Animal Diversity Web

Ge­o­graphic Range

Neotrop­i­cal cor­morants breed from Cape Horn, South Amer­ica to north­ern Texas, south­west­ern Louisiana, and south­ern Ari­zona. In win­ter, they have been recorded wan­der­ing as far out­side their breed­ing range as Cal­i­for­nia, Saskatchewan, and Penn­syl­va­nia. Gen­er­ally they are re­stricted to the south­ern United States, Cen­tral Amer­ica, the West In­dies, and South Amer­ica. They are non-mi­gra­tory, but are no­madic dur­ing the non-breed­ing sea­son. (How­ell, 1995)

• Biogeographic Regions
• nearctic
  • native
• neotropical
  • native

Habi­tat

Neotrop­i­cal cor­morants are found in a va­ri­ety of habi­tats, al­though close prox­im­ity to deep water is pre­ferred. Avail­abil­ity of perches for sun­ning and dry­ing their wings is also im­por­tant in habi­tat pref­er­ences. Neotrop­i­cal cor­morants can be found in fresh, brack­ish, or salt water, bays, la­goons, streams, salt ponds, seashores, and lakes. In the United States, they are com­monly found in coastal marshes and swamps. El­e­va­tion is not a con­cern, as birds are found from sea level wet­lands to high moun­tain lakes in the Andes. (Stiles, 1989; Telfair and Mor­ri­son, 1999)

• Habitat Regions
• temperate
• tropical
• saltwater or marine
• freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• coastal
• brackish water

• Wetlands
• marsh
• swamp
• bog

• Other Habitat Features
• riparian
• estuarine

• Range elevation

  0 to 5000 m

  0.00 to 16404.20 ft

Phys­i­cal De­scrip­tion

Neotrop­i­cal cor­morants are jet black, aquatic birds, weigh­ing be­tween 1.2 and 1.4 kilo­grams. They range in length from 63.5 to 68.5 cm, with an ap­prox­i­mate wingspan of 102 cm. A pale green gular patch at the base of the bill with a white “v” out­line dis­tin­guishes them from sim­i­lar species, such as dou­ble-crested cor­morant (Pha­lacro­co­rax au­ri­tus). They have roughly equiv­a­lent neck and tail lengths, but are eas­ily de­tectable in flight. Dou­ble-crested cor­morants have shorter tails. A faint green­ish shine on the upper wings and back may be de­tectable under cor­rect light­ing con­di­tions. Ju­ve­nile birds lack this green shine and are gen­er­ally paler. Their breasts are brown in­stead of black, and their beaks may ap­pear yel­lower. Ju­ve­niles may be es­pe­cially dif­fi­cult to tell apart from other cor­morant species due to their dull gular patches. There is no dis­cernible sex­ual di­mor­phism. (How­ell, 1995; Sib­ley, 2000; Telfair and Mor­ri­son, 1999)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Range mass

  1.2 to 1.4 kg

  2.64 to 3.08 lb

• Range length

  63.5 to 68.5 cm

  25.00 to 26.97 in

• Average wingspan

  102 cm

  40.16 in

Re­pro­duc­tion

Neotrop­i­cal cor­morants are monog­a­mous through­out the breed­ing sea­son. They en­gage in in­tri­cate dis­plays to at­tract mates. Males choose the nest site and fe­males as­sess the lo­ca­tion, ei­ther ac­cept­ing or re­ject­ing the of­fered nest. Courtship dis­plays are char­ac­ter­ized by birds wav­ing their wings and call­ing. A va­ri­ety of dif­fer­ent dis­plays exist, in­clud­ing the gap­ing dis­play (necks are stretched up­ward and calls are made), point­ing (the neck slowly and silently sways), kink throated dis­play (an arched neck pos­ture), and both pre-take­off and post-land­ing dis­plays. Monogamy is thought to be an­nual, as neotrop­i­cal cor­morants pick new mates each year. (Mor­ri­son, 1979; Telfair and Mor­ri­son, 1999)

• Mating System
• monogamous

Neotrop­i­cal cor­morants have com­par­a­tively long breed­ing sea­sons, last­ing from June to mid-Oc­to­ber in Texas, April to June in Ar­gentina, and Oc­to­ber to No­vem­ber along the Patag­on­ian coast. Males choose nest sites in small trees or other struc­tures. Nor­mally nests are lo­cated be­tween 0.9 and 6.1 me­ters in height. While males choose nest sites and bring nest ma­te­r­ial, it is the fe­male that ac­tu­ally con­structs the nest. Por­tions of pre­vi­ous nests are often re-used. Nests are usu­ally com­posed of a thick outer layer of twigs and sticks, lined with soft grasses and sea­weed. The mean ex­ter­nal di­am­e­ter of nests is 34.4 cm, with a height of 14.2 cm. Neotrop­i­cal cor­morants nest com­mu­nally, spac­ing nests at a min­i­mum of 70 to 75 cm apart. Colonies may be mas­sive, up to sev­eral thou­sand in­di­vid­u­als. Eggs are oval, with light blue and chalky white hues. Av­er­age di­men­sions are 54.54 by 33.68 mm. Mean clutch size is 3 to 4 eggs, though the range is from 1 to 7. An av­er­age of 2.1 young sur­vive past the first ten days after hatch­ing. Eggs are laid at two day in­ter­vals. In­cu­ba­tion be­gins after two days and lasts 23 to 26 days with a mean of 24.6. Eggs hatch asyn­chro­nously. (Mor­ri­son, 1979; Quin­tana, 2004; Telfair and Mor­ri­son, 1999)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

• Breeding interval

  Neotropical cormorants breed once yearly.

• Breeding season

  Neotropical cormorants have comparatively long breeding seasons lasting from June to mid-October in Texas, April to June in Argentina, and October to November along the Patagonian coast.

• Range eggs per season

  1 to 7

• Average eggs per season

  3-4

• Range time to hatching

  23 to 26 days

• Average time to hatching

  24.6 days

• Average fledging age

  8 weeks

• Average time to independence

  11 weeks

Neotrop­i­cal cor­morant hatch­lings are al­tri­cial and are at­tended to for eleven weeks. At 8 weeks the young are ca­pa­ble of swim­ming and div­ing. By twelve weeks the young are com­pletely in­de­pen­dent. Until then, the par­ents brood, feed, and pro­tect their chicks. In the heat, the chicks are shaded, and, in the cold, they are brooded. Chicks emit a dis­tinc­tive call for feed­ing, and both par­ents re­spond by re­gur­gi­tat­ing liq­uid into their mouths. As the chicks de­velop, they are even­tu­ally fed whole fish. Stud­ies doc­u­ment 3 to 8 feed­ings per day. Par­ents en­gage in no nest san­i­ta­tion tech­niques and feces and rot­ten fish fre­quently build up in the nest. (Mor­ri­son, 1979; Telfair and Mor­ri­son, 1999)

• Parental Investment
• altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female

Lifes­pan/Longevity

The old­est re­ported wild neotrop­i­cal cor­morant was caught after being banded for 12 years and 7 months. Gen­er­ally, mor­tal­ity rates are high­est in the ini­tial stages of life. Fledg­lings often die when par­ents aban­don their nest fol­low­ing human dis­tur­bance, star­va­tion, or storms. At this point preda­tors such as com­mon rac­coons (Pro­cyon lotor) and grack­les (Quis­calus) ex­ploit open, un­pro­tected nests. (Telfair and Mor­ri­son, 1999)

• Range lifespan
  Status: wild

  12 (high) years

• Average lifespan
  Status: wild

  151 months

  Bird Banding Laboratory

Be­hav­ior

Neotrop­i­cal cor­morants awk­wardly wad­dle on land but are ef­fec­tive perchers and agile swim­mers. Flight is char­ac­ter­ized by glid­ing with rounded wings. To take-off, cor­morants ori­ent to­wards the wind and run along the water to pro­mote lift. In water, neotrop­i­cal cor­morants sit quite low. Their set back, webbed feet and their sleek bod­ies allow for ef­fec­tive un­der­wa­ter pur­suit of prey. After swim­ming, much time is spent in preen­ing and sun­ning in the wing-spread po­si­tion to dry their feath­ers. Neotrop­i­cal cor­morants often fly in a V for­ma­tion and are gre­gar­i­ous nesters. Be­sides de­fense of nest site, there are in­fre­quent in­traspe­cific an­tag­o­nis­tic in­ter­ac­tions. Out­side of the breed­ing sea­son, neotrop­i­cal cor­morants are usu­ally soli­tary. How­ever, it is not un­com­mon to see birds en­gag­ing in flock feed­ing. (Quin­tana, 2004; Telfair and Mor­ri­son, 1999)

• Key Behaviors
• flies
• glides
• natatorial
• diurnal
• motile
• nomadic
• solitary
• colonial

Com­mu­ni­ca­tion and Per­cep­tion

The ma­jor­ity of in­traspe­cific com­mu­ni­ca­tion is through vo­cal­iza­tions. When alarmed, neotrop­i­cal cor­morants emit a sim­ple gut­tural call. Dur­ing flock feed­ing, calls are com­mon. Males are gen­er­ally more vocal than fe­males, but both sexes are usu­ally silent out­side of the breed­ing sea­son. Hatch­lings use food-beg­ging calls to beg for food. Neotrop­i­cal cor­morants also com­mu­ni­cate through vi­sual dis­plays, pri­mar­ily dur­ing courtship. (Telfair and Mor­ri­son, 1999)

• Communication Channels
• visual
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Some re­search sug­gests that neotrop­i­cal cor­morants are aquatic gen­er­al­ists, eat­ing fish, frogs, tad­poles, and drag­on­fly nymphs. Other re­search in­di­cates that fish and shrimp com­prise an over­whelm­ing ma­jor­ity of their diets. To for­age, neotrop­i­cal cor­morants gen­er­ally pur­suit dive. How­ever, in large flock feed­ing sit­u­a­tions, birds also en­gage in plunge-div­ing tech­niques. Some­times birds may even line up to "herd" fish. Stud­ies show adults are more adept feed­ers than ju­ve­niles, who take some time to learn ef­fec­tive for­ag­ing meth­ods. (King, 1989; Telfair and Mor­ri­son, 1999)

• Primary Diet
• carnivore
  • piscivore
  • eats non-insect arthropods

• Animal Foods
• amphibians
• fish
• insects
• aquatic crustaceans

Pre­da­tion

Rac­coons and grack­les, both great-tailed and boat-tailed, feed on eggs and young. How­ever, grack­les seem to raid nests only after human dis­tur­bance has caused the cor­morants to aban­don their nests for a short pe­riod. In­ter­est­ingly, neigh­bors tend to pro­tect other birds’ nests when the par­ents leave to for­age. (Mor­ri­son, 1979)

• Known Predators

  • raccoons (Procyon lotor)
  • great-tailed grackles (Quiscalus mexicanus)
  • boat-tailed grackles (Quiscalus major)

Ecosys­tem Roles

In­ter­spe­cific com­pe­ti­tion with dou­ble-crested cor­morants could con­tribute to lim­it­ing the ex­tent of their north­ern range. An in­ter­est­ing mu­tu­al­ism be­tween neotrop­i­cal cor­morants and roseate spoon­bills (Ajaia ajaja) has been ob­served in Texas, in which in­di­vid­u­als of both species group to­gether for more ef­fec­tive preda­tor pro­tec­tion. More­over, stud­ies have shown that neotrop­i­cal cor­morant guano pro­vides vital bi­otic sus­te­nance for aquatic ecosys­tems, and helps main­tain nu­tri­ent lev­els. (Telfair and Mor­ri­son, 1999)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Some fish­er­men use neotrop­i­cal cor­morants to lo­cate abun­dant fish schools. Their guano may even help aug­ment bio­mass in aquatic ecosys­tems.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Many fish­er­men think that neotrop­i­cal cor­morants dec­i­mate fish pop­u­la­tions, thereby de­plet­ing fish re­serves. These birds are often shot near fish­eries. (Telfair and Mor­ri­son, 1999)

Con­ser­va­tion Sta­tus

Neotrop­i­cal cor­morants were eval­u­ated as species of least con­cern in 2001 by BirdLife In­ter­na­tional due to their large range (18 mil­lion km^2) and large pop­u­la­tion size (es­ti­mated 2 mil­lion in­di­vid­u­als). How­ever, the species is pro­tected under the Mi­gra­tory Bird Treaty Act. Neotrop­i­cal cor­morants still face human threats, as they are hunted, poi­soned by pes­ti­cides, and dri­ven from their habi­tats. (Telfair and Mor­ri­son, 1999)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  Protected

• CITES

  No special status

Con­trib­u­tors

Tanya Dewey (ed­i­tor), An­i­mal Di­ver­sity Web.

Daniel Karp (au­thor), Stan­ford Uni­ver­sity, Terry Root (ed­i­tor, in­struc­tor), Stan­ford Uni­ver­sity.

Ref­er­ences

How­ell, S. 1995. Guide to the Birds of Mex­ico and North­ern Cen­tral Amer­ica. Ox­ford: Ox­ford Uni­ver­sity Press.

King, K. 1989. Food habits and organochlo­rine con­t­a­m­i­nants in the diet of Oli­va­ceous Cor­morants in Galve­ston Bay, Texas. South­west­ern Nat­u­ral­ist, 34: 338-343.

Mor­ri­son, M. 1979. Breed­ing bi­ol­ogy and spe­cific mor­tal­ity of Oli­va­ceous Cor­morants. South­west­ern Nat­u­ral­ist, 24: 259-266.

Quin­tana, F. 2004. Div­ing be­hav­iour and for­ag­ing areas of the neotropic cor­morant at the ma­rine colony in Patag­o­nia, Ar­gentina. Wil­son Bul­letin, 116: 83-88.

Sib­ley, D. 2000. The Sib­ley Guide to Birds. New York: Chan­ti­cleer/Knopf.

Stiles, G. 1989. The Birds of Costa Rica. Ithaca, New York: Cor­nell Uni­ver­sity Press.

Telfair, R., M. Mor­ri­son. 1999. "Neotropic Cor­morant (Pha­lacro­co­rax brasil­ianus)" (On-line). The Birds of North Amer­ica On­line. Ac­cessed June 12, 2007 at http://​bna.​birds.​cornell.​edu/​BNA/​account/​Neotropic_​Cormorant/​.