Habitat Codes for MBBS Routes

The objective in recording habitats at each stop is to produce information about

  • the overall distribution of habitats along a route

  • any changes in habitats from year to year

We cannot hope to explain the occurrence of every species at every stop. Birds can often be heard from a long way away, and some have specific requirements. So to explain every species' presence or absence would require a major effort to survey habitats in detail over a large area at each stop.

Instead, we want to use our habitat codes to provide an overall description of habitats along each route for comparison with the total counts of species along the entire route.

A simple way to achieve this goal is to record the habitat immediately adjacent to each stop. It is best to keep our codes simple, even though some (but preferably not too many) atypical situations get shoe-horned into strange categories.

The following prcedures put emphasis on distinguishing areas heavily used by humans from all other areas. Studies tend to show that heavy human use has major consequences for avian populations.


(1) Each year take along your codes from previous years and use the same codes again -- except . . .

(2) When you see that the habitat at a stop has changed (for instance, a clear-cut has become overgrown, a new clear-cut or development has replaced forest) -- mark the new habitat code with an asterisk.

(3) Focus on the habitat directly to the left and right of the exact place where you stop (if the stop is at an edge between two kinds of habitat, make a decision about which side of the edge you are on, even if only by one foot!)

(4) Ignore any narrow strip of habitat parallel to the road (for instance, a line of trees or shrubs between the road and a field).

(5) Make a judgment about the predominant habitat within 50 meters (yards) of the road (half the length of a football field).

(6) If more than one code applies to one place, list the appropriate codes in order from the most to the least predominant (three codes maximum, please!).

(7) If there is a building (not permanently abandoned) within 50 meters (yards), record code B first, regardless of what surrounds the building.

Codes for Seven Major Habitat Categories

B -- building(s) (except permanently abandoned ones) and areas heavily used by humans (lawns, athletic fields, golf courses, barnyards)

H -- forest (treetops touching each other) with hardwoods composing more than 90% of the canopy

M - forest with pines and hardwoods mixed in the canopy (hardwoods 50-90% of the canopy)

P -- forest with more than half the canopy pines (hardwoods less than 50% of the canopy)

S -- second-growth (including areas with shrubs or scattered trees)

0 -- open areas with low vegetation (recent clear-cuts, agricultural fields including fallow and hay fields) -- but not lawns and athletic fields (these are coded B as explained above)

W -- water (lake, pond, river, stream) -- often used as a secondary code after one of the above codes


If you have time . . .

revisit your habitat codes from preceding years and bring them into compliance with the new guidelines (especially by adding asterisks for codes that have changed in the preceding year) . . .

we can then make any adjustments in our overall database.