Anous minutus

Geographic Range

Black noddies are found in the marine tropics and subtropics. They have a circum-equatorial distribution, being found in tropical and subtropical areas of the Pacific, Atlantic, and Indian oceans and the Caribbean Sea. Throughout their range black noddies are primarily found near breeding islands, where they are resident throughout the year, although some long-distance movements of individuals occurs. They are most common within about 80 km of breeding islands. In the Americas they are found on islands off the coasts of Central and South America. In the Atlantic and Indian Oceans they are found on Ascension, St. Helena, and Gulf of Guinea Islands, as well as Ashmore reef off the northwest coast of Australia. In the Pacific Ocean they are found mainly in the southwest and central Pacific, including the Hawaiian archipelago, Johnston Atoll, Marcus and Wake Islands, islands off the coast of the Philippines, New Guinea, and northeastern Australia, Lord Howe, Norfolk, Philip, and Kermadec Islands, the Mariana Islands, Palau, Caroline Islands, Marshall Islands, Bismarck Archipelago, New Caledonia, Nauru, Gilbert Islands, Tuvalu, Fiji, Tonga, Samoa, Cook Islands, Tokelau, Phoenix Islands, Line Islands, Austral Islands, Society Islands, Tuamotu Archipelago, and the Marquesas Islands.

• Biogeographic Regions
• neotropical neotropical
  • native native
• australian australian
  • native native
• oceanic islands oceanic islands
  • native native
• indian ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

Habitat

Black noddies are found on tropical and subtropical oceanic islands, from sandy atolls to rocky islands. Black noddies are the only marine terns ( Sterninae ) that build large nests and one of the only tree or shrub-nesting tern species. They nest and roost mainly in vegetation, although nests on coastal cliffs and in caves are common in the Hawaiian Islands, Clipperton Island, and in islands in their Atlantic range. A wide variety of vegetation types are used for nesting and roosting. Nests are usually constructed in forests dominated by Pisonia grandis trees, ironwood ( Casuarina equisetifolia ), mangroves ( Avicennia and Rhizophora ), and coastal shrubs (naupaka Scaevola sericea , tree heliotrope Tournefortia argentea ). Black noddies forage in nearshore, warm-water areas during breeding and non-breeding seasons. During long distance movements or migrations they fly over large expanses of open water. Closely related brown noddies ( Anous stolidus ) are often found one the same islands in similar habitats, but nest mainly on the ground.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial
• saltwater or marine saltwater or marine

• Terrestrial Biomes
• desert or dune desert or dune
• forest forest
• scrub forest scrub forest

• Aquatic Biomes
• coastal coastal

Physical Description

Black noddies are medium-sized terns with uniformly dark, sooty plumage and a white cap, the reverse of the common tern color pattern. The white cap blends gradually into the grey of the body. They measure 35 to 40 cm in length, 65 to 72 cm in wingspan, and weigh from 85 to 140 grams. They have small, white markings on the lower and upper rims of their eyelids. The bill is black and the legs and feet are reddish-brown to orange. The mouth lining and tongue is orange-yellow in the northwestern Hawaiian Islands and Atlantic populations, yellow in Caribbean Islands, and the mouth lining is pink and the tongue yellow in Australia. The tail is 105 to 130 mm and is wedge-shaped with a central notch. Males and females are similar, juveniles are also similar, but are slightly more pale in color and the white cap is sharply differentiated from the gray body plumage.

There is some slight geographic variation in size, plumage color, and foot color of black noddies. Seven subspecies are recognized: A. m. americanus (Caribbean populations), A. m. atlanticus (tropical Atlantic), A. m. diamesus (Clipperton and Cocos Islands), A. m. melanogenys (main island of Hawaii, also called the "light phase" form), A. m. marcusi (northwest Pacific, including northwestern Hawaiian islands, also called the "dark phase" form), A. m. worcesteri (Sulu and Java seas), and A. m. minutus (Flores Sea and southwestern Pacific).

Black noddies are considered conspecific with their close relatives, lesser noddies ( Anous tenuirostris ), by some authors. Under this classification scheme the two species are known as white-capped noddies, A. tenuirostris . However, black noddies are distinguishable from lesser noddies by size, plumage color, and wing quill formula, as well as their separate nesting habits.

Black noddy basal metabolic rate has been estimated at 54.8 kj/d. Mean oxygen consumption is 1.28 cubic centimeters/g/hr. Mean daytime body temperature of adults while incubating is 39.5 to 41.9 degrees Celsius (in shade and sun, respectively).

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Black noddies form monogamous pair bonds that are long-lasting. In one study 86% of mated pairs remained together through mating seasons. Pairs tend to be made up of birds of similar ages. Courtship behaviors include flying together and a high-flight display in which birds ascend together and then glide at a steep angle back to sea level. Males attract females to a nest site with a "bridling" display - a rhythmic backwards and forwards movement of the head paired with opening and closing of the bill - followed by a "nodding" display in which birds nod their heads forward. Pairs avoid antagonism through the use of the a foot-looking display, where they suddenly look down as if to inspect their feet for several seconds, and gaping displays, where they hold their bills open and pointing downwards to display the colorful tongue and mouth.

• Mating System
• monogamous monogamous

Black noddy pairs stay together throughout the year or come together approximately 2 months before egg-laying. They build or reinforce large, untidy nests in trees (from less than 1 meter to over 20 meters tall) or on cliff ledges or sea caves. Nest sites seem to be selected mainly for their proximity to the breeding colony and even unsuitable nest sites are occupied if they are near other nesting pairs. Nests in trees may be mainly built on the leeward side of the tree for protection against wind. Males collect nesting material and females construct nests. Black noddies defecate at nests, helping to hold nest materials together and enlarging cliff ledges. The timing of breeding varies regionally. In some areas the breeding season is short and regular, in other areas breeding is irregular, and in some areas breeding may occur throughout the year. Within colony islands, the timing of breeding can vary annually as well. On Ascension Island birds breed at 8 to 10 month intervals, so the timing of the breeding season is earlier each year. Some populations have 2 clutches per year, 5 months apart. The timing of breeding may be most influenced by the availability of prey species.

Black noddies lay 1 egg per clutch. Two egg nests are sometimes observed, but these are thought to be eggs that have rolled or fallen from adjacent nests. Eggs are large (23.7 to 25.2 g), oval, and buffy marked with spots and streaks of reddish brown. If an egg fails or is lost, a replacement egg is laid. Black noddies may even lay replacement eggs after the loss of nearly fledged young. Incubation begins immediately after egg-laying and lasts for about 34 days. Both males and females incubate the eggs, leaving for only about a minute at a time. In cold weather they sit on the egg and in hot conditions they may wet their ventral feathers to help cool the egg. Young fledge in 39 to 52 days, depending on the availability of prey. Development may be prolonged by periods of low prey availability. Although weight gain and morphological development slows during such periods, this does not seem to result in juvenile mortality. This may be an adaptation to unpredictable resources. Fledglings remain near their parents for up to 17 weeks after fledging, although they roost with other juveniles during that time. Black noddies may breed as early as 2 years old, although 3 years is more typical.

In artificially enlarged broods, black noddy parents were able to successfully compensate for the nutritional demands of additional young. Enlarged broods did not apparently adversely impact nestling development or survival. However, the nutritional stress associated with enlarged broods resulted in slowed wing and feather development. Broods with differences in ages of the nestlings, however, experienced more competition between nestlings for food, with younger nestlings not able to compete as well as older nestlings.

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

Males and females incubate, feed, and protect their young. Incubating parents are reluctant to leave the nest when the other parent comes to relieve them. One parent may physically push the other off the nest. Allopreening or feeding behaviors may accompany one parent replacing the other at the nest during incubation. Chicks hatch without help from parents. Young black noddies are semiprecocial; they have downy feathers in the same color pattern as the adult and remain in the nest until they fledge. Hatchlings are brooded and fed by regurgitation by both parents. Chicks are fed about every 1 to 2 hours when young and about every 11 hours when closer to fledging. Young black noddies place their bills in their parent's open mouth and then rapidly open and close their bills to stimulate regurgitation. Adult mass is attained at about 3 weeks after hatching. Hatchlings lose weight in the last week before they fledge but still typically fledge at masses greater than or equal to adult mass. Hatchlings that fall from nests are typically abandoned, although some older hatchlings are fed by their parents on the ground. Adults do not feed hatchlings that aren't recognized as their own. Adults continue to feed young up to 17 weeks after fledging.

• Parental Investment
• precocial precocial
• 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
  • protecting
    • male
    • female

Lifespan/Longevity

The oldest recorded black noddy was at least 25 years old. Other black noddies have been recorded at over 15 years old. Survivorship in Fiji averaged 75% over 9 years. Significant mortality of eggs and hatchlings occurs when strong winds blow them out of nests or when exposed to cold or heat in the nest. Hatchlings may also starve to death occasionally when stormy weather prevents adult foraging. El Niño Southern Oscillation events have been associated with widespread egg and hatchling abandonment and death. Unexplained periodic epidemics cause widespread mortality in colonies. Adults and young are also sometimes trapped in the sticky fruits of pisonia trees.

Behavior

Black noddies are gregarious, nesting and roosting in large colonies. Nests that are next to each other in a nesting tree often merge together and these birds tolerate close proximity of other pairs. Populations tend to be found near breeding islands throughout most of the year, although some long-distance dispersal or migration occurs in individuals and in some colonies. Breeding populations on Heron Island (Great Barrier Reef, Australia), Christmas Island (Pacific), and Clipperton Island (eastern Pacific) migrate to established roosting islands in the non-breeding season. Migration routes and behavior are poorly known, as these birds are rarely observed away from breeding or roosting islands. Migration may be in response to depleted food resources around breeding islands with particularly dense populations. Individuals in sedentary populations sleep and roost on their nests throughout the year.

Black noddies typically walk only when picking up nest material from the ground. They are found on the ground only when roosting or sunbathing. They typically fly low above the water and flight is described as slow and direct. Black noddies are maneuverable in flight. They frequently preen themselves and their mates.

• Key Behaviors
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• sedentary sedentary
• social social
• colonial colonial

Home Range

Home range sizes are not reported in this species. Small nesting territories are defended, but nests are often very close together and close proximity of conspecifics is tolerated. Only the immediate vicinity of the nest is defended, often only as far as the bird can reach while sitting on the nest. Black noddies defend nests with ritualized visual displays and by jabbing intruders with their bills. Fights are rare. When adults are not on the nest, hatchlings and juveniles defend the nest from intruders for up to 4 months after fledging. Occasionally fledglings defend a roosting spot near the nest.

Communication and Perception

Black noddies use a variety of vocalizations and visual displays to communicate with conspecifics. Young use a begging call to beg for food. Main call types are identified as "chatters," "rattles," and "croaks." Black noddies do not sing and vocalizations don't vary seasonally. Foraging flocks constantly call and calls are common when nesting and roosting. Chatters are typically used in flight and may be a contact call. Rattles are alarm calls. Croaks may be given when an intruder is detected. Black noddies also use bill clacking during visual displays.

Black noddies employ a variety of visual displays to attract mates and in agonistic interactions. Displays include "nodding," "gaping," "foot-looking," "head-shaking," "bridling," "chin-up," and "appeasement." Many of these visual displays are used both in agonistic interactions, as when directed aggressively at an intruder, and in mating interactions. For example, nodding occurs when an intruder is approaching and also when a mate approaches. In the former context it is used to drive the intruder away, in the latter context it is used to greet a mate. Bridling - which involves forward and backward movements of the head, accompanied by opening and closing of the bill - advertises territory ownership to both mates and intruders. Appeasement displays are usually by juveniles, who point their bills downwards to avoid an aggressive interaction. This is similar to foot-looking, which also is used to avoid aggression.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Black noddies eat a wide variety of prey and are opportunistic predators. Their diet is mainly made up of small fish, squid, and crustaceans. The composition of the diet varies substantially with the region and seasonal abundance of prey. Prey are typically small, averaging 34 mm in length, fish prey averaged 19 to 64 mm in length. Analysis of regurgitated food for young suggest that fish are the dominant prey. Black noddies take prey from the ocean surface in nearshore areas, including lagoons, bays, and brackish coastal ponds. Most individuals are observed foraging within 10 km of breeding or roosting islands. Unlike most terns , black noddies do not dive for their prey. Instead they skim or dip at the surface or sometimes briefly land on the water to grab prey. They eat prey immediately and do not carry prey in their bills, which is consistent with their habit of regurgitating food for young. Black noddies typically forage in large, mixed-species flocks over schools of foraging predatory fish, such as tunas ( Scombridae ) or jacks ( Caranx ). In the Hawaiian islands black noddies forage over schools of skipjack tuna ( Katsuwonus pelamis ) 75% of the time and target the same prey fish and size of fish. They typically leave colonies in the morning and return in the evening, although night-time foraging has also been suggested.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans

Predation

Predators of black noddies vary regionally because of their large, circum-equatorial range. Most predators are avian, as nesting and roosting islands typically lack native mammalian predators. However, introduced predators are a serious threat in many areas. Introduced mammalian predators include feral cats ( Felis catus ), rats ( Rattus ), and domestic dogs ( Canis lupus familiaris ). These predators have been implicated in the local extinctions of colonies throughout the world. Other introduced predators are common mynas ( Acridotheres tristis , Hawaii) and ants ( Pheidole megacephala , Tern Island). Recorded native predators are: great frigatebirds ( Fregata minor ), Laysan finches ( Telespiza cantans ), bristle-thighed curlews ( Numenius tahitiensis ), Pacific golden-plovers ( Pluvialis fulva ), Micronesian starlings ( Aplonis opaca ), Pacific reef egrets ( Egretta sacra ), silver gulls ( Larus novaehollandiae ), white-breasted sea eagles ( Haliaeetus leucogaster ), and Ascension frigatebirds ( Fregata aquila ). Humans have also been known to prey on black noddies.

Black noddy adults do not readily leave their nests when threatened. Most predators prey on unattended nests and eat eggs and small hatchlings. Black noddies will circle and attack avian predators to drive them away. Pacific reef egrets ( Egretta sacra ) and white-breasted sea eagles ( Haliaeetus leucogaster ) take adults. Ants in the northwestern Hawaiian islands attack nestlings and feed on the anterior margin of their foot webbing, which doesn't cause death but can negatively affect ability to take off from water later in life.

Ecosystem Roles

Black noddies are parasitized by chewing lice ( Quadraceps hopkinsi ). Black noddies are often seen "sunning" themselves: holding their wings spread in direct sunlight. It has been demonstrated that this behavior kills chewing lice and helps to control parasite loads. Feather lice on black noddies include Actornithophilus ceruleus , Actornithophilus incisus , Austromenopon species, and Saemundssonia species. Other ectoparasites include feather mites ( Larinyssus orbicularis ), chiggers ( Guntheria domrowi and Neoschoengastia ewingi ), hippoboscid flies ( Ornithocia and Alfersia aenescens ), and ticks. Argasid ticks ( Ornithodoros capensis ) are found in nests (average 159 per nest). These ticks which carry arboviruses that cause encephalitis. Antibodies to arboviruses have been detected in black noddy populations as well as antibodies to human influenza and Newcastle Disease. Unexplained periodic epidemics seem to cause high levels of mortality in some populations. Nematode parasites ( Contracaecum magnipapillatum ) and two species of kidney flukes ( Renicola foliata and Renicola caudescens ) are known endoparasites.

Black noddy nesting colonies result in significant additions of nutrients to the soils where they nest. Black noddies nesting on Heron Island, in the Great Barrier Reef, are estimated to add 45 tons per year of guano to the soil. This effectively transfers about 1.4 tons per year of phosphorus from the surrounding ocean waters to the terrestrial ecosystem, influencing vegetation communities on nesting islands. Guano deposits also add significant amounts of nitrogen, potassium, and magnesium to soils.

Economic Importance for Humans: Positive

Black noddy colonies produce huge guano deposits on roosting and breeding islands, impacting local terrestrial and marine ecosystems and resulting in large deposits of harvestable fertilizer and phosphorus.

• Positive Impacts
• produces fertilizer

Economic Importance for Humans: Negative

There are no adverse effects of black noddies on humans.

Conservation Status

Black noddies are considered a species of least concern by the IUCN. Nesting populations are apparently mostly stable and population estimates are from 1 to 1.5 million. Humans and introduced mammalian predators have driven some populations to extinction. Human degradation of habitats is a serious threat to nesting and roosting colonies, as nesting trees are cleared. Introduced rabbits ( Oryctolagus cuniculus ), goats ( Capra hircus ), and scale insects ( Parasaissetia nigra ) have seriously degraded native vegetation on many tropical islands. Black noddies seem to tolerate human presence well, if nesting, roosting, and foraging habitats are not degraded. Adults are reluctant to leave nests when approached and can easily be taken in hand when incubating or brooding.

Many black noddy nesting islands are protected and human hunting is illegal in most areas. But laws and their enforcement vary considerably across the black noddy range.

Other Comments

The generic name Anous comes from the Greek for "unmindful," reflecting the fact that noddies seem indifferent to humans. The origin of the name "noddy" is not clear. It may refer to movements associated with regurgitating food for their young or it may refer to a common sailor's term for "simpleton" - "noddy." Black noddies are generally easy to capture on the nest by hand, so sailors may have referred to them with this term.

Other common names for black noddies are: white-capped noddy, Hawaiian noddy, Hawaiian tern, noio (Hawaiian), eki'eki (Hawaiian), golondrina-boba negra (Spanish), tiñosa negra (Spanish), tiñosa chocora (Spanish), noddi noir (French).

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (author), Animal Diversity Web.

References

Allaway, W., A. Ashford. 1984. Nutrient input by seabirds to the forest on a coral island of the Great Barrier reef. Marine Ecology , 19: 297-298.

Congdon, B. 1990. Brood Enlargement and Post-Natal Development in the Black Noddy Anous minutus. Emu , 90: 241-247.

Gauger, V. 1999. Black noddy (Anous minutus). Pp. 1-32 in The Birds of North America , Vol. 412. Philadelphia: The Birds of North America, Inc..

Moyer, B., G. Wagenbach. 1995. Sunning by black noddies (Anous minutus) may kill chewing lice (Quadraceps hopkinsi). The Auk , 112: 1073-1077.