Editing Bird nest (section)

=== Scrape ===
<!-- [[Scrape nest]] redirects to this heading. -->
[[File:Gniazdo sieweczki RB.JPG|thumb|alt=Three eggs, bluish with black speckling, sit atop a layer of white mollusc shells pieces, surrounded by sandy ground and small bits of bluish stone.|Some nest linings, such as the shell fragments in this ''[[Charadrius]]'' [[plover]] scrape, may help to prevent the eggs from sinking into muddy or sandy soil.]]

The simplest nest construction is the ''scrape'', which is merely a shallow depression in soil or vegetation.<ref>{{Harvnb|Campbell|Lack|1985|p=390}}</ref> This nest type, which typically has a rim deep enough to keep the eggs from rolling away, is sometimes lined with bits of vegetation, small [[rock (geology)|stone]]s, [[seashell|shell]] fragments or [[feather]]s.<ref>{{Harvnb|Ehrlich|Dobkin|Wheye|Pimm|1994|p=xxii}}</ref> These materials may help to camouflage the eggs or may provide some level of insulation; they may also help to keep the eggs in place, and prevent them from sinking into muddy or sandy soil if the nest is accidentally flooded.<ref>{{Harvnb|Ehrlich|Dobkin|Wheye|Pimm|1994|p=441}}</ref> Ostriches, most [[tinamou]]s, many ducks, most [[shorebird]]s, most [[tern]]s, some [[falcon]]s, [[pheasant]]s, [[quail]], [[partridge]]s, [[bustard]]s and [[sandgrouse]] are among the species that build scrape nests.

Eggs and young in scrape nests, and the adults that brood them, are more exposed to [[predator]]s and the [[weather|elements]] than those in more sheltered nests; they are on the ground and typically in the open, with little to hide them. The eggs of most ground-nesting birds (including those that use scrape nests) are cryptically coloured to help camouflage them when the adult is not covering them; the actual colour generally corresponds to the substrate on which they are laid.<ref>{{Harvnb|Campbell|Lack|1985|p=174}}</ref> Brooding adults also tend to be well camouflaged, and may be difficult to flush from the nest. Most ground-nesting species have well-developed [[distraction display]]s, which are used to draw (or drive) potential predators from the area around the nest.<ref>{{Harvnb|Campbell|Lack|1985|p=145}}</ref> Most species with this type of nest have [[precocial]] young, which quickly leave the nest upon hatching.<ref>{{Citation |title=The Nature Handbook: A Guide to Observing the Great Outdoors |first=Ernest Herbert |last=Williams |year=2005 |publisher=Oxford University Press, US |page=115 |isbn=978-0-19-517194-5}}</ref>

[[File:Peregrine falcon nest-scraping, Derby Cathedral.webm|thumb|Female [[peregrine falcon]] nest-scraping on artificial ledge on [[Derby Cathedral]]. Both sexes contribute to the creation of a bare, shallow depression in soil or gravel.]]

In cool climates (such as in the high [[Arctic]] or at high elevations), the depth of a scrape nest can be critical to both the survival of developing eggs and the fitness of the parent bird incubating them. The scrape must be deep enough that eggs are protected from the [[convective]] cooling caused by cold winds, but shallow enough that they and the parent bird are not too exposed to the cooling influences of ground temperatures, particularly where the [[permafrost]] layer rises to mere centimeters below the nest. Studies have shown that an egg within a scrape nest loses heat 9% more slowly than an egg placed on the ground beside the nest; in such a nest lined with natural vegetation, heat loss is reduced by an additional 25%.<ref name=Reid>{{Citation |doi=10.1046/j.1365-2435.2002.00632.x |journal=Functional Ecology |first1=J. M. |last1=Reid |first2=W. |last2=Cresswell |first3=S. |last3=Holt |first4=R. J. |last4=Mellanby |first5=D. P. |last5=Whitby |first6=G. D |last6=Ruxton |volume=16 |issue=3 |pages=305–316 |title=Nest scrape design and clutch heat loss in the Pectoral Sandpiper (''Calidris melanotos'') |year=2002 |postscript=.}}</ref> The insulating factor of nest lining is apparently so critical to egg survival that some species, including [[Kentish plover]]s, will restore experimentally altered levels of insulation to their pre-adjustment levels (adding or subtracting material as necessary) within 24 hours.<ref>{{Citation |doi=10.1163/156853902320262844 |journal=Behaviour |title=Do Kentish plovers regulate the amount of their nest material? An Experimental Test |first1=István |last1=Szentirmai |first2=Tamás |last2=Székely |volume=139 |issue=6 |pages=847–859 |year=2002 |jstor=4535956 |postscript=.}}</ref>

[[File:Pluvialis dominica eggs and nest.jpg|thumb|left|alt=Four beige eggs, heavily speckled with black, sit in a shallow depression lined with pale greenish-white lichen.|Other nest linings, like the [[lichen]] in this [[American golden-plover]] scrape, may provide some level of insulation for the eggs, or may help to camouflage them.]]
In warm climates, such as [[desert]]s and [[Salt pan (geology)|salt flat]]s, heat rather than cold can kill the developing embryos. In such places, scrapes are shallower and tend to be lined with non-vegetative material (including shells, feathers, sticks and soil),{{sfn|Grant |1982|p=11}} which allows convective cooling to occur as air moves over the eggs. Some species, such as the [[lesser nighthawk]] and the [[red-tailed tropicbird]], help reduce the nest's temperature by placing it in partial or full shade.{{sfn|Grant |1982|p=60}}<ref>{{Citation |doi=10.2307/1365438 |title=Temperature Regulation in the Red-tailed Tropicbird and the Red-footed Booby |first1=Thomas R. |last1=Howell |first2=George A |last2=Bartholomew |journal=The Condor |volume=64 |issue=1 |pages=6–18 |year=1962 |postscript=.|jstor=1365438 }}</ref> Others, including some shorebirds, cast shade with their bodies as they stand over their eggs. Some shorebirds also soak their breast feathers with water and then sit on the eggs, providing moisture to enable [[evaporative cooling]].{{sfn|Grant |1982|p=61}} Parent birds keep from overheating themselves by [[gular panting]] while they are incubating, frequently exchanging incubation duties, and standing in water when they are not incubating.{{sfn|Grant |1982|p=62}}

The technique used to construct a scrape nest varies slightly depending on the species. Beach-nesting terns, for instance, fashion their nests by rocking their bodies on the [[sand]] in the place they have chosen to site their nest,<ref>{{Harvnb|del Hoyo|Elliott|Sargatal|1996|p=637}}</ref> while [[Skimmer (bird)|skimmers]] build their scrapes with their feet, kicking sand backwards while resting on their bellies and turning slowly in circles.<ref>{{Harvnb|del Hoyo|Elliott|Sargatal|1996|p=673}}</ref> The ostrich also scratches out its scrape with its feet, though it stands while doing so.<ref>{{Harvnb|del Hoyo|1992|p=80}}</ref> Many tinamous lay their eggs on a shallow mat of dead [[leaves]] they have collected and placed under [[shrub|bush]]es or between the [[root]] buttresses of trees,<ref>{{Harvnb|del Hoyo|1992|p=119}}</ref> and [[kagu]]s lay theirs on a pile of dead leaves against a log, tree trunk or vegetation.<ref>{{Harvnb|del Hoyo|Elliott|Sargatal|1996|p=222}}</ref> [[Marbled godwit]]s stomp a grassy area flat with their feet, then lay their eggs, while other grass-nesting waders bend vegetation over their nests so as to avoid detection from above.<ref>{{Harvnb|del Hoyo|Elliott|Sargatal|1996|p=473}}</ref> Many female ducks, particularly in the northern [[latitude]]s, line their shallow scrape nests with [[down feather]]s plucked from their own breasts, as well as with small amounts of vegetation.<ref>{{Harvnb|del Hoyo|1992|p=558}}</ref> Among scrape-nesting birds, the [[three-banded courser]] and [[Egyptian plover]] are unique in their habit of partially burying their eggs in the sand of their scrapes.<ref>{{Harvnb|del Hoyo|Elliott|Sargatal|1996|p=371}}</ref>