Editing Bird (section)

====Territories, nesting and incubation====
{{See also|Bird nest}}
[[File:Bird-nest (2).jpg|alt=two unused bird nest|thumb|left|A bird nest which fell from a tree.]]
Many birds actively defend a territory from others of the same species during the breeding season; maintenance of territories protects the food source for their chicks. Species that are unable to defend feeding territories, such as [[seabird]]s and [[Swift (bird)|swift]]s, often breed in [[Bird colony|colonies]] instead; this is thought to offer protection from predators. Colonial breeders defend small nesting sites, and competition between and within species for nesting sites can be intense.<ref>{{cite journal |last1=Kokko |first1=H |last2=Harris |first2=M |last3=Wanless |first3=S |year=2004 |title=Competition for breeding sites and site-dependent population regulation in a highly colonial seabird, the common guillemot ''Uria aalge'' |journal=Journal of Animal Ecology |volume=73 |issue=2| pages=367–376 |doi=10.1111/j.0021-8790.2004.00813.x|doi-access=free |bibcode=2004JAnEc..73..367K }}</ref>

All birds lay [[amniotic egg]]s with hard shells made mostly of [[calcium carbonate]].<ref name = "Gill"/> Hole and burrow nesting species tend to lay white or pale eggs, while open nesters lay [[camouflage]]d eggs. There are many exceptions to this pattern, however; the ground-nesting [[nightjar]]s have pale eggs, and camouflage is instead provided by their plumage. Species that are victims of [[brood parasites]] have varying egg colours to improve the chances of spotting a parasite's egg, which forces female parasites to match their eggs to those of their hosts.<ref>{{cite journal | last1 = Booker | first1 = L | last2 = Booker | first2 = M | year = 1991 | title = Why Are Cuckoos Host Specific? | journal = [[Oikos (journal)|Oikos]] | volume = 57 | issue = 3| pages = 301–309 | doi = 10.2307/3565958 | jstor=3565958}}</ref>
[[File:Golden-backed Weaver.jpg|thumb|left|alt=Yellow weaver (bird) with black head hangs an upside-down nest woven out of grass fronds.|Male [[golden-backed weaver]]s construct elaborate suspended nests out of grass.]]
Bird eggs are usually laid in a [[Bird nest|nest]]. Most species create somewhat elaborate nests, which can be cups, domes, plates, mounds, or burrows.<ref name = "Hansell">{{cite book |last1=Hansell |first1=M |year=2000 |title=Bird Nests and Construction Behaviour |publisher=University of Cambridge Press |isbn=0-521-46038-7}}</ref> Some bird nests can be a simple scrape, with minimal or no lining; most seabird and wader nests are no more than a scrape on the ground. Most birds build nests in sheltered, hidden areas to avoid predation, but large or colonial birds—which are more capable of defence—may build more open nests. During nest construction, some species seek out plant matter from plants with parasite-reducing toxins to improve chick survival,<ref>{{cite journal | last1 = Lafuma | first1 = L. | last2 = Lambrechts | first2 = M. | last3 = Raymond | first3 = M. | year = 2001 | title = Aromatic plants in bird nests as a protection against blood-sucking flying insects? | journal = Behavioural Processes | volume = 56 | issue = 2| pages = 113–120 | doi = 10.1016/S0376-6357(01)00191-7 | pmid = 11672937 }}</ref> and feathers are often used for nest insulation.<ref name = "Hansell"/> Some bird species have no nests; the cliff-nesting [[common guillemot]] lays its eggs on bare rock, and male [[emperor penguin]]s keep eggs between their body and feet. The absence of nests is especially prevalent in open habitat ground-nesting species where any addition of nest material would make the nest more conspicuous. Many ground nesting birds lay a clutch of eggs that hatch synchronously, with [[precocial]] chicks led away from the nests ([[nidifugous]]) by their parents soon after hatching.<ref>{{cite book |author1=Collias, Nicholas E. |title=Nest building and bird behavior |author2=Collias, Elsie C. |publisher=Princeton University Press |year=1984 |isbn=0691083584 |place=Princeton, NJ |pages=16–17, 26}}</ref>

[[File:Eastern Phoebe-nest-Brown-headed-Cowbird-egg.jpg|thumb|alt= Nest made of straw with five white eggs and one grey speckled egg|Nest of an [[eastern phoebe]] that has been parasitised by a [[brown-headed cowbird]]]]
[[Egg incubation|Incubation]], which regulates temperature for chick development, usually begins after the last egg has been laid.<ref name = "Gill"/> In monogamous species incubation duties are often shared, whereas in polygamous species one parent is wholly responsible for incubation. Warmth from parents passes to the eggs through [[brood patch]]es, areas of bare skin on the abdomen or breast of the incubating birds. Incubation can be an energetically demanding process; adult albatrosses, for instance, lose as much as {{convert|83|g}} of body weight per day of incubation.<ref>{{cite book |last1=Warham |first1=J. |year=1990 |title=The Petrels: Their Ecology and Breeding Systems |location=London |publisher=[[Academic Press]] |isbn=0-12-735420-4}}</ref> The warmth for the incubation of the eggs of [[megapode]]s comes from the sun, decaying vegetation or volcanic sources.<ref>{{cite book |last1=Jones |first1=DN |last2=Dekker |first2=René WRJ |last3=Roselaar |first3=Cees S |year=1995 |chapter=The Megapodes |title=Bird Families of the World 3. |publisher=[[Oxford University Press]] |location=Oxford |isbn=0-19-854651-3}}</ref> Incubation periods range from 10 days (in [[woodpecker]]s, [[cuckoo]]s and [[passerine]] birds) to over 80 days (in albatrosses and [[Kiwi (bird)|kiwi]]s).<ref name = "Gill"/>

The diversity of characteristics of birds is great, sometimes even in closely related species. Several avian characteristics are compared in the table below.<ref name="AnAge">{{cite web|title=AnAge: The animal ageing and longevity database|url=http://genomics.senescence.info/species/|publisher=Human Ageing and Genomics Resources|access-date=26 September 2014}}</ref><ref name="ADW">{{cite web|title=Animal diversity web|url=http://animaldiversity.ummz.umich.edu/|publisher=University of Michigan, Museum of Zoology |access-date=26 September 2014}}</ref>

{| class="wikitable sortable"
|-
! Species
! Adult weight<br />(grams)
! Incubation<br />(days)
! Clutches<br />(per year)
! Clutch size
|-
| [[Ruby-throated hummingbird]] (''Archilochus colubris'')
| 3
| 13
| 2.0
| 2
|-
| [[House sparrow]] (''Passer domesticus'')
| 25
| 11
| 4.5
| 5
|-
| [[Greater roadrunner]] (''Geococcyx californianus'')
|  376
| 20
| 1.5
| 4
|-
| [[Turkey vulture]] (''Cathartes aura'')
| 2,200
| 39
| 1.0
| 2
|-
| [[Laysan albatross]] (''Phoebastria immutabilis'')
| 3,150
| 64
| 1.0
| 1
|-
| [[Magellanic penguin]] (''Spheniscus magellanicus'')
| 4,000
| 40
| 1.0
| 1
|-
| [[Golden eagle]] (''Aquila chrysaetos'')
| 4,800
| 40
| 1.0
| 2
|-
| [[Wild turkey]] (''Meleagris gallopavo'')
| 6,050
| 28
| 1.0
| 11
|}