Editing Secretarybird (section)

=== Breeding ===
[[File:20170525 Pairi Daiza Sagittarius serpentarius con huevos.jpg|thumb|right|Captive secretarybird with two eggs in its nest|alt=long-legged grey bird standing in large nest of sticks and grass]]
Secretarybirds form [[Monogamy in animals|monogamous]] pairs and defend a large territory of around {{cvt|50|km2}}. They can breed at any time of the year, more frequently in the late [[dry season]]. During [[Courtship display|courtship]], they exhibit a nuptial display by soaring high with undulating flight patterns and calling with [[guttural]] croaking. Males and females can also perform a ground display by chasing each other with their wings up and back, which is also the way they defend their [[Territory (animal)|territory]]. They mate either on the ground or in trees.<ref name=brown1982>{{ cite book |editor1-last=Brown |editor1-first=L. H. |editor2-last=Urban |editor2-first=E. K. |editor3-last=Newman |editor3-first=K. |year=1982 |title=The Birds of Africa |volume=1 |location=London |publisher=Academic Press |isbn=978-0-12-137301-6 |pages=437–440}}</ref><!--p. 439-->

The nest is built by both sexes at the top of a dense thorny tree, often an ''Acacia'', at a height of between {{cvt|2.5|and|13|m|ft|sigfig=1}} above the ground. The nest is constructed as a relatively flat platform of sticks {{cvt|1.0|-|1.5|m|ft|sigfig=1}} across with a depth {{cvt|30|-|50|cm|in|sigfig=2}}. The shallow depression is lined with grass and the occasional piece of dung.<ref name=brown1982/>

Eggs are laid at 2- to 3-day intervals until the clutch of 1–3 eggs is complete. The elongated chalky bluish green or white eggs average {{cvt|78|x|57|mm}} and weigh {{cvt|130|g}}.<ref name=brown1982/> Both parents incubate the eggs, starting as soon as the first egg is laid, but it is usually the female that remains on the nest overnight. The incubating parent greets its partner when it returns with a display of bowing and bobbing its head with neck extended. The tail is held upright with feathers fanned out, and the chest feathers are puffed out.<ref name=kemp1995>{{ cite journal |last=Kemp |first=Alan C. |year=1995 |title=Aspects of the breeding biology and behaviour of the secretarybird ''Sagittarius serpentarius'' near Pretoria, South Africa |journal=Ostrich |volume=66 |issue=2–3 |pages=61–68 |doi=10.1080/00306525.1995.9633760 |bibcode=1995Ostri..66...61K}}</ref>

The eggs hatch after around 45 days at intervals of 2–3 days.<ref name="brown1982" /> Both parents feed the young. The adults regurgitate food onto the floor of the nest and then pick up items and pass them to the chicks.<ref name="kemp1995" /> For the first 2 or 3 weeks after the eggs hatch the parents take turns to stay at the nest with the young.<ref name="hbwfamily" /> Despite the difference in nestling size due to the asynchronous hatching, little sibling aggression has been observed.<ref name="brown1982" /> Under favourable conditions all chicks from a clutch of three eggs [[fledge]],<ref>{{cite journal |last1=Herholdt |first1=J. J. |last2=Anderson |first2=M. D. |year=2006 |title=Observations on the population and breeding status of the African whitebacked vulture, the black-chested snake eagle, and the secretarybird in the Kgalagadi Transfrontier Park |journal=Ostrich |volume=77 |issue=3&4 |pages=127–135 |doi=10.2989/00306520609485523 |bibcode=2006Ostri..77..127H |s2cid=85889249}}</ref> but if food is scarce one or more of the chicks will die from starvation.<ref name="brown1982" /> The young may be preyed upon by [[Corvus (genus)|crows]], ravens, [[hornbill]]s, and large owls.<ref name="hbwfamily" /> 
[[File:Faune de la Sénégambie (Planche V) BHL34755809.jpg|thumb|right|Illustration of chick, from ''Faune de la Sénégambie'' (1883), by [[Alphonse Trémeau de Rochebrune]]|alt=line drawing of long-legged chick]]
The young are born covered in grey-white [[Down feather|down]] that becomes darker grey after two weeks. Their bare facial skin and legs are yellow. Crest feathers appear at 21 days, and flight feathers by 28 days. They can stand up and feed autonomously after 40 days, although the parents still feed the nestlings after that time. At 60 days, the now fully-feathered young start to flap their wings. Their weight gain over this period changes from {{cvt|56|g}} at hatching, to {{cvt|500|g}} at 20 days, {{cvt|1.1|kg}} at 30 days, {{cvt|1.7|kg}} at 40 days, {{cvt|2|kg}} at 50 days, {{cvt|2.5|kg}} at 60 days, and {{cvt|3|kg}} at 70 days. The time they leave the nest can be anywhere between 65 and 106 days of age, although it most typically occurs between 75 and 80 days of age. Fledging is accomplished by jumping out of the nest or using a semi-controlled glide to the ground.<ref name=brown1982/>

Juveniles remain in their natal range before dispersing when they are between 4 and 7 months of age. The usual age at which they first breed is uncertain but there is a record of a male bird breeding successfully at an age of 2 years and 9 months, which is young for a large raptor.<ref name=whitecross2019>{{cite journal |last1=Whitecross |first1=M. A. |last2=Retief |first2=E. F. |last3=Smit-Robinson |first3=H. A. |year=2019 |title=Dispersal dynamics of juvenile secretarybirds ''Sagittarius serpentarius'' in southern Africa |journal=Ostrich |volume=90 |issue=2 |pages=97–110 |doi=10.2989/00306525.2019.1581295 |bibcode=2019Ostri..90...97W |s2cid=195422587 |url=https://figshare.com/articles/dataset/Dispersal_dynamics_of_juvenile_Secretarybirds_i_Sagittarius_serpentarius_i_in_southern_Africa/8223827 |archive-date=9 October 2023 |access-date=3 November 2022 |archive-url=https://web.archive.org/web/20231009234811/https://figshare.com/articles/dataset/Dispersal_dynamics_of_juvenile_Secretarybirds_i_Sagittarius_serpentarius_i_in_southern_Africa/8223827 |url-status=live |url-access=subscription }}</ref>