Leucophaeus pipixcan Wagler, 1831
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Leucophaeus pipixcan, Larus pipixcan
Basis for Listing
The Franklin's gull is largely a bird of the northern Great Plains. Its main breeding range extends from western Minnesota through eastern North Dakota, southwestern Manitoba, central and southern Saskatchewan, and eastern Alberta. Breeding has also been recorded in states south of this range, including Iowa, South Dakota, Idaho, Wyoming, and Oregon (Burger and Gochfeld 1994).
The Franklin's gull is a medium-sized gull. During the breeding season, they have a black head, white eye crescents, and a red bill. Outside the breeding season, they have a gray cap that extends just around the eyes, and a white forehead and chin. The uppersurface of the wings is dark gray, with black and white tips. The Franklin's gull is one of several gulls with a black head, but it is the only such species that regularly nests in Minnesota. Of the other species of gulls with black heads that may occur in Minnesota, all are very rare except for the Bonaparte's gull (Larus philadelphia), which is common during spring and fall migration. Slightly smaller in size, the Bonaparte's gull is best distinguished from the Franklin's gull by the prominent white wedge on the uppersurface of its wings, which is absent in the Franklin's gull.
Large prairie marshes are critical breeding habitat for the Franklin's gull, as they nest over water and in colonies. They prefer areas with low vegetation density, or areas along the interface between cattails and open water. Habitat with patches of low or intermediate vegetation densities interspersed with areas of open water is considered optimal breeding habitat (Burger and Gochfeld 1994). Summer feeding habitats for this species include wet pastures, farm fields, and marshes, with bays and estuaries used during the winter (Burger and Gochfeld 1994).
Biology / Life History
Migration is highly synchronous within a given Frankliln's gull colony. Birds fly south, beginning in August, to wintering grounds in coastal bays and estuaries. Large numbers of this species have been observed wintering in coastal Peru. Spring migration timing may be related to insect availability (Burger and Gochfeld 1994). Flocks choose a new breeding colony site each spring, depending on water level and vegetation density. Water must be deeper than 80 cm (31.5 in.), and patches of sparse or moderate vegetation are preferred. Franklin's gull colonies are usually monospecific, consisting of hundreds, thousands, or tens of thousands of gulls. As males arrive in spring, each claims a territory and calls to attract a mate. Each male may also begin construction of a floating nest platform, but nests are not completed until pairs form. These nests, created from marsh vegetation such as bulrushes or cattails, consist of a platform, cup, and ramp leading to the nest. Franklin's gulls often steal material from other nests instead of cutting their own. Both parents add new nest material throughout the breeding season after a rainfall or as decaying nest material sinks (Burger and Gochfeld 1994). Breeding is highly synchronous within each colony. In Minnesota, females lay a clutch of 2-3 smooth, brown or olive eggs in mid-May. Both parents incubate eggs, and pairs defend an area 2-3 m (7-10 ft.) around the nest. After 23-26 days, the semiprecocial young hatch. Chicks leave the nest after 32-35 days (usually around the 4th of July in Minnesota) and disperse. Due to short summers in the north, there is no time for a second brood (Burger and Gochfeld 1994).
Conservation / Management
Franklin's gulls are highly susceptible to disturbance. Early in the breeding cycle, human disturbance may cause all birds to abandon a colony site. Later in the cycle, chicks may leave the nest and get lost or drown if disturbed by people. Fluctuating water levels may also cause colony desertion or increased mortality. Increased water levels due to storms can threaten eggs and chicks. Decreasing water levels, due to drawdown or other factors, can leave chicks more vulnerable to land predators such as raccoons (Procyon lotor), foxes, and skunks (Burger and Gochfeld 1994). Aerial predators, such as great horned owls (Bubo virginianus), and northern harriers (Circus cyaneus), and aquatic predators such as mink (Mustela vison), prey on chicks and adults. If predator numbers are high, adults may abandon nests at night, leaving chicks to die of exposure. Nest site competition between Franklin's gulls and American coots (Fulica americana) can also cause Franklin's gulls to abandon the area (Burger and Gochfeld 1994). Additionally, nests may be damaged by moose (Alces alces) as they travel through a marsh.
Conservation Efforts in Minnesota
The DNR's Nongame Wildlife Program funded a survey of Franklin's gulls in 1984. The survey located two active colonies at North Heron Lake in Jackson County. However, the researchers noted that flooding in June followed by low water levels (45 cm (17.7 in.)) in July caused most Frankllin's gulls to abandon the colony that year (Vorland 1984). In 1997, nesting colonies were confirmed at Agassiz National Wildlife Refuge and Thief Lake Wildlife Management Area in Marshall County, and at Rocky Point in Lake of the Woods County, North Long Lake in Crow Wing County, and Lake Osakis in Douglas and Todd counties. Monitoring of all current nesting sites is suggested to ensure healthy colonies and document any population changes. Habitat conservation and protection from human disturbance and water level fluctuations is imperative at these sites. Searches for other colonies should be initiated. Habitat restoration of historical Franklin's gull colony sites is also warranted.