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What the sources say

Black SwanCygnus atratus

Every figure, record and mechanism on the Black Swan profile was written from a source, and this is the working table behind it: 55 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

The IUCN Red List of Threatened Species 2018

Cygnus atratus. The IUCN Red List of Threatened Species 2018: e.T22679843A131907524.

The page saysLeast Concern
The source saysIUCN Red List category: Least Concern (LC).

Source
02

New Zealand Birds Online

Black swan | Kakīānau. New Zealand Birds Online.

The page saysA crinkle-feathered wing display
The source saysThe larger male raises its elaborately crinkled upper wing feathers (coverts and tertials) in sexual and threat displays.
The page saysa bright red bill with a white band near the tip
The source saysThe bill is a bright red with a terminal white bandNote: "near the tip" also fits the Australian Museum's "a distinct narrow white band towards the end"
The page saysflight feathers that flash pure white when the wings lift or the bird takes flight
The source saysWhen the wings are lifted, or when flying, pure white flight feathers are visible
The page saysAdults measure 110 to 140 cm long
The source saysLength: 110 - 140 cm
The page saysMales typically weigh 5 to 7 kg, and females are markedly smaller, at 4 to 6 kg
The source saysWeight: 5 - 7 kg (male), 4 - 6 kg (female) ... Females are markedly smaller than males
The page saysIn New Zealand, where black swans were introduced in the 1860s
The source saysBlack swans were deliberately introduced, initially from Melbourne, in the 1860s.
The page saysthe oldest known bird lived to 15 years
The source saysMaximum longevity 15 years - mean adult survival 0.84Note: New Zealand Birds Online (Williams 2013, updated 2023), scoped to New Zealand in the sentence; ADW's 2004 'forty years in the wild' figure was not used
The page saysWhen submerged plants are sparse or out of reach, they will graze lakeside pastures
The source saysWhen lakes levels are high and submerged plants unreachable, or when submerged plants are sparse, swans will graze lakeside pastures
The page saysThe larger male raises the elaborately crinkled feathers on his upper wings, called coverts and tertials, in courtship and threat displays.
The source saysThe larger male raises its elaborately crinkled upper wing feathers (coverts and tertials) in sexual and threat displays.Note: "courtship" for the source's "sexual"
The page saysBlack swans also hiss when defending their young.
The source saysHisses when defending young or when threatening.
The page saysshare incubation, which lasts 36 days on average
The source saysIncubation behaviour shared Incubation length (mean) 36 days
The page saysThe larger male raises the elaborately crinkled feathers on his upper wings, called coverts and tertials, in courtship and threat displays.
The source saysThe larger male raises its elaborately crinkled upper wing feathers (coverts and tertials) in sexual and threat displays.Note: FAQ 2

Source
03

Australian Museum 2024

Black Swan. Australian Museum, 2024.

The page saysSubmerged water plants and algae, reached by plunging its neck up to a metre underwater; occasionally grazes on land
The source saysThe Black Swan is a vegetarian. Food consists of algae and weeds, which the bird obtains by plunging its long neck into water up to 1 m deep. Occasionally birds will graze on land, but they are clumsy walkers.
The page saysFreshwater lakes, brackish estuaries, and coastal wetlands across Australia
The source saysBlack Swans prefer larger salt, brackish or fresh waterways and permanent wetlandsNote: unchanged stats.habitat, rechecked against sources
The page saysa body that is mostly black
The source saysIn adult Black Swans the body is mostly black
The page saysBlack swans are vegetarians.
The source saysThe Black Swan is a vegetarian.
The page saysThey feed on algae and submerged water plants, reaching them by plunging their long neck into water up to a metre deep
The source saysFood consists of algae and weeds, which the bird obtains by plunging its long neck into water up to 1 m deep.Note: "submerged water plants" for "weeds": NZBO, "entirely herbivorous, preferring submerged freshwater plants"
The page saysthough they are clumsy walkers
The source saysthey are clumsy walkers
The page saysThey are found throughout Australia except the Cape York Peninsula, and are more common in the south
The source saysBlack Swans are found throughout Australia with the exception of Cape York Peninsula, and are more common in the south.
The page saysThey are now common in New Zealand, and rarely reach New Guinea
The source saysThe Black Swan has been introduced into several countries, including New Zealand, where it is now common, and is a vagrant to New Guinea.Note: "rarely reach" for the source's "vagrant"
The page saysTaking off needs at least 40 metres of open water
The source saysrequiring 40 m or more of clear water to take off
The page saysPairs stay together for life
The source saysThey pair for life, with both adults raising one brood per season.
The page saysA clutch can hold up to ten eggs.
The source saysClutch size: Up to 10Note: Australian Museum (2024) over NZBO's table (clutch max 7), whose text also reports 7-14 egg clutches from dumped nests

Source
04

BirdLife Australia

Black Swan. BirdLife Australia.

The page saysThey can turn up wherever there is a wetland, from river estuaries, bays and large lakes to flooded pasture
The source saysThey can occur wherever there is a wetland, from river estuaries, bays and great lakes to inundated pasture and water-meadows.Note: "flooded" for the source's "inundated"
The page saysWhere wetlands dry out for part of the year, they disperse over wide distances looking for water
The source sayswhere the wetlands dry out for part of the year, swans are forced to disperse over wide distances in search of suitable water
The page saysWhen a wetland dries out for part of the year, black swans are forced to disperse over wide distances in search of suitable water, and have even been recorded swimming on isolated waterholes surrounded by vast tracts of arid, stony desert.
The source sayswhere the wetlands dry out for part of the year, swans are forced to disperse over wide distances in search of suitable water, and have even been recorded swimming in isolated waterholes surrounded by vast tracts of arid stony desertNote: FAQ 1

Source
05

Animal Diversity Web, University of Michigan

Cygnus atratus (black swan). Animal Diversity Web, University of Michigan.

The page saysbacked by loud, warning wing-beats
The source saysthe wings of black swans make a louder sound than mute swans
The page saysa wingspan that can stretch to 200 cm
The source saysThe wingspan ranges between 160 to 200 cm.
The page saysTheir threats come with noise: a black swan's wingbeats are louder than a mute swan's
The source saysThe threatening behavior of black swans is similar to mute swans; they both flap and wave their wings with two or three strokes followed by a call. However, the wings of black swans make a louder sound than mute swans.
The page saysit faces predators with its neck held erect and its bill pointed down
The source saysblack swans flap their wings which produce loud noises and threaten predators with their necks erect and bills pointed down

Source
06

Karawita et al. 2023

Karawita et al. (2023). The swan genome and transcriptome, it is not all black and white. Genome Biology.

The page sayswhose black plumage is linked to a pigment gene
The source saysWe also implicate genetic differences in SLC45A2 gene in the iconic plumage of the black swanNote: tagline
The page saysthat is cut short in the white mute swan
The source saysWe observed that SLC45A2 in the mute swan had a nucleotide deletion in the open reading frame instigating a frame-shift mutation and an in-frame early stop codonNote: tagline; "cut short" for the source's "early stop codon"
The page saysA 2023 genome study of black and mute swans
The source saysHere, we generate the first chromosome-length black and mute swan genomesNote: "2023" is the paper's publication year (reference metadata; the source text carries "© The Author(s) 2023")
The page sayschecked genes linked to feather colour in other birds
The source saysGenomic analysis of genes known to be associated with plumage color in other birds
The page saysIt found a deletion in the mute swan's copy of SLC45A2
The source saysWe observed that SLC45A2 in the mute swan had a nucleotide deletion in the open reading frame instigating a frame-shift mutation and an in-frame early stop codon
The page saysa gene involved in making the pigment melanin
The source saysSLC45A2 encodes a transporter protein involved in melanin synthesis
The page saysthat the black swan's copy lacks
The source saysPosition of the frame-shift mutation in the mute swan SLC45A2 compared to the black swan genome
The page saysThe deletion scrambles the gene's code and cuts it short, and may have stopped the gene working.
The source saysidentified a potential frame-shift mutation in the first exon of SLC45A2 in the mute swan, which may have led to pseudogenization of this geneNote: "scrambles the code and cuts it short" for frame-shift plus early stop codon; "stopped the gene working" for pseudogenization
The page saysThe authors suggest it is a candidate change that could explain white feathers in white swans.
The source saysThese results suggest that this deletion in SLC45A2 is a candidate genetic change that could be responsible for the white plumage in white swans
The page saysBlack may once have been the normal swan colour.
The source saysInstead, it would appear that at one point in history black plumage for the swan was the norm rather than the exception.Note: blockquote lead-in, hedged with 'may' for the source's 'would appear'
The page saysIf this mutation is what gave the two species their different colours, the authors write, it would suggest their last common ancestor was black.
The source saysshould a mutation of SLC45A2 have resulted in the differential plumage of the black and mute swan, it would suggest that the last common ancestor of these birds was, in fact, blackNote: blockquote
The page saysThe 2023 study also describes earlier infection experiments: unlike mallards and mute swans, black swans are extremely sensitive to highly pathogenic avian influenza, a severe form of bird flu, and die within two to three days of infection.
The source says© The Author(s) 2023 ... Unlike mallard ducks and mute swans, the black swan is extremely sensitive to HPAI, succumbing to the disease within 2 to 3 days post-infection. ... These experimental studies are consistent with reports of natural infectionsNote: the paper reports this from earlier experiments it cites ([2, 3]), not its own; "2023" is the publication year
The page saysThe researchers' own genome work showed that, unlike other wild waterfowl, black swans lack an expanded set of immune genes and mount a poorly controlled inflammatory response to the virus.
The source saysWe use these genomes and transcriptomes to show that unlike other wild waterfowl, black swans lack an expanded immune gene repertoire, lack a key viral pattern-recognition receptor in endothelial cells and mount a poorly controlled inflammatory response to highly pathogenic avian influenza.
The page saysA 2023 genome study found that the mute swan's copy of SLC45A2
The source saysWe observed that SLC45A2 in the mute swan had a nucleotide deletion in the open reading frame instigating a frame-shift mutation and an in-frame early stop codonNote: FAQ 3; "2023" is the publication year (reference metadata; "© The Author(s) 2023" in the source text)
The page saysa gene involved in making the pigment melanin
The source saysSLC45A2 encodes a transporter protein involved in melanin synthesisNote: FAQ 3
The page sayshas a deletion that the black swan's copy lacks
The source saysPosition of the frame-shift mutation in the mute swan SLC45A2 compared to the black swan genomeNote: FAQ 3
The page saysThe authors suggest it is a candidate change that could explain white feathers in white swans.
The source saysThese results suggest that this deletion in SLC45A2 is a candidate genetic change that could be responsible for the white plumage in white swansNote: FAQ 3
The page saysIf it is what gave the two species different colours, they write, that would suggest their last common ancestor was black.
The source saysshould a mutation of SLC45A2 have resulted in the differential plumage of the black and mute swan, it would suggest that the last common ancestor of these birds was, in fact, blackNote: FAQ 3; the source's own condition and hedge kept

Source
07

van Dongen et al. 2015

van Dongen et al. (2015). Variation at the DRD4 locus is associated with wariness and local site selection in urban black swans. BMC Evolutionary Biology.

The page saysHow wary a swan is may be partly down to its genes.
The source saysOur results suggest that wariness in swans is partly genetically-determined
The page saysA study of black swans at two wetlands in Victoria, Australia
The source saysField work was conducted at two wetlands in Victoria, Australia
The page sayslinked a gene called DRD4 to how wary each bird was of people
The source saysnon-urban swans initiated escape from humans earlier than urban swans. We found no inter-individual variation in the SERT gene, but identified five DRD4 genotypes and an association between DRD4 genotype and wariness
The page saysAt a restricted-access wastewater site in a non-urban area
The source saysthe Western Treatment Plant, Werribee (WTP; 37°54’S, 144° 40’E), a restricted-access wastewater processing site in a non-urban environment
The page saysswans fled an approaching person at a mean distance of about 96 metres, against about 13 metres
The source saysthe mean flight initiation distance was 13 ± 0.4 m at the urban site and 96 ± 15.9 m at the non-urban siteNote: "fled" for flight initiation distance, the distance at which a swan initiated escape from an approaching human; scoped to the two study sites
The page saysat an urban park lake with around 5 million visitors a year
The source saysAlbert Park Lake (APL; 37°50’S, 144° 58’E), an urban recreational park, which receives around 5 million visitors per annum

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.