Butorides sundevalli was previously considered a subspecies of striated herons, Butorides striata. They are indistinguishable in the juvenile form, and in addition, some adult lava herons have a greenish back and streaked neck, which may be a polymorphism, a result of interbreeding, or evidence of recent divergence.
Lava herons are a relatively quiet species and appear to be far less vocal than some similar species. When annoyed or distressed, lava herons emit a high-pitched "keyow" or "keuk." They also have specific, raspy territorial calls to frighten away invaders. Male vocalization in the form of "skow" calls also play a big part in attracting females. "Cooing" is an important part of the courtship ritual for both sexes.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Lava herons appear to be common on the Galapagos Islands, but population sizes are mostly unknown. Illegal fishing and destruction of mangroves by shrimp farming may pose future threats to this species. On the IUCN red list, Butorides sundevalli and Butorides striata are listed together as "least concern."
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
There are no known adverse effects of Butorides sundevalli on humans.
Lava herons are among the many unique island species that attract ecotourists to the Galapagos Islands.
Positive Impacts: ecotourism
Lava herons are important predators of crabs and fish and most likely help to keep these populations in check. Lava herons themselves are not often preyed upon, but this bird species does sometimes provide food for other species. Lava herons are not known to take part in any parasitic or mutualistic relationships. The species does, however, appear to have commensal relationships with Galapagos penguins and California sea lions. By flying in front of the penguins and sea lions swimming near shore, lava herons apparently increase their food capture rates.
Mutualist Species:
Lava herons feed in the shore zone, from boats, on land, and in trees. They primarily eat small fish and crabs, but are also known to eat lizards, insects, prawns, and some small birds. In many cases, they will bite off just the legs of crabs and eat these while the crab runs away. They have been recorded catching crabs at a rate of 2 to 3 crabs per minute. Occasionally, they may eat eggs or chicks of various finch and mockingbird species. They do not typically seek out the other birds as prey but will strike at one if it happens to wander by while the herons are searching for food. Because some of their prey, like crabs, take a long time to eat, lava herons often lose food to lava gulls, Galapagos hawks, and frigatebirds.
Lava herons feed at all tide levels. To catch their food, they will crouch stealthily and stab at unsuspecting prey in the water or on land, or they can dive for fish. They walk extremely slowly (as slow as 1 m per min) in shallow water, in branches, or on the shore. They sometimes rake their feet across the ground in search of food. It is possible that lava herons, like many closely related species, also use baiting techniques to catch prey. Individuals typically have their own favorite places to forage and, instead of covering a large area, fly between these smaller places. Individual birds also tend to have their own preferred prey and feeding behaviors.
Animal Foods: birds; reptiles; fish; eggs; insects; terrestrial non-insect arthropods; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods)
Galapagos herons, also known as lava herons, are found only in the Neotropical region. They are endemic to the Galapagos Islands in South America and are not found anywhere else. They are commonly found on all of the islands in the Galapagos.
Biogeographic Regions: neotropical (Native )
Other Geographic Terms: island endemic
Galapagos herons live and nest along the lava-rock coastlines, saltwater lagoons, and mangrove forests of all of the Galapagos Islands.
Habitat Regions: tropical ; terrestrial
Aquatic Biomes: coastal
Other Habitat Features: estuarine
While information regarding longevity of lava herons is scarce, the oldest known wild individuals from the same genus are recorded at 7.9 years for Butorides striata and 11.6 years Butorides virescens. There is no information on lava herons in captivity.
Range lifespan
Status: wild: 7.9 to 11.6 years.
Adult Butorides sundevalli individuals are a uniform ashy-gray over the entire body. Males are slightly larger and more colorful than females, particularly during the mating season. The bill, 6.35 cm in length, is gray. The bills of males turn shiny black during the mating season. There is a crest on top of the head, which is shorter than that of most other heron species. Legs are normally gray, but during the mating season both female and male legs turn bright orange and the lores turn from green to bright blue. These are relatively small and compact herons. Juveniles are mostly brown in color, with streaking on the breast, a dark crown, and a grayish back. Juveniles are indistinguishable from juveniles of their close relative, striated herons (Butorides striata).
Range mass: 193 to 235 g.
Average length: 35 cm.
Average wingspan: 63 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; male more colorful
Adult lava herons do not have many predators in the Galapagos. They are sometimes preyed on by magnificent frigatebirds (Fregata magnificens). For most bird species on the Galapagos Islands, invasive species pose the most serious threat to eggs and hatchlings. Black rats, feral pigs, and fire ants attack and eat bird eggs and hatchlings. Introduced cats may prove a threat as the birds have not developed a fear of cats. Lava herons have a coloration that closely matches the gray basalt rocks on which they live and nest, which can provide some protection from predators. They also produce alarm calls that may frighten off predators or alert nearby herons of danger.
Known Predators:
Anti-predator Adaptations: cryptic
Males advertise by vocalization, and may perform circle flights and pursuit flights until they attract a female. When a female arrives, the males stretch, bow and coo. The female remains about one meter away from the male and does the same. They also poke each other with their bills and preen their wings, chest, and back. However, reproduction does not necessarily require these displays. Displays by lava herons are typically less elaborate and have less aerial activity than those of closely related species. Although not much is known specifically about lava heron mating, heron species tend to be monogamous.
Mating System: monogamous
In general, the breeding behavior of lava herons is poorly known. The usual age at first breeding of closely related species is at about 2 years, although they may attempt to breed while still in juvenile plumage. Lava herons breed throughout the year, most often after heavy rainfalls that break droughts, and in the months from September through March. Before mating, both males and females cooperate to make a suitable nest of twigs; these nests are usually shallow and about 20 to 40 cm in diameter. Building the nest may take up to two weeks, and parents continue to maintain and improve the nest during the nesting period. Nests are solitary, except in areas with an abundance of food, where there may be two or three nests in close proximity. The nests are in the territory of the male and are usually built within 1 m of the ground in bushes, mangroves, or under rocks. They typically lay one to three eggs at a time and may mate up to three times per year, although survival rates may be low according to one study, in which only one of the chicks lived to adulthood. There is no recorded information on eggs of the lava heron, but eggs of closely related species are pale blue-green and average about 37 x 28 mm in size.
Breeding interval: Lava herons can breed up to three times per year.
Breeding season: Lava herons breed year round, but mostly during the months of September through March.
Range eggs per season: 3 to 9.
Range time to hatching: 21 to 22 days.
Range fledging age: 34 to 35 days.
Average time to independence: 14 days.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Eggs are incubated for 21 to 22 days by both male and female parents. After hatching, very little information is known on the parental investment of lava herons. However, in the closely related striated heron, hatching is asynchronous and may take 3 to 4 days. The chicks are born semi-altricial. They are covered with light gray down and have limited mobility. Parents feed the chicks by regurgitation. They can climb after one week, jump among branches after 15 days, and fly by 34 to 35 days. Both parents care for the chick until it leaves the nest, after about two weeks, but adult care appears to continue for some time after young have left the nest.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female)
The lava heron (Butorides sundevalli), also known as the Galápagos heron, is a species of heron endemic to the Galápagos Islands of Ecuador. It is considered by some authorities — including the American Ornithological Society and BirdLife International — to be a subspecies (or even just a colour morph) of the striated heron (B. striata), and was formerly "lumped" with this species and the green heron (B. virescens) as the green-backed heron.[1]
The adult is slate-grey to black, which allows it to blend in with the hardened lava. The back feathers typically have a silvery sheen and it has a short crest on its head. When breeding, the heron has a black beak and bright orange legs, but these fade to grey after the breeding season.[2]
These highly territorial birds are found in intertidal zones and mangrove swamps on all of the islands of Galápagos Province.
The lava heron stalks small crabs and fish slowly before quickly spearing and eating them. They have also been known to eat the flies that gather near cacti and occasionally smaller birds.[3]
These birds have little fear of humans. It has been noted they have flight behaviors, some of which may carry the purpose of territory defense/advertising.[4]
Lava herons are typically seen hunched over and they have a sharp alarm call (described as a scow sound).[4] During aggressive behavior they will use a skuk-skuk call.[4]
Unlike most herons, these birds nest in solitary pairs for one breeding season in either the lower branches of mangrove trees or under lava rocks. [2][4] They can breed year-round, though typically from September to March, and can mate up to three times a year and have up to ten eggs each time.[2]
Resources
The lava heron (Butorides sundevalli), also known as the Galápagos heron, is a species of heron endemic to the Galápagos Islands of Ecuador. It is considered by some authorities — including the American Ornithological Society and BirdLife International — to be a subspecies (or even just a colour morph) of the striated heron (B. striata), and was formerly "lumped" with this species and the green heron (B. virescens) as the green-backed heron.
