Larus spp. Linnaeus, 1758

Gull

The 'seagull' that nests on flat rooftops and commutes to landfills.

Order: Charadriiformes
Family: Laridae
Group: Birds
Ontario status: Native, nuisance at landfills/rooftops

Why it matters

Rooftop colonies foul membranes and clog drains; aggressive nest defense endangers rooftop workers; landfill foraging spreads waste.

Origin

Native coastal and inland waterbirds; several species learned that flat rooftops are cliffs and landfills are shorelines.

Behavior

Diurnal; highly social and intelligent; aggressively defends nests, dive-bombing intruders. Long-lived and site-faithful.

Living conditions

Colonial nesters on flat rooftops, islands, and industrial sites; forage at landfills, parking lots, and waterfronts.

Signs of presence

Scrape nests of grass and debris on flat rooftops
Whitewash and feather accumulation on roof membranes
Aggressive dive-bombing near rooftop access points in spring
Flocks commuting between rooftops and landfills

Weaknesses

Colonial: the whole problem is one rooftop, exclude it and the colony relocates
Nesting is seasonal, exclusion installed before spring prevents the season
Food-driven: waste management at the source shrinks the local population

Myths and facts

Myth Gulls only live at the sea.
Reality Many gull species nest on flat rooftops and feed at landfills far inland, the 'seagull' is a city bird now.

Research notes

Morphology

Herring gull exemplar: body 55-65 cm, wingspan 120-140 cm, weight 800-1300 g. White-grey plumage, yellow bill with red spot, pink legs. Juveniles mottled brown, maturing over 4 years.

Diagnostics

Large white-grey gull with yellow bill; raucous calls; webbed feet; colonial rooftop scrapes in season.

Easily confused with

Ring-billed gull (Larus delawarensis) Smaller with a black ring on a yellow bill; the commonest inland Ontario gull, management approach is the same.

Life cycle

Adult: Lifespan 15-30+ years; breeding from age 4
Egg: Clutch 2-3; incubation 26-28 days
Egg to adult: Hatch to fledging ~40 days; maturity at 4 years
Generations per year: 1 brood/year
Nymph or larva: Chicks fledge at ~35-40 days; dependent for weeks after

Development

Oviparous; semi-precocial chicks.

Reproduction

2-3 eggs per clutch × 1 brood/year.

Distribution

Global: Worldwide (genus)
Native range: Coastal and inland North America (species-dependent)
Ontario: Native, nuisance colonies on flat rooftops and at landfills

Ecology

Colonial ground-nesters; opportunistic omnivores; extreme site fidelity, colonies reuse rooftops for decades; long-lived K-selected life history.

Resistance

Unknown.

IPM implications

Rooftop exclusion (netting, wire systems) installed before nesting season; nest management where permitted; waste management at the source. Colonial nesting means site-level work, and timing is everything, many gull species are protected under migratory bird conventions, so species ID and permits come before action.

Chemical ecology

Limited; vocal and visual communication dominate. Preen-gland secretions for waterproofing.

Genetics and DNA

No reference genome published as of 2026.

Taxonomy

Order Charadriiformes › family Laridae › genus Larus spp. Genus-level entry; American herring gull (L. smithsonianus) used as the Ontario exemplar.

Open questions

Species-level rooftop colony dynamics in the GTA are undocumented.

References

Cornell Lab of Ornithology, Herring Gull (All About Birds)
Internet Center for Wildlife Damage Management, Gulls