Razorbills are medium-sized seabirds that belong to the alcid family. They are closely related to auks and puffins and breed in colonies on rocky cliffsides and islands. Razorbills have black heads, backs, and wings during the breeding season which then fades to black-brown in winter. Their bellies are white and their thick bills are black and blunt-tipped.
How big do razorbills get?
Razorbills are medium-sized birds, averaging about 16-18 inches (40-46 cm) in length with a wingspan of around 25-27 inches (64-69 cm). Their bodies are plump and they weigh on average around 1.5 pounds (680 grams). Males tend to be slightly larger than females.
Some key size measurements for razorbills include:
| Measurement | Size |
|---|---|
| Length | 16-18 inches (40-46 cm) |
| Wingspan | 25-27 inches (64-69 cm) |
| Weight | Around 1.5 lbs (680 g) |
So in summary, razorbills are medium-sized seabirds, similar in length to their close relatives the puffins and guillemots. Their plump body shape gives them a stocky appearance compared to some other alcid species.
How do razorbill sizes compare to other birds?
Compared to other seabird species, razorbills are medium in size:
- Smaller than gulls like herring gulls and great black-backed gulls
- Similar in size to thick-billed murres
- Larger than little auks
- Smaller than gannets and cormorants
Some specific size comparisons:
| Bird Species | Length | Wingspan |
|---|---|---|
| Razorbill | 16-18 in (40-46 cm) | 25-27 in (64-69 cm) |
| Atlantic Puffin | 12-16 in (30-40 cm) | 20-27 in (50-69 cm) |
| Thick-billed Murre | 16-18 in (40-46 cm) | 26-29 in (66-74 cm) |
| Herring Gull | 25 in (63 cm) | 59 in (150 cm) |
So razorbills are around the same size as puffins and murres, but smaller than the predatory gulls they share habitat with.
How much variation is there among individual razorbills?
There can be some moderate variation in size among individual razorbills. Some key points:
- Males tend to average slightly larger than females in most measurements
- Older birds tend to be larger than younger ones
- Size can vary slightly across different populations and subspecies
- The largest razorbills measure up to 21 inches (53 cm) long with a 30 inch (76 cm) wingspan
However, most measurements for any given population cluster around the averages mentioned earlier. Significant deviations from the norm in terms of length, wingspan, and weight are uncommon in healthy adult birds.
Why is body size important for razorbills?
A razorbill’s body size impacts many aspects of its life and ecology, including:
- Flight ability – Their small-medium size with stubby wings makes them agile flyers capable of rapid takeoff from water, but less efficient at long-distance sustained flight than some larger seabirds
- Diet – Their bill size and shape allows them to catch small fish, crustaceans and other food items
- Reproduction – Males must be large enough to defend nesting sites and attract mates
- Thermoregulation – Their plump body shape helps retain heat in cold northern environments
- Predator avoidance – Their compact shape allows them to dive and swim away from aerial predators. Their medium size means they are vulnerable to some predators but less so than smaller auks
So a razorbill’s body size represents an evolutionary adaptation to its lifestyle and environment. Significant deviations from normal size could negatively impact the bird’s ability to thrive.
How do young razorbills grow to adult size?
Like most birds, razorbills are relatively small and helpless when they hatch. They grow rapidly to adult size within their first few months of life. Some key facts about their growth process:
- Hatchlings weigh only around 1.5-2 oz (40-60 grams) and measure 3-4 inches (8-10 cm)
- They depend completely on their parents for food and protection early on
- They start to grow flight feathers around 15-21 days and make their first flights by 35-40 days
- They reach about 75% of adult mass by around 50 days old
- They fledge and leave the nest by 40-45 days old, but still can’t feed independently
- They reach full adult size by around 3-4 months old
Razorbill chicks grow remarkably fast, increasing their body mass 50-100 times over in just a few months. This rapid development is essential so they can leave their nesting colonies and head out to sea before the winter arrives.
Conclusion
In summary, razorbills are medium-sized seabirds that measure 16-18 inches long with a wingspan around 25-27 inches. Their body size is well-adapted to their lifestyle hunting small fish and other prey in northern coastal environments. Their growth from tiny hatchlings to full adult size in just months is incredibly rapid. While individual variation in size occurs, most adult razorbills cluster around the typical size ranges for the species.
