Evolution and Systematics
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.
Molecular Biology and Genetics
Statistics of barcoding coverage
|Specimen Records:||215||Public Records:||119|
|Specimens with Sequences:||148||Public Species:||28|
|Specimens with Barcodes:||145||Public BINs:||32|
|Species With Barcodes:||27|
- This article is about the bird. For the aircraft, see Gloster Nightjar.
Nightjars are medium-sized nocturnal or crepuscular birds with long wings, short legs and very short bills. They are sometimes referred to as goatsuckers from the ancient folklore that they sucked milk from goats (the Latin for goatsucker is Caprimulgus). Some New World species are named as nighthawks. Nightjars usually nest on the ground.
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.
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.
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. 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 70 species, and the Chordeilinae, or nighthawks of the New World with about 9 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)
- Genus Eurostopodus (5 species)
- Genus Lyncornis (2 species
- Genus Nyctiprogne (2 species)
- Genus Lurocalis (2 species)
- Genus Chordeiles (6 species)
Subfamily Caprimulginae (typical nightjars)
- Genus Nyctidromus – Pauraque
- Genus Phalaenoptilus – Common Poorwill
- Genus Siphonorhis (2 living species)
- Genus Nyctiphrynus (4 species)
- Genus Caprimulgus (some 40–50 species, including the European Nightjar)
- Genus Gactornis – Collared Nightjar
- Genus Antrostomus (11 species)
- Genus Macrodipteryx – Long-primaried nightjars (2 species)
- Genus Hydropsalis (2 species)
- Genus Uropsalis (2 species)
- Genus Macropsalis – Long-trained Nightjar
- Genus Eleothreptus – Sickle-winged Nightjar
Also see a list of nightjars, sortable by common and binomial names.
- 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.
- 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.2007.78.3.2.313.
- Jackson, H.D. (1985). "Commentary and Observations on the Alleged Transportation of Eggs and Young by Caprimulgids". Wilson Bulletin 97 (3): 381–385.
- Handbook of the Birds of the World, Volume 5, Birdlife International/Lynx Edicions, 1999
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