Field notebook
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Field notebook
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Permanent editions
Published facts keep their original date, evidence and correction trail. Drafts and withdrawn editions are never mixed into this index.
The black band running down a great tit's yellow underside varies in width between individuals. Broader, blacker stripes are associated with dominance and with male quality, making the marking a visible badge rather than mere plumage pattern.
Radar and trap records show that migrant hoverflies, dominated by the marmalade hoverfly, arrive over southern Britain in numbers estimated in the billions each year. Their larvae eat aphids on arrival, making the migration a large and unmanaged pest-control service.
Market squid live less than a year, so a single warm ocean season can remove nearly the whole stock. During strong El Nino events, landings have collapsed from over a hundred thousand tonnes to almost nothing.
Both upper and lower canines in a male wild boar grow continuously through life. Each time the jaw closes the lower tusk grinds against the upper, and that repeated contact keeps a working edge on the lower weapon.
Males build a twin-walled avenue of sticks and decorate it with collected objects, overwhelmingly blue ones. No eggs are ever laid there. The female builds a separate cup nest in a tree and raises the young alone.
A flying fish does not beat its fins in the air. It builds speed underwater, leaves the surface, and holds its pectoral fins rigid as wings, using the longer lower lobe of its tail to sculch the water and start another glide.
The white open-mouthed display that names the species is a warning, not a prelude to attack. Field studies in which researchers deliberately stood on and handled wild cottonmouths recorded overwhelmingly defensive responses rather than pursuit.
The European rabbit is a byword for uncontrollable increase in Australia, yet in Iberia, where it evolved, myxomatosis and rabbit haemorrhagic disease have cut it so far that the IUCN lists the species as Endangered.
During El Niño years the algae marine iguanas eat collapse, and individuals lose length as well as weight. Repeated measurements of marked animals showed adults shortening by several centimetres and regrowing when food returned, a change that must involve bone as well as soft tissue.
The shimmering fan a peacock raises is built from elongated upper tail coverts, the feathers that normally cover the tail base. The real tail feathers are short, stiff and brown, hidden behind, doing the work of holding the display upright.
A summer pea aphid gives birth to live daughters that are themselves already carrying developing embryos. Three generations exist inside one animal at once, which is why an aphid colony can appear on a plant in days.
When its swamp dries, the West African lungfish burrows down, secretes a mucus cocoon around itself and breathes air through a tube to the surface. Metabolism drops sharply, and individuals have survived this dormancy for well over a year.
Superb lyrebirds are outstanding mimics, but the mechanical sounds that made them famous come almost entirely from captive individuals. Wild lyrebirds overwhelmingly imitate other forest birds, and documented wild chainsaw imitation is vanishingly rare.
Dasypeltis swallows a bird egg whole, then drives it against downward-projecting spines on the underside of its neck vertebrae. The shell splits, the contents are squeezed out, and the flattened shell is regurgitated.
The image of a female mantis routinely beheading her mate comes largely from early laboratory work with confined, hungry insects. Field and enclosure studies find cannibalism occurs in a minority of matings, and the rate rises sharply with the female's hunger.
Most flightless birds keep reduced wings. Moa went further than any other known bird, discarding the forelimb completely: no wing survives, and beyond a vestigial shoulder girdle and a tiny humerus in a few specimens, the arm skeleton is simply gone.
At roughly 18 to 30 kilograms, the Eurasian lynx is far smaller than the roe deer and chamois that dominate its diet in much of Europe. It is the only lynx that regularly takes ungulates several times its own mass.
Populations of Pantala flavescens sampled from continents separated by whole oceans show almost no genetic structure. The species crosses open sea in such numbers, and interbreeds so freely on arrival, that geography has failed to divide it into regional lineages.
A nesting titan triggerfish guards a volume shaped like an upward-widening cone above its nest. Swimming upward to escape moves a diver further into the territory, which is why the correct retreat is horizontal.
The pain that tops the Schmidt index is produced largely by poneratoxin, a small peptide that jams sodium channels in nerve cells so they misfire. The sting is agonising and the ant is not aggressive.
Its paralytic tetrodotoxin is produced by symbiotic bacteria living in the octopus's salivary glands, not synthesised by the animal itself. Pufferfish and several other marine animals carry the same compound, and bacteria are the leading explanation there too.
One of the largest freshwater fishes in the world does not hunt. Adult Mekong giant catfish lose their teeth and barbels and feed on algae and plant matter scraped from the riverbed, growing to nearly 300 kilograms on a diet with no meat in it.
Satellite tags fitted to Chilean devil rays near the Azores recorded repeated descents past 1,000 metres, the deepest close to 1,900 metres. The rays carry a network of blood vessels around the brain that appears to buffer it against the cold.
The noisy miner is native to eastern Australia, yet its colonies drive smaller birds out of the woodland they occupy. Its aggression is so effective that its own overabundance is listed as a threat to other native species.