The Cycle

A House Finch nesting cycle is six phases that line up almost identically every time, riding a weather window that doesn’t. This page is the constant: the stages light up as biology arms them, and the charts below grow by a day every twenty-four hours, drawn straight from what the classifier saw.

The cup is in a wall sconce above the workbench. The cameras have been running since the evening of May 29 — and unlike round one, which was first found at a finished clutch, this time we were here for the front half: the building, the first egg, the long settle.

What the cameras are seeing

Reading the bird in the data

The male you can finally see. A House Finch pair is unmistakable in daylight: the male carries a wash of red across his crown, throat and rump — carotenoid pigment he can only get from his diet, which is why his color is, quite literally, a foraging résumé the female reads. Round one’s cameras were infrared on the cup every night and smeared that red to grey for thirty-one straight days. This round’s daylight angle finally caught it: the red head at the rim, leaning in to feed her. Those “two adults in one frame” moments are courtship feeding — the male provisioning the female so she can stay on the eggs.

She does all the sitting. Only the female House Finch develops a brood patch — a bare, blood-rich spot of belly skin that presses warmth into the clutch — so incubation is hers alone. That biology is what the “Coming home” chart is actually drawing: empty-cup frames pile up while she’s still building and laying and slipping off to forage, then fall away to almost nothing once the eggs need a body on them. The data didn’t decide she was incubating; she did, and the empty-frame count simply noticed.

Why all five will hatch at once. A finch lays one egg per morning but doesn’t start warming them until the clutch is nearly complete — incubation onset is delayed. Every embryo therefore starts its clock on the same day, so a clutch laid across five mornings hatches across one or two. We logged the first egg the morning of June 2 and the settle to tight incubation on June 7; counting roughly thirteen days of warmth from there puts hatch around June 19–21 — landing, by accident of timing, almost exactly on the solstice.

The laying chapter — and what the footage could and couldn’t tell us

Round two existed to capture the part round one missed, and it did: the cup going from grass bowl to five eggs, one arriving most mornings between June 2 and June 6. We went back through the laying-window footage frame by frame to try to date each egg’s arrival precisely. The honest result is a seam worth showing. Eggs are only countable in the rare moments the female is off the cup, and from about June 5 she increasingly isn’t — she settles and covers the clutch with her body. So while the footage clearly corroborates the growing clutch (you can see four pale eggs tucked under her on June 7), the exact per-egg laying order is below what this single daylight angle can resolve. The clutch is five. The order in which the last two arrived, the cameras kept to themselves.

Next

The female will sit for roughly twelve to fourteen days, lifting only briefly. Watch the “empty cup” line stay flat — that’s a healthy incubation. Hatch should land in the June 19–21 window: synchronous, the female removing the shell halves within hours. Then the cycle flips from stillness to a feeding frenzy — both parents shuttling food, and unusually for a songbird, House Finches raise their young almost entirely on regurgitated plant matter rather than insects. Fledging follows about twelve to fifteen days after that.