Butorides sundevalli
lava heron
(Also: Galapagos heron)

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. (Castro and Phillips, 1996)

Galapagos herons live and nest along the lava-rock coastlines, saltwater lagoons, and mangrove forests of all of the Galapagos Islands. (Castro and Phillips, 1996)

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). (Castro and Phillips, 1996; Grant, 1986; Hall and Heinzel, 2000; Hancock and Kushlan, 2005; Harris, 1974; Kushlan, 1983; Swash and Still, 2000)

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. (Clapp, Klimkiewicz, and Kennard, 1982)

Lava herons are primarily solitary animals. They are very territorial, a behavior which develops at an early age. They are also relatively sedentary, leaving their territories only to mate or forage. When other lava herons enter their territory, they will raise their crest and chase intruders away. However, they are not timid of most other species, and will even let humans approach as close as a foot away. This may be because they have evolved in isolation from predators, unlike their ancestors on the South American mainland. They tend to fly very little, preferring to walk. When lava herons do fly, their flights are low, short, and direct. When flying, their feet trail behind, displaying the brightly colored soles of their feet. (Hall and Heinzel, 2000; Harris, 1974)

Home Range

Lava herons have territories arranged linearly along the coastline, with individual territories ranging from 300 to 500 m in length. Territories can change over time. Size of a territory most likely depends on the amount of food available within the territory; one study found that territory size was inversely related to crab density. Each individual bird has his or her own territory. Nests are in the male territories. While mating, a female is allowed into the male territory, but she also appears to maintain her own territory. Females and juveniles are eventually kicked out of the male territory. (Kushlan, 1979; Kushlan, 1983)

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. (Hall and Heinzel, 2000; Hancock and Kushlan, 1984; Hancock and Kushlan, 2005; Kushlan, 1983; Swash and Still, 2000)

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. (Grant, 1986; Hall and Heinzel, 2000; Hancock and Kushlan, 1984; Hancock and Kushlan, 2005; Harris, 1974; Kushlan, 1979; Kushlan, 1983)

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. (Grant, 1986; Hall and Heinzel, 2000; Hancock and Kushlan, 1984; Hancock and Kushlan, 2005; Harris, 1974; Kushlan, 1979; Kushlan, 1983)

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. (Castro and Phillips, 1996; Eilperin, 2006)

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. (Kushlan, 1979)

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.

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." (Hancock and Kushlan, 1984)

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. (Hall and Heinzel, 2000)