On this page, a "tick" is the first confirmed breeding record of a species in an atlas block. Ticks are an important unit of progress for the California Bird Atlas. Every new tick means atlasers have documented a species actually breeding in a block it hadn't yet been confirmed.
Ticks and milestones (e.g., "Project's 10,000th tick!") get recalculated from scratch every time the data is downloaded, so if a checklist is edited/added/removed things will get reshuffled. Don't get too attached and remember these are just for fun! Ticker tape giveth and taketh away: some days you might "lose" a milestone, but some days you might gain one.
We try to update this page once per day (usually overnight).