Northern Prairie Wildlife Research Center
A Comprehensive Review of Observational and Site Evaluation Data of Migrant Whooping Cranes in the United States, 1943-99
Although the data are observational only, and cannot provide unbiased information on habitat use by whooping cranes, there is some merit in continuing to collect data on incidental sightings of whooping cranes during migration, and to collect some specific habitat information at those locations. One example of the data's value is the recent use of whooping crane locations and dates of occurrence by flyway biologists to examine possible conflicts between the snow goose conservation action with migrating whooping cranes. Continuation of data collection, with periodic reviews, will likely provide insights into areas used by migrant whooping cranes and possible shifts in stopover areas. However, we strongly recommend that future data collection efforts be carefully considered and designed to reduce the biases inherent in observational data. The main database probably always will have inherent biases because of unequal observation effort among regions or years, and this needs to be recognized at all times. However, states or regions within states could be targeted for more objective data collection. Areas of particular interest could be targeted to systematically survey for whooping cranes and to document their use-days and habitat use. With appropriate design, such surveys could address questions about effects of habitat condition (e.g., occurrence or use-days of whooping cranes during drought periods) or management (e.g,. moist-soil management or other water management efforts). Caution must be exercised, however, in interpreting data; information collected in 1 area cannot be assumed to apply to other, unsurveyed areas.
The current system of data collection and entry needs to be thoroughly reviewed and revised, mainly to improve efficiency of translating field observations into an electronic records and to simplify field observations. The current system evolved over several decades which included the advent of personal computers and changing ideas about database management and what should be recorded. We believe simplifying the information recorded in the field would enhance the participation of observers by making the task more attractive and requiring less time. But coordinators of such a database also must develop incentives to encourage more participation to contribute both confirmed sightings and habitat data, especially in states or areas within states where there appear to be gaps. For example, local wildlife area managers, active birders, or interested ranchers in more remote regions (e.g., Nebraska Sandhills region, southwestern North Dakota) could be encouraged to participate through educational efforts and improved communication.
Although data sheets for observers in the field can be simplified, especially in terms of the habitat information collected, it also is important to tighten up the protocol for data collection and the definitions so that the data collected are more consistent and more accurate across observers and states. We recommend that the USFWS engage an experienced biologist to simultaneously develop the new database and to more carefully define categories, protocol, and possibly survey designs. The new database should be fully compatible with the existing database but also designed for more efficient data entry and management. If specific states or organizations decide to collect information beyond that in the USFWS efforts, it will be important to coordinate with those groups for consistency in protocol and data sharing.
From our experience working with the current data, we provide below some recommendations on both general data collection and management aspects and on the various variables recorded. The recommended changes made below should be carefully considered and discussed with biologists/observers from different states before implementation. One should consider what whooping cranes encounter in their migration range and what is of real significance (e.g., is it important to differentiate between use of green rye vs. green spring wheat). Also, these measures of "use" must be broad enough to encompass the entire flyway with some consistency and with some biological value. More specific examination of habitat use (e.g., use of CRP vs. alfalfa) should be the focus of targeted studies that will have more intensive measures of use and availability.
- Continue to have 1 person or office responsible for data collation, entry, and periodic review or summation. This person would maintain paper records and the central electronic database, as well as inform and coordinate with biologists or other observers in each state. Ideally, this person or office should be with USFWS, which is charged with the management and protection of this endangered species.
- Combine variables currently used in the Observation and Site Evaluation databases into a single data reporting form and data set. This would allow for more direct linking of variables and minimize errors between data sets. One could still have multiple sub-observations and site locations within 1 main observation, but have a specific category indicating which records have site evaluation variables recorded. Such a data reporting form would have 2 sections, 1 for basic observation information (as currently recorded in Observations) and a separate section for site evaluation data. See recommendations below for specific suggestions on changes to both sections.
- Use numeric observation and location codes, as we created here, to identify unique records and to allow for easy extraction of information. Continue current system of sequential numbering of main and sub-observations reported.
- Develop data collection protocol for cooperators and the data manager, including clear, concise definitions of each variable and instructions on how to complete the data form in the field. Biologists or key observers from all states should be consulted during development of the protocol to ensure clarity, consistency, and simplicity, and to circumvent possible differences in interpretation of requested information.
- Maintain a paper copy of each submitted, confirmed observation, even if the report is submitted by phone or e-mail. The main value of paper copies is for map locations (see below), data proofing, and potential source of miscellaneous comments that might not fit into the data structure.
- For all confirmed observations, require field observers to plot observations clearly on a county or township-scale map which shows township, range, and section information; locations should be clearly marked and, if multiple observations occur, clearly labeled. This will allow the data manager to readily proof and enter the legal description data with minimal error and effort. Other maps sources, such as NWI maps, soil maps, NRCS crop photographs, or other pertinent types of maps, may be desirable but should be considered as supplemental. These maps should be maintained in the file with any paper copies of all confirmed observations.
- Maintain the database in Access. We assume this database software will remain a standard of the Department of Interior and many states for some time and that this format will be readily convertible to other software systems. Data entry in Access can be structured to provide pull-down menus, numeric-limited entry, or other constraints or options to ensure high quality of data entered.
- Summarize data annually and provide a state and national summary to participating states and key observers to reward and encourage their continued participation. As part of this, convert legal descriptions to Albers equal area projection in order to plot locations. Such reports also may provide an opportunity for cooperators to note possible errors or areas of concern.
- Develop well-defined seasons based on biological factors. The current determination of fall versus winter seasons seems somewhat arbitrary and more driven by location than date. Currently, observations of cranes in or near Aransas NWR and those of marked birds that previously had been sighted that fall/winter in Aransas NWR are classified as winter. Thus, a crane observed in Aransas NWR in mid-November is classified as winter whereas another crane observed in central Texas in mid- to late December would be classified as fall. Further, unmarked cranes may not stay near Aransas NWR, but any December observations elsewhere would be classified as fall since no additional information was available. Although this approach may seem appropriate for defining a migrant crane versus 1 that has arrived at its winter location, it allows no flexibility if cranes do not winter at Aransas NWR, or if they subsequently move away from the Aransas area. Similarly, we found some confusion in the original files in classifying spring versus summer records if cranes still were present in the United States after mid-May.
Observation Data Set Variables:
- Site and location identifier: As noted above, maintain a system of sequential, numeric codes to identify each unique observation.
- Location: Keep a text field (minimum of 60 characters) to allow field observers to describe site locations, in particular in relation to named rivers, public land areas, or lakes. Encourage observers to include such named features where appropriate, and to keep in a consistent format (e.g., spelled or abbreviated consistently) so that one could search within this field for a specific name or feature. For data entry, it may be helpful to include a pull-down menu that includes some of the most common sites (e.g., Cheyenne Bottoms SWA, Medicine Lake NWR, Funk Lagoon WPA).
- Legal description of location: Record township, range, section, quarter-section, and quarter-of-quarter section as separate variables or data fields. This will allow easy conversion of location information into x and y coordinates (Albers equal area projection) for plotting or other GIS-related examinations.
- Map: Add new variable to indicate whether location(s) are plotted on a map, and to indicate the map type (county/township, NWI, soil, U.S. Department of Agriculture crop map or photograph, public-land area map, other).
- Observation dates: Continue to maintain record of the first and last date that cranes were observed on this site. These variables should be defined specifically as a date variable in Access to allow calculations of time or plotting of chronology. Use only in observation component of data set.
- Time of initial sighting, and time of departure: Include times of initial sighting and departure of whooping cranes only in observation component of data set; drop from site evaluation component.
- Markers: Provide text field of at least 60-80 characters to record presence of color-marked, radio-tagged, or leg-banded birds. Record only in the observation component of the data set.
- Source: This variable allows data to be attributed to specific studies (e.g., specific telemetry studies) and could be modified to allow the data manager to assess data by study or by the type of data collection (e.g., records collected via systematic telemetry or observations vs. incidental observations). The current categories should be more clearly defined and, where possible, a citation given (e.g., Howe 1987). The acronym, "USFWS," which is currently used for incidental observations, should be changed to "incidental observations - general" or similar category. New categories could be added as needed. Use only in observation component of data set.
- Comments: Add a text field of 100-120 characters to allow for additional comments.
Site Evaluation Data Set Variables:
- Site use: Continue differentiating the 4 site uses (roost, feeding, dual-use, and unknown), but provide clear definitions of the types in the protocol.
- Wetland system: Follow NWI format and code (e.g., PEMCx for palustrine emergent seasonal excavated). The subsystem level (littoral and limnetic for lacustrine; tidal, lower and upper perennial, and intermittent; no subsystems for palustrine) probably does not provide useful information for whooping cranes. We strongly recommend that all levels of the wetland classification, in particular water regime and other special modifiers (e.g., salinity modifier, and if wetland is excavated, partially drained, impounded, etc.) be determined for the entire basin (using deepest water regime of the entire basin as the regime) based on observations in the field, at the time of the crane observation, rather than from the NWI map. NWI maps are now more than 15 years old, and some aspects of the wetland characteristics on many have changed since the original mapping (e.g., drainage, long-term flooding resulting in change in water regime), or errors were made in the original classification. Classifying the wetland based on the deepest water regime will better characterize the type of wetlands used; more detailed mapping of the location on NWI maps or other map sources could be used to provide supplemental information on areas within the wetland. We also suggest adding a salinity modifier (see Cowardin et al. 1979:24-25) to provide information that in the past was recorded under water quality. Clarify in the protocol how flooded croplands should be recorded; if the area is truly a wetland and not just sheet water, one could record "tilled" as a special modifier (Cowardin et al. 1979:26).
- Wetland size: Use of size classes is most appropriate because field observers rarely have accurate or current information on wetland size. Keep wetland size classes as currently recorded.
- River width: Measurement of river width requires additional time and effort in the field, which likely discourages field observers from completing this information. We recommend recording river width by class, similar to wetland size, to encourage more frequent recording of this variable. Classes could be established by examining existing GIS databases for the distribution of riverine widths throughout the migration area, in concert with current knowledge of the pattern of river widths used by cranes for roosting.
- Water depth: Obtaining this information in the field takes extra effort and time and often would require permission to enter private property; these problems likely discourage observers from fully completing the data form. In addition, previous records suggest some measures were estimated from a distance whereas others were carefully measured. We believe additional collection of this data for incidental observations will not provide any significant new insights. Therefore, we recommend dropping this variable. This variable could be recorded in a separate, targeted study if deemed significant to the objectives of such a study. If this variable is retained, only maximum depths should be recorded, perhaps as classes, and separate variables should be used to distinguish between water depth of wetland in general and water depth at the site within the wetland where cranes were observed.
- Water quality: We believe little further insight would be gained by continuing to collect water quality data, therefore we recommend dropping this variable. This variable would be of most value for specific studies targeting feeding ecology in which other, more detailed habitat information also was collected. Information on whether a wetland was saline (e.g., on Salt Plains NWR) is important to retain but could be more appropriately recorded under wetland classification.
- Substrate: Current information on wetland substrate appears adequate unless a specific study seeks to target this variable. Drop this variable in the new database. If this variable is retained, an "unknown" category should be added.
- Slope of shoreline: We suspect it is difficult to get consistent field data for shoreline, and it is apparent from the data presented here that cranes rarely use wetlands with steep (>5%) slopes. We recommend dropping this variable, and recording any unique situations where slope is greater than 5% under a comment section.
- Dominant emergent vegetation: Allow only 1 category to represent dominant emergent vegetation at the site; add categories such as "mixed" or "cattail/bulrush/sedge" to cover commonly-occurring mixes of interest or common occurrence. Also, add "willow" as category.
- Distribution of vegetation: Keep current system to describe distribution of vegetation, but clearly define each category and allow only 1 category for this variable instead of multiple categories.
- Roost site description: We found this alternative descriptor of the roost site provided valuable additional information, particularly for error-checking other variables (e.g., if recorded here as flooded cropland, it should not have wetland classification data). It is important to provide careful descriptions of each category to ensure consistency among observers. Record only 1 category for this variable.
- Feeding site description: Feeding site description should be simplified from the current listing of multiple habitat crop types to a shorter list of main types (e.g., lump types least encountered under "other"). Add "various types" or similar category to cover situations where the site includes more than one habitat or crop type. Record a single category of habitat type and add separate variable to delineate a single crop type. Provide general categories of habitat or crop types (e.g., "row crop stubble" and "small-grain crop stubble") for situations where an observer either cannot distinguish (e.g., barley vs. wheat) or there may be multiple types within that category. Provide more specific definitions of each category. Also, pool CRP with all planted perennial cover.
- Primary adjacent habitat within 1.6 km (1 mi): We are uncertain of the value of information on adjacent habitats. Some streamlined categories or descriptors could be used, depending on the nature of the information desired here. We suggest that examination of surrounding habitat characteristics also could rely on GIS techniques, which could be conducted periodically (e.g., every 5-10 years). Sources of data layers could include NWI, state GAP analyses for cover types, and possibly Natural Resources Conservation Service for cropland data.
- Distance to feeding site: Record only a single distance (the shortest) between feeding site and roost or dual-use sites.
- Visibility: Data on visibility in this data set and in earlier, more detailed studies seem to provide adequate characterization of this variable for incidental observations, therefore we suggest dropping this variable in future observational data. However, specific studies that target habitat use or disturbance in greater detail would be valuable for understanding how these factors may affect crane habitat use; in such studies, visibility should be carefully defined and examined relative to a suite of other variables.
- Distance to nearest utility lines: We are uncertain of the value, from incidental observations, of data on the distance to utility lines. The USFWS data system does not allow distinguishing between rural phone or power lines and more substantial power lines which might provide more serious concerns for cranes, but the Nebraska data forms did distinguish among types (Report Form 6). Are smaller, local telephone or power lines of concern? If only larger, power-distribution lines are of concern, this feature could be examined using GIS (data layers of major utility lines).
- Distance to nearest human development: Distance to nearest human development may not have been consistently defined by observers, and thus any continued use needs to be carefully defined in the protocol. It is undefined in the USFWS forms but is recorded in greater detail in the Nebraska forms (Report Form 6). Some GIS data layers could provide some of this information, e.g., for roads, main power lines, and buildings.
- Primary potential food source, and foods observed eaten by cranes: Although some interesting observations of actual foods consumed by cranes were recorded, such observations were rare. We recommend dropping both of these variables and recording any observations of foods actually consumed under a comments section.
- Site security: The definition or interpretation of site security appeared to vary among observers, from the apparent standard (whether the habitat characteristics of the site could or will be seriously degraded, e.g., wetland drainage) to whether the cranes were immediately threatened by human disturbance, including hunters. We recommend this variable be dropped because of the difficulties of accurately determining potential or real threats to the landscape.
- Extent of similar habitat within 16 km (10 mi) radius: Observers provided a crude ranking of extent of similar habitat within 16 km, and we felt the information provided was not very meaningful. We recommend that examination of surrounding habitat characteristics rely instead on GIS techniques, which could be conducted periodically (e.g., every 5-10 years). Sources of data layers could include NWI, state GAP analyses for cover types, and possibly Natural Resources Conservation Service for cropland data.
- Site ownership: Record site ownership only as single code rather than 1 to many codes; add a specific category for those sites where cranes were observed on lands under several types of ownership (e.g., state and federal, federal and non-government organization [NGO]). Also, add new category to denote ownership by non-governmental conservation organizations (NGO; e.g., The Nature Conservancy, National Audubon Society).
- Number of birds: The recording of the total number of cranes would be unnecessary if observation and site evaluation data are directly linked in a single data form and data set. Total crane numbers could be directly determined from number of adults and number of juveniles. In the observations component of the data set, however, an additional category of "unknown" is needed to more accurately record number of cranes of known and unknown ages.
- Observation date: Use for specific date when the site was visited to collect site evaluation data.
- Photograph taken: The Grand Island Office of USFWS has a wealth of photographs, including slides, negatives, and prints, which may at some time be of value, e.g., for future reports or studies of habitat changes at particular locations. Therefore, it may be worthwhile to keep this variable. Photographs could be kept with the paper copies, as they are currently, for easy access.
- Comments: Add a text field of 100-120 characters to allow for additional comments specifically related to site evaluation data.
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