Breeding Bird Atlas Handbook


  • The objective of atlasing is to detect the vast majority of breeding birds occurring in a Priority Block or Special Block (designated areas about 10 mi2) and obtain evidence of breeding. The atlas project will occur for 6 years (2005-2010) and blocks can be surveyed in a single year or in multiple years.
  • Contact your county coordinator or project coordinator (John Castrale or 812 849-4586) to get an assigned block to atlas
  • Make sure you have turned in a volunteer form to the project coordinator.
  • Consult the “safe dates” table to determine the most efficient dates to atlas and to target certain species.
  • When atlasing, take your maps, field cards, safe date table, pencil, optics, and other atlas materials with you.
  • Cruise roads within the block, stopping frequently to observe different habitats or likely nesting locations. Walk public areas or visit private areas if you have the landowner’s permission.
  • Once a bird species is detected, watch awhile, and match your observation to the highest degree of breeding evidence possible listed on the field card. If the behavior is not in the confirmed breeding category, consult the safe date table to see if the record is acceptable (if not, re-visit the same site during safe dates). Record the date each time a breeding evidence code is upgraded.
  • Atlasing is most productive in the early morning or late evening, but can be done any time of day. A nighttime visit or two is usually necessary to detect nocturnal birds.
  • Atlasing can occur from January to September (or longer), but is most efficient from May to August, the peak months being June and July.
  • More than one atlas block can be visited in a day and subsequent visits should usually be scheduled at least a week apart to take advantage of the T code and the varying breeding schedules of different birds.
  • Feel free to write on maps (locations of less common species) or make notes on the field card. One field card should be used each year and in subsequent years the field cards should be marked to indicate the highest breeding evidence code obtained to date. Use pencil on the field cards since you will be tallying individuals for the Summer Bird Count or reporting field observations.
  • Strive to upgrade breeding evidence codes to the highest one possible, but especially to the confirmed category. Once a species is in the confirmed category, concentrate on other species.
  • All observations should be within the boundaries of the priority block. Many blocks cross county boundaries that can be ignored. If you are working on a block that adjoins a neighboring state, make sure to include only those observations within Indiana. If a rare bird (or confirmed nesting by any bird species) is observed outside the priority block boundary, record it on an Incidental Bird Observation Form with a detailed description (lat/long preferred) about its location.
  • A separate Incidental Observation Form should be used by each participant, but can be used for many species or multiple years. Records are only useful if they can be assigned to a block; use a GPS to get an accurate location or mark the sighting on a map.
  • The median number of species detected in a block will be about 70, although blocks will vary widely due to habitats present. It will take about 15-20 hours to cover a block adequately but again this will vary because of differences in birding skills and habitat diversity and types. About 70 percent of species should be in the probable or confirmed breeding categories. Move on to a new block once expected species have been detected.  


(3/18/05 revision)
Edward M. Hopkins and John Castrale


The first Breeding Bird Atlas in Indiana was conducted from 1985-1990 and published by the Indiana Department of Natural Resources in 1998 as the Atlas of Breeding Birds of Indiana (Castrale, J.S., E.M. Hopkins, and C.E. Keller). Twenty years after the initial effort, the project is being repeated in 2005-2010 to document changes in the distribution and frequency of occurrence of Indiana’s breeding birds. The field methods and sampling frame are virtually identical this time in order to make valid comparisons to the previous project. Changes in the methodology are mostly related to changes in technology and especially internet-based systems to communicate, enter and display data, and disseminate information and forms.


The primary purpose of the six-year Indiana Breeding Bird Atlas Project is to sample and plot the distribution of the breeding birds on a map of the state of Indiana.

The collection of information will be undertaken primarily by volunteer field cooperators or atlasers. The atlasers will record the breeding status of every individual species encountered within each of approximately 650 similar-sized and evenly distributed Priority Blocks. They will use a set of evidence codes based on observable breeding criteria.


A complete, systematic inventory of the breeding birds in Indiana has value in both its immediate goals and as a permanent record for the future. The main objectives are to:

  1. Provide the data necessary to produce accurate and up-to-date distribution maps for every species breeding in Indiana.
  2. Provide more accurate information on the breeding occurrences and habitats of rare species in Indiana so that future management and resource use decisions can be made on a sound factual basis.
  3. Identify fragile or unusual habitats supporting rare species that could become the focus of specialized conservation efforts.
  4. Provide baseline data against which future changes in the status of breeding birds in Indiana can be measured.
  5. Provide a database for use in environmental project reviews.
  6. Involve the birders of Indiana in a cooperative conservation effort and introduce them to a interesting and scientifically valuable form of birding.


The basis of the Atlas Project is a mapping grid system. The most readily available base map system is the U.S. Geological Survey 7.5 minute topographic map. Each named map is referred to as a quadrangle, quad, or topo. Adhering as closely as possible to the standards set by European breeding bird atlases, each USGS quadrangle has been divided into 6 equal-area blocks of about 9.5 mi2, which is slightly smaller than the European 5 km X 5 km standard. The boundaries of these blocks form the basic atlasing unit. All Atlas Project activity will be related to these atlas blocks.

Each USGS map quadrangle is referred to by its name. Each of 6 blocks within a quad has been numbered from 1 through 6 as illustrated below.

Atlas Quad with Block Number Assignment. The Priority Block is #3 (west central).

NW (1) NE (2)
WC (3) CE (4)
SW (5) SE (6)

There are about 650 USGS quadrangles covering the state of Indiana. Because of the large number of quads, one block per quad will be targeted for complete atlasing. Block number 3 has been chosen as the standard Priority Block to be targeted for the Indiana Breeding Bird Atlas Project. All other blocks are considered Non-priority Blocks. Blocks are referred to by their quadrangle name and block number (1-6). If adequate manpower is available, a limited number of Special Blocks may also be identified and covered. These consist of areas managed for natural resources such as parks, wildlife management areas, recreational areas, military areas, natural areas, and state and national forests.

Atlasers will be provided a map of their assigned Priority Block. These are color copies of portions of a topo map with the block boundary shown in red. These maps will also show roads, topography, and general land uses (green for forest, pink for human development, blue for water, white for fields). Because many of these maps are several decades old, keep in mind that many features may have changed. Atlasers should also use other maps (road maps, county plat books, the DeLorme Indiana Atlas and Gazeteer) to navigate an area. A hand-held Global Positioning System (GPS) would be handy for identifying and recording the locations of rare species outside of Priority Blocks.

In order to better map the distribution of rare species, incidental observations of rarer species may be incorporated into the final atlas maps. Rare species are indicated on the field card and any encounters with these species during safe dates or with confirmed breeding evidence should be reported on Incidental Bird Observation forms. GPS units, the use of DeLorme 3-D Topo Quads software, and internet sites that provide topographic maps and aerial photos (, are helpful in assigning sightings to a particular atlas block. The preferred units for reporting locations is latitude and longitude using degrees and decimals of the degrees (e.g., N 40.250 degrees, W 86.783 degrees), although other units (UTMs, degrees/minutes/seconds, township/range/section) are acceptable. If an atlaser cannot determine the priority block, it can be assigned at a later time. In all cases, it is desirable to mark the location on a detailed field map with the date, species, and behavior information.

Since manpower is limited for atlas projects, priorities for data collection have been established.

Most Important

  1. Systematic and complete coverage of Priority Blocks.

Moderate Importance

  1. Systematic cataloging of confirmed breeding sites for rare species (e.g, great blue heron colonies, bald eagle nests) in Priority and Non-priority blocks.
  2. Incidental Bird Observations of confirmed breeding for rare species in

Non-priority Blocks

  1. Incidental Bird Observations for rare species in Non-priority blocks.
  2. Systematic and complete coverage of Special Blocks.

Least Important

  1. Incidental Bird Observations of confirmed breeding for common species in Non-priority blocks.
  2. Systematic coverage of Non-priority blocks.
  3. Incidental Bird Observations for common species in Non-priority blocks.


County coordinators volunteer to facilitate atlasing at the local level. Some coordinators may have responsibilities for multiple counties.

Responsibilities of county coordinators are to:

  1. Identify and solicit other birders to atlas local Priority Blocks.
  2. Identify Special Blocks in their county.
  3. Assign atlas blocks to atlasers.
  4. Explain atlas methods and the use of materials such as maps and forms.
  5. Distribute (or have the state coordinator send) atlas materials (maps, forms) to atlasers.
  6. At the end of breeding season, contact atlasers to make sure field efforts have been entered on the atlas web site. If the atlaser does not have internet access or is unable to enter data, the coordinator can enter the data or send it to the state coordinator for entry.
  7. Check the entered data for errors and possible misinterpretations and contact atlasers to correct them. Approve the submitted records.
  8. Encourage atlasers to fill out rare species documentation when necessary.
  9. Help atlas local blocks.


Actual field work for the Indiana Breeding Bird Atlas Project will be accomplished primarily by volunteer block atlasers. The responsibilities of a block atlaser are to:

  1. Contact the county coordinator or state coordinator to express an interest in atlasing one or more priority blocks.
  2. Fill out and return a Volunteer Form prior to atlasing.
  3. Get atlas materials (forms, maps) from the atlas web site, county coordinators, or state coordinator.
  4. Review atlas materials and understand atlasing goals and methodology.
  5. Confine systematic atlasing activities within the boundaries of assigned Priority Blocks or Special Blocks using one Atlas Field Card for each block. Use Incidental Bird Observation forms to record significant bird observations in Non-priority blocks.
  6. At the end of the breeding season, enter field data from Field Cards and Incidental Bird Observation forms on the Atlas web site. If the atlaser does not have internet access or is unable to enter data, contact the county or state coordinator.
  7. Fill out a documentation form for rare species.


The primary responsibility of a block atlaser is to record the breeding status of each species encountered within a particular block and confirm as many as possible using the breeding criteria codes listed on the field card. A species needs to be confirmed in a particular block only once. For example, one Killdeer nest in a block means that Killdeer is confirmed for that block for the six–year atlas period.

All atlas activity must be confined within the boundaries of a particular atlas block and may cross county boundaries. For blocks that include areas in adjacent states, count only those individuals that are within Indiana. For Special Blocks, count only those species within the boundary of the special area. Special Blocks may require multiple field cards in they fall in different blocks. Those that are also in Priority Blocks would require separate accounting of species.

Use the Atlas Field Card for reports within one of the standard Priority Blocks or the Special Blocks. If you encounter a rare species (indicated on Field Card) report it on an Incidental Bird Observation Form. Location data must be specific enough to be able to assign it to a block.

When assigned a map and its Priority Block, study it to familiarize yourself with the block boundaries, roads and other important features. Before the breeding season, survey the area by car or on foot to become familiar with access points and the various habitats in your block. If necessary, obtain permission for access to specific areas at this time. Observe private property boundaries and do not trespass.

You do not need to cover every square foot to properly atlas a block. You should be able to account for the majority of the species present by checking representative samples of each habitat type in the block. Most atlasing is done from roadsides, although more thorough coverage is attained if larger or rarer habitat blocks are accessed by foot.


As birds are encountered during the breeding season, they will be observed for evidence of breeding within an Atlas block. A set of breeding evidence criteria have been developed along with a set of one and two letter abbreviated codes to be used on the field forms. Please study the criteria carefully and become familiar with them. See the Breeding Evidence Criteria and Codes.

The breeding evidence criteria are divided into four categories of breeding status: OBserved, POssible, PRobable and COnfirmed. The criteria are printed in order of increasing importance. If at all possible, strive to upgrade evidence criteria within each status category or elevate it to a higher category.

An effort should be made to place a majority of the detected species into the confirmed category for each atlas block. Upgrading the status of all breeders from the Observed and Possible categories to Probable during the project is the minimum goal.


he experience of other Atlas Projects has shown that 75-85 percent of the expected species in a block should be found within 35 hours of field work in representative sample of all major habitat types present. Additional time spent beyond this amount results in decreasing return for the effort expended. About half of the encountered species will be in the confirmed Category at the end of the recommended period.

Blocks encompassing large areas of cropland, open water, suburbia or portions of other states may require less time to cover adequately. The opposite should occur in blocks with high habitat diversity or few roads, and more time may be needed to achieve the desired results. A rule of thumb may be that an observer should keep making trips to a block until no new species are added to the block list.




  • Atlas Field Card
  • Incidental Bird Observation Forms 1 | 2
  • Listing of Safe Dates
  • Priority Block map (can be e-mailed but files are large and should be printed on a color printer).

Recommended materials (not provided)

  • County road map or plat book
  • DeLorme Indiana Atlas and Gazeteer
  • USGS topographic map
  • Handheld GPS unit
  • Clipboard, pencil
  • Flashlight (for dusk/dawn/night birding)
  • Binoculars
  • Spotting scope
  • Bird field guides
  • Bird tapes (to be studied prior to the breeding season)
  • Sunscreen/insect repellant


The Indiana Breeding Bird Atlas Field Card will be used in everyday atlasing. One Field Card will be used during an entire season and will be associated with a particular atlas block. To obtain a more accurate accounting of the time used to cover a particular block, each observer should carry a card. One person should be the block leader who will collect and summarize the data at the end of the breeding season.

Evidence of species breeding status will be observed and recorded in the correct Evidence Code column as a one or two letter abbreviation found in the Breeding Criteria and Code section of the Field Card. Using a pencil will allow easier upgrading of the breeding status within a particular Evidence Code column.

If atlasing continues over more than on breeding season, save the previous year’s Field Card so that time will not be wasted upgrading the breeding status of a species that may already be in the COnfirmed column.

This project is not concerned with migrants or pre-season, post-season and non-breeding wanderers. Use the Safe Date periods, but do not record them on the Field Cards in the PO or PR columns. If you believe, from past experience, that a species may not be a migrant, use the OBserved column. If the species is encountered again within the Safe Dates, it might then be upgraded. Because the level of evidence is high enough in the COnfirmed category, there is no need to be concerned with the use of Safe Dates in the CO column. Be sure to read the specifications of all the codes.

Besides the breeding evidence, a column is provided for the date on which a species is observed and will be changed when a species is upgraded to a higher evidence code. Having the date is necessary to enter data on the web site. Only the more common species are listed on the main part of the card, and rarer species are listed in a separate box. If you encounter these species, write them in on the card. The field card can be used to record numbers of individuals of each species encountered to be used for breeding evidence code M or for use on Summer Bird Counts. Numbers will not be entered for atlas purposes.

At the end of the breeding season, enter the highest evidence codes and date observed for each particular species. To do so, each participant must be entered into the site and assigned the appropriate block by the county coordinator.


Use the Incidental Bird Observation Form (1 | 2) to record significant sightings outside of Priority or Special Blocks. One form can be used for species in multiple blocks or locations. This includes encounters with species for which you have found evidence that places them in the confirmed category or any encounter with rare species within safe dates. The field card indicates species (with an asterisk on the main list plus the box with rare species) for which incidental observations are desired.

To be useful, locations must be precise enough to allow sightings to be assigned to an atlas block. On many occasions, the atlaser may not have a USGS map of the area where a species is observed. Special care should be taken to describe the exact location using a GPS unit, or detailed directions and distances to nearby towns, numbered county or state road intersections or other special landmarks. The Atlas Project staff will attempt to match the location with atlas quad and block numbers if the observer gives a complete enough description. All species breeding data will be cross referenced with a quad name and block number pair. If a species cannot be located closely enough to be assigned to a particular block, the information cannot be used for the purposes of this study.


Some extraordinary bird sightings should be accompanied with a written description of the species and other information that will help validate it. Recognizable photographs are also helpful. To determine which species need documentation, click here. In some cases, county coordinators may ask for details or documentation. Documentation forms can be obtained here or from the county or project coordinators.



Each county will have from four to fifteen Priority Blocks plus possible Special Blocks nominated by atlasers and other environmental experts. Many of these blocks will cross county boundaries. Please ignore the county lines and atlas the whole block. For atlas blocks that cross state boundaries, only include those observations that fall within Indiana. For Special Blocks, observations should be made within the boundary of the Special Blocks, but one card will be needed for each Priority or Non-priority block in which the Special Block occurs.

The amount of time a particular individual can give to the Atlas Project as a volunteer atlaser will vary. If an atlaser goes to a block on five Saturday mornings for three hours each during June and July plus several evenings for an hour each plus a few short periods sometime between March and September then a block could be adequately covered in one year. Thus, if the atlaser helps for the full five years, then five blocks will be covered.

The number of blocks one atlaser can cover will vary. If you have a limited amount of time per summer, work on one block until it is adequately covered. If more time is available, more blocks can be covered simultaneously.

You can visit an atlas block over more than one atlas season. If you cover a block fairly thoroughly and consider the effort adequate, but in a subsequent year find a number of species within the block that can be upgraded, please do so.

The atlas results will provide baseline data for follow-up studies. Therefore, it is important to cover all the Priority Blocks no matter how uninteresting they are. If local atlasers cannot do all their nearby blocks, outside atlasers will have to be solicited.

Feel free to mark atlas maps with specific locations, dates, numbers, and notes for significant bird sightings.

Remember that birds are most active in the early morning from pre-dawn to about 8 am EST and to a lesser extent just before sunset for a few hours. To find nocturnal species such as Woodcock, Whip-poor-will, owls and others, you will have to plan visits for about an hour preceding dawn or following sunset. Even some diurnal birds will vocalize during moon-lit nights.


For species whose evidence of breeding puts them in the confirmed status, there is no fixed season. Generally, February through early September would be practical dates. In the other status categories, most species will be recorded on the Field Card only during June and July. Common sense will have to be used when using the Observed, Possible and Probable status categories. Use the Safe Dates as a guide for using the codes in these categories because many migrants with Indiana populations can be seen exhibiting evidence of breeding such as singing, territoriality or loitering for periods of more than a week in duration.

For all practical purposes, the primary nesting season for most Indiana species is in June and early July. Many species will be found nesting earlier or later than this. Some owls and hawks may be found nesting as early as February while Henslow’s Sparrow, Sedge Wren and American Goldfinch may nest in July and August.


The U.S. Fish and Wildlife Breeding Bird Survey, the Indiana Audubon Society’s Summer Bird Count and to a lesser extent the IAS Big May Bird Count are done during part of the Indiana Breeding Bird Atlas period. They all differ from the Indiana Breeding Bird Atlas in that you must count the individuals of each species. In some, you must keep track of your mileage.

The minimum status of all birds seen on bird counts held during the breeding season will be either in the OBserved (O) or POssible (X, S) categories for the Atlas. However, you must be able to assign the species to a particular atlas block.

There is enough room on you Field Card to note the number of individuals seen if you want to do two activities at once. But remember to change to another method of accounting when you wander outside the boundaries of your Atlas block. If you encounter a rare species during a bird count, you can note the location for the Atlas on an Incidental Bird Observation Form.


The Indiana Breeding Bird Atlas is designed to be a qualitative survey, not a quantitative census. Although the Atlas is not concerned with numbers of individuals of each species, accuracy of identification is of utmost importance. A small but accurate species list is obviously of greater value than a larger list with dubious entries. Tentative identification should not be recorded on the date forms. It is fine to note tentative identifications to be verified later, but please be positive before recording data on the web site.


It is very important to obtain permission before entering private property. It may be expedient to do so before actual field work starts. You might take a copy of this handbook to explain the program to the landowner. A letter announcing you as an official Atlas participant may be obtained from the Atlas office.


You may be able claim a charitable deduction for automobile mileage from home and back when traveling to atlas a block or other expenses incurred while atlasing. Coordinators making arrangements for Atlas coverage may be able to deduct expenses for telephone charges and postage. Consult the Internal Revenue Service about charitable deductions for volunteer workers for state-sponsored projects. Questions or further information can be obtained from John Castrale (or 812 849-4586).