Editing Bird (section)

===Defence and intraspecific combat===
A few species are able to use chemical defences against predators; some [[Procellariiformes]] can eject an unpleasant [[stomach oil]] against an aggressor,<ref>{{Cite journal|last=Warham |first=John |date=1 May 1977|title=The incidence, function and ecological significance of petrel stomach oils |journal=Proceedings of the New Zealand Ecological Society |volume=24 |pages=84–93 |url=http://www.newzealandecology.org/nzje/free_issues/ProNZES24_84.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.newzealandecology.org/nzje/free_issues/ProNZES24_84.pdf |archive-date=9 October 2022 |url-status=live |issue=3}}</ref> and some species of [[pitohui]]s from [[New Guinea]] have a powerful [[neurotoxin]] in their skin and feathers.<ref>{{Cite journal|last1=Dumbacher |first1=J.P. |date=October 1992 |title=Homobatrachotoxin in the genus ''Pitohui'': chemical defense in birds? |journal=Science |volume=258 |issue=5083 |pages=799–801 |doi=10.1126/science.1439786 |pmid=1439786 |last2=Beehler |first2=BM |last3=Spande |first3=TF |last4=Garraffo |first4=HM |last5=Daly |first5=JW|bibcode=1992Sci...258..799D }}</ref>

A lack of field observations limit our knowledge, but intraspecific conflicts are known to sometimes result in injury or death.<ref name=long>{{cite journal |last1=Longrich |first1=N.R. |last2=Olson |first2=S.L. |title=The bizarre wing of the Jamaican flightless ibis Xenicibis xympithecus: a unique vertebrate adaptation |journal=Proceedings of the Royal Society B: Biological Sciences |date=5 January 2011 |volume=278 |issue=1716 |pages=2333–2337 |doi=10.1098/rspb.2010.2117 |pmid=21208965 |pmc=3119002}}</ref> The screamers ([[Anhimidae]]), some jacanas (''[[Jacana (genus)|Jacana]]'', ''[[Hydrophasianus]]''), the spur-winged goose (''[[Plectropterus]]''), the torrent duck (''[[Merganetta]]'') and nine species of lapwing (''[[Vanellus]]'') use a sharp spur on the wing as a weapon. The steamer ducks (''[[Tachyeres]]''), geese and swans (''[[Anserinae]]''), the solitaire (''[[Pezophaps]]''), sheathbills (''[[Chionis]]''), some guans (''[[Crax]]'') and stone curlews (''[[Burhinus]]'') use a bony knob on the [[alula]]r metacarpal to punch and hammer opponents.<ref name=long/> The jacanas ''[[Actophilornis]]'' and ''[[Irediparra]]'' have an expanded, blade-like radius. The extinct ''[[Xenicibis]]'' was unique in having an elongate forelimb and massive hand which likely functioned in combat or defence as a jointed club or flail. [[Cygnus olor|Swans]], for instance, may strike with the bony spurs and bite when defending eggs or young.<ref name=long/>