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What the sources say

European Storm PetrelHydrobates pelagicus

Every figure, record and mechanism on the European Storm Petrel profile was written from a source, and this is the working table behind it: 43 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

BTO BirdFacts

Storm Petrel. BTO BirdFacts.

The page saysmost adults weigh between 22.5 and 29.1 grams
The source saysAll adults 25.6±4.9 g (22.5-29.1 g, N=20482)Note: BTO's 5th/95th percentile range for all adults (British ringing data)
The page sayswith a wing just over 12 centimeters long
The source saysAll adults 122.6±3 mm (118-127 mm, N=22122)Note: 122.6 mm converted to cm
The page saysThe oldest ringed storm petrel on the BTO's books reached 38 years and 17 days, a record set in 2017
The source saysMaximum age from a ringed bird 38 years, 17 days (set in 2017)
The page saysa typical life expectancy of 11 years for a bird that reaches breeding age, with breeding typically starting at four
The source saysTypical life expectancy of bird reaching breeding age 11 years with breeding typically at 4 years
The page saysBTO nest records show both parents incubate the single egg, typically for 38 to 50 days.
The source saysClutch Size Typical number 1 eggs Observed minimum and maximum 1 eggs Source Incubation Incubation by Male + Female Typical duration 38-50 daysNote: 'single egg' from the quote's clutch size of 1 (minimum and maximum 1)
The page saysOnce hatched, the downy chick typically takes 56 to 73 days to fledge.
The source saysFledging Type of chick Altricial, downy Typical duration 56-73 days
The page saysweightKg: 0.026
The source saysAll adults 25.6±4.9 g (22.5-29.1 g, N=20482)Note: settle #889
The page saysa seabird weighing about 25 grams
The source saysAll adults 25.6±4.9 gNote: settle #889 (vibe.reason)

Source
02

The IUCN Red List of Threatened Species 2021

Hydrobates pelagicus. The IUCN Red List of Threatened Species 2021: e.T22698477A166331807.

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

Source
03

Bolton 1996

Bolton (1996). Energy expenditure, body-weight and foraging performance of Storm Petrels Hydrobates pelagicus breeding in artificial nesting chambers. Ibis.

The page saysif that oil supplies all its energy, it accounts for 76% of the weight lost each day on the nest
The source saysAssuming the metabolic requirements during incubation are furnished entirely from stomach oil, 76% of the daily mass lost represented stomach oil catabolism.Note: 'all' restates the source's own assumption ('furnished entirely from stomach oil')
The page saysthe partner comes back once it has regained a threshold body mass of about 31 grams, however long it has spent at sea
The source saysThe body mass of birds returning from foraging was relatively constant and was unrelated to the amount of time spent foraging at sea, indicating that the decision rule to return from foraging was the acquisition of a threshold level of body mass (about 31 g)
The page saysIf a sitting storm petrel's energy during incubation comes entirely from the oil stored in its stomach, as the study assumed, then burning that oil accounts for 76 percent of the weight it loses each day on the nest.
The source saysAssuming the metabolic requirements during incubation are furnished entirely from stomach oil, 76% of the daily mass lost represented stomach oil catabolism.
The page saysA study of storm petrels breeding in artificial nest chambers measured how fast sitting birds burn energy, both from their carbon dioxide output and from how quickly they lose weight.
The source saysDirect measurement of carbon dioxide production using standard respirometry techniques and estimations of metabolic rate based on the rates of mass loss during incubation indicated close agreement between the two methods of estimating energy consumption.
The page saysA shift on the egg usually ends when the foraging partner returns
The source saysShifts were usually terminated by the return of the foraging partner.

Source
04

Medeiros et al. 2012

Medeiros et al. (2012). Molecular Evidence for Gender Differences in the Migratory Behaviour of a Small Seabird. PLoS ONE.

The page saysThe Atlantic's smallest seabird, weighing about 25 grams but migrating from the north-east Atlantic to winter off southern Africa.
The source saysH. pelagicus is the smallest Atlantic seabird (∼25 g), and a long-distance migrant between the breeding colonies in the north-east Atlantic and the wintering areas in the south Atlantic and Indian oceans, off southern Africa.
The page sayswintering as far as the seas off southern Africa
The source saysthe wintering areas in the south Atlantic and Indian oceans, off southern Africa
The page saysthe smallest seabird in the Atlantic Ocean
The source saysH. pelagicus is the smallest Atlantic seabird (∼25 g)
The page saysit migrates from breeding colonies in the north-east Atlantic to wintering grounds off southern Africa, in the south Atlantic and Indian oceans
The source saysa long-distance migrant between the breeding colonies in the north-east Atlantic and the wintering areas in the south Atlantic and Indian oceans, off southern Africa
The page saysResearchers used DNA to sex pre-breeding birds drawn in by recorded calls on their northward migration past south-west Europe, and found the catch ran 80.8% to 89.7% female across seven years.
The source saysMolecular sexing revealed an unexpectedly strong female bias in the sex ratio of pre-breeding European Storm Petrels ( Hydrobates pelagicus ), attracted to playback of conspecific calls during their northwards migration past SW Europe. This bias was consistent across seven years, ranging from 80.8% to 89.7% female
The page saysSamples from breeding colonies showed no such bias, and the researchers suggest the sexes may differ in migration route or in their colony-prospecting behaviour during migration.
The source saysThe sex ratio did not differ significantly from unity (i.e., 50% female) among (i) Storm Petrel chicks at a breeding colony in NW France, (ii) adults found dead on beaches in Southern Portugal, (iii) breeding birds attending nest burrows in the UK ... The preponderance of females captured in Southern Europe suggests that the sexes may differ in migration route or in their colony-prospecting behaviour during migration

Source
05

Wilkinson et al. 2026

Wilkinson et al. (2026). Under the cover of darkness: Foraging behaviour increases on cloudy, new moon nights in a pelagic seabird. Ibis.

The page saysMany nocturnal seabirds forage more under moonlight, but GPS tracking of storm petrels from one colony found that offshore they forage under the darkest conditions, a pattern strongly influenced by cloud cover.
The source saysNocturnal foraging, identified using GPS‐accelerometry data and a Hidden Markov Model, was concentrated in two areas: shallow coastal waters near the colony and deeper offshore waters near the shelf edge. Generalized additive models revealed that, in offshore areas, European Storm‐petrels forage under the darkest nocturnal conditions, contrasting with the increased activity under moonlit conditions reported for many other nocturnally foraging seabirds. This was strongly influenced by cloud cover
The page sayssmell probably helps the birds detect patches of prey at night, and that bioluminescence may help them spot individual prey by eye
The source saysolfaction probably plays an important role in detecting prey patches at night, bioluminescence may aid visual detection of individual prey items

Source
06

Carboneras, Jutglar & Kirwan 2020

Carboneras, Jutglar & Kirwan (2020). European Storm-Petrel (Hydrobates pelagicus). Birds of the World.

The page saysPelagic north-east Atlantic and Mediterranean waters
The source saysEastern Atlantic Ocean, breeding in northeastern Atlantic, from southern Iceland and western Norway south through northern and western Britain to northwestern France, northern Spain and Canary Islands. ... Mediterranean from eastern Spain east to Greece
The page saysMainly plankton picked from the sea surface by hovering; the Mediterranean subspecies feeds mainly by diving for pelagic fish instead
The source saysIt feeds mainly on plankton by hovering over the surface ... It feeds mainly on pelagic fishes by diving, unlike nominate
The page saysAtlantic birds feed mainly by hovering over the surface and picking off plankton
The source saysIt feeds mainly on plankton by hovering over the surface
The page saysthe larger, heavier-billed Mediterranean subspecies, melitensis, feeds mainly by diving for pelagic fish
The source saysdiffers in its larger size with proportionally smaller tail and heavier bill ... It feeds mainly on pelagic fishes by diving, unlike nominate
The page saysBirds of the World lists them as two subspecies of one species, but notes the Mediterranean race "may be better treated as a distinct species."
The source saysSubspecies (2) ... Thalassidroma melitensis Schembri, 1843 [type locality: Malta]. This race may be better treated as a distinct species.
The page saysIt is larger, with a heavier bill and a proportionally smaller tail.
The source saysSimilar to nominate, but differs in its larger size with proportionally smaller tail and heavier bill.
The page saysThe two also differ in voice and coloration
The source saysThe two also differ in voice and coloration
The page saysthe Mediterranean birds breed earlier
The source saysBesides, melitensis breeds earlier than pelagicus
The page saysfeeds mainly by hovering just over the sea, picking plankton off the surface
The source saysIt feeds mainly on plankton by hovering over the surfaceNote: settle #889 (vibe.reason)

Source
07

Watson, Bolton & Monaghan 2014

Watson, Bolton & Monaghan (2014). Out of sight but not out of harm's way: Human disturbance reduces reproductive success of a cavity-nesting seabird. Biological Conservation.

The page saysnesting in crevices in stone walls, boulder beaches and old buildings
The source saysstorm petrels nest in crevices in dry stone walls, boulder beaches, loose rock scree, and abandoned buildings
The page saysStorm petrels are active in their colonies only at night
The source saysstorm petrels are only active within the colony at night
The page saysOn Shetland's Mousa they nest in crevices in dry stone walls, boulder beaches, rock scree and abandoned buildings
The source saysOn Mousa, storm petrels nest in crevices in dry stone walls, boulder beaches, loose rock scree, and abandoned buildings
The page saysMousa has no mice, rats or cats, and its only mammalian predator, the Eurasian otter, rarely takes storm petrel nests
The source saysThe island remains free from mice, rats and cats; the only mammalian predator present is the Eurasian otter Lutra lutra, which rarely predates on storm petrel nests
The page saysa 2014 study reported that the colony had more than doubled in size since 1996
The source saysThe storm petrel colony at Mousa has more than doubled in size since 1996Note: 2014 is the year of Watson, Bolton & Monaghan (the cited reference)

Source
08

Ruffino et al. 2009

Ruffino et al. (2009). Invasive rats and seabirds after 2,000 years of an unwanted coexistence on Mediterranean islands. Biological Invasions.

The page saysAcross a survey of about 300 western Mediterranean islands, rat presence was a limiting factor, at the regional scale, only for the storm petrel's abundance, while the three shearwater species there were shaped more by island characteristics
The source saysA database gathering information on approximately 300 Western Mediterranean islands was analyzed ... At the regional scale, rat presence was only a limiting factor in the abundance of the smallest seabird, the storm petrel (Hydrobates pelagicus), while the distribution and abundance of the three shearwaters were more influenced by island characteristics.

Source
09

Belliure, Mínguez & De León 2003

Belliure, Mínguez & De León (2003). Self-odour recognition in European storm-petrel chicks. Behaviour.

The page saysits chicks can apparently recognize their own body odor
The source saysbetween their own odour and the body scent of a conspecific chick. Storm-petrel chicks can apparently recognize their own body odour, even when tested against the body scent of a conspecific.
The page sayschicks can apparently recognize their own body odor, even when tested against the scent of another storm petrel chick
The source saysbetween their own odour and the body scent of a conspecific chick. Storm-petrel chicks can apparently recognize their own body odour, even when tested against the body scent of a conspecific.
The page saysthe researchers suggest such individual odors may help a bird recognize its nest
The source saysIndividually distinctive odours may play an important role in facilitating nest recognition.

Source
10

Sanz-Aguilar et al. 2020

Sanz-Aguilar et al. (2020). Infestation of small seabirds by Ornithodoros maritimus ticks: Effects on chick body condition, reproduction and associated infectious agents. Ticks and Tick-borne Diseases.

The page saysIn a cave colony on Espartar Island in Spain's Balearic Islands, researchers studied the soft tick Ornithodoros maritimus.
The source sayssoft tick Ornithodoros maritimus ... storm petrels Hydrobates pelagicus breeding in a large colony in a cave of Espartar Island, in the Balearic archipelago
The page saysFewer chicks survived deep in the cave, the most infested area, than near the entrance, and chicks carrying more ticks were in poorer body condition.
The source saysLower nestling survival was recorded in the most infested area, deep in the cave, compared to the area near the entrance. The parasite load was negatively associated with the body condition of the nestlings.
The page saysSome pools of ticks tested positive for a Borrelia bacterium with 99% sequence identity to B. turicatae, a relapsing-fever Borrelia.
The source says4 pools tested positive for a Borrelia species which was determined by targeted nested PCR to have a 99% sequence identity with B. turicatae, a relapsing fever Borrelia

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.