Black-headed gulls (Chroicocephalus ridibundus) are medium-sized gulls that are found across much of Europe, Asia, and North America. They are a common sight around lakes, rivers, coasts, and urban areas. But just how big are these ubiquitous birds?
Wingspan
The wingspan of an adult black-headed gull averages around 1.1-1.3 meters (3.6-4.3 feet). This makes them slightly larger than your average ring-billed gull, but smaller than herring gulls and great black-backed gulls.
Juveniles tend to have slightly shorter wingspans, averaging around 1 meter (3.3 feet). Their wings don’t reach full adult size until they are 2-3 years old.
Body Length
From the tip of the beak to the tip of the tail, adult black-headed gulls measure 35-39 cm (14-15 inches) long. Like the wingspan, juveniles are a bit smaller, averaging around 30 cm (12 inches) from beak to tail.
Here is a size comparison of black-headed gulls relative to some other common gull species:
Species | Length (cm) | Wingspan (m) |
---|---|---|
Black-headed gull | 35-39 | 1.1-1.3 |
Ring-billed gull | 51 | 1.2 |
Herring gull | 58 | 1.5 |
Great black-backed gull | 68 | 1.7 |
Weight
Adult black-headed gulls typically weigh between 180-300 grams (6-10 ounces). Males tend to be at the heavier end of that range, while females are usually closer to 180-220 grams (6-8 ounces).
Newly hatched chicks only weigh around 20 grams (.7 ounces). They reach about 75% of adult weight by the time they fledge at 4-5 weeks old.
Differences Between Males and Females
Male and female black-headed gulls are similar in size, but some subtle differences exist:
- Males tend to be slightly larger, weighing 180-300g compared to 180-220g for females.
- Males have longer wingspans on average, around 5-10cm more than females.
- Males tend to have stouter, thicker bills than females.
- Females have a more pronounced hood than males during breeding season.
But without measuring the birds or observing breeding behavior, it can be challenging to distinguish the sexes by size alone.
Changes Across Breeding and Non-Breeding Season
The size of black-headed gulls can fluctuate somewhat across seasons:
- During breeding season, the head and body feathers become more prominent, making them appear larger overall.
- Just before molting season, they may appear smaller as their feathers become worn down from the year.
- Their weight can decrease by up to 20% outside of breeding season as food becomes scarcer.
But in general, the breeding season changes in size are minor and seasonal weight fluctuations are quickly regained after molting occurs.
Subspecies Variations
There are several subspecies of black-headed gull that show slight variations in size:
- C. r. ridibundus: Nominate, found in Europe and western Asia. Medium size.
- C. r. capistratus: Found in Iceland. Tend to be smaller with darker plumage.
- C. r. vulgaris: Breeds in south-central Asia. Slightly larger than nominate with more white on forehead.
- C. r. taimyrensis: Northern central Asia. Larger with pale grey mantle.
But in general, these subspecies are all very similar in dimensions and the differences are minor.
Size Relative to Other Species
Compared to other gull species, black-headed gulls are medium-sized. They are noticeably smaller than the large species like herring, great black-backed, and glaucous gulls. But they are larger than little gulls and Bonaparte’s gulls.
Relative to other types of birds, black-headed gulls are about the same size as pigeons, crows, and ravens. They are smaller than most raptors like hawks, eagles, and osprey. And they are larger than songbirds like sparrows and warblers.
Usefulness of Size
A black-headed gull’s size helps it in several key ways:
- Their medium size and agility makes them well-suited for aerial hunting of insect swarms over land and water.
- Their wings provide enough power for migration while not being overly large and cumbersome.
- Their compact body size reduces heat loss in cold environments.
- Their thick bills are adapted for catching fish as well as scavenging.
So the black-headed gull’s size gives it versatility to exploit several food sources and adapt to different habitats across a wide geographic range.
Conclusion
In summary, black-headed gulls are a medium-sized gull species. Adults average 35-39 cm long with a wingspan of 1.1-1.3 meters and weight of 180-300 grams. Males tend to be slightly larger than females. Their size helps them adapt as aerial insectivores as well as opportunistic scavengers and predators. While subtle geographic variation exists, the species maintains a fairly consistent medium size across its widespread range.