What do these ranks mean? ORBIC's ranking definitions

Horned Grebe

Podiceps auritus

List 2S2B,S5N
Bufflehead

Bufflehead

Bucephala albeola

List 2S2B,S5N
Common Nighthawk

Common Nighthawk

Chordeiles minor

List 4S5B
Black-Tailed Jackrabbit

Black-Tailed Jackrabbit

Lepus californicus

List 4S5
Northern Sagebrush Lizard

Northern Sagebrush Lizard

Sceloporus graciosus graciosus

List 4S5
Western Rattlesnake

Western Rattlesnake

Crotalus oreganus

List 4S5
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