Bird Ecology

This lesson was created by Drs. Raymond Pierotti and Cynthia Annett


Birds are one of the groups of organisms that is most useful for assessing the condition of an environment. Birds are the most diverse group of terrestrial vertebrates, and occupy a wide range of ecological niches, ranging from predators through insectivores (insect eaters) and seed eaters. Familiarity with common birds is essential for a well-trained field ecologist.

Surveys of birds and assessments of species diversity and abundance have become a major tool in examination of habitat quality and environmental change. Birds are both highly observable and sensitive to habitat alteration or destruction. Unlike mammals, which are good at living around people without allowing themselves to be seen, birds can be observed and censused readily.

In the United States and Canada, two major efforts are dedicated to bird surveys on a national scale. The most important is the Breeding Bird Survey (BBS).  The purpose of the Breeding Bird Survey is to assess the distribution and abundance of every species of bird that breeds within the U.S. or Canada. The winter counterpart to the BBS is the Christmas Bird Count (CBC) coordinated by the Audubon Society. The Christmas Bird Count is run in late December and is intended to monitor the distribution and abundances of bird species that overwinter in the U.S. and Canada.

Data used for the BBS and CBC are collected by observers who travel along set routes, stopping at intervals to count birds that they see or hear. In the case of the Breeding Bird Survey, each route is 50 km long and designed to include a variety of habitats within a region. In addition to bird species and numbers, observers record the times at which they start and end their routes, the weather conditions, and the habitats in which they stop. The records from each route are collected and combined. An example of the field sheet can be downloaded from the attachment section below.

Much of the Breeding Bird Survey and Christmas Bird Count data has been analyzed by the Cornell Ornithology Lab. Their website provides excellent online bird identification guides, help with learning how to become an expert birder, and information on the status of bird populations in North America.


We will conduct this exercise by running two surveys 10 weeks apart. This will allow us to see how avian communities change in composition and abundance from season to season-- for example, at the beginning and end of the fall semester (= late summer and late fall surveys) or at the beginning and end of the spring semester (winter and spring survey). Make sure that you pick days with good weather, since wind, rain, snow, etc. will interfere with your ability to see and hear birds.

Field Procedures

General: During these surveys you should bring a notebook for recording data, a pair of binoculars and bird identification guides. The data that you will collect will be a list of bird species seen and a count of the number of individuals of each species observed in each area. You should note the weather conditions, habitat, date and time of the observations, as well as locations you visited (including places where you looked for birds but did not see any). 

Keeping Field Notes: As a field biologist you will be expected to keep carefully written field notes. For example, if you wish to take part in the Citizen Science Program you will need to be careful to fill out all of the information required by the project. It will be interesting to compare your notes from year to year, so make sure that you give the full date (day, month, year) and make notes explaining any abbreviations that you use in case you forget. Field notes should be taken on water resistent paper with a pencil or a special pen that will not run if it gets wet. Do not erase your notes or black out mistakes, use a simple line to indicate mistakes (that way you can still read it in case it turns out to be useful information after all). If you are a beginning birder, try identifying birds by their common name and to the lowest taxonomic level that you are comfortable with (for example, heron, woodpecker, goose). As you gain experience you can be more and more specific about the identification (for example, Great Blue Heron, Red Bellied Woodpecker, Canada Goose).
Dr. Cynthia Annett,
May 26, 2010, 4:57 PM