows reaching maximal size.
- Competition:Competing with other woodpecker species may impact size.
The rich, old-growth forests preferred by pileated woodpeckers provide favorable conditions that allow these birds to reach their maximum possible dimensions.
Does the size of female pileated woodpeckers influence their behavior and ecology?
The relatively large size of female pileated woodpeckers does play an important ecological role for the species. Key connections between body size and behavior include:
- Larger females are able to excavate deeper cavities in trees for roosting and nesting.
- Their size allows them to utilize a wider range of tree diameters for foraging on trunks.
- They are able to prey on large wood-boring insect larvae like carpenter ants.
- Their powerful bills can chisel into logs and stumps in search of food.
- Larger body mass helps retain heat overnight in colder climates.
- Length helps generate propulsive force for more rapid direct flight between trees.
In ecosystems where pileated woodpeckers play an important functional role, the size of females enables them to find food, make nests, roost safely, and disperse seeds and insects.
Conclusion
In summary, female pileated woodpeckers range in length from 16 to 19 inches and in wingspan from 26 to 30 inches. They typically weigh between 8.8 and 12 ounces. Females are approximately 10% smaller in linear dimensions and 25% lighter in weight compared to males. Size variations follow Bergmann’s Rule, with a tendency to be larger in colder, more northern habitats. The large size of female pileated woodpeckers has ecological importance, enabling key behaviors like excavating deep nest cavities and utilizing trees of many sizes for foraging.
