Northern Prairie Wildlife Research Center
The New Mexico Breeding Bird Atlas Project
Visits to atlas blocks for breeding birds can begin as soon as the Great Horned Owls begin courtship in January and can continue until September or October when the last young fledge from the last nest of late nesting species such as the American Goldfinch. Fortunately, only a very few species nest very early or late in the year (Appendix A). The peak of the breeding season for most species includes late May, June, July, and early August.
June is the primary month for building a species list for a block because most birds are on territory and are very vocal. In piņon-juniper habitats (cover type group code GCCW, see Cover Type Group Codes), however, the last half of May can be very important for hearing Gray Vireos and Black-throated Gray Warblers. July and August are the optimal months for recording birds in the probable and confirmed breeding categories. Although most singing activity has greatly decreased by July, it is a time when noisy fledglings accompany parents or beg for food in a nest, and parent birds are more likely to be seen carrying food for young. Also, species with multiple broods are re-nesting in July and early August.
Caution is urged in recording the "FL" code (fledged young, see Breeding Codes and Interpretations) since young birds able to fly well could have been raised outside the block you are covering. The "FL" code should be used with caution especially for species such as starlings and swallows that may move relatively great distances soon after fledging. This code should be used only for recently fledged passerines in the natal areas that are still dependent on parents. Remember that young birds begin to disperse once the parents have discontinued feeding them. This can be two or three weeks after fledging.
Migrants create a particularly difficult threat to atlas accuracy. Remember that some migrants will sing during migration. For many species, there is a period of overlap where residents have initiated breeding activities while other individuals of the same species are still migrating farther north.
The best time of the day for your visits is early morning from about daylight (5:00 - 5:30 a.m.) to mid-morning (9:00-10:00 a.m.). The majority of birds are most active and relatively easier to confirm during this period. Don't, however, refrain from making visits at other times of the day. Crepuscular (active at twilight or just before dawn) and nocturnal (active at night) species will require visits in the early evening, after dark, or at dawn. Common Snipe, Common Nighthawk, Common Poorwill, and owls are most easily recorded at such times.
Number of Visits
How much effort should be expended to ensure adequate coverage and consider a block to be complete? This is a difficult question that other atlases have struggled with. There is no simple or straightforward answer. The following is from the Wisconsin Breeding Bird Atlas handbook and is offered as a guideline, goal, or target:
Visit or cover all habitats within the block, and survey every habitat at different times within the breeding season. Every acre of the block does not need to be examined, but thorough coverage of all available habitats is necessary. Obviously, a block with uniform habitat will take considerably less time to cover adequately than one with a diversity of habitats.A list from the Missouri atlas project suggests the following potential visits. Conducting all of the following visits is not required: March to check for early nesters and get familiar with the terrain and ownerships; late April or early May for early nesters; early June to build a species list and note where males are singing; mid-June to re-check on the singing males and add more species; early July and early August to get more species into the confirmed category; and include some night-time hours in either early morning or late evening in both spring and summer. At least 1 trip should be taken after sunset.
Thus, spend 10-40 hours (20-30 hours as an ideal average) actually in the block actively surveying, spread over 4-8 occasions. Be sure to record the actual dates and number of hours spent in your block on your field observation card. For safety, a minimum of two people should conduct nighttime visits.
Most species in a block will be encountered in the first few hours. Atlas work in other states has shown that over 85% of the breeding species present in a block can be found in 20-30 hours by checking all the major habitat types in the block. Additional time spent beyond this period usually results in rapidly diminishing returns, and 100% of the species present may not be found even if hundreds of hours are spent in a block. After about 25 hours your time will probably be more productive if you turn your attention to another block. Blocks with high habitat diversity, however, may require more than 25 survey hours.
Don't miss an opportunity to spend an hour or two in any block just because you feel you cannot record enough species in the confirmed breeding category. In an hour or two, as many as half the species in a block can be recorded by an experienced birder as "possible breeding." It is recommended, if possible, that you keep making trips until the number of new species added drops to zero for at least 2 trips or for at least 4 hours.
The number of species found in a block will vary depending on the diversity of habitats present and its location in the state. As few as 20 species may occur in an urban block; other blocks may contain as many as 100 species. You may find it helpful to make an estimate of the number of species that are known to occur in your region. Your regional organizer can help you determine the species to be expected in your region. This number is a best guess, but at least provides a target number for which you should strive.
Target 50% of the species recorded in the block to be in the confirmed category, with about 25% listed in each of the probable and possible categories. Some states have combined this "percent confirmed" method of estimating coverage with a target percent of the potential species list as the primary measure of adequacy of coverage. Reaching a 50% confirmation level is probably a better measure of completeness. In the process of attaining half of the species in the confirmed category, you will probably be near or above the 75% of species expected target used by several other atlas projects.
Fieldwork for a block can be done in one year or spread out over two or more years, but once you attain an acceptable level of coverage in your block, please ask for another block. Contact your regional organizer to find out which Statistical or Habitat Priority Blocks are without coverage or in need of help.
Remember that your goal is to confirm nesting for as many species as possible; absences on your field observation card should reflect real absences, not species missed. On the other hand, we need to cover many blocks in New Mexico, so make the most of your time. Use your time as you see fit, after all, you're the one donating it. If you wish, discuss any concerns about ceasing or continuing to atlas a block with your regional organizer.
Estimating Relative Abundance
Accurately estimating the abundance of birds in each block would be extremely time consuming and is not a goal of the New Mexico Breeding Bird Atlas Project. Knowing something about the relative abundance of each species across the state, however, is useful for land managers.
To estimate relative abundance, visit a minimum of eight kilos (see Mapping Squares and Blocks) of your choice within your block. During these visits keep a two-hour timed record of the birds observed in each of the selected kilos. Try to visit kilos that are spread throughout the block and cover all available habitats. Sometimes this is not possible or practical, but do the best you can. Atlas observations during the relative abundance counts should also be conducted in the same manor as at other times, namely try to document breeding behaviors for each observed species. Visits for relative abundance should be conducted when birds are actively singing and thus most detectable. These visits may be in late May for some piņon or juniper habitats, or late July for some high elevation habitats. The timed record for each kilo may be divided in any way that is convenient. For example, a one-hour visit may be made in early June with the second hour in early July. You will report your results using the relative abundance card.
Eleven species of owls and four species of nightjars are currently documented to breed in New Mexico. The best way to confirm their presence is by nocturnal surveys in the very early morning (pre-dawn) or early evening hours, preferably with no wind. Depending on the species, elevation, and time of year, response to tape recorded calls is variable. Many of these species breed early and can be difficult to locate after young have hatched. For best results, all owls should be surveyed before the end of May. The peak calling activity for many species is during April and May. Great Horned, Long-eared, Western Screech, and Northern Saw-whet owls, however, respond best between January and March. Similar to daytime surveys, night surveys need to be done in as many of the block's habitats as possible.
If enough time is spent after dark during peak calling periods, you can often hear different species of owls and nightjars calling on their own. If time is limited, however, a tape recorder will be needed to broadcast their call to get a response (especially for smaller owls). Tapes should be used sparingly and not too loudly, just enough to get a response. (You do not need to see owls and nightjars to identify themmost have distinct calls.) We do not want to disturb their normal nesting activities. Playing tapes will not lead you to a nest, but may help you decide if a single owl or a pair of owls is in your block. When playing tapes, play smaller species first, since smaller species will probably not respond once you've played a Great Horned Owl call. Also, remember that playing tape-recorded calls is prohibited in most National Park Service areas unless special permission is obtained first.
Unless you know of a nest site or find recently fledged young, confirming breeding of nocturnal species is very difficult. However, just the presence of a bird or pair of birds in proper habitat during its breeding season is valuable information
Record Keeping and Reporting
Everyone has a different way of keeping track of observations. Some use small notebooks or index cards. The field observation card was designed for use in the field and we seriously urge you to have it with you on every block visit. The field observation card will prompt you for important information that you may otherwise not record in a notebook. At the very least, all breeding codes and visit information should be transcribed onto the card soon after each survey is conducted on your block. Do not wait until the end of the season to transfer all your notes to the observation card. You may find this to be a greater chore than you realize when the end of the season due date comes around. Small notebooks can also be quite useful for keeping notes on special things (e.g. nest locations, unusual species or behavior).
Check and recheck your field observation card before sending it to your regional organizer. Double-checking your card is very important to avoid errors. We recommend, also, that you return the original field observation card rather than transferring the information to another card. This will eliminate the chance of making mistakes while transferring codes. Be sure to keep a clear photocopy of your card for reference if additional visits to the same block are needed the next year, or in case your regional organizer has any questions.
Average Block Survey Summary -- A "To Do" list
Here is a list that may be helpful in surveying your block. Each point is a reminder of an important part of the atlas methods: