Evolution and Systematics

Functional Adaptations

Functional adaptation

Gular fluttering dissipates heat: nightjars

The gular sack of nightjars helps to dissipate heat efficiently by vibrating.

  "An important environmental adaptation for many caprimulgiformes is the ability to withstand high ambient temperature (Ta). Birds of this order are most common in warm climates, and frogmouths, potoos, and nightjars all roost and nest in the open where they can be subjected to long periods of direct sun exposure. In these circumstances, they avoid hyperthermia by using evaporative cooling strategies. Nightjars dissipate heat by gular fluttering, during which the mouth is opened, the rate of blood flow to the buccal area is increased, and the moist gular area is rapidly vibrated." (Fowler and Miller 2003: 225)

"When poorwills are exposed to high temperatures, they increase evaporation of water by initiation of gular flutter and by some increase in breathing rate. Gular flutter supplements evaporation due to respiration, and involves a rapid vibration of the moist membranes of the gular region, driven by the hyoid. The rate of gular flutter in the poorwill is relatively constant and independent of heat load, and evaporation due to flutter is modulated by varying the amount of time spent fluttering, as well as the amount of air moved per flutter." (Lasiewski 1969:1504)

Watch Video (doesn't show gular fluttering, but beautiful!)

Watch Video (gular fluttering of a heron chick)
  Learn more about this functional adaptation.
  • Fowler, ME; Miller, RE. 2003. Zoo and Wild Animal Medicine. Philadelphia: W.B. Saunders Co.
  • Lasiewski RC. 1969. Physiological responses to heat stress in the poorwill. American Journal of Physiology. 217(5): 1504-1509.
  • Sturkie PD; Whittow GC. 2000. Avian physiology. Ithaca, NY: Cornell University Press. 685 p.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:258
Specimens with Sequences:196
Specimens with Barcodes:188
Species With Barcodes:33
Public Records:138
Public Species:28
Public BINs:33
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Barcode data

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This article is about the family of birds. For the aircraft, see Gloster Nightjar. For the cryptid sometimes called "goat sucker", see Chupacabra.

Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae, characterized by long wings, short legs and very short bills. They are sometimes called goatsuckers, due to the ancient folk tale that they sucked the milk from goats (the Latin for goatsucker is Caprimulgus). Some New World species are called nighthawks. Nightjars usually nest on the ground.

The English word 'nightjar' originally referred to the European nightjar.

Nightjars are found around the world. They are mostly active in the late evening and early morning or at night, and feed predominantly on moths and other large flying insects.

Most have small feet, of little use for walking, and long pointed wings. Their soft plumage is cryptically coloured to resemble bark or leaves. Some species, unusual for birds, perch along a branch, rather than across it. This helps to conceal them during the day. Bracken is their preferred habitat.

The common poorwill, Phalaenoptilus nuttallii is unique as a bird that undergoes a form of hibernation, becoming torpid and with a much reduced body temperature for weeks or months, although other nightjars can enter a state of torpor for shorter periods.[1]

Nightjars lay one or two patterned eggs directly onto bare ground. It has been suggested that nightjars will move their eggs and chicks from the nesting site in the event of danger by carrying them in their mouths. This suggestion has been repeated many times in ornithology books, but while this may accidentally happen, surveys of nightjar research have found very little evidence to support this idea.[2][3]

Conservation challenge[edit]

Working out conservation strategies for some species of nightjar presents a particular challenge common to other hard-to-see families of birds; in a few cases, humans do not have enough data on whether a bird is rare or not. This has nothing to do with any lack of effort. It reflects, rather, the difficulty in locating and identifying a small number of those species of birds among the 10,000 or so that exist in the world, given the limitations of human beings. A perfect example is the Vaurie's nightjar in China's south-western Xinjiang. It has been seen for certain only once, in 1929, a specimen that was held in the hand. Surveys in the 1970s and 1990s failed to find it.[4] It is perfectly possible that it has evolved as a species that can only really be identified in the wild by other Vaurie's nightjars, rather than by humans. As a result, scientists do not know whether it is extinct, endangered, or even locally common.


Traditionally, nightjars have been divided into two subfamilies: the Caprimulginae, or typical nightjars with about 80 species, and the Chordeilinae, or nighthawks of the New World with about 19 species. The two groups are similar in most respects, but the typical nightjars have rictal bristles, longer bills, and softer plumage. In their pioneering DNA-DNA hybridisation work, Sibley and Ahlquist found that the genetic difference between the eared-nightjars and the typical nightjars was, in fact, greater than that between the typical nightjars and the nighthawks of the New World. Accordingly, they placed the eared-nightjars in a separate family: Eurostopodidae.

Subsequent work, both morphological and genetic, has provided support for the separation of the typical and the eared-nightjars, and some authorities have adopted this Sibley-Ahlquist recommendation, and also the more far-reaching one to group all the owls (traditionally Strigiformes) together in the Caprimulgiformes. The listing below retains a more orthodox arrangement, but recognises the eared-nightjars as a separate group. For more detail and an alternative classification scheme, see Caprimulgiformes and Sibley-Ahlquist taxonomy.

Subfamily Chordeilinae (nighthawks)

Subfamily Caprimulginae — (typical nightjars)

Also see a list of nightjars, sortable by common and binomial names.



  1. ^ Lane JE, Brigham RM, Swanson DL (2004). "Daily torpor in free-ranging whip-poor-wills (Caprimulgus vociferus)". Physiological and Biochemical Zoology 77 (2): 297–304. doi:10.1086/380210. PMID 15095249. 
  2. ^ Jackson, H.D. (2007). "A review of the evidence for the translocation of eggs and young by nightjars (Caprimulgidae)". Ostrich: Journal of African Ornithology 78 (3): 561–572. doi:10.2989/OSTRICH.2007. 
  3. ^ Jackson, H.D. (1985). "Commentary and Observations on the Alleged Transportation of Eggs and Young by Caprimulgids". Wilson Bulletin 97 (3): 381–385. 
  4. ^ Handbook of the Birds of the World, Volume 5, Birdlife International/Lynx Edicions, 1999
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Eared nightjar

The eared nightjars are a small group of nocturnal birds in the nightjar family, although the taxonomy is uncertain. There are seven species, mainly found in forest and scrub from China to Australia. 5 species are placed in the genus, Eurostopodus, the other two species in Lyncornis. They are long winged birds with plumage patterned with grey and brown to camouflage them when resting on the ground. They feed on insects caught in flight. A single white egg is laid directly on the ground and incubated by both adults. The chicks can walk soon after hatching.


The order Caprimulgiformes contains several families of nocturnal insectivores, these are the frogmouths, the potoos, the oilbird and the nightjars. The latter family is normally split into two subfamilies, the American nighthawks, Chordelinae, and the typical nightjars Caprimulginae.[1] The eared nightjars are sometimes considered a subfamily Eurostopodinae of the Caprimulgidae but some studies have them as a sister group,[2] while others treat them as a clade within the caprimulgids;[3] others consider that the genus Eurostopodus may not be monophyletic.[4][5][6]

The eared nightjars consist of seven extant species in two genera, Eurostopodus and Lyncornis:[7]


The eared nightjars are large compared to many nightjars, but otherwise are similar in structure. They are long-winged and long-tailed, and are light for the wing area, making them powerful and agile in flight. An important difference from typical nightjars is the lack of bristles around the beak. They are nocturnal and have a reflective tapetum lucidum at the back of the eye. The beaks are small, but these birds have a very large gape for catching insects in flight. The feet and legs are small and weak, and the toes are partly webbed. the middle toe's claw has a comb-like pecten on its inner edge, which may be used for plumage care.[8]

The plumage is cryptically patterned with browns and greys, to make these ground-nesting birds difficult to see when resting during the day. Some species have white patches in the wings, and two, Great and Malaysian, have "ear tufts" at the rear of the crown.[9] The songs of these birds are three or more repeated notes, sometimes with whistles or bubbling sounds, and are typically given at dawn or dusk.[10]

Distribution and habitat[edit]

The eared nightjars are found from China through Southeast Asia to Australia. Tropical populations are mostly sedentary, but the two Australian species (spotted and white-throated nightjars) are partial migrants. These are birds of open woodland or forest clearings and edges.[10]



No nest is built, the single white egg is laid directly on to the ground or leaf litter. The female incubates the egg during the day, relying mainly on the excellent camouflage of the plumage to avoid predators. The male takes over incubation during the night, but roosts some distance away when the female is brooding.[11] If necessary, the female will attempt to distract the intruder away from the eggs, or perform a defence display with spread wings, puffed throat and hissing sounds. The eggs hatch in three to four weeks, and the young can walk soon after hatching. the chicks are fed by both parents.[10]


All eared nightjars feed almost entirely on insects caught in flight, typically moths and beetles. They hunt at twilight and in the night, and eat their prey on the wing. The flight is buoyant and twisting,[12] and may be interspersed with periods of resting on the ground, a road, or in a tree.[10] These birds drink in flight, gliding low over the water and dipping the beak.[12]


  1. ^ Cleere (1998) p. 15
  2. ^ Mariaux, J & Michael J Braun (1996). "A Molecular phylogenetic survey of the nightjars and allies (Caprimulgiformes) with special emphasis on the potóos (Nyctibiidae)". Molecular Phylogenetics and Evolution 6 (2): 228–244. doi:10.1006/mpev.1996.0073. PMID 8899725. 
  3. ^ Barrowclough, George F., Groth, Jeff G., and Mertz, Lisa A. (2006). "The RAG-1 exon in the avian order Caprimulgiformes: phylogeny, heterozygosity, and base composition". Molecular Phylogenetics and Evolution 41 (1): 238–48. doi:10.1016/j.ympev.2006.05.013. PMID 16814574. 
  4. ^ Braun, MJ; Huddleston, Christopher J. (2009). "A molecular phylogenetic survey of caprimulgiform nightbirds illustrates the utility of non-coding sequences". Molecular Phylogenetics and Evolution 53 (3): 948–60. doi:10.1016/j.ympev.2009.08.025. PMID 19720151. 
  5. ^ Kin-Lan Han, M.S. (2006) Molecular systematics of nightjars and nighthawks (Caprimulgidae) MS Thesis. University of Maryland
  6. ^ Larsen, C; Michael Speed; Nicholas Harvey; Harry A. Noyes (2007). "A molecular phylogeny of the nightjars (Aves: Caprimulgidae) suggests extensive conservation of primitive morphological traits across multiple lineages". Molecular Phylogenetics and Evolution 42 (3): 789–796. doi:10.1016/j.ympev.2006.10.005. PMID 17123840. 
  7. ^ Han, K.-L., M.B. Robbins, and M.J. Braun. 2010. "A multi-gene estimate of phylogeny in the nightjars and nighthawks (Caprimulgidae)". Molecular Phylogenetics and Evolution 55: 443–453. doi:10.1016/j.ympev.2010.01.023. 
  8. ^ Cleere (1998) p. 24
  9. ^ Cleere (1998) pp. 106–112
  10. ^ a b c d Cleere (1998) pp. 174–184
  11. ^ Cleere (1998) pp. 24–35
  12. ^ a b Cleere (1998) pp. 32–33

Cited text[edit]

  • Cleere, Nigel; Nurney, David (1998). Nightjars: A Guide to the Nightjars, Frogmouths, Potoos, Oilbird and Owlet-nightjars of the World. Pica/Christopher Helm. ISBN 1-873403-48-8. 
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