Editing Secretarybird (section)

== Behaviour and ecology ==
[[File:Secretarybird-pair.jpg|thumb|right|A pair atop a tree|alt=A pair of Sercetarybirds standing on branches at the top of a tree]]
Secretarybirds are not generally [[gregarious]] aside from pairs and their offspring. They usually [[Bird#Resting and roosting|roost]] in trees of the genus ''[[Acacia]]'' or ''[[Balanites]]'', or even introduced pine trees in South Africa.<ref name=brown1982/> They set off 1–2 hours after dawn, generally after spending some time [[Preening (bird)|preening]].<ref name=hbwfamily/> Mated pairs roost together but may forage separately, though often remaining in sight of one another. They pace around at a speed of {{convert|2.5|–|3|km/h|mph|abbr=on}}, taking 120 steps per minute on average.<ref name=brown1982/> After spending much of the day on the ground, secretarybirds return at dusk,<ref name="Dean">{{ cite journal |last1=Dean |first1=W. R. J. |last2=Milton |first2=S. J. |last3=Jeltsch |first3=F. |year=1999 |title=Large trees, fertile islands, and birds in arid savanna |journal=Journal of Arid Environments |volume=41 |issue=1 |pages=61–78 |doi=10.1006/jare.1998.0455 |bibcode=1999JArEn..41...61D}}</ref> moving [[Windward and leeward|downwind]] before flying in upwind.<ref name=brown1982/> Birds encountered singly are often unattached males, their territories generally in less suitable areas. Conversely, larger groups of up to 50 individuals may be present at an area with a localised resource such as a waterhole in a dry area or an irruption of rodents or locusts fleeing a fire.<ref name=hbwfamily/>

Secretarybirds soar with their primary feathers splayed to manage turbulence. Their wings can flap, though in a slow laborious manner and requiring uplift to be sustained; otherwise they may become exhausted. In the heat of the day, they use [[thermal]]s to rise up to {{cvt|3800|m}} above the ground.<ref name=hbwfamily/>

The bird's average lifespan is thought to be 10 to 15 years in the wild and up to 19 years in captivity.<ref name="sandiegozoo" /> The oldest confirmed secretarybird in the wild was a 5-year-old that was [[Bird ringing|banded]] as a nestling on 23 July 2011 in [[Bloemfontein]] and recovered {{cvt|440|km|mi}} away in [[Mpumalanga]] on 7 June 2016.<ref>{{cite journal |last1=de Swardt |first1=Dawid H. |title=Secretarybird ''Sagittarius serpentarius'' resighted after five years |journal=Biodiversity Observations |date=2016 |volume=7 |issue=26 |pages=1–2 |url=http://bo.adu.org.za/content.php?id=219}}</ref> 

Secretarybirds, like all birds, have haematozoan blood parasites that include ''[[Leucocytozoon beaurepairei]]'' (Dias 1954 recorded from Mozambique).<ref>{{cite journal |author1=Greiner, Ellis C. |author2=Kocan, A. A. |year=1977 |title=Leucocytozoon (Haemosporida; Leucocytozoidae) of the Falconiformes |journal=Canadian Journal of Zoology |volume=55 |issue=5 |pages=761–770 |doi=10.1139/z77-099 |pmid=406030 |bibcode=1977CaJZ...55..761G}}</ref><ref>{{cite journal |author1=Bennett, G. F. |author2=Earlé, R. A. |author3=Peirce, M. A. |year=1993 |title=The Leucocytozoidae of South African birds: The Falconiformes and Strigiformes |journal=Ostrich |volume=64 |issue=2 |pages=67–72 |doi=10.1080/00306525.1993.9634206 |bibcode=1993Ostri..64...67B}}</ref> Wild birds from Tanzania have been found to harbor ''[[Hepatozoon ellisgreineri]]'', a genus that is unique among avian haematozoa in maturing within [[granulocyte]]s, mainly [[neutrophil]]s.<ref>{{cite journal |author1=Valkiūnas, G. |author2=Mobley, K. |author3=Iezhova, T. A. |title=''Hepatozoon ellisgreineri'' n. sp. (Hepatozoidae): description of the first avian apicomplexan blood parasite inhabiting granulocytes. |journal=Parasitology Research |volume=115 |pages=609–613 |year=2016 |issue=2 |doi=10.1007/s00436-015-4777-4 |pmid=26472715 |s2cid=18151844}}</ref> Ectoparasites include the lice ''Neocolpocephalum cucullare'' ([[Christoph Gottfried Andreas Giebel|Giebel]]) and ''Falcolipeurus secretarius'' (Giebel).<ref>{{cite journal |last1=Martin-Mateo |first1=M. P. |last2=Gallego |first2=J. |date=1992 |journal=Journal of the Entomological Society of South Africa |volume=55 |issue=1 |pages=137–147 |title=Redescription of two species of Mallophaga (Insecta) parasites on ''Sagittarius serpentarius'' (Miller) (Aves) |url=https://journals.co.za/doi/10.10520/AJA00128789_3205}}<!--also hdl=10520/AJA00128789_3205 --></ref>

=== 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>

=== Food and feeding ===
[[File:Sagittarius serpentarius -Namib-Naukluft National Park, Namibia -eating-8.jpg|thumb|Juvenile with lizard kill at [[Namib-Naukluft National Park]], Namibia|alt=brownish bird with small dead lizard in its mouth]]
Unlike most [[bird of prey|birds of prey]], the secretarybird is largely [[Terrestrial animal|terrestrial]], hunting its prey on foot. Adults hunt in pairs and sometimes as loose familial flocks, stalking through the habitat with long strides.<ref name="Janzen">{{ cite journal |last1=Janzen |first1=D. H. |year=1976 |title=The depression of reptile biomass by large herbivores |journal=American Naturalist |volume=110 |issue=973 |pages=371–400 [374–375] |doi=10.1086/283074 |jstor=2459760 |bibcode=1976ANat..110..371J |s2cid=83955487 |url=https://www.researchgate.net/publication/249139243}}</ref> Prey may consist of insects such as [[locust]]s, other [[grasshopper]]s, [[wasp]]s, and [[beetle]]s, but small vertebrates often form main biomass. Secretarybirds are known to hunt [[rodent]]s, frogs, lizards, small [[tortoise]]s, and birds such as [[warbler]]s, [[lark]]s, [[dove]]s, small [[hornbill]]s, and [[domestic chicken]]s. They occasionally prey on larger mammals such as [[hedgehog]]s, [[mongoose]]s, small [[felid]]s such as cheetah cubs, [[striped polecat]]s, young [[gazelle]]s, and both young and full-grown [[hare]]s.<ref name=hbwfamily/><ref name="Ferguson-Lees"/><ref name="Janzen" /><ref>{{Cite journal |last=Harrison |first=J. Spranger |date=1944 |title=From an angler's note-book |journal=Ostrich |volume=15 |issue=2 |pages=130–134 |doi=10.1080/00306525.1944.9634703 |bibcode=1944Ostri..15..130H}}</ref><ref>{{Cite journal |last1=Mills |first1=M. G. L. |last2=Mills |first2=M. E. J. |year=2014 |title=Cheetah cub survival revisited: a re-evaluation of the role of predation, especially by lions, and implications for conservation |journal=Journal of Zoology |volume=292 |number=2 |pages=136–141 [139] |doi=10.1111/jzo.12087 |doi-access=}}</ref>  The importance of snakes in the diet has been exaggerated in the past, although they can be locally important, and venomous species such as [[Bitis|adders]] and [[cobra]]s are regularly among the types of snakes preyed upon. Secretarybirds do not eat [[carrion]], though they occasionally eat dead animals killed in grass or bushfires.<ref name=brown1982/><ref>{{cite journal |last1=Davies |first1=G. B. P. |last2=Retief |first2=E. F. |last3=Smit-Robinson |first3=H. |year=2014 |title=Snakes in the diet of Secretarybirds ''Sagittarius serpentarius'': an example from Balfour, Mpumalanga |journal=Ornithological Observations |volume=5 |pages=361–364 |url=https://journals.uct.ac.za/index.php/BO/article/view/251 |archive-date=27 November 2020 |access-date=4 April 2020 |archive-url=https://web.archive.org/web/20201127145528/https://journals.uct.ac.za/index.php/BO/article/view/251 |url-status=live }}</ref>

The birds often flush prey from tall grass by stomping on the surrounding vegetation. Their crest feathers may raise during a hunt, which may serve to help scare the target and provide shade for the face.<ref name=hbwfamily/> A bird will chase after prey with the wings spread and kill by striking with swift blows of the feet. Only with small prey items such as wasps will the bird use its bill to pick them directly. There are some reports that, when capturing snakes, a secretarybird will take flight with their prey and then drop them to their death, although this has not been verified. Even with larger prey, food is generally swallowed whole through the birds' considerable gape. Occasionally, like other raptors, they will hold down a food item with their feet while tearing it apart with their bill.<ref name=hbwfamily/>
[[File:Secretary bird skeleton.jpg|thumb|upright|Secretarybird skeleton; the feet are used for killing prey|alt=skeleton of long-legged bird of prey]]
Food that cannot be digested is regurgitated as pellets {{cvt|40|-|45|mm}} in diameter and {{cvt|30|-|100|mm}} in length. These are dropped on the ground usually near the roost or nest trees.<ref name=hbwfamily/> The secretarybird has a relatively short digestive tract in comparison to large African birds with more mixed diets, such as the [[kori bustard]]. The [[foregut]] is specialised for the consumption of large amounts of meat and there is little need for the mechanical breakdown of food. The [[Crop (anatomy)|crop]] is dilated and the [[gizzard]] is nonmuscular, as in other carnivorous birds.<ref>{{cite journal |last1=Maloiy |first1=G. |first2=C. N. |last2=Warui |first3=E. T. |last3=Clemens |title=Comparative gastrointestinal morphology of the Kori bustard and secretary bird |journal=Zoo Biology |volume=6 |issue=3 |year=1987 |pages=243–251 |doi=10.1002/zoo.1430060307}}</ref> The large intestine has a pair of vestigial [[cecum|ceca]] as there is no requirement for the fermentative digestion of plant material.<ref>{{ cite journal |last1=Clench |first1=Mary H. |last2=Mathias |first2=John R. |year=1995 |title=The avian cecum: a review |journal=Wilson Bulletin |volume=107 |issue=1 |pages=93–121 [100–101] |url=https://sora.unm.edu/sites/default/files/journals/wilson/v107n01/p0093-p0121.pdf}}</ref>

Secretarybirds specialise in stomping their prey until it is killed or immobilised.<ref name=portugal>{{cite journal |last1=Portugal |first1=Steven J. |first2=Campbell P. |last2=Murn |first3=Emily L. |last3=Sparkes |first4=Monica A. |last4=Daley |title=The fast and forceful kicking strike of the secretary bird |journal=Current Biology |volume=26 |issue=2 |year=2016 |pages=R58–R59 |doi=10.1016/j.cub.2015.12.004 |pmid=26811886 |s2cid=4965363 |doi-access=free |bibcode=2016CBio...26..R58P}}</ref> This method of hunting is commonly applied to lizards or snakes.<ref name="Sinclair02">{{ cite book |last1=Sinclair |first1=I. |last2=Ryan |first2=P. |last3=Christy |first3=P. |last4=Hockey |first4=P. |year=2003 |title=Birds of Africa: South of the Sahara |location=Cape Town |publisher=Struik |isbn=978-1-86872-857-2}}</ref> An adult male trained to strike at a rubber snake on a force plate was found to hit with a force equal to five times its own body weight, with a contact period of only 10–15 milliseconds. This short time of contact suggests that the secretarybird relies on superior visual targeting to determine the precise location of the prey's head. Although little is known about its visual field, it is assumed that it is large, frontal and binocular. Secretarybirds have unusually long legs (nearly twice as long as other ground birds of the same body mass), which is thought to be an adaptation for the bird's unique stomping and striking hunting method. However, these long limbs appear to also lower its running efficiency. Ecophysiologist Steve Portugal and colleagues have hypothesised that the extinct [[Phorusrhacidae]] (terror birds) may have employed a similar hunting technique to secretarybirds because they are [[Convergent evolution|anatomically similar]], although they are not closely related.<ref name=portugal /><!-- cites previous 6 sentences -->

Secretarybirds rarely encounter other predators, except in the case of [[tawny eagle]]s, which will [[Kleptoparasitism|steal their kills]]. Eagles mainly steal larger prey and will attack secretarybirds both singly or in pairs. Secretarybird pairs are sometimes successful in driving the eagles away and may even knock them down and pin them to the ground.<ref name=hbwfamily/>