What this shows:

Each row is a species. Each square represents a year (since 1950).

Tip: Shows trends over the years of appearance in Essex County of each rare species.

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Colour meaning:

• Dark red – exceptional year for that rarity with many observation dates
• Orange – species recorded multiple days that year
• Light orange – few records
• No colour – no records for that year

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Data is based on historical checklist frequency in Essex County.