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What the sources say

Common BlackbirdTurdus merula

Every figure, record and mechanism on the Common Blackbird profile was written from a source, and this is the working table behind it: 40 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 2024

Turdus merula. The IUCN Red List of Threatened Species 2024: e.T103888106A264548442.

The page saysLeast Concern
The source saysLeast ConcernNote: GBIF copy of the Red List, taxon id checked against the DOI

Source
02

Dominoni et al. 2013

Dominoni et al. (2013). Urban-like night illumination reduces melatonin release in European blackbirds (Turdus merula): implications of city life for biological time-keeping of songbirds. Frontiers in Zoology.

The page sayswhose night-time hormones shift under city light
The source saysDaily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons.
The page saysBlackbirds are widespread in Europe and breed successfully in cities.
The source saysBlackbirds are widespread in Europe and breed successfully in cities
The page saysResearchers caught adult males in Munich and in a forest 40 km away, moved them indoors
The source sayswe caught adult male European blackbirds (urban = 20, rural = 20) with mist-nets set up at dawn in the city of Munich ... in a rural forest near the village of Raisting ... 40 km southwest of Munich ... birds were moved indoors into individual cages
The page sayskept one group under a dim 0.3 lux glow at night, the level recorded on free-living city blackbirds, and the other in near darkness (0.0001 lux)
The source saysThe control group was exposed to 0.0001 lux (almost darkness), while the experimental group was exposed to 0.3 lux at night, simulating conditions recorded previously on free-living urban blackbirds.
The page saysThe glowing group released less melatonin
The source saysDaily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons. In winter, melatonin concentrations of light-at-night birds were lower in the early and late night than in those of birds kept in darkness. In summer, melatonin concentrations of the light-at-night birds were lower through all night
The page saysa hormone that is normally released at night
The source saysit is released at night and suppressed by daylight
The page saysThey were also more active, with activity rising sharply before dawn.
The source saysLocomotor activity in light-at-night birds was overall higher than in control individuals, both during the day and at night, and it increased sharply before dawn.
The page saysIn a captive study, yes. Blackbirds lit at 0.3 lux overnight had lower melatonin than birds in near darkness, and were more active, with a sharp rise before dawn. The authors suggest the birds responded as if the day were longer.
The source saysexperimental group was exposed to 0.3 lux at night ... In summer, melatonin concentrations of the light-at-night birds were lower through all night compared to birds kept in darkness. Locomotor activity in light-at-night birds was overall higher ... and it increased sharply before dawn ... we suggest that birds responded to light-at-night as if they were exposed to a longer day than birds kept under dark nights

Source
03

Dominoni, Quetting & Partecke 2013

Dominoni, Quetting & Partecke (2013). Artificial light at night advances avian reproductive physiology. Proceedings of the Royal Society B: Biological Sciences.

The page saysUnder the same faint night light, captive blackbirds had their reproductive system developed up to a month ahead of birds given dark nights, and their moult came earlier too.
The source saysCaptive city and forest blackbirds were exposed to either dark nights or very low light intensities at night (0.3 lux). Birds exposed to light at night developed their reproductive system up to one month earlier, and also moulted earlier, than birds kept under dark nights.
The page saysA second study tested the calendar.
The source saysThen we used these measurements to test for the effect of light at night on timing of reproductive physiology.

Source
04

Nemeth & Brumm 2010

Nemeth & Brumm (2010). Birds and Anthropogenic Noise: Are Urban Songs Adaptive? The American Naturalist.

The page saysWhere traffic fills a city with low rumble, birds have been seen singing both louder and higher.
The source saysIn cities with intense low-frequency traffic noise, birds have been observed to sing louder and at a higher pitch.
The page saysResearchers picked blackbirds and great tits, two species that sing higher in urban areas, and modelled how far each species' song carries in city noise and in forest.
The source saysHere we present models of signal transmission ... two bird species that sing with higher pitch in urban areas, the great tit (Parus major) and the blackbird (Turdus merula). For both species, we calculated communication distances in response to different levels of urban noise and in their natural forest habitats.
The page saysIn the models, a higher pitch only marginally increased how far a song carried, while singing louder had a strong and significantly larger effect.
The source saysHere we present models of signal transmission ... an increase in vocal pitch increased communication distance only marginally. In contrast, vocal amplitude adjustments had a strong and significantly larger effect.
The page saysThe authors say their results indicate that raising the pitch is not very effective at beating traffic masking.
The source saysOur results indicate that frequency changes of urban songs are not very effective in mitigating masking from traffic noise
The page saysModelled against city traffic, a blackbird's song carried much further when sung louder than when pitched higher.
The source saysHere we present models of signal transmission ... an increase in vocal pitch increased communication distance only marginally. In contrast, vocal amplitude adjustments had a strong and significantly larger effect.Note: vibe.reason

Source
05

British Trust for Ornithology

BirdFacts: Blackbird. British Trust for Ornithology.

The page saysGardens, parks, hedgerows, woodland and farmland across Britain and Ireland, almost everywhere except the highest ground
The source sayscan be found almost everywhere in Britain & Ireland, apart from the highest ground
The page saysBTO measurements of live birds put the adult average at 101.8 g, and 90 percent of adults weigh between 87 and 122 g
The source saysWing length and body weights are from live birds ... 5th and 95th percentiles and sample size in brackets ... All adults 101.8±12.1 g (87-122 g, N=65475)Note: BTO gives 5th and 95th percentiles in brackets, so 90 percent of adults lie between them
The page saysA bird that survives to breeding age typically lives about 3 years.
The source saysTypical life expectancy of bird reaching breeding age 3 years with breeding typically at 1 year
The page saysThe oldest ringed blackbird in Britain was 15 years, 2 months and 5 days old, a record set in 2000.
The source saysMaximum age from a ringed bird 15 years, 2 months, 5 days (set in 2000)
The page saysIn Britain and Ireland blackbirds turn up almost everywhere except the highest ground
The source sayscan be found almost everywhere in Britain & Ireland, apart from the highest ground
The page saysThe UK held 5.1 million breeding pairs in 2016
The source saysUK (breeding) 5.1 million pairs (2016)
The page saysits breeding population was 21 percent lower in 2024 than in 1967
The source saysUK breeding population -21% (1967 to 2024)
The page saysBritish ringing data put the typical life expectancy of a bird that reaches breeding age, usually at 1 year old, at about 3 years. The oldest ringed bird in Britain, a record set in 2000, was 15 years, 2 months and 5 days old.
The source saysbased on BTO ringing and nest recording data ... Typical life expectancy of bird reaching breeding age 3 years with breeding typically at 1 year ... Maximum age from a ringed bird 15 years, 2 months, 5 days (set in 2000)
The page saysAbout 100 g. BTO weighings of live adults average 101.8 g, and nine in ten adults fall between 87 and 122 g.
The source saysWing length and body weights are from live birds ... 5th and 95th percentiles and sample size in brackets ... All adults 101.8±12.1 g (87-122 g, N=65475)Note: BTO gives 5th and 95th percentiles in brackets, so nine in ten adults lie between them; about 100 g rounds 101.8 g
The page saysAlmost everywhere in Britain
The source sayscan be found almost everywhere in Britain & Ireland, apart from the highest ground

Source
06

Welsh Wildlife Trusts

Blackbird. Welsh Wildlife Trusts.

The page saysA blackbird is about 24 cm long with a 36 cm wingspan.
The source saysLength: 24cm Wingspan: 36cm
The page saysMales are entirely black, set off by a yellow bill and a yellow eye-ring.
The source saysMale blackbirds are unmistakable - they are entirely black, with a yellow bill and yellow ring around the eye.
The page saysFemales are dark brown with streaking on the chest and throat.
The source saysFemales are dark brown, with streaking on the chest and throat.
The page saysheads cocked to one side, listening for earthworms
The source sayscan be seen with their heads cocked to one side, listening for earthworms
The page saysThey also eat insects, berries and fruit.
The source saysThey also feed on insects and berries
The page saysListening for worms on the lawn
The source sayslistening for earthworms

Source
07

RSPB

Blackbird. RSPB.

The page saysA lawn-hopping songster whose night-time hormones shift under city light.
The source saysOften seen hopping on the ground or turning over leaves.
The page saysGardens, parks, hedgerows, woodland and farmland
The source sayscommon garden visitor, denizen of the local park, bird of hedgerow and woodland, coastal scrub and farmland
The page saysWorms, insects, berries and fruit
The source sayseating worms, insects, berries and fruit
The page saysA leading voice in the UK's dawn chorus
The source saysThey’re a leading voice in the UK’s dawn chorus
The page saysThey also eat insects, berries and fruit.
The source sayseating worms, insects, berries and fruit
The page saysMost UK blackbirds stay all year, though some northern birds migrate south for winter, and large numbers from northern Europe join the residents each autumn.
The source saysMost UK Blackbirds stay all year, although some northern birds migrate south in winter. ... in autumn, we are joined by large numbers from northern Europe
The page saysThe song runs year-round, but peaks between March and June
The source saysThe song can be heard all year round, but most regularly during the breeding season between March and June.
The page saysblackbirds are a leading voice in the UK's dawn chorus
The source saysThey’re a leading voice in the UK’s dawn chorus

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.