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 Drafts and withdrawn editions are never mixed into this index.
Eiderdown is the insulating breast down a female eider plucks to line her nest. In Iceland and elsewhere it is collected from nests by hand, in a centuries-old practice where the colonies are protected and the birds are left alive.
The Texas blind salamander has no habitat above ground at all. Its entire world is the water inside the Edwards Aquifer, and biologists see it mostly when the current pushes individuals out through springs and wells.
A nuthatch that finds a cavity with too wide an entrance does not look elsewhere. It carries mud to the hole and builds the rim inward until the opening is just large enough for itself, excluding larger competitors.
Courting males produce structured sequences of ultrasonic calls above 30 kilohertz, well beyond human hearing. The syllables repeat in patterns and vary between individuals, which is why the vocalisations are described as song rather than as simple squeaks.
Reviews of records from several continents document mantises, the Chinese mantis prominent among them, seizing and feeding on small birds. Nearly all cases involve hummingbirds at feeders in North America, and the behaviour is rare rather than routine.
South Florida is the single place on Earth where a naturally occurring crocodile and a naturally occurring alligator share the same wetlands. They separate largely by salinity, with the crocodile in brackish mangroves and the alligator in fresh water.
The gelatinous mass sometimes found on submerged branches is not an egg sac, a fungus or a single organism. It is a bryozoan colony: thousands of millimetre-long individuals sharing a secreted jelly matrix.
Harmonia axyridis displaces native ladybirds partly by eating their larvae. A 2013 paper argued it also carries microsporidian parasites lethal to competitors, but that lethality was shown by injection, and a feeding test later found a far weaker effect.
The dhole's signature contact call is a clear, rising whistle that carries through dense forest, which is why it is sometimes called the whistling dog. It suits a hunter that pursues prey out of sight of its own pack members.
Genetic work moved the genus Piranga out of the true tanager family and into Cardinalidae, alongside cardinals and grosbeaks. The name is a holdover from classification by appearance, and the bill shape had been quietly signalling the truth for years.
Male Japanese rhinoceros beetles vary enormously in horn length, and the difference is set before adulthood. Nutrition during the larval stage determines final body size, and the horn grows disproportionately faster than the rest.
Nemerteans strike prey with an eversible proboscis housed in its own fluid-filled chamber above the digestive tract. Squeezing that chamber turns the proboscis inside out and shoots it forward, entirely independent of the mouth.
Water vole numbers in Britain collapsed through the twentieth century. Habitat loss set the stage, but the decisive agent was the American mink, a predator small enough to follow a female vole into her burrow, against which the vole has no evolved defence.
The deep two-note territorial hoot of a Eurasian eagle-owl is consistent enough between calls and stable enough over time that recordings can distinguish individual birds, allowing researchers to census territories without ever trapping an owl.
Almost all seals live in cold seas. The Hawaiian monk seal is a tropical exception with a population in the low thousands, and its closest relative, the Caribbean monk seal, was declared extinct within living memory.
Georg Steller documented the animal in 1741 while shipwrecked in the Bering Sea. The surviving population was small and confined to two islands, and hunting by fur-trade crews finished it by about 1768, some twenty-seven years later.
Tardigrades tolerate vacuum, radiation and extreme cold because those exposures are survived in a dried, metabolically halted state called a tun. Active, hydrated tardigrades are ordinary animals killed by ordinary conditions.
A single mountain pine beetle boring into a healthy pine is usually drowned in resin. The beetle wins by summoning thousands of others with pheromones, so the tree's defences are exhausted within days.
Purple martins east of the Rockies have almost entirely abandoned natural cavities and now breed in gourds and apartment-style boxes put up by people. The tradition predates European settlement, with Indigenous communities hanging gourds for the birds.
Greater honeyguides lead human honey-hunters to bee nests and take beeswax from the opened comb. Experiments in Mozambique showed the birds respond specifically to the traditional call local hunters use, more than to other human sounds.
A meerkat on watch is usually the safest animal in the group. Sentinels tend to be well fed, stand near a bolthole and are typically the first to reach it, which undercuts the standard story of selfless guarding.
The Galapagos flightless cormorant has wings roughly a third the length needed for flight, yet it still comes ashore and holds them open in the classic cormorant drying posture, a behaviour retained after the wings lost their original function.
Seen from below, a fish in the twilight zone is a dark shape against faint daylight. Marine hatchetfishes cancel that silhouette by shining light downward at an intensity tuned to the light falling from above.
Coconut octopuses collect coconut halves and clam shells, then stack them and walk them across open sand on stiffened arms. The shell offers no protection while being carried, which is what makes the behaviour interesting.