Nazca Booby Sula granti

Sections

Appearance

Distinguishing Characteristics

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Detailed Description

Sexual dimorphism is highly marked (with respect to other Sula species) where females are bigger than males. Additionally, males present dark purple feet with olive-brownish tones, whereas females have more deeply colored purple feet. (García & López-Victoria, 2008)

Adults: Orange bill with a dark mask around the bill; white head, body and coverts; dark wing’s primaries and secondaries and tail (often with central white feathers); dark patches on the back and olive to gray legs and feet (variable according to locality) (Pitman and Jehl, 1998).

Juveniles: Pale bill. Dorsal areas are grayish-brown with upper back usually dark; if a white collar is present between the head and upper back, it is narrow or incomplete. Feathers on the head and neck tend to be uniform grayish-brown. Central tail feathers tend to be pale at the base (Pitman and Jehl, 1998).

Molts

Immature individuals take 2 to 3 years to reach adult plumage (Pitman and Jehl, 1998).

Bare Parts

Iris = Orange

Bill = In general is orange. In females tend to be pinkinsh orange and in males deep orange (Pitman and Jehl, 1998).

Legs and feet =

Galápagos population: olive or kaki in males and gray and olive in females. Malpelo population: yellowish-oive in males and blue-gray with hint of magenta in females. San Benedicto population: gray for both sexes. Clipperton population: blue-gray/greenish-yellow for both sexes (Pitman and Jehl, 1998).

Measurements

Linear measurments of Sula granti (populations of Galápagos, Malpelo, Guatemala, Perú and Gulf of Panama) (Pitman and Jehl, 1998)

 

 

Bill length (mm)

Bill depth (mm)

Bill ratio

Wing (mm)

Tail (mm)

Tarsus (mm)

Male (n=20)

mean

101.9

33.3

0.32

473.8

175.4

54.1

range

96.3 - 107.2

30.4 - 35.8

0.29 - 0.36

410 - 467

165 - 185

50 - 60.4

Female (n=16)

mean

105

35.4

0.34

460.8

179.9

57.43

range

100 - 113.2

33.5 - 38

0.32 - 0.34

438 - 483

160 - 194

52.3 - 63

Recommended Citation

Nazca Booby (Sula granti), In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/nazboo1