Air sac

A thin-walled structure joined to the lungs of a bird, involved in respiration. There are usually nine air sacs, which may extend into some of a bird's hollow bones. Birds that plunge-dive into water, such as gannets, have modified air sacs beneath their skin to help cushion the impact.

Reference

Projects
This article is part of Project Glossary, an All Birds project that aims to write comprehensive articles on each term related to animals. Project Glossary Glossary v • t • e A Abdomen • Aberrant • Abmigration • Abrasion • Absolute magnitude • Absorption line • Abyssal • Abyssal plain • Abyssal zone • Accelerating universe • Accidental • Accretion • Acquisition • Active galaxy • Active prominence • Adaptive radiation • Addition • Adult • Adult plumage • Aerie • African parrot • Air mass • Air sac • Airfoil • Alarm call • Albedo • Albino • Allopatric • Allopreening • Altazimuth mounting • Altitude • Altricial • Alula • Americas • Anadromous • Anaerobic • Anatomy • Annual parallax • Annual proper motion • Annualar eclipse • Anoxic • Antarctic Circle • Ant-follower • Anterior • Anticyclone • Anting • Antimatter • Antiparticle • Antiphonal song • Aperture • Apogee • Apparent magnitude • Arachnoid • Arboreal • Arctic Circle • Argon • Arm • Asexual reproduction • Asterism • Asteroid • Astronomical unit • Asynchronous hatching • Atmosphere • Atoll • Atom • Auricular • Auricular patch • Aurora • Autapomorphy • Authigenic • Autotroph • Autumnal equinox • Avian influenza • Axillaries • Azimuth B Back • Background radiation • Backshore • Backwash • Baleen • Band • Bank • Bar • Barbel • Barbule • Barnard • Barrage • Barred • Barred spiral galaxy • Barrier island • Barrier reef • Baryon • Basal (phylogenetics) • Basic I • Basin • Bathyal • Beach face • Belly • Beryllium • Benthos • Berm • Bib • Big Bang • Big Crunch • Big Rip • Binary star • Binomial nomenclature • Biodiversity • Biogenic • Bioluminescence • Biomass • Biome • Bioturbation • Bipedalism • Bird anatomy • Bird diets • Bird egg • Bird flight • Bird hybrid • Bird intelligence • Bird migration • Bird nest • Bird of prey • Bird reproduction • Bird senses • Bird song • Black body • Black dwarf star • Black hole • Black smoker • Blazar • BL lacterae object • Bloom • Blue shift • Body fossil • Bok globule • Booted • Bore • Brackish • Breaker zone • Breakwater • Breast • Breastband • Breeding plumage • Brood parasite • Brown dwarf star • Bustle • Buzzard • Bycatch C Calcareous • Calcium carbonate • Calendar year • Caldera • Callosity • Calve • Carapace • Carbon cycle • Carnivore • Carpal • Carpal bar • Casque • Casual • Catadromous • Cere • Cheek • Chemosynthesis • Chevron • Chin • Chlorophyll • Chromatophore • Cilia • Clade • Class • Cline • Cloaca • Coast • Cob • Cold seep • Collar • Colonial • Colour morph • Commensalism • Commic terns • Commissure • Common name • Concordant coast • Congeneric • Conservation status • Conspecific • Continental crust • Continental margin • Continental rise • Continental shelf • Continental slope • Convection • Convergent evolution • Coral bleaching • Coral reef • Coralline • Coriolis effect • Coverts • Crepuscular • Crest • Cretaceous • Crissum • Critically Endangered • Crown • Crown patch • Cryptic • Culmen • Current • Cusp • Cyclone D Dactyly • Dark zone • Dawn chorus • Deforestation • Delta • Demersal • Deposit feeding • Depositional coast • Detritus • Deuterium • Dewlap • Diagnostic • Digital object identifier • Dihedral • Discordant coast • DNA • DNA sequence • Doldrums • Dorsal • Drift • Drowned coast • Dune E Ear tuft • Earth • Echolocation • Echo-sounding • Eclipse plumage • Eddy • Egg • Egg tooth • Ekman effect • El Nino • Emargination • Emergent coast • Endangered • Endangered species • Endemic • Endemism • ENSO • Eocene • Equator • Erosional coast • Estuary • Eustatic • Eutrophication • Evolution of birds • Extant • Extinct • Extinct in the wild • Extinction • Exoskeleton • Eye • Eye line • Eye ring • Eye stripe • Eye wattle • Eyebrow F Face skin • Facial disk • Family • Fast ice • Fathom • Fault •Feather • Feather fringe • Fecal sac • Femur • Feral • Ferrel cell • Fertilization • Fetch • Filoplume • Filter feeding • Finger • Fjord • Flagellum • Flank • Fledgling • Flight feathers • Flightless bird • Flipper • Fluke • Foot • Foot projection • Forced wave • Forecrown • Forehead • Foreneck • Foreshore • Forest • Forewing • Fossil • Fractal • Frazil ice • Fringing reef • Frons • Front • Frontal shield G Gabion • Gander • Gape • Gape flange • Genus • Gibber • Gill rakers • Glacier • Gleaning • Glide • Gonydeal angle • Gonys • Gorget • Gravitational lens • Grease ice • Grease ice • Groyne • Guano • Gular • Gular fluttering • Guyot • Gynandromorph • Gyre H H1N1 • Habitat • Habitat loss • Hackle • Hadal • Hadley cell • Half-hood • Halocline • Hand • Hatchling • Hawk • Headland • Heat capacity • Helium • Herbig-Haro object • Herbivore • Hermaphrodite • Hibernation • Hindneck • Holdfast • Holoplankton • Hood • Hotspot • Hover • Humerus • Hurricane • Hybrid • Hydrocarbon • Hydrogen • Hydrothermal vent I-K Ice age • Iceberg • Ice cap • Ice lead • Ice rafting • Ice sheet • Ice shelf • Igneous rock • Immature • Incertae sedis • Infraorder • Insectivore • Intermediate coast • Internal wave • International Standard Book Number • Introduced species • Intertropical convergence zone • Invertebrate • Iridescence • Irradiance • Irruption • Island arc • Isolating mechanisms • Isotasy • IUCN • Juvenile • Katabatic wind • Keel • Kite (verb) • Kleptoparasitism • Krypton This article is part of Project Anatomy, a All Birds project that aims to write comprehensive articles on each anatomical term related to birds.