What bird makes a knocking sound?

A fast knocking from a tree, a pole, a downspout or your siding is almost always a woodpecker drumming, its stand-in for a song, often at dawn. A short, gentle roll under a second points to a Downy or Red-bellied Woodpecker; a longer roll of nearly two seconds, sometimes on metal, to a Northern Flicker; a powerful roll that fades at the end to a Pileated; a burst that breaks into scattered knocks to a Yellow-bellied Sapsucker. A deep thumping that speeds up into a whir in spring woods is a Ruffed Grouse, beating the air with its wings.

Listen: drumming, not drilling

Woodpeckers do not sing, so they drum. Kenn Kaufman, writing in Audubon, explains that drumming works like a songbird's song: it claims a territory, attracts a mate and keeps a pair in touch. The bird picks whatever makes the most noise, a hard dead branch or even a metal pipe. Penn State Extension adds that houses act as resonators and amplifiers, and that woodpeckers often drum at dawn on downspouts, chimney caps, antennas and siding.

Drilling is different. Woodpeckers drill into trees mainly to find food and to dig nests, and that tapping comes at random, with no set rhythm. Kaufman notes that random tapping in the trees cannot be identified, but a rapid roll echoing through the woods is surely a woodpecker. On a house, damage peaks in spring and fall, and several woodpeckers working the same wall can mean insects in the siding are the real attraction.

The small, gentle rolls come from two common backyard birds. A Downy's drum usually lasts less than a second, with about 12 to 17 fairly slow beats. The Red-bellied Woodpecker drums at a similar pace, 13 to 17 beats in under a second, and often gives loud calls between rolls. Red-bellieds have adapted well to wooded suburbs and are popular visitors at backyard feeders.

Louder knockers: flicker, Pileated and sapsucker

The flicker's drum is only moderately fast, but it is long, close to two seconds with up to 30 beats. The point of drumming is to be as loud as possible, so flickers sometimes choose metal objects, and they can even dig cavities into houses with stucco or weak wooden siding. Flickers breed from about February to July and live in open places near trees across most of North America, including yards and parks, often feeding on the ground at ant colonies.

If jackhammer came to mind, consider the Hairy Woodpecker, a larger Downy lookalike that packs about 26 beats into one second, so fast the strikes blur into an angry buzz.

The Pileated is about the size of a crow and the largest woodpecker in the country apart from the extremely rare Ivory-billed. Its drum is loud and slow, then softer at the end. It lives in mature conifer and mixed hardwood forest with plenty of dead trees and leaves large oval to rectangular holes in snags, live conifers and even utility poles.

Kaufman calls the sapsucker's drumming the most distinctive of all: a rapid burst followed by irregular single or double knocks, something like TRRRRRR, TR TR TR, T-T, TT, T-T. Sapsuckers also drill neat rows of small holes for sap, so a tree banded with tiny holes nearby is a strong clue.

A deep thump in the woods: the Ruffed Grouse

No wood is being hit here. The Pennsylvania Game Commission explains that the male grouse stands on a large log or rock with his tail fanned and beats the air sharply with his wings, and the rush of air sounds like drumming. It starts slowly and accelerates until the separate thuds blend into a whir. Males drum to attract females in March and April, in brushy forest less than 20 years old across much of the northern part of the continent.

How to tell which one you heard

• Even or broken. An even roll is a woodpecker drumming. A burst that falls apart into scattered knocks is a sapsucker. Random, uneven tapping is a bird feeding or digging a nest.
• Length and speed. Under a second and almost countable: Downy or Red-bellied. One second of blurred buzz: Hairy. Nearly two seconds: flicker. Loud, slow and fading at the end: Pileated.
• Between rolls. Red-bellied Woodpeckers and flickers often call between bouts.
• Thumps from the ground. A low, accelerating thump in brushy spring woods is a grouse, not a woodpecker.
• On your house. Dawn drumming on a downspout or chimney cap is advertising. New holes in the siding suggest insects.

If the drummer also calls, let Warble listen; a voice gives it, and you, far more to go on than knocking alone.

Questions people ask

Warble is a game, not a field guide. Facts about birds on this page come from the sources above.