Brown-hooded Gull Chroicocephalus maculipennis Scientific name definitions

The Brown-hooded Gull is a small hooded gull of southern South America. Though it is commonly found on the coasts, the species generally breeds in freshwater marshes, sometimes with other colonial waterbirds such as White-faced Ibis (Plegadis chihi). During the non-breeding season, Brown-hooded Gulls mix with other small gulls such as Franklin's and Gray-hooded Gulls and feed on aquatic invertebrates gleaned from the surface of the water. They can be identified by relatively small size, a powdery brown half-hood (alternate adults), white outer primaries with black tips from above, and a black patch on the primaries from below.

35–37 cm; 280–361 g. Two-year gull. The breeding adult has the frontal hood chocolate brown to dark brown, darker at rear, forming blackish margin; white crescents behind eye  ; neck white; underparts white, commonly suffused with pink; back and upperwings  grey; outer primaries white, all but outermost primaries tipped black; undersurface of primaries black , with broad white triangle at wingtip (pattern visible at a distance); tail white; bill dark red, blackish distally; legs  orange-red; eye brown. Similar to allopatric Black-headed Gull (Chroicocephalus ridibundus); adults differ in having a more extensive white flash on the outer upperwing; five white outer primaries lacking black tips, at least in southern populations; more northern birds have more restricted white on the outer primaries with a black subapical zone, a pattern approaching that of L. serranus (1 Fjeldså, J., and N. Krabbe (1990). Birds of the High Andes: A Manual to the Birds of the Temperate Zone of the Andes and Patagonia, South America. Zoological Museum, University of Copenhagen and Apollo Books, Copenhagen and Svendborg, Denmark. Close ). Non-breeding adult (from mid Feb) has white head with few dark spots behind eye; moults back to breeding plumage in Jun–Jul. Juvenile mottled brown on back, wings and head, with narrow black trailing edge to wing, and narrow black subterminal tail bar; bill dull orange, with black tip; legs brownish. Back and wing-coverts become greyish in first-winter. First-summer birds have a partial dark hood.

SC Chile and SE Brazil (Rio Grande do Sul) S to Tierra del Fuego and Falkland Is. Winters N to N Chile and CE Brazil.

Sea coasts , rivers, lakes and marshes; in winter also frequents sewage outfalls, slaughterhouses, harbours and fields. Breeds mainly on freshwater or alkaline lakes and esteros (marshes) among emergent vegetation (Scirpus), but also on rocky peninsulas or high shingle beaches; in Chile among rushes at lakes or rivers close to the sea; in Falklands up to 5 km inland, and in Argentina far inland.

Relatively sedentary, dispersing to large rivers and coastal areas after breeding.

Largely insectivorous, but in Chile breeding birds feed mainly on small fish  ; takes offal and carrion when available . Forages over marshes, damp fields or pastures, and agricultural land; frequently feeds behind plough. It is strongly associated with ploughing activities on the Argentinian pampas, where insects and earthworms are the most important prey categories. Among the former Coleoptera are the main prey in Sept and Orthoptera in Mar; they are important consumers of white beetle grubs, mainly Philochloenia bonariensis and Cyclocephala signaticollis, that are serious crop pests locally (2 Ghys, I. and Favero, M. (2004). Espectro trófico de la Gaviota Capucho Café (Larus maculipennis) en agroecosistemas del sudeste de la provincia de Buenos Aires, Argentina. Ornitología Neotropical. 15: 493–500. Close ). Occasionally hawks flying insects. Known to attend rubbish and fish dumps in coastal Patagonia but the main attraction there may be insects and other live prey using the dumps (3 Yorio, P., and M. Giaccardi (2002). Urban and fishery waste tips as food sources for birds in northern coastal Patagonia, Argentina. Ornitología Neotropical 13:283–292. Close ). Recorded eating a crab and foot-stirring in shallow waters. Recorded locally hunting regularly at night under harbour illumination, feeding on crustaceans and polychaete worms by rapid surface pecking while swimming but also performing shallow vertical plunge-dives (4 Leopold, M.F., Philippart, C.J.M. and Yorio, P. (2010). Nocturnal feeding under artificial light conditions by Brown-hooded Gull (Larus maculipennis) in Puerto Madryn harbour (Chubut Province, Argentina). El Hornero. 25(02): 55–60. Close ). Kleptoparasitism of other birds often occurs. Gulls wintering at the Mar Chiquita coastal lagoon, Buenos Aires province, Argentina, particularly parasitize American Oystercatcher (Haematopus palliatus) and Red-gartered Coot (Fulica armillata). They select large prey items when stealing food, the clam Tagelus plebeius from oystercatchers and the crab Cyrtograpsus angulatus from coots (Fulica spp.) (5 García, G.O., Favero, M. and Vassallo, A.I. (2012). Interspecific kleptoparasitism by Brown-headed Gulls (Chroicocephalus maculipennis) on two hosts with different foraging strategies: a comparative approach. Emu. 112(3): 227–233. Close ).

Thin and high-pitched; a shrill, ternlike “zhree” and a short “kip kip kip”. Gives a harsh, guttural “kwarr” in nest defence (1 Fjeldså, J., and N. Krabbe (1990). Birds of the High Andes: A Manual to the Birds of the Temperate Zone of the Andes and Patagonia, South America. Zoological Museum, University of Copenhagen and Apollo Books, Copenhagen and Svendborg, Denmark. Close ).

Lays Nov–Dec in Chile, from late Oct to early Jan in Argentina, from Dec in Falkland Is. Sometimes solitary, but usually nests in colonies of 5–50 nests, occasionally over 500. In Argentina nests with White-faced Ibis (Plegadis chihi, L. cirrocephalus (6 Josens, M. L., Pretelli, M. G. and Escalante, A. H. (2009). Censos de aves acuáticas en sus colonias reproductivas en lagunas del sudeste de la provincia de Buenos Aires. El Hornero. 24(1): 7–12. Close ) and grebes; in Falklands with South American Terns (Sterna hirundinacea) and Dolphin Gulls (Larus scoresbii). Nests close together, particularly where plant stems reduce visibility of neighbours. Usurps grebe nest, or may assemble floating nest platform; on dry ground builds bulky grass nest, with cup 25 cm across. Usually 2–3 eggs  (1–4; mean 2·6); mobs various intruders, including shorebirds and caracaras; incubation and fledging periods not documented. Chicks remain on nest platform if not disturbed. Solitary breeders sometimes more successful than colonial birds, suffering lower predation by grebes and caracaras. First breeding at three years.

Not globally threatened (Least Concern). Status poorly known. Total population probably 50,000–100,000 pairs and apparently increasing; The population in the Falklands is estimated at 4200–7800 birds (7 Wetlands International (2015). Waterbird Population Estimates. Wetlands International, Wageningen, The Netherlands. Close ). Common in Chile; usually considered common in E Argentina. Breeding status in Tierra del Fuego unclear.