{{Short description|Species of bird}} {{speciesbox | image = Ixobrychus involucris.jpg | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 12 November 2021">{{cite iucn |author=BirdLife International |date=2016 |title=''Ixobrychus involucris'' |volume=2016 |article-number=e.T22697294A93606613 |doi=10.2305/IUCN.UK.2016-3.RLTS.T22697294A93606613.en |access-date=12 November 2021}}</ref> | genus = Botaurus | species = involucris | authority = (Vieillot, 1823) | synonyms = | range_map = Ixobrychus involucris map.svg }}
The '''stripe-backed bittern''' ('''''Botaurus involucris''''') is a South American bird species belonging to the family Ardeidae. It was formerly placed in the genus ''Ixobrychus''. Commonly found near freshwater swamps, marshes, lake shores and streams, stripe-backed bitterns are distributed in two disjunct populations in the north and south of the continent, spanning both sides of the Andes.<ref name=":1">{{Cite journal |last=Behrstock |first=Robert A. |date=1996 |title=Voices of Stripe-backed Bittern ''Ixobrychus involucris'', Least Bittern I. exilis, and Zigzag Heron Zebrilus undulatus, with notes on distribution |url=https://www.neotropicalbirdclub.org/wp-content/uploads/2014/12/Cotinga-05-1996-55-61.pdf |journal=Cotinga 5 |issue=5 |page=56 |via=Neotropical Birding and Conservation}}</ref> Although increasingly researched worldwide, many details of its life history life are lacking, especially compared to other species in its sister clade like the least bittern (''Botaurus exilis'').
== Taxonomy == The stripe-backed bittern was formally described in 1823 by the French ornithologist Louis Vieillot under the binomial name ''Ardea involucris''.<ref>{{ cite book | last=Vieillot | first=Louis Pierre | author-link=Louis Pierre Vieillot | year=1823 | title=Tableau encyclopédique et méthodique des trois règnes de la nature. Ornithologie | language=French | volume=3 | location=Paris | publisher=Mme veuve Agasse | page=1127 livrason 93 | url=https://www.biodiversitylibrary.org/page/51213191 }}</ref><ref>{{ cite book | editor1-last=Mayr | editor1-first=Ernst | editor1-link=Ernst Mayr | editor2-last=Cottrell | editor2-first=G. William | year=1979 | title=Check-List of Birds of the World | volume=1 | edition=2nd | publisher=Museum of Comparative Zoology | location=Cambridge, Massachusetts | page=238 | url=https://www.biodiversitylibrary.org/page/16108878 }}</ref> Vieillot based his account on the "Garza varia" that had been described in 1805 by Spanish naturalist Félix de Azara in his book ''Apuntamientos para la historia natural de los páxaros del Paragüay y Rio de la Plata''.<ref>{{ cite book | last=Azara | first=Félix de | author-link=Félix de Azara | year=1805 | title=Apuntamientos para la historia natural de los páxaros del Paragüay y Rio de la Plata | volume=3 | language=Spanish | location=Madrid | publisher=Imprenta de la Hija de Ibarra | page=185, No. 361 | url=https://www.biodiversitylibrary.org/page/61818341 }}</ref> The stripe-backed bittern was formerly placed in the genus ''Ixobrychus'' but after a molecular phylogenetic study of the heron family Ardeidae published in 2023 found that ''Ixobrychus'' was paraphyletic, ''Ixobrychus'' was merged into ''Botaurus''.<ref>{{Cite journal | last1=Hruska | first1=J.P. | last2=Holmes | first2=J. | last3=Oliveros | first3=C. | last4=Shakya | first4=S. | last5=Lavretsky | first5=P. | last6=McCracken | first6=K.G. | last7=Sheldon | first7=F.H. | last8=Moyle | first8=R.G. | date=2023 | title=Ultraconserved elements resolve the phylogeny and corroborate patterns of molecular rate variation in herons (Aves: Ardeidae) | journal=Ornithology | volume=140 | issue=2 | article-number=ukad005 | doi=10.1093/ornithology/ukad005}}</ref><ref name=ioc>{{cite web| editor1-last=Gill | editor1-first=Frank | editor1-link=Frank Gill (ornithologist) | editor2-last=Donsker | editor2-first=David | editor3-last=Rasmussen | editor3-first=Pamela | editor3-link=Pamela C. Rasmussen | date=August 2024 | title=Ibis, spoonbills, herons, Hamerkop, Shoebill, pelicans | work=IOC World Bird List Version 14.2 | url=https://www.worldbirdnames.org/bow/pelicans/ | publisher=International Ornithologists' Union | access-date=20 August 2024 }}</ref><ref>{{Cite journal | last1=Chesser | first1=R.T. | last2=Billerman | first2=S.M. | last3=Burns | first3=K.J. | last4=Cicero | first4=C. | last5=Dunn | first5=J.L. | last6=Hernández-Baños | first6=B.E. | last7=Jiménez | first7=R.A. | last8=Johnson | first8=O. | last9=Kratter | first9=A.W. | last10=Mason | first10=N.A. | last11=Rasmussen | first11=P.C. | last12=Remsen | first12=J.V.J. | date=2024 | title=Sixty-fifth Supplement to the American Ornithological Society's Check-list of North American Birds | journal=Ornithology | volume=141 | issue=3 | article-number=ukae019 | doi=10.1093/ornithology/ukae019 | doi-access=free }}</ref> The species is treated as monotypic, meaning no subspecies are recognised.<ref name=ioc/>
==Description== thumbnail|left Stripe-backed bitterns are very small, averaging from 28 to 35 cm in length.<ref name=":3">{{Cite journal |last1=Kilby |first1=Rachel |last2=Ugarte |first2=Mauricio |last3=Timson |first3=Stuart |last4=Góngora Romero |first4=Dennys |date=2018-05-18 |title=First documented record of the Stripe-backed Bittern, ''Ixobrychus involucris'' (Vieillot, 1823) (Aves, Ardeidae) in Peru |url=https://checklist.pensoft.net/articles.php?id=20020 |journal=Check List |volume=14 |issue=3 |pages=519–522 |doi=10.15560/14.3.519 |issn=1809-127X |doi-access=free }}</ref> Their pale brown back is ornamented with both black and yellowish-beige streaks, the latter also running along their broad wings.<ref name=bow>{{cite journal | last1=Martínez-Vilalta | first1=A. | last2=Motis | first2=A. | last3=Kirwan | first3=G.M. | year=2020 | title=Stripe-backed Bittern (''Ixobrychus involucris''), version 1.0 | editor1-last=del Hoyo | editor1-first=J. | editor2-last=Elliott | editor2-first=A. | editor3-last=Sargatal | editor3-first=J. | editor4-last=Christie | editor4-first=D.A. | editor5-last=de Juana | editor5-first=E. | journal=Birds of the World | location=Ithaca, NY, USA | publisher=Cornell Lab of Ornithology | doi=10.2173/bow.stbbit1.01 }}</ref> The colour patterns on their back complements the ones on their wings as to suppress obvious contrast between the two. Black stripes continue their way on the darker brown crown, while the underbelly is lighter brown and striped with white.<ref name=":3" /> As for the beak, the colour can differ from pale green to orange.<ref name=bow/> This bittern species exhibits no sexual dimorphism, making it difficult to distinguish males from females.<ref name=bow/> Furthermore, juveniles are not phenotypically described in the literature. Discriminating sex and age for this species has proved to be a challenge, so has the simple quest to even observe them in the wild. Stripe-backed bitterns tend to adopt an upright stance in which they "freeze" in place to observe their surroundings, making it more efficient to hunt their preys.<ref name=":1" /> When threatened, they respond by pointing their neck and bill skyward. This augments the difficulty to spot them easily. Following a solitary lifestyle, chances of finding them in groups are scarce but sights in pairs have been reported in the past.<ref name=bow/>
=== Similar species === The stripe-backed bittern is easily confused with the least bittern. The most striking difference consist of the contrast between the dark coloured, completely streak less back of the least bittern, compared to its patterned wings.<ref>{{Cite journal |last=Gochfeld |first=Michael |date=1973 |title=Observations on New or Unusual Birds from Trinidad, West Indies, and Comments on the Genus Plegadis in Venezuela |journal=The Condor |volume=75 |issue=4 |pages=474–478 |doi=10.2307/1366575 |jstor=1366575 |issn=0010-5422}}</ref> Least bitterns also differ by the rufous coloration on the sides of their head, also present on the neck of females.<ref name=":3" />
==Distribution and habitat==
=== Distribution === Displaying a disjunct yet wide distribution, stripe-backed bitterns are found on each side of the Andes. The northern population is distributed in large patches across South America, located in Colombia, Venezuela, Guyana, Suriname, French Guiana and the island of Trinidad, while the southern population is found in central and southern South America; in Paraguay, Uruguay, Argentina, Chile, southern Brazil and Bolivia.<ref name=":3" /> In 2018 stripe-backed bitterns have also been confirmed to live in northeastern Ecuador, as well as in southeastern Peru.<ref name=":3" />
=== Habitat === Freshwater sources are the favoured habitat for stripe-backed bitterns. Ideal ecological niches consist of highly vegetated reed beds, swamps, rushes, lakes and mountain streams, marshes, and rice fields.<ref name=":3" /><ref name=bow/> Such aquatic environments are essential in food acquisition and for nest building.
==Behaviour ==
=== Diet === The main food source for stripe-backed bitterns, comprising half of their overall diet, are insects. They primarily consume insects from the orders Odonata, Coleoptera, Hemiptera and Orthoptera.<ref name=":5">{{Cite journal |last1=Leon |first1=Evelina J |last2=Olguin |first2=Pamela F |last3=Beltzer |first3=Adolfo H |date=2016-04-18 |title=Aportes al conocimiento de la dieta del mirasol chico (''Ixobrychus involucris'') (Aves: Ardeidae) en el valle de inundación del río Paraná Medio, Argentina |journal=Fabicib |volume=19 |pages=65–71 |doi=10.14409/fabicib.v19i0.5416 |issn=2362-5546|doi-access=free |hdl=11336/59958 |hdl-access=free }}</ref> The remaining half of their food intake includes small fishes, crustaceans, and arachnids.<ref name=":5" /><ref name=":6">{{Cite book |last=Ulrich; Willett |first=Pedro K.; Julien H. |title=Trends in ornithology research |publisher=Nova Science |year=2010 |isbn=978-1-61942-326-8 |location=New York |pages=49–85}}</ref> Stripe-backed bitterns are diurnal birds, with activities like hunting occurring either early in the morning or in the afternoon, and rest at noon and at sunset.<ref name=":5" /> They have been recorded to feed both alone and in pairs.<ref name=":6" /> Night feeding has also been reported, but only scarcely.
=== Reproduction === The reproductive cycle and breeding details of stripe-backed bitterns have not been extensively studied, and much of it is still unknown. Stripe-backed bitterns makes small nests of tightly bound reeds and stems, which are found above water level, among reeds.<ref name=bow/> Incubation period for eggs is unknown, and breeding seasons appear to vary widely based on location.
=== Eggs === Stripe-backed bitterns have distinctly coloured eggs compared to others in the heron family. Ardeidae typically produce eggs of either elliptical or spherical shape, which are often pale blue in colour.<ref name=":0">{{Cite journal |last=Walters |first=Michael |date=2006 |title=Colour in birds' eggs: the collections of the Natural History Museum, Tring |url=https://www.tandfonline.com/doi/full/10.1080/08912960600640887?needAccess=true |journal=Historical Biology |volume=18 |issue=2 |page=148 |doi=10.1080/08912960600640887 |bibcode=2006HBio...18..145W |s2cid=84171126 |via=Taylor & Francis online|url-access=subscription }}</ref> The translucent layer of their eggs, combining the commonly called cone and palisade layers, allows a glimpse into the blue or white inner shell.<ref name=":0" /> The eggs of stripe-backed bitterns, uniquely, exhibit pale blue cone and palisade layers, covered by an outer translucent green layer.<ref name=":0" /> Although recurrent observations and descriptions have been published, the evolutionary explanation for such a unique egg coloration within the Ardeidae bird family has not yet been determined.
=== Vocalization === Sounds have been elaborately described and are sometimes the best way to determine the presence of stripe-backed bitterns, emitting calls through distinct, low-pitched ''ooks'', or through gargling.<ref name=bow/> Territorial or warning vocalizations consist of four low-pitched short "huu" or "ook" notes, followed by a second type of vocalization; a faster and higher-pitched "g'u'u'u'a'a" gargle.<ref name=bow/>
==Conservation Status== This bittern is considered to be of least concern due to its wide range and its large, stable population.<ref>{{Cite web |date=2016 |title=Stripe-backed bittern |url=https://www.iucnredlist.org/species/22697294/93606613 |website=IUCN Red List}}</ref> Stripe-backed bitterns do not receive much conservation efforts, nor do they constitute a priority for outreach education programs.
== External links == * [https://ebird.org/species/stbbit1 Photos and sounds of stripe-backed bitterns ''Ixobrychus involucris''] - eBird * [https://birdsoftheworld.org/bow/species/stbbit1/cur/introduction Photos of stripe-backed bitterns, Birds of the World] - The Cornell Lab of Ornithology * [https://www.inaturalist.org/taxa/5013-Ixobrychus-involucris Photos of stripe-backed bitterns] - iNaturalist * [https://www.iucnredlist.org/species/22697294/93606613 Conservation status of stripe-backed bitterns] - IUCN Red List of Birds
== References == {{Reflist}} *{{cite book | last = ffrench<!--this name should not be capitalized--> | first = Richard | title = A Guide to the Birds of Trinidad and Tobago | edition = 2nd | year = 1991 | publisher = Comstock Publishing | isbn = 0-8014-9792-2 }} *{{cite book | last1 = Junge | first1 = G.C.A. | last2 = Mees | first2 = G.F. | title = Avifauna of Trinidad and Tobago | year = 1961 | publisher = E.J. Brill }} *{{cite book | last1 = Kushlan | first1 = James A. | last2 = Hancock | first2 = James A. | title = Herons | year = 2005 | publisher = Oxford University Press | isbn = 0-19-854981-4 }} *{{cite web | url = https://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=111516 | title = ''Ixobrychus involucris'' | publisher = Cornell Lab of Ornithology | access-date = 24 February 2015 }}
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stripe-backed bittern Category:Birds of South America Category:Birds of Trinidad and Tobago Category:Birds of the Caribbean stripe-backed bittern Category:Taxa named by Louis Pierre Vieillot Category:Taxonomy articles created by Polbot