---
title: "What the sources say about the Blue-Footed Booby | AnimalTracks.wiki"
description: "48 claims from the Blue-Footed Booby profile, each beside the words of the source that backs it."
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canonical: "https://animaltracks.wiki/animals/blue-footed-booby/sources/"
---

# What the sources say about the Blue-Footed Booby (*Sula nebouxii*)

> 48 claims from the Blue-Footed Booby profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Blue-Footed Booby](https://animaltracks.wiki/animals/blue-footed-booby/)

## Sula nebouxii (blue-footed booby). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Sula_nebouxii/

| The page says | The source says |
| :--- | :--- |
| The sexes are adapted to catch prey of different sizes: the smaller male makes shallow dives, while the heavier female can dive deeper, farther offshore. | the male and the female are adapted for catching prey of different sizes. The male, being smaller, performs shallow dives, while the heavier female is able to make deeper dives farther offshore. |
| Diving in Sync | Then the rest of the flock follows the first diving, into the water with perfectly synchronized movements. |
| Blue-footed boobies breed on arid islands off the Pacific coasts of tropical America | The blue-footed booby breeds on several arid islands off the western coasts of tropical America, Mexico, and northern South America. (note: western coasts of tropical America are its Pacific coasts) |
| A booby may feed alone, but flocks also hunt together: when one bird spots a fish, it whistles to alert the others, and the rest follow it into the water in perfectly synchronized movements. | Despite its habit of feeding alone, the blue-footed booby cooperate in flocks to hunt fish. When one bird in the flock spots a fish, it gives a whistle to alert the others. Then the rest of the flock follows the first diving, into the water with perfectly synchronized movements. |
| A courting male flaunts his blue feet in an exaggerated high-stepping walk and presents pieces of nest material to the female. | Breeding begins with elaborate courtship displays by the male. He flies around his territory, flaunting his blue feet in an exaggerated high-stepping walk, and presents pieces of nest material to the female. |
| Both birds also tip their bills to the sky: he gives a piercing whistle, and she answers with groaning calls. | Then each bird tilts its bill up towards the sky and the male gives a piercing whistle. The female responds with groaning calls, and mating follows shortly afterwards. |
| Bright blue webbed feet | a comical-looking tropical seabird with bright blue webbed feet (note: tagline) |
| a high-stepping courtship walk | flaunting his blue feet in an exaggerated high-stepping walk (note: tagline) |
| Arid islands | The blue-footed booby inhabits arid islands in the Pacific ocean. (note: stats.habitat) |
| A male flaunts his blue feet in an exaggerated high-stepping walk and presents pieces of nest material to the female. | He flies around his territory, flaunting his blue feet in an exaggerated high-stepping walk, and presents pieces of nest material to the female. (note: faq 3) |
| After a courtship flight, he flashes his feet at her as he lands. | After making a courtship flight, the male flashes his feet at the female as he lands. (note: faq 3) |
| Then both birds tilt their bills to the sky: he gives a piercing whistle, she answers with groaning calls, and mating follows shortly afterwards. | Then each bird tilts its bill up towards the sky and the male gives a piercing whistle. The female responds with groaning calls, and mating follows shortly afterwards. (note: faq 3) |
| a male that courts by flaunting his blue feet in an exaggerated high-stepping walk | Breeding begins with elaborate courtship displays by the male. He flies around his territory, flaunting his blue feet in an exaggerated high-stepping walk (note: vibe.reason) |

## Blue-footed Booby. Audubon Field Guide, National Audubon Society.

https://www.audubon.org/field-guide/bird/blue-footed-booby

| The page says | The source says |
| :--- | :--- |
| Females measure 80 to 90 centimetres long and weigh 1.5 to 2 kilograms; males are smaller, at 80 to 85 centimetres and 1.2 to 1.6 kilograms. | Female — Length: 2 ft 8 in- 2 ft 11 in (80 - 90 cm); wingspan: 5 ft- 5 ft 1 in (1.5 - 1.6 m); weight: 3 lb 11 oz- 4 lb 7 oz (1.5 - 2 kg). Male — Length: 2 ft 7 in- 2 ft 9 in (80 - 85 cm); wingspan: 4 ft 10 in - 5 ft (1.4 - 1.5 m); weight: 2 lb 10 oz- 3 lb 8 oz (1.2 - 1.6 kg). |
| in some years small numbers stray north into the southwestern United States, mainly to California's Salton Sea. | In some years, small numbers stray north into the southwestern United States, mainly to the Salton Sea, California. |

## Blue-footed booby. Galapagos Conservation Trust.

https://galapagosconservation.org.uk/species/blue-footed-booby/

| The page says | The source says |
| :--- | :--- |
| The Booby That Dive-Bombs at Up to 60 Miles an Hour | the bird hits the water at speeds up to 60 mph |
| The blue-footed booby (Sula nebouxii) folds back its wings and plunges: its dives can start more than 20 metres above the water, and it hits the surface at speeds up to 60 miles an hour. | the booby folds back its wings, giving it a more streamlined shape, and plunges into the water. Dives may occur from over 20 metres above the water, and the bird hits the water at speeds up to 60 mph |
| Its nostrils are permanently closed, which means it can swim underwater easily, and air sacs in its skull protect its brain from the impact of the dive. | Their nostrils are permanently closed, meaning they can swim underwater easily, and special air sacs in their skulls protect their brains from the high impact of the dive. |
| The Galapagos Conservation Trust gives an average lifespan of 17 years. | Average lifespan: 17 years (note: the Trust gives no wild or captive scope, so the page names it; ADW's older AnAge captive average (18 years) was cut in favour of the current institution page) |
| including the Galápagos | Blue-footed boobies are one of three booby species found on Galapagos. |
| They hunt schools of small fish such as sardines and anchovies, often foraging in groups of up to 200 birds. | they take to the sky in search of schools of small fish such as anchovies and sardines, often foraging in large groups of up to 200 birds. |
| plunge-dives that hit the water at up to 60 mph. | plunges into the water. Dives may occur from over 20 metres above the water, and the bird hits the water at speeds up to 60 mph (note: tagline) |
| often with rocky coasts, along the eastern Pacific, including the Galápagos | Blue-footed boobies are one of three booby species found on Galapagos. They are large, distinctive birds, found along the Eastern Pacific coastline where they often nest on small islands with rocky coasts. (note: stats.habitat) |
| Sardines, anchovies, and other small schooling fish | they take to the sky in search of schools of small fish such as anchovies and sardines (note: stats.diet) |
| plus sealed nostrils and skull air sacs that protect its brain on dives of up to 60 mph. | the bird hits the water at speeds up to 60 mph, snapping up fish in its serrated beak. Their nostrils are permanently closed, meaning they can swim underwater easily, and special air sacs in their skulls protect their brains from the high impact of the dive. (note: stats.superpower) |
| Air sacs in its skull protect its brain from the high impact of a dive that can start more than 20 metres above the water. Its nostrils are also permanently closed, which means it can swim underwater easily. | Dives may occur from over 20 metres above the water ... Their nostrils are permanently closed, meaning they can swim underwater easily, and special air sacs in their skulls protect their brains from the high impact of the dive. (note: faq 2) |

## Velando, Beamonte-Barrientos & Torres (2006). Pigment-based skin colour in the blue-footed booby: an honest signal of current condition used by females to adjust reproductive investment. Oecologia.

https://doi.org/10.1007/s00442-006-0457-5

| The page says | The source says |
| :--- | :--- |
| Feet a Female Reads | Our data indicate that blue-footed booby females are continuously evaluating their mates |
| A male's foot color is both structural, built from arrays of collagen fibres in the skin, and pigment-based, from carotenoids, colored pigments in his food. | male foot colour is structurally (collagen arrays) and pigment based. ... Variation of dietary carotenoids induced comparable changes in cell-mediated immune function and foot colour (note: the second sentence names the pigment as dietary carotenoids) |
| A Signal That Shifts in Two Days | In 48 h foot colour became duller when males were food deprived and brighter when they were re-fed with fresh fish. |
| In one experiment, males' feet turned duller within 48 hours when they were kept from food, and brighter when they were fed fresh fish again. | In 48 h foot colour became duller when males were food deprived and brighter when they were re-fed with fresh fish. |
| Changing the carotenoids in their food shifted their immune function and foot color together. | Variation of dietary carotenoids induced comparable changes in cell-mediated immune function and foot colour |
| The researchers suggest the color is a rapid honest signal of a male's current condition. | These results suggest that pigment-based foot colour is a rapid honest signal of current condition. (note: 'one that reliably reflects it' glosses 'honest signal' for readers) |
| In a second experiment, researchers painted some males' feet a duller blue with make-up the day after the first egg was laid, and their mates laid smaller second eggs than other females. | One day after the first egg was laid we captured the males and modified the foot colour of experimental males with a non-toxic and water resistant duller blue intensive make-up, mimicking males in low condition. Females decreased the size of their second eggs, relative to the second egg of control females, when the feet of their mates were experimentally duller. |
| In this species, brood reduction (the loss of a chick from a nest) is linked to size differences between chicks at hatching, and laying a lighter second egg makes it easier. | Since brood reduction in this species is related to size differences between brood mates at hatching, by laying lighter second eggs females are facilitating brood reduction. (note: the parenthesis glosses the term for readers) |
| The researchers say their data indicate that females keep evaluating their mates. | Our data indicate that blue-footed booby females are continuously evaluating their mates |
| Blue feet colored by collagen and carotenoid pigment, which researchers suggest signal a male's current condition | male foot colour is structurally (collagen arrays) and pigment based. ... Variation of dietary carotenoids induced comparable changes in cell-mediated immune function and foot colour, suggesting that carotenoid-pigmentation reveals the immunological state of individuals. These results suggest that pigment-based foot colour is a rapid honest signal of current condition. (note: stats.superpower) |
| A male's foot color comes from structural collagen in the skin combined with pigment, including carotenoids from his food. | male foot colour is structurally (collagen arrays) and pigment based. ... Variation of dietary carotenoids induced comparable changes in cell-mediated immune function and foot colour (note: faq 1) |
| In one experiment, males' feet turned duller within 48 hours when they were kept from food, and brighter once they were fed fresh fish again. | In 48 h foot colour became duller when males were food deprived and brighter when they were re-fed with fresh fish. (note: faq 1) |
| Changing the carotenoids in their food shifted immune function and foot color together, suggesting that the color reveals a male's immune state. | Variation of dietary carotenoids induced comparable changes in cell-mediated immune function and foot colour, suggesting that carotenoid-pigmentation reveals the immunological state of individuals. (note: faq 1) |
| When males' feet were made duller with make-up, their mates laid smaller second eggs, which the researchers say indicates that females keep evaluating their mates. | One day after the first egg was laid we captured the males and modified the foot colour of experimental males with a non-toxic and water resistant duller blue intensive make-up, mimicking males in low condition. Females decreased the size of their second eggs, relative to the second egg of control females, when the feet of their mates were experimentally duller. ... Our data indicate that blue-footed booby females are continuously evaluating their mates (note: faq 1) |

## Velando, Drummond & Torres (2006). Senescent birds redouble reproductive effort when ill: confirmation of the terminal investment hypothesis. Proceedings of the Royal Society B: Biological Sciences.

https://doi.org/10.1098/rspb.2006.3480

| The page says | The source says |
| :--- | :--- |
| A male's breeding success rises at first, then falls steadily with age. | after initial increase, male reproductive success declines progressively with age. |
| Scientists gave males of two age groups a substance that sets off an immune response, which made them seem less likely to survive. | Before laying, males of two age classes were challenged with lipopolysaccharide to elicit an immune response, which induced symptoms of declining survival prospects. (note: 'a substance' stands for lipopolysaccharide) |
| Breeding success dropped in the mature males but rose 98 percent in the old ones. | Reproductive success of immune-challenged mature males fell, while that of immune-challenged old males showed a 98% increase. |
| That fits terminal investment: the idea that animals should put more effort into breeding as they age and their chances of surviving and breeding again decline. | This study reports an experimental confirmation of the terminal investment hypothesis, a longstanding theoretical idea that animals should increase their reproductive effort as they age and their prospects for survival and reproduction decline. |

## Sánchez-Macouzet, Rodríguez & Drummond (2014). Better stay together: pair bond duration increases individual fitness independent of age-related variation. Proceedings of the Royal Society B: Biological Sciences.

https://doi.org/10.1098/rspb.2013.2843

| The page says | The source says |
| :--- | :--- |
| Blue-footed boobies have a high divorce rate, but pairs that have been together longer do better. | a long-lived marine bird with a high divorce rate. ... pair bond duration increases individual fitness |
| A study of 24 years of records found that they started their clutches five weeks earlier in the season and raised 35 percent more fledglings (chicks old enough to leave the nest), regardless of age or breeding experience. | applying a novel analytical approach to a 24 year database, we found that those pairs which have been together for longer establish their clutches five weeks earlier in the season, hatch more of their eggs and produce 35% more fledglings, regardless of age and reproductive experience. (note: the parenthesis glosses 'fledglings' for readers) |
| Courtship, Divorce, and Old Age | a long-lived marine bird with a high divorce rate. (note: courtship and old age are claimed by the ADW and senescent-2006 sentences in this section) |

## Sula nebouxii. The IUCN Red List of Threatened Species 2021: e.T22696683A168988087.

https://doi.org/10.2305/iucn.uk.2021-3.rlts.t22696683a168988087.en

| The page says | The source says |
| :--- | :--- |
| Least Concern | IUCN Red List category: Least Concern (LC). |