What is the difference between little gull and Bonaparte?

Little gulls and Bonaparte’s gulls are two similar-looking species of seagulls found in North America. While they share some similarities and can be confused with one another, there are several key differences between these two types of gulls.

Appearance

In terms of physical appearance, little gulls and Bonaparte’s gulls look quite alike at first glance. They are both small, slender gulls with long, pointed wings and short, black legs. Adult little gulls measure around 33–38 cm in length with a wingspan of 76–87 cm. Bonaparte’s gulls are very close in size, measuring 34–38 cm in length with a wingspan of 76–80 cm. So in terms of their overall size and proportions, these two species are almost identical.

Looking more closely, some subtle differences in plumage can help distinguish little gulls from Bonaparte’s gulls:

• Adult little gulls in breeding plumage have a black hood with a white crescent shape behind the eye. Bonaparte’s gulls have a black hood but lack the white crescent.
• Little gulls have an entirely black bill, while Bonaparte’s gulls have a black bill with a reddish-orange spot near the tip.
• The legs of little gulls are a dark red color, whereas Bonaparte’s gulls have pinkish legs.
• In flight, little gulls show a dark gray wing underside compared to the white underwing of Bonaparte’s gulls.

In non-breeding plumage, both species appear more alike with dark gray upperparts and white underparts. However, the subtle bill and leg differences can still help identification.

Range and Habitat

These two gull species occupy very different natural ranges in North America:

• Little gulls breed in the interior of Alaska and Northern Canada. They migrate along the Atlantic Coast and the Great Lakes, wintering along the U.S. coast and as far south as Central America and northwestern South America.
• Bonaparte’s gulls breed primarily around inland lakes and marshes in Canada and the northern U.S. They winter along both the Atlantic and Pacific Coasts south to Mexico and the Caribbean.

During migration and winter, little gulls and Bonaparte’s gulls frequent many of the same coastal habitats and inland lakes. But their breeding ranges do not overlap, with little gulls restricted to more northern boreal regions.

Diet

The diets of little gulls and Bonaparte’s gulls are quite similar since they frequent comparable aquatic environments:

• Both species are highly opportunistic feeders.
• They feed extensively on small fish like smelt, anchovies, and minnows.
• They also consume aquatic insects and the eggs and young of other bird species.
• When near shore, they will scavenge scraps and snails, shrimp, and other invertebrates.

Since they inhabit the same types of habitats and fill comparable ecological niches, little gulls and Bonaparte’s gulls generally have very similar diets.

Migration

As mentioned above, little gulls and Bonaparte’s gulls have very different migration patterns and wintering ranges even though their migrations overlap in some areas:

Some key differences stand out:

• Little gulls undertake an extremely long migration, traveling from Alaska all the way down to South America.
• Bonaparte’s gulls migrate shorter distances since their breeding range extends farther south into the northern U.S.
• Little gulls mainly winter along the U.S. Atlantic Coast, while Bonaparte’s gulls are found along both coasts.

So while their migrations overlap along the U.S. coasts, little gulls generally migrate much farther distances compared to Bonaparte’s gulls.

Nesting and Reproduction

As boreal nesters, little gulls have a relatively short, intense breeding season compared to Bonaparte’s gulls:

• Little gulls arrive at their Arctic breeding grounds in late May and nest in June. The female lays 2-3 eggs in a nest built on marshy tundra.
• Bonaparte’s gulls arrive at more southerly nesting sites in April and may not lay eggs until June. Nests are built near ponds or lakes, with 2-4 eggs per clutch.
• Little gull chicks hatch in July and fledge within 3-4 weeks. Bonaparte’s gull chicks fledge after about 4 weeks.
• Little gulls depart breeding sites by late August or early September. Bonaparte’s gulls leave more southern nesting areas in September and October.

So while both species have comparable clutch sizes and chick development times, little gulls are highly time-constrained by the short Arctic summer. They must breed, hatch young, and fledge chicks extremely quickly before migrating south again.

Population Differences

Global population estimates reveal major differences between these species:

• Little gulls have a relatively small total population estimated at 50,000 to 170,000 individuals globally.
• Bonaparte’s gulls are roughly 10 times more abundant, with a global population of approximately 1 to 1.5 million birds.

The little gull is the rarer of these two species and faces greater conservation concerns due to its small population size. Its reliance on vulnerable wetland habitats adds to concerns over habitat loss impacts.

Taxonomy

Little gulls and Bonaparte’s gulls belong to the same genus Chroicocephalus in the gull family Laridae. However, they are classified as two distinct species:

• Little gull: Chroicocephalus minutus
• Bonaparte’s gull: Chroicocephalus philadelphia

Some shared physical traits support their close taxonomic relationship, such as their small size, dark hoods, and slender wings adapted for agile flight over open water. Genetic research confirms they diverged as separate gull species at least 2-3 million years ago.

Conservation Status

The little gull and Bonaparte’s gull differ significantly in their conservation status:

• Little gull: classified as Least Concern by the IUCN Red List but with a decreasing global population. Vulnerable to habitat loss and disturbance on Arctic breeding grounds.
• Bonaparte’s gull: classified as a species of Least Concern with a stable global population estimate. Still common and widespread throughout its range.

While neither species is currently threatened, little gulls face higher risks from climate change, habitat degradation, and human activity in the remote Arctic regions where they breed. Maintaining protected wetland habitats will benefit the conservation of little gulls in the future.

Threats

Some specific threats that disproportionately impact little gulls compared to the more abundant and widespread Bonaparte’s gull include:

• Oil drilling, mining, roads, and development in Arctic nesting areas
• Drying of northern wetlands due to changing precipitation and permafrost thaw
• Expanded Arctic shipping lanes and marine traffic
• Biomagnification of pollutants in marine food webs
• Increased predation pressure from expanding populations of foxes, gulls, and other predators

All gull species face threats from plastics, fishing gear, and lead poisoning. But little gulls are much more vulnerable overall due to their small population size and reliance on remote Arctic ecosystems.

Summary of Differences

In summary, here are some of the key differences that distinguish little gulls from the similar-appearing Bonaparte’s gulls:

• Breeding plumage: Little gulls have a white crescent behind the eye; Bonaparte’s lack this mark
• Bill color: Black in little gulls, black with orange spot in Bonaparte’s
• Legs: Dark red in little gulls, pinkish in Bonaparte’s
• Range: Little gulls breed farther north in the Arctic; Bonaparte’s breed across Canada and the northern U.S.
• Migration: Little gulls undertake a much longer migration down to South America
• Population: Little gulls have a global population under 200,000; Bonaparte’s number over 1 million
• Conservation: Little gulls are more vulnerable with declining populations

Conclusion

In conclusion, while little gulls and Bonaparte’s gulls occupy similar ecological niches and may be confused with one another, they are distinctly different gull species. Careful attention to details of plumage, bill color, breeding range, and population status helps properly differentiate these species. Of the two, little gulls face higher conservation concerns due to their small global population, reliance on threatened Arctic habitats, and extreme long-distance migrations. Continued monitoring and protection of vulnerable wetlands will help safeguard the future of the little gull.