The purple finch is a small but vibrantly colored songbird found across much of North America. With its rosy red head and raspberry-colored body, the purple finch stands out among its mostly brown sparrow relatives. Though beautiful, purple finches are rather small, only reaching about 6 inches in length. Their size can vary based on age, sex, and geographic location. In this article, we’ll take a closer look at just how big purple finches really get.
Average Size of Purple Finches
On average, most purple finches measure between 4.7 and 6.3 inches in length (12 to 16 cm). This makes them slightly smaller than a sparrow. Here is a more detailed breakdown of their average dimensions:
- Total length: 5.1 – 6.3 inches (13 – 16 cm)
- Wingspan: 8.7 – 9.8 inches (22 – 25 cm)
- Weight: 0.6 – 1.1 ounces (18 – 32 grams)
The wingspan measurement refers to the distance from the tip of one wing to the tip of the other when the wings are fully outstretched. The weight range encompasses both male and female finches.
These average sizes can fluctuate slightly based on the bird’s age and sex. But overall, 5-6 inches from head to tail is typical for most purple finches. That’s only a bit smaller than an American robin.
Size Differences Between Males and Females
There are some size differences between male and female purple finches. Males tend to be slightly larger than females.
Here are the average dimensions based on sex:
Male Purple Finches
- Total length: 5.5 – 6.3 inches (14 – 16 cm)
- Wingspan: 9.1 – 9.8 inches (23 – 25 cm)
- Weight: 0.7 – 1.1 ounces (21 – 32 grams)
Female Purple Finches
- Total length: 4.7 – 5.5 inches (12 – 14 cm)
- Wingspan: 8.7 – 9.4 inches (22 – 24 cm)
- Weight: 0.6 – 0.9 ounces (18 – 26 grams)
As you can see, the males tend to be around half an inch longer than females on average. They also have slightly broader wingspans and weigh a bit more as well. These size differences are common among many bird species in which the males are more colorful or ornamented than the females. The size dimorphism is thought to result from sexual selection acting more strongly on males.
Differences Based on Age
A purple finch’s size also depends on its age. Like most birds, purple finches are smallest when they first hatch and grow through a series of molts as they mature.
Here are the average sizes at different ages:
Hatchlings
- Total length: 1.5 – 2 inches (3.8 – 5 cm)
- Weight: 0.2 – 0.3 oz (5 – 8 g)
Fledglings
- Total length: 3.5 – 5 inches (9 – 13 cm)
- Weight: 0.4 – 0.8 oz (12 – 24 g)
Juveniles
- Total length: 4.5 – 5.5 inches (11 – 14 cm)
- Weight: 0.5 – 0.9 oz (15 – 26 g)
Adults
- Total length: 5 – 6.5 inches (13 – 16.5 cm)
- Weight: 0.6 – 1.1 oz (18 – 32 g)
Hatchlings are tiny, weighing less than a quarter ounce. They grow quickly as fledglings and juveniles. By adulthood at 1 year old, they reach their maximum size. Adult dimensions are maintained throughout their lifespan.
Geographic Size Variation
The size of purple finches also shows some geographic variation across different parts of their range. There are four recognized subspecies that display subtle differences in body size:
- Carpodacus purpureus purpureus – Eastern purple finch. Found in eastern North America.
- Carpodacus purpureus californicus – California purple finch. Native to the West Coast.
- Carpodacus purpureus minor – Cassin’s purple finch. Found along the Pacific Coast.
- Carpodacus purpureus oweni – Interior West purple finch. Inhabits Rocky Mountains.
Some research has found that the California, Cassin’s, and Interior West subspecies tend to be slightly larger than the nominate Eastern purple finch. But there is overlap between them, and the differences amount to just a few millimeters in most cases.
Purple Finch Size Compared to Other Birds
How does the purple finch’s size stack up against some other common backyard birds? Here is a chart comparing their average lengths:
| Bird Species | Total Length |
|---|---|
| American Goldfinch | 4.3 – 5.1 inches |
| House Sparrow | 6.3 inches |
| Purple Finch | 5.1 – 6.3 inches |
| Northern Cardinal | 8.3 – 9.1 inches |
| Tufted Titmouse | 5.5 – 6.3 inches |
| American Robin | 7.9 – 10.2 inches |
The purple finch is very similar in size to a tufted titmouse. It’s noticeably smaller than an American robin but larger than a goldfinch or Carolina wren. Its stout, conical bill and distinctly purple plumage help distinguish it from similar-sized birds.
Wingspan Comparisons
In addition to length, wingspan is another useful measurement for comparing bird sizes. Here are how some common species compare in average wingspan:
| Bird Species | Wingspan |
|---|---|
| Mourning Dove | 17.3 inches |
| Blue Jay | 11.8 – 17.1 inches |
| Purple Finch | 8.7 – 9.8 inches |
| Black-capped Chickadee | 7.1 – 10.6 inches |
| American Crow | 33.5 – 39.4 inches |
The purple finch has a wingspan about 2/3 as wide as a mourning dove and roughly 3/4 as wide as a blue jay. It’s only slightly broader than a chickadee. But it’s dwarfed by the expansive wingspan of an American crow.
Factors Influencing Size
Several factors contribute to the range of sizes observed in purple finches:
Sexual Dimorphism
As mentioned earlier, males are larger than females on average. This type of sexual dimorphism is common in many bird species. It may result from sexual selection related to competition between males for mates.
Individual Variation
There is natural individual variation in size, with some birds falling at the smaller or larger end of the range. Larger birds may have an advantage competing for food resources and mates. But smaller birds require less energy, so they may persist in the population despite disadvantages.
Nutritional Status
A bird’s access to food resources directly impacts its growth and development. Purple finches with high quality diets tend to be larger and heavier than nutritionally deprived individuals of the same age and sex.
Subspecies Differences
As mentioned earlier, the four subspecies display subtle geographic variation in body dimensions. These local adaptations may help birds be more suited to conditions in their particular region.
Bergmann’s Rule
This ecogeographic principle predicts that within a species, populations and subspecies in colder climates at higher latitudes tend to be larger. The pattern holds true in purple finches, with larger bodied birds at northern latitudes. The increased size may help conserve heat in cold environments.
Uses for Size Estimates
Knowing the typical size range of purple finches is useful for a few reasons:
- Aids in field identification – Size is one clue to help distinguish lookalike species.
- Tracks developmental progress – Changes in length and weight track a young bird’s growth.
- Highlight conservation needs – If extreme highs or lows are seen, it may indicate habitat or nutritional issues.
- Compares diet quality across range – Birds on high quality diets reach larger maximum sizes.
So while purple finches may seem rather petite, their size can provide meaningful insights into their development, ecology, and conservation status across North America.
Purple Finch Nestlings
To get a full picture of how purple finches grow, we also need to look at their size as nestlings.
Purple finches lay 3-6 eggs per clutch. The eggs are pale blue or greenish-blue with brown speckles. They measure about 0.8 inches long and 0.6 inches wide (2 cm x 1.5 cm).
When the chicks first hatch, they are helpless and only around 1 inch long, weighing just a few grams. But they grow quickly thanks to devoted care from both parents.
Here is how a purple finch nestling develops:
Day 1
- Total length: 1 – 1.25 inches (2.5 – 3.2 cm)
- Weight: Around 0.2 ounces (5-6 g)
- Eyes closed, no feathers
- Feeding via parents’ regurgitation
Day 5
- Total length: 2.2 – 2.5 inches (5.5 – 6.5 cm)
- Weight: 0.3 – 0.5 ounces (8 – 15 g)
- Pin feathers emerging
- Increased appetite
Day 9
- Total length: 3 – 3.5 inches (7.5 – 9 cm)
- Weight: 0.5 – 0.8 ounces (15 – 24 g)
- Feather quills open
- Bright fledgling plumage
Day 13
- Total length: 3.5 – 4 inches (9 – 10 cm)
- Weight: 0.6 – 1 ounce (17 – 30 g)
- Fully feathered
- Ready to fledge
After two weeks of rapid growth, the nestling is ready to leave the nest. It will continue growing for several more weeks as a fledgling and juvenile before reaching mature adult size. Regular measuring of nestlings provides a useful indicator of the colony’s overall health.
Conclusion
So how big do purple finches get after all? Based on their total length, wingspan, and weight, they reach a maximum size of approximately 6 inches long with a 10 inch wingspan and weight of 1 ounce. Males tend to be slightly larger than females on average. Babies grow from 1 inch hatchlings to full adult dimensions within 2 months after hatching. Their petite size compared to other birds makes them adaptable to backyard bird feeders across North America. Keep an eye out for these colorful songbirds, and you’ll see just how diminutive they really are!
