Birds

A Galapagos hawk (Buteo galapagoensis), photographed in 1970 on the rim of Fernandina, one of the most active volcanos in the world. On the far side of the caldera, active fumeroles are emitting steam from fissures in the caldera wall. During our time on the summit of this 5,000-foot volcano, I and my three fellow expedition members heard constant rock slides of the unstable caldera wall, as parts of it fell into the lake below.
A Galapagos hawk (Buteo galapagoensis), photographed in 1970 on the rim of Fernandina, one of the most active volcanos in the world. On the far side of the caldera, active fumeroles are emitting steam from fissures in the caldera wall. During our time on the summit of this 5,000-foot volcano, I and my three fellow expedition members heard constant rock slides of the unstable caldera wall, as parts of it fell into the lake below.
A Galápagos hawk preying on a marine iguana (Fernandina Island). It took this hawk more than four hours to subdue the iguana, which at several different points managed to escape and run into the sea. Each time, the hawk waited patiently, and when the iguana finally surfaced and crawled back on land, the hawk recaptured it. After several such episodes, the hawk succeeded in turning the iguana onto its back, allowing the hawk's access to the iguana's vulnerable belly area. The hawk then began eating the iguana alive before finally killing and devouring it (Sulloway, 2001, p. 297-299).
A Galápagos hawk preying on a marine iguana (Fernandina Island). It took this hawk more than four hours to subdue the iguana, which at several different points managed to escape and run into the sea. Each time, the hawk waited patiently, and when the iguana finally surfaced and crawled back on land, the hawk recaptured it. After several such episodes, the hawk succeeded in turning the iguana onto its back, allowing the hawk's access to the iguana's vulnerable belly area. The hawk then began eating the iguana alive before finally killing and devouring it (Sulloway, 2001, p. 297-299).
Galapagos penguins (Spheniscus mendiculus) on Santiago, with Sombrero Chino visible in the background. Only about 20 inches tall, the Galápagos penguin is the world's second smallest penguin, with the smallest being the Little Blue Penguin, which lives in southern Australia and New Zealand. As noted in Darwin and His Bears (p. 26), penguins obey what is known as Bergmann's rule, becoming smaller in body size as they approach the equator. This rule reflects a biological adaptation for heat regulation, and is widely observed in birds, mammals, reptiles, invertebrates, and even some plants. Bergmann's rule also explains various changes in body size observed in the fossil record in response to changes in the Earth's temperature over time.
Galapagos penguins (Spheniscus mendiculus) on Santiago, with Sombrero Chino visible in the background. Only about 20 inches tall, the Galápagos penguin is the world's second smallest penguin, with the smallest being the Little Blue Penguin, which lives in southern Australia and New Zealand. As noted in Darwin and His Bears (p. 26), penguins obey what is known as Bergmann's rule, becoming smaller in body size as they approach the equator. This rule reflects a biological adaptation for heat regulation, and is widely observed in birds, mammals, reptiles, invertebrates, and even some plants. Bergmann's rule also explains various changes in body size observed in the fossil record in response to changes in the Earth's temperature over time.
A small ground finch (Geospiza fuliginosa) perched in the hand of my colleague Mark Moffett, an evolutionary biologist and wildlife photographer. Darwin was struck by the remarkable tameness of the various birds and animals in the Galápagos, and he reported that he was able to lift a pitcher of water made from a tortoise shell while a mockingbird continued to sip water from it. Regarding this trait of tameness in Galápagos birds, Darwin wrote: "Few young birds in England have been injured by man, yet all are afraid of him: many individuals, on the other hand, both at the Galapagos and at the Falklands, have been injured, but yet have not learned that salutary dread. We may infer from these facts, what havoc the introduction of any new beast of prey must cause in a country, before the instincts of the aborigines become adapted to the stranger's craft or power" (Journal of Researches, 1839, p. 478).
A small ground finch (Geospiza fuliginosa) perched in the hand of my colleague Mark Moffett, an evolutionary biologist and wildlife photographer. Darwin was struck by the remarkable tameness of the various birds and animals in the Galápagos, and he reported that he was able to lift a pitcher of water made from a tortoise shell while a mockingbird continued to sip water from it. Regarding this trait of tameness in Galápagos birds, Darwin wrote: "Few young birds in England have been injured by man, yet all are afraid of him: many individuals, on the other hand, both at the Galapagos and at the Falklands, have been injured, but yet have not learned that salutary dread. We may infer from these facts, what havoc the introduction of any new beast of prey must cause in a country, before the instincts of the aborigines become adapted to the stranger's craft or power" (Journal of Researches, 1839, p. 478).
A freshly killed barn owl (also an endemic subspecies), on the road that transects Santa Cruz island. Every year thousands of birds, too tame for their own good, are hit and killed by speeding motor vehicles on this island. In areas of the island where such deaths are particularly common, it has been necessary to post signs reading Zona de aves--Despacio y pite ("Bird zone--slow and beep").
A freshly killed barn owl (also an endemic subspecies), on the road that transects Santa Cruz island. Every year thousands of birds, too tame for their own good, are hit and killed by speeding motor vehicles on this island. In areas of the island where such deaths are particularly common, it has been necessary to post signs reading Zona de aves--Despacio y pite ("Bird zone--slow and beep").
A cactus finch (Geospiza scandens), one of the currently recognized 17 species of Darwin's finches. In its beak morphology, this species is so un-finch-like that when Darwin collected this bird in 1835, he tentatively placed it in the family of the Icteridae (which includes blackbirds, orioles, and meadowlarks).
A cactus finch (Geospiza scandens), one of the currently recognized 17 species of Darwin's finches. In its beak morphology, this species is so un-finch-like that when Darwin collected this bird in 1835, he tentatively placed it in the family of the Icteridae (which includes blackbirds, orioles, and meadowlarks).
A warbler finch (Certhidea olivacea), a bird Darwin mistook for a "wren" during his Galápagos visit. Owing to Darwin's tentative but erroneous voyage classifications of these famous birds, he did not realize they were all "finches" belonging to a single closely related group until British ornithologist John Gould correctly classified these birds after Darwin's return to England, more than a year after Darwin had collected them (Sulloway, 1982).
A warbler finch (Certhidea olivacea), a bird Darwin mistook for a "wren" during his Galápagos visit. Owing to Darwin's tentative but erroneous voyage classifications of these famous birds, he did not realize they were all "finches" belonging to a single closely related group until British ornithologist John Gould correctly classified these birds after Darwin's return to England, more than a year after Darwin had collected them (Sulloway, 1982).
A woodpecker finch (Camarhynchus pallidus), which is one of the few birds in the world that uses a tool. Woodpecker finches sometimes pry off twigs or cactus spines and use them to extract prey from difficult-to-reach crevices.
A woodpecker finch (Camarhynchus pallidus), which is one of the few birds in the world that uses a tool. Woodpecker finches sometimes pry off twigs or cactus spines and use them to extract prey from difficult-to-reach crevices.
A small ground finch (Geospiza fuliginosa) extracting seeds with a sliding motion of its beak. This behavior is observed much more frequently among birds in this species living in the moist Galápagos highlands than in the lowlands, where the same species tends to pick and chip at their prey. This difference in behavior may in part be genetic, as various "clinal" differences in morphology are known to differentiate birds in this species over a distance of less than 15 miles on this island (Sulloway & Kleindorfer, 2013).
A small ground finch (Geospiza fuliginosa) extracting seeds with a sliding motion of its beak. This behavior is observed much more frequently among birds in this species living in the moist Galápagos highlands than in the lowlands, where the same species tends to pick and chip at their prey. This difference in behavior may in part be genetic, as various "clinal" differences in morphology are known to differentiate birds in this species over a distance of less than 15 miles on this island (Sulloway & Kleindorfer, 2013).
A medium ground finch (Geospiza fortis). Males in most of the species of Darwin's finches acquire a largely or entirely black coloration as they age, so the bird in this photograph is either a female or a juvenile male.
A medium ground finch (Geospiza fortis). Males in most of the species of Darwin's finches acquire a largely or entirely black coloration as they age, so the bird in this photograph is either a female or a juvenile male.
A large ground finch (Geospiza magnirostris). In his "Ornithological Notes p. 264," Darwin commented about this species: "The Gross-beaks are very injurious to the cultivated land; they stock up seeds & plants, buried six inches beneath the surface."
A large ground finch (Geospiza magnirostris). In his "Ornithological Notes p. 264," Darwin commented about this species: "The Gross-beaks are very injurious to the cultivated land; they stock up seeds & plants, buried six inches beneath the surface."
A vegetarian finch (Platyspiza crassirostris). This species represents one of the earliest branching nodes in the evolution of Darwin's finches, with one branch giving rise to this single species and another branch evolving into at least 14 different taxa including 5 tree and 9 ground finches. In addition, the original ancestor of Darwin's finches, which was a tanager (not a finch) and is most closely related to the current warbler finch (Certhidea), has evolved to three distinct species: C. olivacea, C. fusca, and Pinaroloxias inornata--the Cocos Island finch. (Cocos Island is located about 470 miles to the northeast of the Galápagos and about 360 miles south of Costa Rica.) The two species of Certhidea are so similar in appearance that, before genetic testing, they were thought to be a single species. One of these two species (C. fusca) exists in two different forms (or subspecies) that inhabit the lower and drier islands. By contrast, this species does not overlap with (C. olivacea), which inhabits the more elevated islands where it is generally found in the moist highlands. Based on genetic analysis, another species of Darwin's finches (the sharp-beaked ground finch, Geospiza difficilis) is now known to consist of six quite distinct genetic variants, each of which is confined to a separate island (Sato et al.,1999; and Lamichhaney et al., 2015).
A vegetarian finch (Platyspiza crassirostris). This species represents one of the earliest branching nodes in the evolution of Darwin's finches, with one branch giving rise to this single species and another branch evolving into at least 14 different taxa including 5 tree and 9 ground finches. In addition, the original ancestor of Darwin's finches, which was a tanager (not a finch) and is most closely related to the current warbler finch (Certhidea), has evolved to three distinct species: C. olivacea, C. fusca, and Pinaroloxias inornata--the Cocos Island finch. (Cocos Island is located about 470 miles to the northeast of the Galápagos and about 360 miles south of Costa Rica.)

The two species of Certhidea are so similar in appearance that, before genetic testing, they were thought to be a single species. One of these two species (C. fusca) exists in two different forms (or subspecies) that inhabit the lower and drier islands. By contrast, this species does not overlap with (C. olivacea), which inhabits the more elevated islands where it is generally found in the moist highlands. Based on genetic analysis, another species of Darwin's finches (the sharp-beaked ground finch, Geospiza difficilis) is now known to consist of six quite distinct genetic variants, each of which is confined to a separate island (Sato et al.,1999; and Lamichhaney et al., 2015).

Some of the type specimens of Darwin's finches at the British Museum of Natural History (Tring). Many of these type specimens lack island localities on the tags owing to Darwin's failure to record such information during his Galápagos visit. By contrast, all of Captain FitzRoy's specimens do include island localities--information that Darwin found it necessary to request from FitzRoy after the Beagle voyage, when Darwin finally realized the evolutionary significance of such information (Sulloway, 1982b).
Some of the type specimens of Darwin's finches at the British Museum of Natural History (Tring). Many of these type specimens lack island localities on the tags owing to Darwin's failure to record such information during his Galápagos visit. By contrast, all of Captain FitzRoy's specimens do include island localities--information that Darwin found it necessary to request from FitzRoy after the Beagle voyage, when Darwin finally realized the evolutionary significance of such information (Sulloway, 1982b).
The author measuring Darwin's small tree finches (Camarhynchus parvulus) for a study of naris deformation caused by the introduced ectoparasite Philornis downsi (Kleindorfer & Sulloway, 2016).
The author measuring Darwin's small tree finches (Camarhynchus parvulus) for a study of naris deformation caused by the introduced ectoparasite Philornis downsi (Kleindorfer & Sulloway, 2016).
The San Cristóbal mockingbird (Nesomimus melanotis), one of the three species of endemic Galápagos mockingbirds. These birds, more than any others in the Galápagos or elsewhere, initiated the Darwinian revolution, as Darwin first noticed that different islands in the Galápagos group had either different species or varieties as he was examining his mockingbird specimens during the Beagle's voyage to Tahiti (Sulloway, 2009).
The San Cristóbal mockingbird (Nesomimus melanotis), one of the three species of endemic Galápagos mockingbirds. These birds, more than any others in the Galápagos or elsewhere, initiated the Darwinian revolution, as Darwin first noticed that different islands in the Galápagos group had either different species or varieties as he was examining his mockingbird specimens during the Beagle's voyage to Tahiti (Sulloway, 2009).
A Floreana mockingbird (Nesomimus trifasciatus), which exists now only on two very small islands off the Floreana coast following the extinction of this species on Floreana itself sometime during the latter half of the nineteenth century. This extinction event was caused by the introduction of cats and rats on this island. Compared with the San Cristóbal mockingbird, the Floreana mockingbird is browner and darker, especially in the breast feathers.
A Floreana mockingbird (Nesomimus trifasciatus), which exists now only on two very small islands off the Floreana coast following the extinction of this species on Floreana itself sometime during the latter half of the nineteenth century. This extinction event was caused by the introduction of cats and rats on this island. Compared with the San Cristóbal mockingbird, the Floreana mockingbird is browner and darker, especially in the breast feathers.
Two mockingbirds engaged in mobbing a Galápagos hawk. The hawk grew sufficiently annoyed by a succession of these aerial attacks that it finally flew away. Although mobbing behavior has evolved in many bird and also some animal species, it is generally restricted to those species in which the young suffer from frequent predation.
Two mockingbirds engaged in mobbing a Galápagos hawk. The hawk grew sufficiently annoyed by a succession of these aerial attacks that it finally flew away. Although mobbing behavior has evolved in many bird and also some animal species, it is generally restricted to those species in which the young suffer from frequent predation.
A male large-billed flycatcher (Myiarchus magnirostris). These birds are particularly tame and curious about people. One once followed me around, and when I tried to photograph it, approached even more closely and finally landed on the end of my telephoto lens as I was looking through my camera's viewfinder.
A male large-billed flycatcher (Myiarchus magnirostris). These birds are particularly tame and curious about people. One once followed me around, and when I tried to photograph it, approached even more closely and finally landed on the end of my telephoto lens as I was looking through my camera's viewfinder.
A young male vermillion flycatcher (Pyrocephalus nanus), an endemic species. This bird has not yet acquired its full red plumage.
A young male vermillion flycatcher (Pyrocephalus nanus), an endemic species. This bird has not yet acquired its full red plumage.
A Galápagos barn owl (Tyto alba punctatissima), an endemic subspecies. Unlike the Galápagos short-eared owl, this species is nocturnal.
A Galápagos barn owl (Tyto alba punctatissima), an endemic subspecies. Unlike the Galápagos short-eared owl, this species is nocturnal.
A yellow warbler (Dendroica petechia aureola), displyaing the characteristic fearlessness of most Galápagos birds.
A yellow warbler (Dendroica petechia aureola), displyaing the characteristic fearlessness of most Galápagos birds.
A Galápagos short-eared owl (Asio flammeus galapagoensis). Although John Gould later declared this owl to be a new species, endemic to the Galápagos, it is today generally considered an endemic subspecies belonging to a widespread grassland species that is found on all continents except Australia and Antarctica.
A Galápagos short-eared owl (Asio flammeus galapagoensis). Although John Gould later declared this owl to be a new species, endemic to the Galápagos, it is today generally considered an endemic subspecies belonging to a widespread grassland species that is found on all continents except Australia and Antarctica.
A flightless Galápagos cormorant (Nannopterum harrisi) drying its wings. Because the wings of these birds trap air, natural selection has favored a reduction in wing size to assist with submarine diving. The wings are about one-third the size necessary for actual flight (Grémillet et al., 2005).
A flightless Galápagos cormorant (Nannopterum harrisi) drying its wings. Because the wings of these birds trap air, natural selection has favored a reduction in wing size to assist with submarine diving. The wings are about one-third the size necessary for actual flight (Grémillet et al., 2005).
A blue-footed booby (Sula nebouxii), one of the most common seabirds in the Galápagos.
A blue-footed booby (Sula nebouxii), one of the most common seabirds in the Galápagos.
Frigatebirds (Frigata magnificens) nesting on San Cristóbal. In the Origin of Species (1859:185), Darwin called attention to the fact that frigatebirds have webbed feet, a vestigial trait, since they never alight on the water. He explained such vestigial traits as being once-functional traits no longer of service owing to evolutionary changes in habits or ecology.
Frigatebirds (Frigata magnificens) nesting on San Cristóbal. In the Origin of Species (1859:185), Darwin called attention to the fact that frigatebirds have webbed feet, a vestigial trait, since they never alight on the water. He explained such vestigial traits as being once-functional traits no longer of service owing to evolutionary changes in habits or ecology.
Flamingos (Phoenicopterus ruber glyphorhynchus) in flight near Punta Espumilla on Santiago. Darwin collected a specimen of this bird, which is now recognized as an endemic Galápagos subspecies.
Flamingos (Phoenicopterus ruber glyphorhynchus) in flight near Punta Espumilla on Santiago. Darwin collected a specimen of this bird, which is now recognized as an endemic Galápagos subspecies.
Nazca boobies (Sula granti ) on Española, with a single chick. Boobies usually lay one or two eggs, but especially when the food supply is low, the alpha chick will peck at and kill the younger chick. Parents do not intervene in these acts of siblicide, as it is not in their Darwinian interests to do so (Mock, Drummond, & Stinson, 1990; Sulloway, 2010).
Nazca boobies (Sula granti ) on Española, with a single chick. Boobies usually lay one or two eggs, but especially when the food supply is low, the alpha chick will peck at and kill the younger chick. Parents do not intervene in these acts of siblicide, as it is not in their Darwinian interests to do so (Mock, Drummond, & Stinson, 1990; Sulloway, 2010).