The term “seagull” is a common name for birds belonging to the family Laridae, which are more accurately called gulls. There is no single answer to how much a gull weighs because the family includes over 50 species that vary dramatically in size and mass. An individual bird’s weight is a dynamic measurement, constantly shifting due to its species, age, sex, and the season. Understanding the weight of these birds requires looking at both the typical range of common species and the extremes found across the globe.
The Typical Weight Range for Common Gulls
Gulls frequently encountered in coastal and inland areas of North America and Europe, such as the Herring Gull and the Ring-billed Gull, define a common weight spectrum. A medium-sized Ring-billed Gull typically weighs between 300 and 700 grams (about 10.6 to 24.7 ounces). These are the smaller, more slender gulls often seen scavenging in parking lots and fields. A larger, more robust species like the American Herring Gull ranges between 800 and 1,250 grams (about 1 pound 12 ounces to 2 pounds 12 ounces). The average gull a person is likely to see weighs somewhere between two-thirds of a pound and nearly three pounds.
How Species Differences Determine Size
The variation in weight is revealed when comparing the smallest and largest members of the Laridae family. The Little Gull, the smallest species globally, can weigh as little as 120 grams (about 4.25 ounces), barely heavier than a common songbird. At the opposite end is the Great Black-backed Gull, the largest gull species in the world, which can weigh up to 2.3 kilograms (about 5 pounds 1 ounce). The difference in mass between the Little Gull and the Great Black-backed Gull spans nearly twenty times, illustrating the massive range within the family. The substantial weight of the Great Black-backed Gull allows it to dominate other seabirds.
Individual Factors Affecting Weight
Even within a single species, an individual gull’s weight can fluctuate significantly due to biological and environmental factors. One consistent variable is sexual dimorphism, where adult males are typically larger and heavier than females of the same species. For instance, male Great Black-backed Gulls average about 1,830 grams, while females average around 1,488 grams. A bird’s age also influences its mass, as gulls take several years to reach full adult size and plumage. Juvenile gulls are lighter than their mature counterparts until they complete their development, which can take up to four years in larger species.
Seasonal changes cause dramatic shifts in body mass as the birds prepare for migration or breeding. Gulls, like many migratory birds, accumulate substantial fat reserves in a process called hyperphagia before long flights. This strategic weight gain, primarily stored as fat to fuel the energetically demanding migration journey, causes a peak in body mass in the late winter or early spring. Conversely, weight tends to be at its lowest point during the intense physical demands of the breeding season as energy is expended on incubation, parental care, and flying to forage.